326 results on '"Xanthoproteic reaction"'
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2. Inhibition properties of new amino acids for prevention of hydrate formation in carbon dioxide–water system: Experimental and modeling investigations
- Author
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Ali Dashti, Farshad Varaminian, Hadi Roosta, and S. Hossein Mazloumi
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chemistry.chemical_classification ,Aqueous solution ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Xanthoproteic reaction ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Amino acid ,chemistry.chemical_compound ,020401 chemical engineering ,chemistry ,Chemical affinity ,Glycine ,Carbon dioxide ,Materials Chemistry ,Side chain ,Organic chemistry ,0204 chemical engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Hydrate ,Spectroscopy - Abstract
In the present work, the effect of new structures of amino acids is studied for prevention of hydrate formation in the carbon dioxide–water system. These amino acids consist of L-proline (as amino acid with nonpolar side chain), L-serine and L-glutamine (as amino acids with polar side chain), and L-histidine (as amino acid with charged side chain). The inhibition effects of these amino acids were compared with glycine, L-threonine, and poly-N-vinylpyrrolidone (PVP). Experiments were performed in the concentration range of 0.5–2 wt.%. Investigation on the experimental results shows that inhibition properties of amino acids in an aqueous solution was due to hydrophobicity, the net charge of amino acid, and electrically charge of the side chain. Based on the experimental results, the ranking of amino acids (to decrease the hydrate growth rate) is as follows: L-histidine > glycine > L-proline ≈ L-serine ≈ L-threonine > L-glutamine, although the inhibition effect of some amino acids is not significant. In addition, the inhibition effects of these amino acids are quantitatively described by the chemical affinity model. The predicted results confirm that some of the applied amino acids decrease CO 2 hydrate formation rate.
- Published
- 2016
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3. Influence of biopolymers on the solubility of branched-chain amino acids and stability of their solutions
- Author
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Chi Rac Hong, Seung Jun Choi, Gyu Whan Lee, Hyun-Dong Paik, and Pahn-Shick Chang
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Whey protein ,Branched-chain amino acid ,02 engineering and technology ,Food chemistry ,010402 general chemistry ,01 natural sciences ,Analytical Chemistry ,Whey protein isolate ,law.invention ,chemistry.chemical_compound ,Biopolymers ,law ,Organic chemistry ,Crystallization ,Solubility ,Amino Acids ,chemistry.chemical_classification ,biology ,Proteins ,General Medicine ,021001 nanoscience & nanotechnology ,Xanthoproteic reaction ,0104 chemical sciences ,Amino acid ,chemistry ,biology.protein ,0210 nano-technology ,Amino Acids, Branched-Chain ,Food Science - Abstract
This study confirmed the possibility of biopolymer-type stabilizers to increase the saturation concentration of branched-chain amino acids by preventing their crystallization/precipitation. Although microfluidization increased the initial solubility, it failed to increase the saturation concentration of the branched-chain amino acids. The saturation concentration of the branched-chain amino acids increased from 3.81% to 4.42% and 4.85% after the incorporation of food hydrocolloids and proteins, respectively. However, the branched-chain amino acids:stabilizer ratio did not affect the solubility. In the case of food hydrocolloid-based solutions, crystal formation and growth of branched-chain amino acids occurred during storage, resulting in the precipitation of branched-chain amino acid crystals. However, food proteins effectively increased the stability of the solubilized branched-chain amino acids. The improved solubility and stability of the solubilized branched-chain amino acids could be attributed to interactions between the functional groups (carboxyl, amine, sulfate, aliphatic, aromatic, etc.) of the stabilizer and the branched-chain amino acid molecules.
- Published
- 2017
4. Xanthoproteic reaction for the evaluation of wool antifelting treatments
- Author
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Claudio Tonin, Franco Ferrero, and Gianluca Migliavacca
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chemistry.chemical_classification ,Materials Science (miscellaneous) ,General Chemical Engineering ,Tryptophan ,Electrophilic aromatic substitution ,Xanthoproteic reaction ,Amino acid ,chemistry.chemical_compound ,chemistry ,Chemistry (miscellaneous) ,Wool ,Nitric acid ,Organic chemistry ,Dyeing ,Tyrosine - Abstract
The substances responsible for the yellowing of wool treated with nitric acid are two amino acid constituents of the fibre: tryptophan and tyrosine. Nitric acid penetrates the fibres and carries out electrophilic aromatic substitution on the two above-mentioned amino acid residues, producing different colour yields. The intensity of yellowing depends in various ways on the treatment conditions (time, temperature, nitric acid concentration, agitation, and liquor ratio). Yellowing evaluation shows abnormal yellowing depending on acid concentration in the range 5.6-5.9 M. Working in this region makes it possible to use the chromatic reaction in order to show the damage done to wool fibres by the oxidising agents utilised in normal antifelting treatments. Wool damage by the oxidants is usually evaluated by dyeing methods based on different affinity of damaged fibres. By contrast, the xanthoproteic reaction yields chromogens as a function of the accessibility of tryptophan and tyrosine residues for the action of nitric acid on damaged fibres, and can be used for assessing the degree of antifelting treatment and its possible unevenness through the development on the treated wool of a yellow coloration more intense than on untreated wool.
- Published
- 2014
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5. Amine neutralized amino acid as CO2 absorbents: A quantitative 13C-NMR study
- Author
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Hallvard F. Svendsen, Ardi Hartono, and Arlinda F. Ciftja
- Subjects
Alanine ,chemistry.chemical_classification ,Taurine ,Management, Monitoring, Policy and Law ,Pollution ,Xanthoproteic reaction ,Industrial and Manufacturing Engineering ,Amino acid ,Serine ,chemistry.chemical_compound ,General Energy ,chemistry ,Zwitterion ,Organic chemistry ,Peptide bond ,Amine gas treating - Abstract
Amino acids, fully or partially neutralized with amines, are a new class of CO 2 absorbents that have the possibility to combine the ionic character of amino acids with the better CO 2 absorbing properties of the amines to form a more energy efficient solvent with improved environmental footprint. This work studies the effect of differences in p K a and structural properties between the amine and amino acid on the resulting active amino group in the blend. Equimolar mixtures of the amino acids, glycine, l -alanine, l -proline, taurine and l -serine, with alkanolamines, monoethanoamine (MEA) and 2-amino-2-methyl-1-propanol (AMP), were quantitatively studied by 13 C nuclear magnetic resonance spectroscopy (NMR) at 25 °C. The amino acids tested in the present work were chosen based on their solubility in water and on their relative basicity (p K a ) to that of the amines. It is observed that in amino acid-MEA blended systems, carbamate formation from both MEA and the amino acids occur and that generally, the amine group with highest p K a value is most favored when neutralizing the amino acid carboxylic group. If this is the amino acid an amino acid zwitterion may be formed, or, if amine has the highest p K a value, an amine–amino acid complex may be formed, rendering the amino acid amine group active toward CO 2 absorption. However, the experimental data show that not only the p K a value of the amino acid is important but that also steric effects play a role in determining the preferred carbamate forming position. In the amino acid-AMP systems almost all carbamate is formed on the amino acid amine group due to the steric hindrance in AMP. Generally, addition of amine to an aqueous amino acid solution increases the amino acid solubility. In this work solid precipitation was only observed at higher CO 2 loadings for l -alanine blended with both MEA and AMP. NMR spectroscopy analysis showed that the precipitate consists mainly of amino acid and bicarbonate/carbonate with very small amounts of amine.
- Published
- 2014
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6. Proteins and Albumin
- Author
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Roger L. Bertholf
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chemistry.chemical_classification ,Stereochemistry ,Carboxylic acid ,Biochemistry (medical) ,Clinical Biochemistry ,Tripeptide ,Xanthoproteic reaction ,Photo-reactive amino acid analog ,Amino acid ,chemistry ,Biochemistry ,Glycine ,Peptide bond ,Peptide sequence - Abstract
Proteins are large polymers of amino acids linked by peptide bonds (Figure 1). The amino acid subunits of proteins are organic molecules that include a carboxylic acid linked through a carbon atom to a primary (or secondary, in proline) amine with the chemical formula H 2 N-CHR-COOH, in which R is a side group that largely determines the chemical properties of the amino acid. The simplest amino acid is glycine, H 2 N-CH 2 -COOH, in which the R side group is a hydrogen atom. Although this chemical template can be modified into an infinite array of molecules based on variations in the R group, only approximately 20 amino acids occur in proteins. The R groups confer acidic, alkaline, polar, or nonpolar properties to the various amino acids.
- Published
- 2014
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7. Effect of pH on the solubilities of divalent and trivalent amino acids in water at 298.15K
- Author
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Ching-Yi Lee, I-Min Shiah, Wen-Tung Chang, and Jui-Tang Chen
- Subjects
chemistry.chemical_classification ,Aqueous solution ,General Chemical Engineering ,Inorganic chemistry ,General Physics and Astronomy ,Xanthoproteic reaction ,Amino acid ,Glutamine ,chemistry.chemical_compound ,Isoelectric point ,chemistry ,Zwitterion ,Aspartic acid ,Physical and Theoretical Chemistry ,Solubility - Abstract
The objective of this study is to report the effects of pH on the solubility of amino acids in water at 298.15 K. Two divalent amino acids, asparagine and glutamine, and three trivalent amino acids, tyrosine, aspartic acid and glutamic acid, were examined. The pH range studied was from 2 to 10. The solubility of amino acids in water is affected by the pH of the solution because amino acids dissociate into different ionic forms in aqueous solution: zwitterions, cations and anions. A chemical model was employed to describe the dissociation equilibria of all amino acid species with hydrogen ions in water. Moreover, for asparagine, glutamine and tyrosine, the chemical model indicated that the formation of cations and anions is insignificant in the isoelectric solution, with almost 100% of the amino acids exist as zwitterions. However, in the case of trivalent amino acids with acidic side chain groups, the zwitterion is not the only species present at the isoelectric point. Therefore, for aspartic acid and glutamic acid, at least three different ionic forms must be considered. To correlate the solubility data for amino acids in water, a non-random two liquid (NRTL) model was used to describe the non-idealities in the solution. The results calculated with two adjustable parameters were quite satisfactory, with an overall deviation of 2.21%.
- Published
- 2013
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8. Reactivity of chlorine dioxide with amino acids, peptides, and proteins
- Author
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Mary Sohn and Virender K. Sharma
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chemistry.chemical_classification ,chemistry ,Tryptophan ,Chlorine ,Environmental Chemistry ,Organic chemistry ,chemistry.chemical_element ,Reactivity (chemistry) ,Tyrosine ,Chloramination ,Xanthoproteic reaction ,Histidine ,Amino acid - Abstract
Amino acids, proteins, and peptides are found ubiquitously in waters. They can form harmful byproducts during water treatment by reaction with disinfectants. Chlorination and chloramination of water containing natural organic matter is known to result in the production of toxic substances, often referred to as disinfection byproducts. The main advantage of using chlorine dioxide (ClO2) over other known chlorine-containing disinfectants is the minimization of the formation of harmful trihalomethanes. Because ClO2 is a promising alternative to other chlorine-containing disinfectants, the chemistry of ClO2 interactions with amino acids, proteins, and peptides should be understood to ensure the safety of potable water supplies. Here, we present an overview of the aqueous chemistry of ClO2 and its reactivity with amino acids, peptides, and proteins. The kinetics and products of the reactions are reviewed. Only a few amino acids have been reported to be reactive with ClO2, and they have been found to follow second-order kinetics for the overall reaction. The rate constants vary from 10−2 to 107 M−1 s−1 and follow an order of reactivity: cysteine > tyrosine > tryptophan > histidine > proline. For reactions of histidine, tryptophan, and tyrosine with ClO2, products vary depending largely on the molar ratios of ClO2 with the specific amino acid. Products of ClO2 oxidation differ with the presence or absence of oxygen in the reaction mixture. Excess molar amounts of ClO2 relative to amino acids are associated with the production of low molecular weight compounds. The oxidation of the biochemically important compounds bovine serum albumin and glucose-6-phosphate dehydrogenase by ClO2 suggests a denaturing of proteins by ClO2 by an attack on tryptophan and tyrosine residues and relates to the inactivation of microbes by ClO2.
- Published
- 2012
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9. Nitration of α-chloronaphthalene-α-sulphonic acids
- Author
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M. Shawky, A. Y. Salem, I. F. Mohtasseb, and H. F. Bassilios
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chemistry.chemical_compound ,chemistry ,Group (periodic table) ,Nitric acid ,Nitration ,Electrophile ,Nitro ,Organic chemistry ,General Chemistry ,Xanthoproteic reaction - Abstract
Nitration of α-chloronaphthalene-α-sulphonic acids using mixed acids or fuming nitric acid gives α-substituted nitro derivatives. The deactivation of the aromatic nucleus by the two electrophilic groups is increased as the sulphonic group passes from the 4- to the 5- and finally to the 8-position.
- Published
- 2010
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10. A synthesis of N-phthaloyl amino acids and amino acid esters under mild conditions
- Author
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D. A. Hoogwater, J. J. Gunneweg, H. C. Beyerman, D. N. Reinhoudt, and T. S. Lie
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chemistry.chemical_classification ,Steric effects ,Stereochemistry ,General Chemistry ,Xanthoproteic reaction ,Photo-reactive amino acid analog ,Chloride ,Amino acid ,chemistry ,Biochemistry ,medicine ,Anhydrous ,Peptide bond ,Amino acid synthesis ,medicine.drug - Abstract
The racemization-free synthesis of N-phthaloyl amino acids (Pht-amino acids) from amino acid esters, by using o-methoxycarbonylbenzoyl chloride in anhydrous media, is described. The N-phthaloyl amino acids and esters from proteins were obtained in high yields. Three N-phthaloyl amino acids were synthesized for the first time: N-Pht-LTrp, N-Pht-S-Bzl-LCys and N-Pht-Nim-Bzl-LHis. In the case of some sterically hindered amino acids, LIle and α-amino-isobutyric acid, the intermediate N-(o-methoxycarbonylbenzoyl) amino acid derivative could be isolated.
- Published
- 2010
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11. Single Turnover Kinetics of Tryptophan Hydroxylase: Evidence for a New Intermediate in the Reaction of the Aromatic Amino Acid Hydroxylases
- Author
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Jorge Alex Pavon, Michaela T. Huynh, Bekir Engin Eser, and Paul F. Fitzpatrick
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Phenylalanine hydroxylase ,biology ,Chemistry ,Phenylalanine ,Tryptophan ,Substrate (chemistry) ,Tryptophan Hydroxylase ,Tryptophan hydroxylase ,Photochemistry ,Biochemistry ,Xanthoproteic reaction ,Medicinal chemistry ,Article ,Mixed Function Oxygenases ,Substrate Specificity ,Absorbance ,Amino Acids, Aromatic ,Kinetics ,chemistry.chemical_compound ,Reaction rate constant ,Aromatic amino acids ,biology.protein ,Tyrosine - Abstract
Tryptophan hydroxylase (TrpH) uses a non-heme mononuclear iron center to catalyze the tetrahydropterin-dependent hydroxylation of tryptophan to 5-hydroxytryptophan. The reactions of the TrpH.Fe(II), TrpH.Fe(II).tryptophan, TrpH.Fe(II).6MePH(4).tryptophan, and TrpH.Fe(II).6MePH(4).phenylalanine complexes with O(2) were monitored by stopped-flow absorbance spectroscopy and rapid quench methods. The second-order rate constant for the oxidation of TrpH.Fe(II) has a value of 104 M(-1) s(-1) irrespective of the presence of tryptophan. Stopped-flow absorbance analyses of the reaction of the TrpH.Fe(II).6MePH(4).tryptophan complex with oxygen are consistent with the initial step being reversible binding of oxygen, followed by the formation with a rate constant of 65 s(-1) of an intermediate I that has maximal absorbance at 420 nm. The rate constant for decay of I, 4.4 s(-1), matches that for formation of the 4a-hydroxypterin product monitored at 248 nm. Chemical-quench analyses show that 5-hydroxytryptophan forms with a rate constant of 1.3 s(-1) and that overall turnover is limited by a subsequent slow step, presumably product release, with a rate constant of 0.2 s(-1). All of the data with tryptophan as substrate can be described by a five-step mechanism. In contrast, with phenylalanine as substrate, the reaction can be described by three steps: a second-order reaction with oxygen to form I, decay of I as tyrosine forms, and slow product release.
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- 2010
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12. Fast and Efficient Nitration of Salicylic Acid and Some Other Aromatic Compounds over H3PO4/TiO2-ZrO2Using Nitric Acid
- Author
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Roozbeh Javad Kalbasi, Ahmad Reza Massah, Farzad Zamani, and Hamid Javaherian Naghash
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chemistry.chemical_compound ,chemistry ,Nitric acid ,Nitration ,Yield (chemistry) ,Organic chemistry ,General Chemistry ,Electrophilic aromatic substitution ,Selectivity ,Xanthoproteic reaction ,Salicylic acid ,Catalysis - Abstract
TiO2-ZrO2 (1/1)-surf with Ti and Zr molar ratio of 1/1 was prepared with surfactant through a sol-gel method. The optimum experimental condition was investigated for nitration of salicylic acid. Then, a number of nitration reactions were carried out with a variety of aromatic compounds in the optimum condition. The 25 wt% H3PO4/TiO2-ZrO2 (1/1)-surf catalyst showed good selectivity and yield in a short time for the nitration of salicylic acid and some other aromatic compounds.
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- 2010
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13. Separation of amino acids mixtures containing tyrosine in electromembrane system
- Author
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A.M. Savel’eva, A.E. Bukhovets, and T.V. Eliseeva
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chemistry.chemical_classification ,Chromatography ,Arginine ,Chemistry ,Mechanical Engineering ,General Chemical Engineering ,General Chemistry ,Combinatorial chemistry ,Xanthoproteic reaction ,Amino acid ,Tyrosine transport ,chemistry.chemical_compound ,Membrane ,Aromatic amino acids ,General Materials Science ,Tyrosine ,Histidine ,Water Science and Technology - Abstract
The principal distinction of tyrosine transport in the electromembrane system is revealed. It lies in the absence of electromigration of this amino acid through the cation-exchange membrane MC-40 in a wide range of current density. This is true for any pH value, including the region where tyrosine exists mainly in the form of cations. Only insignificant diffusive transfer of this aromatic amino acid (pI=5.63) is observed. At the same time the dependence of the flux through the anion-exchange membrane on the current density has the traditional form for amino acids with the maximum corresponding to the limiting current. On the basis of the revealed regularity of tyrosine transport, we study the possibility of its separation from the basic amino acid (arginine or histidine) that migrates actively through the cation-exchange membrane.
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- 2009
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14. Nitration of Alkyl Benzoates with Mixed Acid
- Author
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E. Kyaw Naing, O. Klais, and H. Hoffmann
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chemistry.chemical_classification ,General Chemical Engineering ,Carboxylic acid ,Sulfuric acid ,General Chemistry ,Electrophilic aromatic substitution ,Xanthoproteic reaction ,Medicinal chemistry ,Industrial and Manufacturing Engineering ,Koch reaction ,chemistry.chemical_compound ,chemistry ,Nitric acid ,Nitration ,Organic chemistry ,Benzoic acid - Abstract
The nitration of (substituted) benzoic acid esters is usually performed in fed-batch operation. The ester is solved in sulfuric acid charged first. The nitric acid dosed keeps the reaction temperature under control. The safety regarding uncontrolled reaction conditions was investigated under variation of the ratio of nitric acid to charged aromatic compound. A significant decrease in thermal stability of the reaction mixture was observed with excess of nitric acid. Safe operation cannot be assumed in general when the acid is close to or exceeds 10 % molar ratio. The investigation was restricted to aromatic carboxylic acid alkyl esters which form homogeneous mixtures with sulfuric acid. The thermal stability was investigated by differential thermal analysis (closed systems), adiabatic storage tests, and dynamic calorimeters. The reaction products were analyzed by means of NMR and mass spectrometry. The experiments showed that the formation of dinitro compounds cannot cause the thermal instability alone. The formation of dinitro compounds starts at temperatures above the reaction conditions. Another component is responsible for the thermal instability which accumulates in the presence of an ester group at excess nitric acid. It could be deduced that the decomposition reaction is primarily caused by the reaction of surplus nitryl cation (NO 2 + ion) with the nitrated carboxylic acid ester in the presence of sulfuric acid. The decomposition temperature of the reaction mixture depends on the nature of the ester group and the type and number of further substituents on the aromatic ring.
- Published
- 2009
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15. New method for the synthesis of N-methyl amino acids containing peptides by reductive methylation of amino groups on the solid phase
- Author
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Anders Undén and Kalle Kaljuste
- Subjects
chemistry.chemical_classification ,Sodium cyanoborohydride ,Stereochemistry ,Molecular Sequence Data ,Peptide ,Methylation ,Biochemistry ,Xanthoproteic reaction ,Photo-reactive amino acid analog ,Amino acid ,chemistry.chemical_compound ,chemistry ,Trifluoroacetic acid ,Peptide synthesis ,Amino Acid Sequence ,Amino Acids ,Peptides ,Oxidation-Reduction ,Peptide sequence - Abstract
Primary amino groups on the model peptide Xaa-Ala-Pro-Lys(ClZ)-Tyr(2BrZ), synthesized on a p-methylbenzhydryl amine resin with conventional Boc/benzyl protective group strategy, were reacted with 4,4'-dimethoxydityl chloride in dichloromethane, resulting in the introduction of the dimethoxydityl group, which is an acid-labile N-alkyl type of protective group. The secondary amino groups thereby formed can be methylated by treating the peptide-resin with formaldehyde and sodium cyanoborohydride in N,N-dimethylformamide. After the removal of the dimethoxydityl group with trifluoroacetic acid, the resulting N-methylated amino acid residues with a free secondary amino groups are accessible for acylation with the next activated Boc amino acid. With this method majority of the 20 common amino acids can be monomethylated directly on the resin and, in most cases, with very low levels of the side reactions. In the cases where the complete methylation is difficult to achieve, the remaining primary amino groups can be selectively acylated in the presence of secondary amino groups with trimethylacetic acid 1-hydroxybenzotriazole ester. The method provides a convenient general route to synthesize N-methylated derivatives of most of the occurring and synthetic amino acids.
- Published
- 2009
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16. Amino acids with aryl-keto function in their side chains
- Author
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Bednarek Ma
- Subjects
chemistry.chemical_classification ,Chemistry ,Stereochemistry ,Aryl ,Ether ,Anisole ,Biochemistry ,Photo-reactive amino acid analog ,Xanthoproteic reaction ,Amino acid ,Electrophilic substitution ,chemistry.chemical_compound ,Endocrinology ,Friedel–Crafts reaction - Abstract
Amino acids with aryl-keto function in their side-chains were obtained in excellent yields in the reaction of omega-carboxyamino acids with liquid HF in the presence of aromatic compounds susceptible to electrophilic substitution, such as anisole, 2-methoxybiphenyl, butyl phenyl ether or 1,3-dimethoxybenzene. The new amino acids were converted smoothly into N-tert-butyloxycarbonyl or N-fluorenylmethoxycarbonyl derivatives and then incorporated into peptides by conventional coupling methods. During the coupling step, no formation of cyclic Schiff bases was observed for aryl-keto amino acids derived from DL-alpha-aminopimelic acid and from L-alpha-aminosuberic acid. In the crude products, truncated peptides terminated at the keto amino acids were not detected by liquid chromatography-mass spectrometry.
- Published
- 2009
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17. REACTIONS BETWEEN AMINO ACIDS AND ORGANIC ACIDS: REACTION OF TRYPTOPHAN AND PYRUVIC ACID
- Author
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N. T. Chu and Fergus M. Clydesdale
- Subjects
chemistry.chemical_classification ,Paper chromatography ,chemistry.chemical_compound ,chemistry ,Tryptophan ,Organic chemistry ,Nuclear magnetic resonance spectroscopy ,Polymer ,Pyruvic acid ,Xanthoproteic reaction ,Food Science ,Amino acid ,Organic acid - Abstract
A reaction between pyruvic acid and tryptophan, which produced yellow products, was found in this investigation. The isolation and identification of the compounds produced by this interaction were carried out by paper chromatography, UV, IR and NMR spectroscopy, and organic synthetic procedures. Four compounds were isolated: three were identitied as 1,2,3,4-tetrahydroharman-1,3-dicarboxylic acid, an isomer of 1,2,3,4-tetrahydroharman-1,3-dicarboxylic acid and harman. The compound which was not fully identified, was a yellow polymer. The decrease in concentration of pyruvic acid and tryptophan due to this interaction was analyzed by an automatic organic acid analyzer and an automatic amino acid analyzer. It was found that the ratio of pyruvic acid to tryptophan used in this reaction was approximately 1.6:1. This reaction was found to proceed via a 1:1 molecular reaction between tryptophan and pyruvic acid to form 1,2,3,4-tetrahydroharman-1,3-dicarboxylic acid and its yellow isomer followed by the formation of a yellow polymer produced by the interaction of the yellow isomer of 1,2,3,4-tetrahydroharman-1,3-dicarboxylic acid and pyruvic acid.
- Published
- 2008
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18. REACTIONS BETWEEN AMINO ACIDS AND ORGANIC ACIDS: REACTION OF TRYPTOPHAN AND ALPHA-KETOGLUTARIC ACID
- Author
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Fergus M. Clydesdale and N. T. Chu
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chemistry.chemical_classification ,Paper chromatography ,chemistry.chemical_compound ,alpha-Ketoglutaric acid ,chemistry ,Tryptophan ,Organic chemistry ,Infrared spectroscopy ,Organic synthesis ,Xanthoproteic reaction ,Food Science ,Amino acid - Abstract
This study involved an investigation of the discoloration found to be caused by the interaction between α-ketoglutaric acid and tryptophan. Many products were formed by this interaction, but only the five compounds in the highest concentration were isolated: three were blue, one green and one a brown-yellow. Unfortunately, due to instability, these compounds were not identified However, the concentration of both cu-ketoglutaric acid and tryptophan, utilized during the reaction, were analyzed The results indicated that the ratio of α-ketoglutaric acid to tryptophan utilized was approximately 3:1. From these results along with various identification procedures (paper chromatography, UV-Vis, and IR spectroscopy, and organic synthesis) a pathway is postulated for the formation of the colored compounds in this interaction.
- Published
- 2008
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19. Thermal stability of amino acid-(tyrosine and tryptophan) coated magnetites
- Author
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Gabriela Marinescu, Daniela C. Culita, Oana Carp, Luminita Patron, and Lucian Diamandescu
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chemistry.chemical_classification ,Ligand ,Inorganic chemistry ,Tryptophan ,Condensed Matter Physics ,Xanthoproteic reaction ,Amino acid ,Thermogravimetry ,chemistry ,Polymer chemistry ,Thermal stability ,Physical and Theoretical Chemistry ,Tyrosine ,Stoichiometry - Abstract
The thermal stability of two amino acid-(tyrosine and tryptophan) coated magnetite and their corresponding precursors, [Fe 2 III FeII(Tyr)8]·9H2O and [Fe 2 III FeII(Trp)2(OH)4](NO3)2·8H2O (where tyrosine=Tyr and tryptophan=Trp), was analyzed in comparison with free amino acids. The complexes present a lower thermal stability relative to the free ligand, due to the catalytic effect introduced by the iron cation and the presence of NO 3 − groups. The presence of NO 3 − group determines also a different degradation’s stoichiometry of the amino acid anion comparative with the one expressed by the free ligand molecule. The amino acid bonded to magnetite decomposes in two steps, its presence inducing an increasing of γ-Fe2O3→Fe2O3 conversion temperature.
- Published
- 2008
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20. Amino Acid Solution
- Author
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Mark G. Papich
- Subjects
chemistry.chemical_classification ,Chemistry ,Organic chemistry ,Xanthoproteic reaction ,Amino acid solution ,Amino acid - Published
- 2016
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21. Electrochemical determination of aromatic amino acids in extracts containing hydrophilic solvents
- Author
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S. I. Niftaliev, N. Ya. Mokshina, and O. A. Pakhomova
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chemistry.chemical_classification ,Chromatography ,Aqueous solution ,Extraction (chemistry) ,Potentiometric titration ,Salt (chemistry) ,Phenylalanine ,Xanthoproteic reaction ,Analytical Chemistry ,Amino acid ,chemistry.chemical_compound ,chemistry ,Aromatic amino acids ,Organic chemistry - Abstract
Some regularities of the extraction of aromatic amino acids (phenylalanine, tyrosine) with hydrophilic solvents and their mixtures from aqueous salt solutions were found. The electrochemical (potentiometric, conductometric) determination of amino acids was studied directly in the organic extract without their preliminary separation.
- Published
- 2007
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22. Amino Acid Transformation and Decomposition in Saturated Subcritical Water Conditions
- Author
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Tomomi Nakahasi, Wael Abdelmoez, and Hiroyuki Yoshida
- Subjects
Alanine ,chemistry.chemical_classification ,Vapor pressure ,Chemistry ,General Chemical Engineering ,General Chemistry ,Activation energy ,Xanthoproteic reaction ,Decomposition ,Industrial and Manufacturing Engineering ,Amino acid ,Valine ,Organic chemistry ,Proline - Abstract
The reactions of amino acids under subcritical water conditions in the temperature range 503−563 K using a pressure value corresponding to the saturated vapor pressure of water at the employed reaction temperature (hereafter called saturated subcritical water) were investigated. As reactants, solutions containing a single amino acid or a mixture of 17 different amino acids were used, and the obtained results in both cases were compared. Glysine, alanine, valine, and proline were produced as intermediate products during the thermal transformation of other amino acids. Generally, the results showed that the existence of amino acids together in a mixture decreased the overall stability since the activation energy values of decomposition of individual amino acids reduced significantly due to their presence in a mixture of amino acids. Most of the amino acids were found to be labile at acidic and near-natural pH values and more stable at a highly basic pH value.
- Published
- 2007
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23. Heterocyclic quinones. VIII. Synthesis and spectra of new carbazoloquinone derivatives of naturally occurring amino acids
- Author
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A. S. Hammam
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chemistry.chemical_classification ,Substitution reaction ,S-tag ,Stereochemistry ,Chemistry ,Acidic amino acids ,Moiety ,Xanthoproteic reaction ,Basic amino acids ,Photo-reactive amino acid analog ,Amino acid - Abstract
Fifteen naturally occurring amino acids representing basic, neutral and acidic members were interacted with 4,4′-dimethoxydiquinone (I). Basic amino acids reacted readily to give amino acid substituted carbazoloquinones (III), while neutral and acidic amino acids reacted only after addition of an acid binding agent. Using an excess of any of the amino acids resulted in the substitution of the quinonoid methoxyl group in compounds (III) by an amino acid moiety. In the case of basic amino acids, this substitution reaction was preferentially influenced by a terminal amino or guanidino amino rather than by an α-amino group. Moreover, basic amino acids could be reacted with two moles of (I) to produce dicarbazoloquinones (X). The i.r. and u.v.-visible spectra of the various carbazoloquinone products were determined and discussed.
- Published
- 2007
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24. The enthalpies of interaction of polyvinylbenzyltrimethylammonium hydroxide with amino acids in aqueous solutions
- Author
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V. D. Kopylova, A. V. Astapov, and Yu. S. Peregudov
- Subjects
Exothermic reaction ,chemistry.chemical_classification ,Aqueous solution ,Exothermic process ,Enthalpy ,Inorganic chemistry ,Medicinal chemistry ,Xanthoproteic reaction ,Amino acid ,chemistry.chemical_compound ,chemistry ,Glycine ,Hydroxide ,Physical and Theoretical Chemistry - Abstract
The enthalpies of interaction of polyvinylbenzyltrimethylammonium (PVTA) hydroxide with glycine, glutamic acid, and tyrosine anions were determined calorimetrically. The interaction of PVTA with amino acid anions was shown to be an exothermic process. The enthalpy of interaction depended on the nature and concentration of the amino acid. The reaction became less exothermic and the time of the establishment of equilibrium increased as the concentration of amino acids grew.
- Published
- 2007
- Full Text
- View/download PDF
25. Microwave-Enhanced Copper-Catalyzed N-Arylation of Free and Protected Amino Acids in Water
- Author
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Svenja Roettger, Mats Larhed, and Per J. R. Sjoeberg
- Subjects
chemistry.chemical_classification ,Spectrometry, Mass, Electrospray Ionization ,Chemistry ,Electrospray ionization ,Aryl ,Water ,General Medicine ,General Chemistry ,Mass spectrometry ,Xanthoproteic reaction ,Catalysis ,Amino acid ,Solvent ,chemistry.chemical_compound ,Copper catalyzed ,Organic chemistry ,Amino Acids ,Microwaves ,Racemization ,Copper ,Microwave - Abstract
A microwave-enhanced copper-catalyzed protocol for N-arylation using water as the solvent is reported. This fast transformation allows the reaction between various amino acids or amino acid esters and a diverse set of substituted aryl bromides in less than 40 min, affording good yields of non-protected N-arylated amino acids with only minor racemization (6% or less). In addition, online ESI-MS and MS/MS analysis were used to "fish-out" an anionic Cu-containing amino acid complex directly from an ongoing N-arylation reaction.
- Published
- 2007
- Full Text
- View/download PDF
26. Protein Tyrosine Nitration Induced by Heme/Hydrogen Peroxide: Inhibitory Effect of Hydroxycinnamoyl Conjugates
- Author
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M. Carmen Recio, José Luis Ríos, Ana Olmos, Salvador Máñez, and Rosa M. Giner
- Subjects
Hemeproteins ,Coumaric Acids ,Bicarbonate ,Pharmaceutical Science ,Heme ,Asteraceae ,Catalysis ,Analytical Chemistry ,Inhibitory Concentration 50 ,chemistry.chemical_compound ,Nitration ,Drug Discovery ,Leukocytes ,Humans ,Tyrosine ,Nitrite ,Hydrogen peroxide ,Pharmacology ,Nitrates ,Organic Chemistry ,Hydrogen Peroxide ,Hydrogen-Ion Concentration ,Xanthoproteic reaction ,Complementary and alternative medicine ,chemistry ,Biochemistry ,Molecular Medicine ,Phytotherapy ,Hemin - Abstract
The present study was designed to optimize the experimental conditions that govern the heme-catalyzed nitration of protein tyrosine residues by nitrite, and, within this framework, to study the effects of 3,5-dicaffeoylquinic acid and its methyl ester, both of which have been previously reported to be antioxidants and inhibitors of leukocyte functions. Although the presence of hydrogen peroxide is essential in cell-free systems, an excess of this compound was found to be detrimental, so much so that an increase in hemin concentration actually resulted in an inverse effect on the reaction, depending on the levels of fixed hydrogen peroxide. Unlike previous reports on nitrite-induced albumin tyrosine nitration, the optimal pH here was found to be 7.0. The two caffeoyl conjugates tested were found to be effective inhibitors of protein nitration, with IC50 values ranging from 20 - 30 microM, regardless of the presence of bicarbonate. For the inhibition of myeloperoxidase-catalyzed protein nitration by human polymorphonuclear leukocytes stimulated by phorbol ester, the potencies obtained were up to two times higher. This is the first time that caffeoylquinic esters have been reported as inhibitors of heme-based protein nitration.
- Published
- 2006
- Full Text
- View/download PDF
27. Behavior of amino acid production from hydrothermal treatment of fish-derived wastes
- Author
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Kilyoon Kang and Byung-Soo Chun
- Subjects
Alanine ,chemistry.chemical_classification ,General Chemical Engineering ,General Chemistry ,Xanthoproteic reaction ,Decomposition ,Amino acid ,Serine ,Hydrolysis ,chemistry ,Yield (chemistry) ,Glycine ,Organic chemistry ,Nuclear chemistry - Abstract
The effect of operating parameters (temperature and time) and various reaction modes(batch, semi-batch and continuous flow) on the behavior of amino acid production from hydrothermal decomposition of fish-derived wastes was investigated. The amino acids obtained in batch experiments at 523 K were mainly alanine (Ala) and glycine (Gly) at maximum yield of 65 and 28 mg/g-dry fish, respectively. At a relatively lower temperature of 473 K, the relative concentration of high-molecular-weight amino acids such as aspartic acid (Asp) and serine (Ser) is significantly high, but decreases as temperature increases. It is likely that high-molecular-weight amino acids decompose faster than low-molecular ones. Semi-batch and continuous flow modes of reaction suppressed decomposition of amino acids into organic acids (or volatile materials) by continuously removing the products from the reaction zone as soon as they were formed. Thus, a large amount of high-molecular-weight amino acids such as Asp and Ser at these reaction modes was observed. This increases the yield of total amino acids at short reaction time and at temperature relatively higher than 523 K. It was also observed that the composition of the resulting products also depends on the modes of reaction.
- Published
- 2004
- Full Text
- View/download PDF
28. Behavior of hydrothermal decomposition of silk fibroin to amino acids in near-critical water
- Author
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Kilyoon Kang and Byung-Soo Chun
- Subjects
chemistry.chemical_classification ,Aqueous solution ,Formic acid ,General Chemical Engineering ,Alkalinity ,Fibroin ,General Chemistry ,Xanthoproteic reaction ,Amino acid ,chemistry.chemical_compound ,Oleic acid ,Hydrolysis ,chemistry ,Organic chemistry - Abstract
The behavior of protein decomposition to amino acids in near-critical water is elucidated by using silk fibroin as a model compound. Results show that serine (Ser), aspartic acid (Asp) and other complex amino acids, obtained initially in significant amount, gradually decreased as reaction time and temperature were increased. At temperature higher than 523 K, it is likely that Gly and Ala underwent further decomposition. Regarding the effect of various additives, no significant effect on the yield of amino acids was observed with the addition of oleic acid. However, the presence of NaOH and formic acid (FA), both in 5 mol% aqueous solution, had significant effect on the yield. The effect of alkalinity and acidity, the production of amino acids was enhanced in either acidic or basic conditions.
- Published
- 2004
- Full Text
- View/download PDF
29. Photooxidation of Amino Acids and Proteins Mediated by Novel 1,8-Naphthalimide Derivatives
- Author
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Bindu Abraham and Lisa A. Kelly
- Subjects
chemistry.chemical_classification ,Quenching (fluorescence) ,Chemistry ,Tryptophan ,Photochemistry ,Xanthoproteic reaction ,Surfaces, Coatings and Films ,Amino acid ,chemistry.chemical_compound ,Materials Chemistry ,Aromatic amino acids ,Physical and Theoretical Chemistry ,Tyrosine ,Lysozyme ,Histidine - Abstract
The ground- and excited-state interactions of N-(2-ethanoic acid)-1,8-naphthalimide (NI-ala), along with tryptophan and tyrosine-substituted 1,8-naphthalimide derivatives (NI-trp and NI-tyr), with amino acids and native proteins have been studied in aqueous buffered solution. The singlet excited state of NI-ala reacts with the aromatic amino acids, tryptophan, tyrosine, and histidine with a rate constant at or exceeding the diffusion-controlled limit. Reactivity with bovine serum albumin (BSA) and lysozyme was also demonstrated. However, in all cases, no long-lived redox products were observed from the singlet state quenching. The reactivity of the triplet excited state of NI-ala with the individual amino acids and proteins was studied using laser flash photolysis. Triplet-state reactivity was demonstrated with tryptophan and tyrosine, along with BSA and lysozyme proteins. In the case of tryptophan, tyrosine, and lysozyme, long-lived redox products were observed and quantified. Neutral tryptophan and tyrosyl radicals were observed by transient spectroscopy as quenching products. Upon photolysis of all three 1,8-naphthalimide derivatives, both cleavage and cross-linking of the lysozyme are observed. These studies have identified the potential oxidative targets in native proteins and demonstrated the utility of our naphthalimide derivatives to photomodify native proteins.
- Published
- 2003
- Full Text
- View/download PDF
30. Free radical-mediated oxidation of free amino acids and amino acid residues in proteins
- Author
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Earl R. Stadtman and Rodney L. Levine
- Subjects
chemistry.chemical_classification ,Methionine ,Antioxidant ,Free Radicals ,medicine.medical_treatment ,Organic Chemistry ,Clinical Biochemistry ,Proteins ,Protein aggregation ,Reactive Nitrogen Species ,Biochemistry ,Xanthoproteic reaction ,Photo-reactive amino acid analog ,Amino acid ,chemistry.chemical_compound ,chemistry ,Metals ,medicine ,Aromatic amino acids ,Humans ,Amino Acids ,Reactive Oxygen Species ,Oxidation-Reduction ,Cysteine - Abstract
We summarize here results of studies designed to elucidate basic mechanisms of reactive oxygen (ROS)-mediated oxidation of proteins and free amino acids. These studies have shown that oxidation of proteins can lead to hydroxylation of aromatic groups and aliphatic amino acid side chains, nitration of aromatic amino acid residues, nitrosylation of sulfhydryl groups, sulfoxidation of methionine residues, chlorination of aromatic groups and primary amino groups, and to conversion of some amino acid residues to carbonyl derivatives. Oxidation can lead also to cleavage of the polypeptide chain and to formation of cross-linked protein aggregates. Furthermore, functional groups of proteins can react with oxidation products of polyunsaturated fatty acids and with carbohydrate derivatives (glycation/glycoxidation) to produce inactive derivatives. Highly specific methods have been developed for the detection and assay of the various kinds of protein modifications. Because the generation of carbonyl derivatives occurs by many different mechanisms, the level of carbonyl groups in proteins is widely used as a marker of oxidative protein damage. The level of oxidized proteins increases with aging and in a number of age-related diseases. However, the accumulation of oxidized protein is a complex function of the rates of ROS formation, antioxidant levels, and the ability to proteolytically eliminate oxidized forms of proteins. Thus, the accumulation of oxidized proteins is also dependent upon genetic factors and individual life styles. It is noteworthy that surface-exposed methionine and cysteine residues of proteins are particularly sensitive to oxidation by almost all forms of ROS; however, unlike other kinds of oxidation the oxidation of these sulfur-containing amino acid residues is reversible. It is thus evident that the cyclic oxidation and reduction of the sulfur-containing amino acids may serve as an important antioxidant mechanism, and also that these reversible oxidations may provide an important mechanism for the regulation of some enzyme functions.
- Published
- 2003
- Full Text
- View/download PDF
31. Selective determination of amino acids using flow injection analysis coupled with chemiluminescence detection
- Author
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Simon W. Lewis, Jason W. Costin, and Paul S. Francis
- Subjects
chemistry.chemical_classification ,Chromatography ,Tryptophan ,Phenylalanine ,Biochemistry ,Xanthoproteic reaction ,Analytical Chemistry ,Luminol ,law.invention ,Amino acid ,chemistry.chemical_compound ,Potassium permanganate ,chemistry ,law ,Environmental Chemistry ,Tyrosine ,Spectroscopy ,Chemiluminescence - Abstract
The determination of the amino acids proline, histidine, tyrosine, arginine, phenylalanine and tryptophan using flow injection analysis (FIA) with chemiluminescence detection is described. Proline was the only amino acid to exhibit chemiluminescence with the tris(2,2-bipyridyl)ruthenium(III) reaction at pH 10. While, histidine was found to selectively enhance the reaction of luminol with Mn(II) salts in a basic medium. Acidic potassium permanganate chemiluminescence was able to selectively determine tyrosine at pH 6.75. Low pressure separations using a C18 guard column allowed the simultaneous determination of tyrosine and tryptophan or phenylalanine and tryptophan with acidic potassium permanganate and copper(II)–amino acid–hydrogen peroxide chemiluminescence, respectively. Precision for each method was less than 3.9% (R.S.D.) for five replicates of a standard (1×10−5 M) and the detection limits ranged between 4×10−9 and 7×10−6 M. Preliminary investigations revealed that the methodology developed was able to selectively determine the individual amino acids in an equimolar mixture of the 20 naturally occurring amino acids.
- Published
- 2003
- Full Text
- View/download PDF
32. Effects of alkali or acid treatment on the isomerization of amino acids
- Author
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Yuta Mutaguchi, Taketo Ohmori, Katsumi Doi, and Toshihisa Ohshima
- Subjects
chemistry.chemical_classification ,Dipeptide ,Stereochemistry ,Bioengineering ,Peptide ,Alkalies ,Applied Microbiology and Biotechnology ,Xanthoproteic reaction ,Chemistry Techniques, Analytical ,Amino acid ,Residue (chemistry) ,chemistry.chemical_compound ,Isomerism ,chemistry ,Organic chemistry ,Acid hydrolysis ,Amino Acids ,Peptides ,Acids ,Isomerization ,Racemization ,Biotechnology - Abstract
The effect of alkali treatment on the isomerization of amino acids was investigated. The 100 × D /( D + L ) values of amino acids from peptide increased with increase in the number of constituent amino acid residues. Furthermore, the N-terminal amino acid of a dipeptide was isomerized to a greater extent than the C-terminal residue.
- Published
- 2012
- Full Text
- View/download PDF
33. An Efficient and Practical N-Methylation of Amino Acid Derivatives
- Author
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Hong-Yong Kim, Denis Har, Oljan Repic, Mahavir Prashad, Thomas J. Blacklock, and Bin Hu
- Subjects
chemistry.chemical_classification ,Organic Chemistry ,Water ,General Medicine ,Methylation ,N methylation ,Sulfuric Acid Esters ,Medicinal chemistry ,Biochemistry ,Xanthoproteic reaction ,Amino acid ,Sodium hydride ,Catalysis ,Reaction rate ,chemistry.chemical_compound ,Dimethyl sulfate ,chemistry ,Sodium hydroxide ,Sodium Hydroxide ,Organic chemistry ,Amino Acids ,Physical and Theoretical Chemistry - Abstract
[reaction: see text] An efficient and practical N-methylation of amino acid derivatives with dimethyl sulfate in the presence of sodium hydride and a catalytic amount of water is described. Reaction of water with sodium hydride generated highly reactive dry sodium hydroxide, which led to much faster reaction rates than powdered sodium hydroxide itself.
- Published
- 2002
- Full Text
- View/download PDF
34. Labeling Proteins via Hole Burning of Their Aromatic Amino Acids: Pressure Tuning Spectroscopy of BPTI
- Author
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Markus Stübner, Christoph Hecht, and Josef Friedrich
- Subjects
chemistry.chemical_classification ,Chromatography ,Staining and Labeling ,Biophysics ,Proteins ,Sensitivity and Specificity ,Xanthoproteic reaction ,Amino acid ,Bovine Pancreatic Trypsin Inhibitor ,Amino Acids, Aromatic ,chemistry.chemical_compound ,Crystallography ,Aprotinin ,chemistry ,Pressure ,Aromatic amino acids ,medicine ,Tyrosine ,Pressure tuning ,Spectrophotometry, Ultraviolet ,Spectroscopy ,Research Article ,medicine.drug - Abstract
We demonstrate hole burning on a protein by using an intrinsic aromatic amino acid as a probe. The protein is bovine pancreatic trypsin inhibitor (BPTI), the labeled amino acid is tyrosine. Only one of the four tyrosines could be burned. As an application we present pressure tuning experiments from which the local compressibility around the burned tyrosine probe is determined.
- Published
- 2002
- Full Text
- View/download PDF
35. Real-time Measurements of Amino Acid and Protein Hydroperoxides Using Coumarin Boronic Acid*
- Author
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Ewa Gapys, Balaraman Kalyanaraman, Radosław Michalski, Joy Joseph, Andrzej Marcinek, and Jacek Zielonka
- Subjects
Azoles ,macromolecular substances ,Isoindoles ,Biochemistry ,chemistry.chemical_compound ,Computer Systems ,Coumarins ,Organoselenium Compounds ,Fluorometry ,Tyrosine ,Amino Acids ,Molecular Biology ,Histidine ,Fluorescent Dyes ,chemistry.chemical_classification ,Chromatography ,Glutathione peroxidase ,musculoskeletal, neural, and ocular physiology ,Tryptophan ,Proteins ,Cell Biology ,Xanthoproteic reaction ,Boronic Acids ,Amino acid ,Peroxides ,chemistry ,nervous system ,Boronic acid ,Molecular Biophysics ,Cysteine - Abstract
Hydroperoxides of amino acid and amino acid residues (tyrosine, cysteine, tryptophan, and histidine) in proteins are formed during oxidative modification induced by reactive oxygen species. Amino acid hydroperoxides are unstable intermediates that can further propagate oxidative damage in proteins. The existing assays (oxidation of ferrous cation and iodometric assays) cannot be used in real-time measurements. In this study, we show that the profluorescent coumarin boronic acid (CBA) probe reacts with amino acid and protein hydroperoxides to form the corresponding fluorescent product, 7-hydroxycoumarin. 7-Hydroxycoumarin formation was catalase-independent. Based on this observation, we have developed a fluorometric, real-time assay that is adapted to a multiwell plate format. This is the first report showing real-time monitoring of amino acid and protein hydroperoxides using the CBA-based assay. This approach was used to detect protein hydroperoxides in cell lysates obtained from macrophages exposed to visible light and photosensitizer (rose bengal). We also measured the rate constants for the reaction between amino acid hydroperoxides (tyrosyl, tryptophan, and histidine hydroperoxides) and CBA, and these values (7-23 M(-1) s(-1)) were significantly higher than that measured for H2O2 (1.5 M(-1) s(-1)). Using the CBA-based competition kinetics approach, the rate constants for amino acid hydroperoxides with ebselen, a glutathione peroxidase mimic, were also determined, and the values were within the range of 1.1-1.5 × 10(3) M(-1) s(-1). Both ebselen and boronates may be used as small molecule scavengers of amino acid and protein hydroperoxides. Here we also show formation of tryptophan hydroperoxide from tryptophan exposed to co-generated fluxes of nitric oxide and superoxide. This observation reveals a new mechanism for amino acid and protein hydroperoxide formation in biological systems.
- Published
- 2014
36. [Untitled]
- Author
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I. M. Lapina and L. M. Pevzner
- Subjects
chemistry.chemical_classification ,General Chemistry ,Alkaline hydrolysis (body disposal) ,Xanthoproteic reaction ,Amino acid ,Acylation ,chemistry.chemical_compound ,Hydrolysis ,chemistry ,Furan ,Aromatic amino acids ,Organic chemistry ,lipids (amino acids, peptides, and proteins) ,Triethylamine - Abstract
Acylation of aromatic amino acids with furancarboxylic acid chlorides effectively proceeds in water-acetone medium at pH 8-9. Aliphatic amino acids are acylated at higher pH values, but under these conditions hydrolysis of acid chlorides becomes the main process. Acylation of chlorohydrates of methyl esters of aliphatic amino acids proceeds smoothly in chloroform in the presence of triethylamine. Alkaline hydrolysis of obtained products leads to N-acylated amino acids containing furan heteroring in the acyl radical.
- Published
- 2001
- Full Text
- View/download PDF
37. FEEDING EXPERIMENTS WITH MIXTURES OF HIGHLY PURIFIED AMINO ACIDS. VIII. ISOLATION AND IDENTIFICATION OF A NEW ESSENTIAL AMINO ACID*
- Author
-
Curtis E. Meyer, William C. Rose, and Richard H. McCoy
- Subjects
chemistry.chemical_classification ,Nutrition and Dietetics ,Spatial configuration ,Chemistry ,Stereochemistry ,Medicine (miscellaneous) ,chemistry.chemical_element ,Complete protein ,Hydroxyglutamic acid ,Nitrogen ,Xanthoproteic reaction ,Essential amino acid ,Amino acid - Abstract
The hitherto unknown growth essential has been isolated in pure, crystalline form, san indentified as one of the four optically isomeric α-amino-β-hydroxy-n-butyric acids. Several of its derivatives have been prepared and described. On reduction of new amino acid yields d-α-amino-n-butyrie acid. The spatial configuration around the β-carbon atom remians to be determined, and is now being investigated. With an otherwise adequate diet, appromiately 0.6 per cent of α-amino-β-hydroxybutyric acid is the minimum amount necessary to induce maximum growth. The feeding trails herein described constitute the first successful attempt to rear animals on a ration contraining purified a mino acids as the sole source of nitrogen. Inasmuch as satisfactory growth has been secured by the use of diets devoid of hydroxyglutamic acid and citruiline, these two amino acids are not indispensable components of the food. Experiments designed to determine the physological importance of the remaining amino acids are now under way.
- Published
- 2009
- Full Text
- View/download PDF
38. [Untitled]
- Author
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Bernd M. Rode and Yuttana Suwannachot
- Subjects
chemistry.chemical_classification ,Stereochemistry ,Peptide ,General Medicine ,Tripeptide ,Xanthoproteic reaction ,Amino acid ,chemistry ,Space and Planetary Science ,Diglycine ,Glycine ,Chemical ligation ,Peptide sequence ,Ecology, Evolution, Behavior and Systematics - Abstract
The presence of some amino acids and dipeptides under the conditions of the salt-induced peptide formation reaction (aqueous solution at 85 °C, Cu(II) and NaCl) has been found to catalyze the formation of homopeptides of other amino acids, which are otherwise produced only in traces or not at all by this reaction. The condensation of Val, Leu and Lys to form their homodipeptides can occur to a considerable extent due to catalytic effects of other amino acids and related compounds, among which glycine, histidine, diglycine and diketopiperazine exhibit the most remarkable activity. These findings also lead to a modification of the table of amino acid sequences preferentially formed by the salt-induced peptide formation (SIPF) reaction, previously used for a comparison with the sequence preferences in membrane proteins of primitive organisms
- Published
- 1999
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39. Chemical modification of usnic acid 2. Reactions of (+)-usnic acid with amino acids
- Author
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Marina P. Polovinka, Nariman F. Salakhutdinov, Olga A. Luzina, and Tolstikov Genrikh A
- Subjects
chemistry.chemical_classification ,chemistry.chemical_compound ,Chemistry ,Stereochemistry ,Usnic acid ,Chemical modification ,Organic chemistry ,General Chemistry ,Xanthoproteic reaction ,Enamine ,Amino acid - Abstract
The condensation of amino acids with (+)-usnic acid involves the 2-positioned acetyl group of the latter and gives derivatives containing an enamine fragment.
- Published
- 2007
- Full Text
- View/download PDF
40. Chemical Burn with Nitric Acid and Xanthoproteic Reaction
- Author
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Netzahualpilli Delgado-Figueroa and Daniel A. González-Padilla
- Subjects
Adult ,Male ,business.industry ,Chemical burn ,Proteins ,medicine.disease ,Nitric Acid ,Xanthoproteic reaction ,chemistry.chemical_compound ,Explosive Agents ,chemistry ,Nitric acid ,Burns, Chemical ,Emergency Medicine ,Humans ,Medicine ,business ,Nuclear chemistry - Published
- 2015
- Full Text
- View/download PDF
41. Reduction of methionine sulfoxide with : Compatibility with peptides containing cysteine and aromatic amino acids
- Author
-
Fina Capdevila, Ernest Giralt, Ernesto Nicolás, and Marta Vilaseca
- Subjects
chemistry.chemical_classification ,Methionine sulfoxide ,Stereochemistry ,Organic Chemistry ,Cystine ,Tryptophan ,Biochemistry ,Xanthoproteic reaction ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Aromatic amino acids ,Organic chemistry ,Amino acid synthesis ,Histidine ,Cysteine - Abstract
The reduction of methionine sulfoxide with ammonium iodide in trifluoroacetic acid has been studied in peptides containing cysteine, histidine, tyrosine or tryptophan residues. While histidine and tyrosine have proved to be stable under the experimental conditions, cysteine is oxidized to cystine and tryptophan dimerizes to form 2-indolylindolenine derivatives. The use of methyl sulfide to increase the reduction rate minimizes the problem and protection of indole ring with the formyl group avoids the side reaction for this amino acid.
- Published
- 1998
- Full Text
- View/download PDF
42. Macrocyclic Polyazacycloalkane-poly-N-carboxylate Anion as a Receptor for Amino Acid
- Author
-
Mutsuo Kodama
- Subjects
chemistry.chemical_classification ,chemistry.chemical_compound ,Residue (chemistry) ,Chemistry ,Stereochemistry ,Tryptophan ,Phenylalanine ,Protonation ,General Chemistry ,Carboxylate ,Tyrosine ,Xanthoproteic reaction ,Amino acid - Abstract
The doubly-protonated 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetracarboxylate anion (H2teta2−), 1,4,7,10,13-pentaazacyclopentadecane-1,4,7,10,13-pentacarboxylate anion (H2pepa3−), and 1,4,7,10,13,16-hexaazacyclooctadecane-1,4,7,10,13,16-hexacarboxylate anion (H2heha4−) have been shown to form stable 1 : 1 ratio complexes with amino acids in aqueous solutions. Their association constants, βL, were determined polarographically. The greater association constants obtained indicate that H2teta2− and H2pepa3− anions selectively interact with an amino acid which has a planar aromatic moiety. The results show the importance of hydrophobic interaction, such as CH–π interaction between the aliphatic CH2 residue of acetate pendant of receptor and the planar aromatic moiety of substrate, amino acid, in holding the protonated macrocyclic polyazacycloalkane-poly-N-polycarboxylate anion and amino acid together. Thus, they act as selective receptors for phenylalanine, tyrosine, tryptophan(e), and their derivatives.
- Published
- 1996
- Full Text
- View/download PDF
43. Synthesis of Aromatic Amino Acid Amides
- Author
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Indra Prakash and David J. Ager
- Subjects
chemistry.chemical_compound ,Ammonium hydroxide ,Aqueous solution ,Amino esters ,Chemistry ,Organic Chemistry ,Aromatic amino acids ,Organic chemistry ,Electrophilic aromatic substitution ,Xanthoproteic reaction ,Toluene - Abstract
Aromatic amino esters, in toluene or water, react with aqueous ammonium hydroxide to give moderate to high yields of the corresponding amides.
- Published
- 1996
- Full Text
- View/download PDF
44. An experimental study on gold solubility in amino acid solution and its geological significance
- Author
-
Zhang Jingrong, Yang Fan, Wu Jingwei, Jianjun Lu, and Zhu Fahua
- Subjects
chemistry.chemical_classification ,chemistry ,Geochemistry and Petrology ,Inorganic chemistry ,chemistry.chemical_element ,Solubility ,Xanthoproteic reaction ,Nitrogen ,Oxygen ,Sulfur ,Histidine ,Amino acid ,Amino acid solution - Abstract
The experiments on gold solubility in amino acid solution indicate that gold is very intensively soluble in amino acid (or other organic acids), which is extensively present in geological bodies, and is most soluble in histidine. The temperature and concentration, acidity and type of amino acid in the solution are important factors affecting gold-amino acid complexing. The solubility of gold in amino acid is different under different conditions of temperature, amino acid concentration and pH value of the solution. At 80°C and pH=6–8, gold is most soluble in amino acid. Gold dispersed in water and rocks could be concentrated and transported by amino acid and then precipitated in favorable loci. Amino acids might have played an important role in metallogenesis as well as in the formation of source beds of gold. Nitrogen, oxygen and sulfur in amino acid might have reacted with gold to form soluble complex ions.
- Published
- 1996
- Full Text
- View/download PDF
45. Inhibition ofd-amino acid oxidase by α-keto acids analogs of amino acids
- Author
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JoséA. Moreno, Miguel A. Galán, J. Catalán, and Francisco J. Montes
- Subjects
D-Amino-Acid Oxidase ,Swine ,Stereochemistry ,D-amino acid oxidase ,Bioengineering ,Kidney ,Binding, Competitive ,Applied Microbiology and Biotechnology ,Biochemistry ,Substrate Specificity ,Valine ,Animals ,Amino Acids ,Enzyme Inhibitors ,Alanine ,chemistry.chemical_classification ,Tryptophan ,Keto Acids ,Xanthoproteic reaction ,Photo-reactive amino acid analog ,Amino acid ,Kinetics ,chemistry ,Flavin-Adenine Dinucleotide ,Leucine ,Biotechnology - Abstract
The inhibition of D-amino acid oxidase by certain alpha-keto acids products of the reaction with D-amino acids, in particular alpha-keto acids that are analogs of the amino acids alanine, valine, leucine, phenylanaline, phenylglycine, tyrosine and tryptophan, is reported. All the alpha-keto acids assayed behaved as substrate competitive inhibitors of the enzyme. The relationship between the degree of inhibition and the structure of the inhibitor is discussed.
- Published
- 1996
- Full Text
- View/download PDF
46. (1-PYRENYL)METHYL CARBAMATES FOR FLUORESCENT 'CAGED' AMINO ACIDS AND PEPTIDES
- Author
-
Senichi Yamashita, Toshiaki Furuta, Michiko Iwamura, and Shigeto Okada
- Subjects
chemistry.chemical_classification ,Quantum yield ,General Medicine ,Biochemistry ,Medicinal chemistry ,Xanthoproteic reaction ,Fluorescence ,Photo-reactive amino acid analog ,Amino acid ,chemistry.chemical_compound ,chemistry ,Yield (chemistry) ,Organic chemistry ,Physical and Theoretical Chemistry ,Sodium carbonate ,Carbodiimide - Abstract
A highly fluorescent 1-pyrenylmethyloxycarbonyl amino acid (Pmoc-amino acid) is obtained in moderate yield by the reaction of (1-pyrenylmethyl)-4-nitrophenylcarbonate with an amino acid in the presence of sodium carbonate. The condensation of Pmoc-amino acid with an amino acid gives Pmoc-peptide in the presence of 1-ethyl-3-(3-dimethylaminepropyl)carbodiimide and 1-hydroxyben-zotriazole. The amino acid is recovered from an H2O-dioxane (2:3) solution of Pmoc-amino acid by irradiation through a Pyrex filter with a medium pressure Hg lamp or at 340 nm. Although the quantum yield of the photolysis is rather low (ca 0.01), the photolysis proceeds fast and efficiently due to the large absorption coefficient of Pmoc-amino acid at around 340 nm. Thus, the use of Pmoc-amino acid as a “caged” amino acid is promising.
- Published
- 1995
- Full Text
- View/download PDF
47. Quantitation of Protein Tyrosine, 3-Nitrotyrosine, and 3-Aminotyrosine Utilizing HPLC and Intrinsic Ultrviolet Absorbance
- Author
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J.P Crow and Joseph S. Beckman
- Subjects
chemistry.chemical_classification ,Chromatography ,Nitrotyrosine ,Xanthoproteic reaction ,High-performance liquid chromatography ,General Biochemistry, Genetics and Molecular Biology ,Amino acid ,Absorbance ,chemistry.chemical_compound ,Biochemistry ,chemistry ,Nitration ,Tyrosine ,Molecular Biology ,Peroxynitrite - Abstract
Nitrotyrosine has been found in the urine of humans with no known exposure to exogenous nitrating agents. We have shown that peroxynitrite, a nitrating agent formed by the near diffusion-limited reaction of nitric oxide with superoxide, is formed by activated macrophages. Using an antibody which recognizes nitrated tyrosine residues in proteins, we have obtained immunohistological evidence for nitration in a number of pathological conditions amenable to peroxynitrite formation. We have developed an HPLC method as a means of confirming the presence of nitrotyrosine. Quantitation of small amounts of nitrotyrosine in complex protein mixtures presents special problems of sensitivity and specificity which are often exacerbated by traditional amine-derivatization of all amino acids. An HPLC method for proteins hydrolysates is described which relies on intinsic UV absorbance of nitrotyrosine at 280 nm (which is fivefold higher than tyrosine at pH 3.5) for quantitation and on its unique absorbance at 355-365 nm for partial identification. Since only aromatic acids are detected, sample sizes can be increased to permit detection of small amounts of nitrotyrosine without introducing interference. Treatment of BSA with 4mM peroxynitrite resulted in nitration of 12.8% of total tyrosine residues; a small fraction (0.9%) of the total was detected as aminotyrosine. A total of 9.6% of the tyrosine residues in fresh plasma were nitrated as a result of treatment with 4mM peroxytyrosinee during hydrolysis. The advantages of this method over traditional amine-dervatized amino acid analysis are discussed and modifications which would further increase sensitivity to aminotyrosine are presented.
- Published
- 1995
- Full Text
- View/download PDF
48. Formation of 3-nitrotyrosine by riboflavin photosensitized oxidation of tyrosine in the presence of nitrite
- Author
-
Mario Fontana, Laura Pecci, and Carla Blarzino
- Subjects
α-crystallin ,Radical ,Clinical Biochemistry ,elastin ,Riboflavin ,Photochemistry ,Biochemistry ,3-nitrotyrosine ,nitrite ,photosensitizers ,riboflavin ,tyrosine nitration ,chemistry.chemical_compound ,Nitration ,Animals ,Photosensitivity Disorders ,Nitrite ,Tyrosine ,Nitrites ,Serum Albumin ,Singlet oxygen ,Organic Chemistry ,Xanthoproteic reaction ,chemistry ,Yield (chemistry) ,Sunlight ,Cattle ,Oxidation-Reduction - Abstract
The results of the present investigation show the susceptibility of tyrosine to undergo visible light-induced photomodification to 3-nitrotyrosine in the presence of nitrite and riboflavin, as sensitizer. By changing H2O by D2O, it could be established that singlet oxygen has a minor role in the reaction. The finding that nitration of tyrosine still occurred to a large extent under anaerobic conditions indicates that the process proceeds mainly through a type I mechanism, which involves the direct interaction of the excited state of riboflavin with tyrosine and nitrite to give tyrosyl radical and nitrogen dioxide radical, respectively. The tyrosyl radicals can either dimerize to yield 3,3'-dityrosine or combine with nitrogen dioxide radical to form 3-nitrotyrosine. The formation of 3-nitrotyrosine was found to increase with the concentration of nitrite added and was accompanied by a decrease in the recovery of 3,3'-dityrosine, suggesting that tyrosine nitration competes with dimerization reaction. The riboflavin photosensitizing reaction in the presence of nitrite was also able to induce nitration of tyrosine residues in proteins as revealed by the spectral changes at 430 nm, a characteristic absorbance of 3-nitrotyrosine, and by immunoreactivity using 3-nitrotyrosine antibodies. Since riboflavin and nitrite are both present endogenously in living organism, it is suggested that this pathway of tyrosine nitration may potentially occur in tissues and organs exposed to sunlight such as skin and eye.
- Published
- 2012
49. Pico-tag analysis of arogenic acid and related free amino acids from plant and fungal extracts
- Author
-
Norman G. Lewis, Ramon A. Razal, and G.H.Neil Towers
- Subjects
chemistry.chemical_classification ,Chromatography ,biology ,fungi ,Phenylalanine ,Plant Science ,General Medicine ,biology.organism_classification ,Biochemistry ,High-performance liquid chromatography ,Xanthoproteic reaction ,Analytical Chemistry ,Neurospora crassa ,Amino acid ,chemistry.chemical_compound ,Complementary and alternative medicine ,Biosynthesis ,chemistry ,Drug Discovery ,Aromatic amino acids ,Molecular Medicine ,Tyrosine ,Food Science - Abstract
Free amino acids from various plant tissues and fungal mycelia were extracted with buffered ethanol (75%, v/v) in 0.5% 2-amino-2-methyl-1-propanol-hydrochloride pH 11.0. Following removal of proteins and other high molecular weight components by ultrafiltration, free amino acids in the extracts were dried, derivatized with phenylisothiocyanate and analysed by high performance liquid chromatography using a Waters Pico-Tag column. Arogenic acid, a non-aromatic amino acid precursor of phenylalanine and tyrosine, was not detected although both aromatic amino acids were quantitated in all plant and fungal extracts. Nevertheless, arogenic acid in the mycelium of a triply-blocked mutant of Neurospora crassa was readily detected. It is proposed that the absence of arogenic acid in plant extracts suggests that this intermediate does not accumulate in the metabolic pool thereby negating a possible regulatory role during aromatic amino acid biosynthesis.
- Published
- 1994
- Full Text
- View/download PDF
50. Destabilization of tyrosine aminotransferase by amino acids
- Author
-
J. L. Hargrove and C. Liu
- Subjects
chemistry.chemical_classification ,biology ,Transamination ,Organic Chemistry ,Clinical Biochemistry ,Phenylalanine ,Biochemistry ,Xanthoproteic reaction ,Enzyme assay ,Amino acid ,Tyrosine aminotransferase ,chemistry ,biology.protein ,Tyrosine ,Amino acid synthesis - Abstract
Several L-amino acids (tyrosine, glutamate, methionine, tryptophan, and phenylalanine) and penicillamine destabilized purified tyrosine aminotransferase by removing enzyme-bound pyridoxal 5'-phosphate. The destabilization was measured as a progressive loss of enzyme activity in samples taken at intervals from a primary mixture that was incubated at 37°C. Each destabilizing amino acid either served as a substrate for this enzyme or was a product of transamination. In contrast, L-cysteine destabilized the enzyme only if liver homogenate was added, which generated polysulfide by desulfuration. Cysteine complexed free pyridoxal-5'-phosphate but did not remove it from the enzyme. Other amino acids did not destabilize tyrosine aminotransferase at the concentrations tested.
- Published
- 1994
- Full Text
- View/download PDF
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