25 results on '"Chromatography, Reverse-Phase"'
Search Results
2. Volume and composition of semi-adsorbed stationary phases in hydrophilic interaction liquid chromatography. Comparison of water adsorption in common stationary phases and eluents
- Author
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Martí Rosés, Lídia Redón, and Xavier Subirats
- Subjects
Chromatography, Reverse-Phase ,Chromatography ,Hydrophilic interaction chromatography ,Organic Chemistry ,Liquid chromatography ,Water ,General Medicine ,Biochemistry ,Polyvinyl alcohol ,Cromatografia de líquids ,Analytical Chemistry ,Homologous series ,chemistry.chemical_compound ,Adsorption ,chemistry ,Fluid dynamics ,Gas pycnometer ,Phase (matter) ,Dinàmica de fluids ,Methanol ,Acetonitrile ,Hydrophobic and Hydrophilic Interactions ,Chromatography, Liquid - Abstract
Pycnometric and homologous series retention methods are used to determine the volume and mean composition of the water-rich layers partially adsorbed on the surface of several hydrophilic interaction liquid chromatography (HILIC) column fillings with acetonitrile-water and methanol-water as eluents. The findings obtained in this work confirm earlier studies using direct methods for measuring the stationary phase water content performed by Jandera's and Irgum's research groups. Water is preferentially adsorbed on the surface of the HILIC bonded phase in hydroorganic eluents containing more than 40% acetonitrile or 70% methanol, and a gradient of several water-rich transition layers between the polar bonded phase and the poorly polar bulk mobile phase is formed. These layers of reduced mobility act as HILIC stationary phases, retaining polar solutes. The volume of these layers and concentration of adsorbed water is much larger for acetonitrile-water than for methanol-water mobile phases. In hydroorganic eluents with less than 20-30% acetonitrile or 40% methanol the amount of preferentially adsorbed water is very small, and the observed retention behavior is close to the one in reversed-phase liquid chromatography (RPLC). In eluents with intermediate acetonitrile-water or methanol-water compositions a mixed HILIC-RPLC behavior is presented. Comparison of several HILIC columns shows that the highest water enrichment in the HILIC retention region for acetonitrile-water mobile phases is observed for zwitterionic and aminopropyl bonded phases, followed in minor grade for diol and polyvinyl alcohol functionalizations. Pentafluorophenyl bonded phase, usually considered a HILIC column, does not show significant water adsorption, nor HILIC retention.
- Published
- 2021
3. Linear free energy relationship models for the retention of partially ionized acid-base compounds in reversed-phase liquid chromatography
- Author
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Michael H. Abraham, Elisabet Fuguet, Martí Rosés, Sara Soriano-Meseguer, and Adriana Port
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Acetonitriles ,Analytical chemistry ,Liquid chromatography ,Ionic bonding ,Free-energy relationship ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Cromatografia de líquids ,Analytical Chemistry ,Ion ,Column chromatography ,Ionization ,Taft equation ,Ions ,Chromatography, Reverse-Phase ,Chromatography ,Àcids ,Hydrogen bond ,Chemistry ,010401 analytical chemistry ,Organic Chemistry ,Water ,Hydrogen Bonding ,General Medicine ,Reversed-phase chromatography ,Hydrogen-Ion Concentration ,0104 chemical sciences ,Solutions ,Models, Chemical ,Acids - Abstract
The LFER model of Abraham is applied to the retention of the neutral and ionic forms of 94 solutes in a C18 column and 40% v/v acetonitrile/water mobile phase. The results show that polarizability and cav- ity formation interactions increase retention, whereas dipole and hydrogen bonding interactions favours partition to the mobile phase and thus, they decrease retention. The coefficients of the ionic descriptors measure the effect of the electrostatic interactions and their contribution to partition of the cation or anion between the two mobile and stationary chromatographic phases. A new LFER model for application to the retention of partially dissociated acids and bases is derived aver- aging the descriptors of the neutral and ionic forms according to their degrees of ionization in the mobile phase. This new LFER model is satisfactorily compared to other literature modified Abraham models for a set of 498 retention data of partially dissociated acids and bases. All tested models require the calculation of the ionization degrees of the compounds at the measuring pH. Calculation of the ionization degrees in the chromatographic mobile phase (i.e. from pH and p K a in the eluent) give good correlations for all tested models. However, estimation of these ionization degrees from pH -p K a data in pure water gives biased estimations of the retention of the partially ionized solutes.
- Published
- 2021
4. A comprehensive study on retention of selected model substances in β-cyclodextrin-modified high performance liquid chromatography
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Milos Petkovic, Ana Protić, Biljana Otašević, Mira Zečević, Andjelija Malenovic, Nevena Djajić, and Ulrike Holzgrabe
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Acetonitriles ,Magnetic Resonance Spectroscopy ,010402 general chemistry ,01 natural sciences ,Biochemistry ,High-performance liquid chromatography ,Analytical Chemistry ,chemistry.chemical_compound ,Adsorption ,Phase (matter) ,Molecular descriptor ,Acetonitrile ,Chromatography, High Pressure Liquid ,NMR study ,chemistry.chemical_classification ,Chromatography, Reverse-Phase ,Chromatography ,Inclusion complex ,Cyclodextrin ,beta-Cyclodextrins ,010401 analytical chemistry ,Organic Chemistry ,Aqueous two-phase system ,General Medicine ,Hydrogen-Ion Concentration ,0104 chemical sciences ,Models, Chemical ,chemistry ,β-cyclodextrin ,RP-HPLC ,Lipophilicity ,Quantitative structure-retention relationship - Abstract
The quantitative structure-retention relationship (QSRR) models are not only employed in retention behaviour prediction, but also in an in-depth understanding of complex chromatographic systems. The goal of the present research is to enable the comprehensive understanding of retention underlying the separation in β-cyclodextrin (CD) modified reversed-phase high performance liquid chromatography (RP-HPLC) systems, through the development of mixed QSRR models. Moreover, the amount of β-CD adsorbed on the stationary phase surface (β-CDA) is added as the model's input in order to evaluate its contribution to both model performances and retention. Nuclear magnetic resonance (NMR) experiments were conducted to confirm the predicted inclusion complex structures and support the application of in silico tools. The most significant descriptors revealed that retention is governed by the steric factors 7.5 A distant from the geometrical centre of a molecule, 3D arrangement of atoms determining the molecular size and shape, lipophilicity indicated by topological distances, as well as the unbound system's energy, related to the inclusion complex formation. In addition, a notable effect of the pH of the aqueous phase on the retention of ionizable analytes was shown. In the case of pH of the aqueous phase and β-CDA the change in retention behaviour of the studied analytes was observed only at the highest β-CDA value (5.17 μM/m2), but it was not related to the ionization state of analytes. When the analytes did not change the ionization form across the investigated studied pH range, and the acetonitrile content in the mobile phase was 25% (v/v), the retention factor had low values regardless of the β-CDA; under these circumstances the retention is probably acetonitrile driven.
- Published
- 2021
5. Influence of the acid-base ionization of drugs in their retention in reversed-phase liquid chromatography
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Elisabet Fuguet, Martí Rosés, Adriana Port, and Sara Soriano-Meseguer
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Ionization ,Base (chemistry) ,Ionització ,Pyridines ,Analytical chemistry ,Carboxylic Acids ,Liquid chromatography ,Ionic bonding ,02 engineering and technology ,01 natural sciences ,Biochemistry ,Cromatografia de líquids ,Analytical Chemistry ,Phenols ,Phase (matter) ,Environmental Chemistry ,Amines ,Spectroscopy ,Chromatography, High Pressure Liquid ,chemistry.chemical_classification ,Chromatography, Reverse-Phase ,Chemistry ,010401 analytical chemistry ,Drugs ,Reversed-phase chromatography ,Hydrogen-Ion Concentration ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Partition coefficient ,Models, Chemical ,Lipophilicity ,Acid–base reaction ,0210 nano-technology ,Hydrophobic and Hydrophilic Interactions ,Medicaments - Abstract
The effect of the ionization in the RP-HPLC retention of 66 acid-base compounds, most of them drugs of pharmaceutical interest, is studied. The retention time of the compounds can be related to the pH measured in the mobile phase (pwsH) through the sigmoidal equations derived from distribution of the neutral and ionic forms of the drug into the stationary and mobile phases. Fitting of the obtained retention vs. pH profiles provides the retention times of the ionic and neutral forms and the pKa values of the drugs in the mobile phase (pwsKa). The obtained pwsKa values are linearly correlated to the pKa values in water (pwwKa) with two different correlations, one for neutral acids and another for neutral bases that reflect the different influence of the dielectric constant of the medium in ionization of acids and bases. The retention of the neutral species is well correlated to the octanol-water partition coefficient of the drugs as measure of the lipophilicity of the drug, which affects chromatographic retention. Also, the retention time of the ionized forms is related to the retention time of the neutral forms by two different linear correlations, one for anions and the other for cations. These last correlations point out the different retention behaviour of anions and cations: anions are less retained than cations of the same lipophilicity, as measured by the octanol-water partition coefficient of the neutral form. The different retention behaviour of anionic, cationic and neutral forms is confirmed by the hold-up times obtained from different approaches: pycnometry and retention times of anionic (KBr and KI) and neutral (DMSO) markers. Hold-up times obtained by pycnometric measurements agree with those obtained by retention of neutral markers (0.83-0.85 min), whereas hold-up time for anions is mobile phase pH dependent. At acidic pH it is similar to the hold-up time for neutral markers (0.83 min), but then it decreases with the increase of mobile phase pH to 0.65 min at pH 11. The decrease can be explained by the ionization of the silanols of the column and exclusion of anions by charge repulsion. Although not directly measured, the obtained retention data and correlations indicate hold-up time for cations are similar or slightly lower than hold-up time for neutral compounds (0.77-0.83 min). The model proposed and the correlations obtained can be very useful for its implementation in retention prediction algorithms for optimization of separation purposes.
- Published
- 2019
6. Online comprehensive hydrophilic interaction chromatography × reversed phase liquid chromatography coupled to mass spectrometry for in depth peptidomic profile of microalgae gastro-intestinal digests
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Michele Manfra, Fabrizio Merciai, Ettore Novellino, Pietro Campiglia, Francesco Gasparrini, Eduardo Sommella, Alessia Bertamino, Emanuela Salviati, Sommella, E., Salviati, E., Merciai, F., Manfra, M., Bertamino, A., Gasparrini, F., Novellino, E., and Campiglia, P.
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Clinical Biochemistry ,Dispersity ,Pharmaceutical Science ,Peptide ,HILIC × RP ,Mass spectrometry ,Orbitrap ,01 natural sciences ,Mass Spectrometry ,Analytical Chemistry ,law.invention ,Comprehensive two dimensional liquid chromatography ,Chromatography detector ,law ,Drug Discovery ,Microalgae ,Spectroscopy ,chemistry.chemical_classification ,Chromatography, Reverse-Phase ,Chromatography ,010405 organic chemistry ,Chemistry ,Hydrophilic interaction chromatography ,010401 analytical chemistry ,comprehensive two dimensional liquid chromatography ,mass spectrometry ,microalgae ,peptides ,Reversed-phase chromatography ,0104 chemical sciences ,Gastrointestinal Tract ,Security guard ,Peptides ,Hydrophobic and Hydrophilic Interactions ,Porosity - Abstract
In this study, a comprehensive hydrophilic interaction chromatography × reversed phase coupled to high resolution mass spectrometry was developed for the peptide profile of microalgae formulations subjected to gastro-intestinal digestion. A BEH Amide column was employed in the first dimension, while a BIOshell ES-C18 Peptide in the second. As modulation interface, two trapping columns, in house packed with 1.9 μm fully porous monodisperse C18 particles characterized by high retention and efficiency, were tested and compared with SecurityGuard C18 cartridges, together with a dilution flow, to reduce first dimension mobile phase strength. The platform was coupled to both diode array detector and Orbitrap mass spectrometry. The developed setup provided high peak capacity (nc: 957) in only 60 min and a good orthogonality (A0: 0.70). The employment of the custom made C18 traps resulted in improved sensitivity (signal enhancement = 4) and a higher number of peptides detected (+58) especially of short lenght (≤ 6 aminoacids), with respect to the setup based on the security guard C18 traps. 184 phycocyanin-derived peptides were detected in Klamath and Spirulina gastro-intestinal digests, whose sequence and protein origin has been elucidated in detail by mass spectrometry. The results show the potential of the developed HILIC × RP-MS platform for in depth peptide mapping of microalgae and its possible application to highlight the products of gastro-intestinal digestion of other microalgae species.
- Published
- 2019
7. Novel glycosylated mycosporine-like amino acids with radical scavenging activity from the cyanobacterium Nostoc commune
- Author
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Seiichi Matsugo, Kei Matsui, Toshio Sakamoto, Naoki Wada, Shinpei Kunita, and Ehsan Nazifi
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Glycosylation ,Antioxidant ,medicine.medical_treatment ,Glycine ,Biophysics ,Pentose ,Porphyra-334 ,chemistry.chemical_compound ,Pigment ,otorhinolaryngologic diseases ,medicine ,Radiology, Nuclear Medicine and imaging ,Hexose ,Amino Acids ,Chromatography, High Pressure Liquid ,chemistry.chemical_classification ,Chromatography, Reverse-Phase ,Nostoc commune ,Radiation ,Radiological and Ultrasound Technology ,Molecular mass ,Cyclohexanones ,Free Radical Scavengers ,Anhydrobiosis ,In vitro ,Amino acid ,chemistry ,Biochemistry ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,visual_art ,visual_art.visual_art_medium ,UV protectant ,Spectrophotometry, Ultraviolet - Abstract
Mycosporine-like amino acids (MAAs) are UV absorbing pigments, and structurally distinct MAAs have been identified in taxonomically diverse organisms. Two novel MAAs were purified from the cyanobacterium Nostoc commune, and their chemical structures were characterized. An MAA with an absorption maximum at 335 nm was identified as a pentose-bound porphyra-334 derivative with a molecular mass of 478 Da. Another identified MAA had double absorption maxima at 312 and 340 nm and a molecular mass of 1050 Da. Its unique structure consisted of two distinct chromophores of 3-aminocyclohexen-1-one and 1,3-diaminocyclohexen and two pentose and hexose sugars. These MAAs had radical scavenging activity in vitro; the 1050-Da MAA contributed approximately 27% of the total radical scavenging activities in a water extract of N. commune. These results suggest that these glycosylated MAAs have multiple roles as a UV protectant and an antioxidant relevant to anhydrobiosis in N. commune. © 2011 Elsevier B.V. All rights reserved.
- Published
- 2011
8. Investigation of π-π and ion-dipole interactions on 1-allyl-3-butylimidazolium ionic liquid-modified silica stationary phase in reversed-phase liquid chromatography
- Author
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Shengxiang Jiang, Xia Liu, Hongdeng Qiu, Hirotaka Ihara, and Makoto Takafuji
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Spectrophotometry, Infrared ,Ionic bonding ,Infrared spectroscopy ,Ionic Liquids ,Biochemistry ,High-performance liquid chromatography ,Analytical Chemistry ,chemistry.chemical_compound ,PAHs ,Bromide ,Ion-dipole interaction ,Structural isomer ,Polycyclic Aromatic Hydrocarbons ,Nuclear Magnetic Resonance, Biomolecular ,Chromatography, Reverse-Phase ,Chromatography ,Organic Chemistry ,Imidazoles ,General Medicine ,Nuclear magnetic resonance spectroscopy ,Reversed-phase chromatography ,Silicon Dioxide ,Logistic Models ,chemistry ,Ionic liquid-modified silica ,Ionic liquid ,Thermogravimetry ,HPLC ,Hydrophobic and Hydrophilic Interactions - Abstract
1-Allyl-3-butylimidazolium bromide ionic liquid [AyBIm]Br was prepared and used for the modification of mercaptopropyl-functionalized silica through surface radical chain-transfer addition. The obtained ionic liquid-modified silica (SiImBr) was characterized by elemental analysis, infrared spectroscopy, NMR spectroscopy, and thermogravimetric analysis. The selective retention behaviours of polycyclic aromatic hydrocarbons (PAHs) including some positional isomers were investigated using SiImBr as a stationary phase in reversed-phase liquid chromatography. The results showed that SiImBr presented multiple interactions including hydrophobic, π–π, and ion–dipole interactions during the separation of PAHs and dipolar compounds. However, it is proposed that π–π and ion–dipole interactions play important roles in the separation of PAHs and dipolar compounds. These results indicate that the ionic liquid-modified silica stationary phase is promising for future applications. A commercially available monomeric octadecylated silica (ODS) column and a custom-made poly(styrene)-grafted silica (Sil-St n ) column were used as references.
- Published
- 2010
9. Analytical application of polymethylene blue-multiwalled carbon nanotubes modified glassy carbon electrode on anticancer drug irinotecan and determination of its ionization constant value
- Author
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Alp Can, Bediha Akmeşe, Sibel A. Ozkan, Nurgul Karadas, Senem Sanli, Burcu Dogan-Topal, Hitit Üniversitesi, Fen Edebiyat Fakültesi, Kimya Bölümü, and Uşak Üniversitesi, Fen Edebiyat Fakültesi, Kimya Bölümü
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Scanning electron microscope ,Analytical chemistry ,Carbon nanotube ,Electrochemistry ,Irinotecan ,Analytical Chemistry ,law.invention ,Polymerization ,Coulometry ,chemistry.chemical_compound ,Ionization constant ,law ,Limit of Detection ,Electrodes ,Detection limit ,Ions ,Chromatography, Reverse-Phase ,Nanotubes, Carbon ,Lonization Constant ,Buffer solution ,Electrochemical Techniques ,Hydrogen-Ion Concentration ,Antineoplastic Agents, Phytogenic ,Methylene Blue ,Solutions ,Poly (Methylene Blue) ,chemistry ,Reversed-Phase Liquid Chromatography ,Electrode ,Calibration ,Camptothecin ,Carbon Nanotubes ,Differential pulse voltammetry ,Microscopy, Electrochemical, Scanning ,Oxidation-Reduction - Abstract
PubMed ID: 24054682 The voltammetric behavior of anticancer drug irinotecan (IRT) was investigated at poly (methylene blue)/multi-walled carbon nanotube (PMB/MWCNT) modified glassy carbon electrode (GCE). The modified electrode surface was characterized by a scanning electron microscope (SEM). The PMB/MWCNT modified GCE exhibits a distinct shift of the oxidation potential of IRT on the cathodic direction and a considerable enhancement of the peak current compared with bare electrode. The calibration curve was linear between the concentration range 8.0×10-6 and 8.0×10-5 M with the detection limit of 2.14×10-7 M by differential pulse voltammetry in pH 10.0 Britton-Robinson buffer solution. Controlled potential coulometry was applied to find transferred electron numbers due to the oxidation of IRT. In this study, the pKa value of IRT was also determined by the dependence of the retention factor on the pH of the mobile phase. The effect of the mobile phase composition on the ionization constant was studied by measuring the pKa at different acetonitrile-water mixtures, ranging between 35 and 50% (v/v) using the reversed-phase liquid chromatography (RP-LC) method with UV detector. IRT was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions, and the stressed samples were detected by the proposed method. Sensitive, rapid, and fully validated electrochemical and RP-LC methods for the determination of IRT in its dosage form were presented in details. © 2013 Elsevier B.V.
- Published
- 2013
10. Simultaneous estimation and validation of some binary mixtures of antihypertensive drugs by RP-LC methods using two new generation silica columns
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Mehmet Gumustas, Sibel A. Ozkan, Sevinc Kurbanoglu, and Hitit Üniversitesi, Fen Edebiyat Fakültesi, Kimya Bölümü
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Analyte ,Captopril ,LC ,Clinical Biochemistry ,Analytical chemistry ,Pharmaceutical Science ,Binary number ,Tetrazoles ,Dosage form ,Analytical Chemistry ,Zofenopril ,Phase (matter) ,Drug Discovery ,Olmesartan ,Sample preparation ,Spectroscopy ,Antihypertensive Agents ,Chromatography, Reverse-Phase ,Chromatography ,New Generation Columns ,Chemistry ,Imidazoles ,Linearity ,Silicon Dioxide ,Volumetric flow rate ,Hydrochlorothiazide ,Reagent ,Solvents ,Indicators and Reagents - Abstract
Two reversed phase liquid chromatographic (RP-LC) techniques are presented for the rapid, accurate, precise, simultaneous determination of olmesartan-hydrochlorothiazide and zofenopril-hydrochlorothiazide binary mixtures in their dosage forms. The separation of these binary mixtures was carried out by using two new stationary phases that have different surface chemistries which were used for the first time in the determination of these binary mixtures. The analyte peaks were detected at 216nm. Linearity was obtained in different concentration ranges between 0.5 and 20?gmL-1 for all compounds. The proposed methods have been extensively validated and sample preparation, flow rate, run time of the analytical systems were at low levels. The proposed methods would decrease the consumption of organic solvents and reagents further safeguarding to our environment. © 2012 Elsevier B.V.
- Published
- 2013
11. Structure identification and inhibitory mechanism evaluation of three novel angiotensin converting enzyme (ACE) inhibitory peptides from small-aroma chicken.
- Author
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Han, Xin-Xin, Jia, Yun-Qin, Liu, Chun-Yu, Wang, Hao-Yu, and Zhu, Zhen-Yuan
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ANGIOTENSIN converting enzyme , *CHICKENS , *GEL permeation chromatography , *PEPTIDES , *ANGIOTENSIN I , *CHICKEN as food , *ION exchange chromatography - Abstract
Small-aroma chicken with a high protein content, is widely distributed in the mountainous area of Yunnan-Guizhou Plateau, China. In this work, three novel ACE-inhibitory peptides, Leu-Thr-Glu-Lys-Val-Val-Phe (LTQKVVF), Leu-Asp-Asp-His-Phe-Leu (LDDHFL), and Val-Pro-Gly-Pro-Glu-Pro-Lys-Pro (VPGPEPKP), were prepared from the Small-Aroma Chicken breast. The purification and identification protocol employed comprised ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography (RP-HPLC), and nano liquid chromatography-electrospray ionization–tandem mass (Nano-LC-ESI–MS/MS). Compared with VPGPEPKP and VPGPEPKP, LTQKVVF displayed noticeable ACE inhibitory activity, with IC 50 values of 189.34 μM. What's more, the Lineweaver-Burk plots revealed peptides LTQKVVF and LDDHFL acted as the mixed-competitive inhibitor while VPGPEPKP inhibited ACE in a manner similar to uncompetitive inhibition. The binding free energies of LTQKVVF, LDDHFL, and VPGPEPKP for ACE were −8.1 kcal/mol, −8.6 kcal/mol, and −9.6 kcal/mol, respectively. The strong inhibition of ACE by VPGPEPKP may be attributed to the interaction of hydrogen bonds, alkyl, and pi-alkyl, which formed by crucial residues of ACE. [Display omitted] • Three novel peptides were characterized from small-aroma chicken. • The peptides exhibited inhibition activity on angiotensin converting enzyme (ACE). • Lineweaver Burk plots was used to identify the inhibition mode of peptides. • The interactions between peptides and ACE were simulated by molecular docking. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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12. Structural basis for misfolding at a disease phenotypic position in CFTR: Comparison of TM3/4 helix-loop-helix constructs with TM4 peptides
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Charles M. Deber and Cory M. Mulvihill
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Models, Molecular ,Protein Folding ,Circular dichroism ,Cystic Fibrosis ,Molecular Sequence Data ,030303 biophysics ,Size-exclusion chromatography ,Biophysics ,Cystic Fibrosis Transmembrane Conductance Regulator ,Peptide ,Biochemistry ,03 medical and health sciences ,Hydropathy ,Humans ,Amino Acid Sequence ,Amino Acids ,Polyacrylamide gel electrophoresis ,Helix-Turn-Helix Motifs ,030304 developmental biology ,chemistry.chemical_classification ,Chromatography, Reverse-Phase ,Genomic Library ,0303 health sciences ,Ion Transport ,Chromatography ,biology ,Basic helix-loop-helix ,Circular Dichroism ,Sodium Dodecyl Sulfate ,Cell Biology ,Cystic fibrosis transmembrane conductance regulator ,Protein Structure, Tertiary ,Amino acid ,chemistry ,Membrane protein ,Mutation ,Chromatography, Gel ,biology.protein ,Electrophoresis, Polyacrylamide Gel ,Cystic fibrosis transmembrane conductance regulator (CFTR) ,Peptides ,Hydrophobic and Hydrophilic Interactions ,SDS-PAGE - Abstract
Understanding the residue-dependent effects of disease-phenotypic mutations in multi-spanning membrane proteins is an essential step toward the development of corrective therapies. As a systematic approach to further elucidate mutant-dependent mis-folding consequences, we prepared two libraries: one consisting of 20 helix-loop-helix (“hairpin”) constructs derived from helices 3 and 4 of the human cystic fibrosis transmembrane conductance regulator (CFTR) (residues 194–241) in which the CF-phenotypic position Val-232 was substituted individually to each of the 20 commonly-occurring amino acids; and a second library consisting of 20 single-stranded TM4 peptides (CFTR residues 221–241) similarly substituted at position 232. Both libraries were analyzed to measure mutant-dependent variations in mobility on SDS-PAGE; size and shape on size exclusion chromatography; retention times on reverse phase HPLC; and helical content by circular dichroism spectroscopy. Analysis of a scatter plot between TM3/4 hairpin and TM4 peptide retention times showed a strong correlation (r=0.94, p
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13. Multiclass analysis of antibacterial residues in milk using RP-liquid chromatography with photodiode array and fluorescence detection and tandem mass spectrometer confirmation
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Isabela Maia Toaldo, Gabriel Rübensam, Rodrigo Barcellos Hoff, Marilde T. Bordignon-Luiz, Gabriel Zandonadi Gamba, and L.C.A. Picinin
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Analyte ,Chemistry(all) ,Food Contamination ,Mass spectrometry ,Tandem mass spectrometry ,Fluorescamine ,Analytical Chemistry ,Matrix (chemical analysis) ,chemistry.chemical_compound ,Tandem Mass Spectrometry ,Validation ,Animals ,European Union ,Detection limit ,Chromatography, Reverse-Phase ,Chromatography ,Chemistry ,Extraction (chemistry) ,Reproducibility of Results ,Water ,LC-ESI-MS/MS ,Drug Residues ,Anti-Bacterial Agents ,LC-FD/DAD ,Spectrometry, Fluorescence ,Milk ,Multiclass ,Ultrapure water ,Government Regulation ,Antibacterials - Abstract
A simplified procedure for simultaneous quantification of ceftiofur (CEF), fluoroquinolone (FQ) and sulfonamide (SA) antibacterials in bovine milk was developed. The reverse-phase liquid chromatography (RP-LC) multiclass method for analysis of eleven distinct compounds, from three antibacterial classes, was validated in line with Commission Decision 2002/657/EC. Confirmation of the analytes identities was performed by electrospray mass spectrometry detection. The analytes were extracted from milk matrix by liquid–liquid extraction with acidified ultrapure water and directly analyzed in the chromatograph. The SA compounds were pre-column derivatized with fluorescamine for fluorescence detection. The method provided good results regarding the analytical parameters of linearity, selectivity, sensitivity, precision, recovery, decision limit (CC α ), detection capability (CC β ), limit of detection (LOD), limit of quantification (LOQ), stability and robustness. Analytes were extracted by liquid–liquid extraction in the fortified matrix and the compounds identity was confirmed by their precursor ion and fragments through tandem mass spectrometry analysis. Additionally, milk samples from two state capitals in the South Region of Brazil were analyzed by both the quantitative and confirmatory methods. The validation process showed correlation coefficients ( r 2 ) greater than 0.98 for all the analytes, with recovery rates up to 98% for all the studied drugs. LOD and LOQ limits ranged from 8.0 to 20.0 ng mL −1 and 10.0 to 32.0 ng mL −1 , demonstrating good specificity of the method. The intra-day and inter-day precisions for all the analytes were below or equal to 7.40 and 10.13, respectively. The studied antibacterials were not detected in milk samples. The developed method represents an efficient alternative for multi-residue analysis in milk, being suitable and especially viable for monitoring in developing countries.
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14. Purines recognition and quantitative analysis by surface-enhanced Raman spectroscopy.
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Shi, Xiao-Yang, Li, Yun-Chuan, Yu, Lei, Xiao, Bo-Huai, Qian, Gong-Ming, and Guo, Jing
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MICELLAR liquid chromatography , *SERS spectroscopy , *MICELLAR electrokinetic chromatography , *PURINES , *CAPILLARY electrophoresis , *HIGH performance liquid chromatography , *QUANTITATIVE research - Abstract
[Display omitted] • A simple method for the quantitative analysis of purines in beer has been developed. • The SERS probe prepared using a simple electrochemical treatment method on a Ag wire, exhibits a Raman enhancement factor of ∼106. • A linear relationship between SERS intensity and purine concentration in the range of 10−5 to 10−1 mg/mL was obtained for quantification of purines. • The recovery rate of each purine base using the SERS probe exceeds 80% for market beer. The common quantification methods of purines, including high-performance liquid chromatography, micellar electrokinetic chromatography, reverse phase ion pair chromatography, and capillary zone electrophoresis, have been used for the analysis of purines. These conventional techniques are limited by long operation times, large sample volumes, requirements for pretreatment and separation processes, or sophisticated, bulky and expensive equipment. Here, we have developed a simple method to prepare a probe for the quantitative analysis of purines using the surface-enhanced Raman scattering (SERS) method. The SERS probe is a rough Ag wire obtained with simple electrochemical treatment, which is optimized to reach the maximum SERS signal enhancement. The Raman enhancement factor (EF) of Ag wire after roughening can reach ∼106. Under optimized conditions, the rough Ag wire is capable of recognizing four purine bases (namely, guanine, adenine, hypoxanthine, and xanthine) in the range of 10−5 to 10−1 mg/mL with a linear relationship between SERS intensity of signature peak and purine concentration. The recovery rate of each purine base is higher than 80% in the mixture of four purines. The overall method was successfully applied to the monitoring of the level of purines in marketplace beer beverages. The novel wire-based SERS sensor used with portable Raman spectroscopy is prospective in diet safety and personalized point-of-care medical detection. [ABSTRACT FROM AUTHOR]
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- 2024
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15. Exploration of the molecular interactions between angiotensin-I-converting enzyme (ACE) and the inhibitory peptides derived from hazelnut (Corylus heterophylla Fisch.).
- Author
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Liu, Chunlei, Fang, Li, Min, Weihong, Liu, Jingsheng, and Li, Hongmei
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ACE inhibitors , *GEL permeation chromatography , *HAZELNUTS , *PROTEIN-protein interactions , *PROTEIN analysis - Abstract
The mechanism of action of food-derived angiotensin-I-converting enzyme (ACE) inhibitory peptides has not been completely elucidated. In the present study, ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography, and liquid chromatography-electrospray ionization–tandem mass (LC-ESI-MS/MS) were employed for purifying and identifying the ACE inhibitory peptides from hazelnut. To understand the mode of action of these peptides, ACE inhibition kinetics, in vitro and in vivo bioavailability assays, active site analysis, and interaction between the inhibitory peptides and ACE were investigated. The results identified novel ACE inhibitory peptides Ala-Val-Lys-Val-Leu (AVKVL), Tyr-Leu-Val-Arg (YLVR), and Thr-Leu-Val-Gly-Arg (TLVGR) with IC 50 values of 73.06, 15.42, and 249.3 μM, respectively. All peptides inhibited the ACE activity via a non-competitive mode. The binding free energies of AVKVL, YLVR, and TLVGR for ACE were −3.46, −6.48, and −7.37 kcal/mol, respectively. The strong inhibition of ACE by YLVR may be attributed to the formation of cation–pi interactions. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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16. Gram-scale purification of aconitine and identification of lappaconitine in Aconitum karacolicum.
- Author
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Tarbe, M., de Pomyers, H., Mugnier, L., Bertin, D., Ibragimov, T., Gigmes, D., and Mabrouk, K.
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ALKALOIDS , *ALTERNATIVE medicine , *CHROMATOGRAPHIC analysis , *HIGH performance liquid chromatography , *MEDICINAL plants , *PHARMACEUTICAL chemistry , *PLANT extracts , *DESCRIPTIVE statistics - Abstract
Aconitum karacolicum from northern Kyrgyzstan (Alatau area) contains about 0.8–1% aconitine as well as other aconite derivatives that have already been identified. In this paper, we compare several methods for the further purification of an Aconitum karacolicum extract initially containing 80% of aconitine. Reverse-phase flash chromatography, reverse-phase semi-preparative HPLC, centrifugal partition chromatography (CPC) and recrystallization techniques were evaluated regarding first their efficiency to get the highest purity of aconitine (over 96%) and secondly their applicability in a semi-industrial scale purification process (in our case, 150 g of plant extract). Even if the CPC technique shows the highest purification yield (63%), the recrystallization remains the method of choice to purify a large amount of aconitine as i) it can be easily carried out in safe conditions; ii) an aprotic solvent is used, avoiding aconitine degradation. Moreover, this study led us to the identification of lappaconitine in Aconitum karacolicum , a well-known alkaloid never found in this Aconitum species. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
17. Relayed chromatography - Countercurrent chromatography in series with liquid chromatography for the separation of natural products.
- Author
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Huang, Jiao, He, Jian-Ming, and Mu, Qing
- Subjects
- *
COUNTERCURRENT chromatography , *LIQUID chromatography , *REVERSE phase liquid chromatography , *NATURAL products , *CHROMATOGRAPHIC analysis , *NORMAL-phase chromatography - Abstract
• Relayed Chromatography was proposed and fulfilled by in situ concentration. • Combination of different chromatography with retained resolution was realized. • This strategy largely shorten the time for searching optimal solvent system. • This strategy allows CCC to achieve better separation in a non-optimal condition. • Eight natural naphthaquinones involving a new compound were isolated. Chromatography is an essential method for separating natural products. In this study, we proposed the concept of 'relayed chromatography', based on the strategy of combining different chromatography with relayed resolution by in-situ concentration technique. The following chromatographic methods were used: high-speed countercurrent chromatography (HSCCC), silica gel liquid chromatography (silica gel LC), and reverse phase liquid chromatography (reverse phase LC). The proposed strategy was effectively applied to the preparative separation of naturally existing naphthaquinones. After the first separation stage (silica gel LC), acetylalkannin (1) was directly collected, while fractions 1, 4 and 5 were collected and respectively subjected to recycling CCC separation after concentration. Thus, deoxyshikonin (2), 8- O -methyl-11- O -acetylshikonin (6), β -acetoxyisovalerylalkannin (7) and alkannin (8) were collected. Fraction 2 was concentrated and injected in reverse phase LC separation. After collection of isobutyrylalkannin (3), the remaining effluent from reverse phase LC retained the peak resolution (R 4,5 =0.45) and was injected into a recycling CCC elution. Finally, β, β -dimethylacrylalkannin (4), and isovalerylalkannin (5) were collected with sufficient resolution (R 4,5 =1.25). Eight naturally occurring naphthaquinones were thus isolated from Arnebia euchroma. The purities of all the compounds were determined by HPLC to be > 90%, and the chemical structures were determined by spectral method. Among the aforementioned compounds, 8- O -methyl-11- O -acetylshikonin (6) was separated as a new compound from A. euchroma. In conclusion, the relayed strategy that retains the resolution of the previous chromatographic stage can improve CCC separation efficiency, which may expand the range of application of CCC combined with different chromatography to the separation of natural products. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
18. A two-column flash chromatography approach to pyoverdin production from Pseudomonas putida GB1.
- Author
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Duckworth, Owen W., Markarian, Dawn S., Parker, Dorothy L., and Harrington, James M.
- Subjects
- *
PYOVERDINES , *PSEUDOMONAS putida , *COLUMN chromatography , *SIDEROPHORES , *GEL permeation chromatography , *PROTEIN fractionation - Abstract
Our knowledge of the biological and environmental reactivity of siderophores is limited by the difficulty and cost of obtaining reasonable quantities by purification or synthesis. In this note, we describe a modified procedure for the low-cost, mg-scale purification of pyoverdin-type siderophores using a dual-flash chromatography (reverse-phase absorption and size exclusion) approach. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
19. Proteomic analysis of Moroccan cobra Naja haje legionis venom using tandem mass spectrometry.
- Author
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Malih, Ibtissam, Ahmad rusmili, Muhamad Rusdi, Tee, Ting Yee, Saile, Rachid, Ghalim, Noreddine, and Othman, Iekhsan
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- *
MOROCCANS , *EGYPTIAN cobra , *VENOM , *TANDEM mass spectrometry , *GEL permeation chromatography , *HIGH performance liquid chromatography , *PROTEOMICS - Abstract
Abstract: The proteome of the venom of Naja haje legionis, the only medically important elapid species in Morocco, has been elucidated by using a combination of proteomic techniques that includes size exclusion chromatography, reverse-phase HPLC, Tricine/SDS-Page, tryptic digestion, Q-TOF tandem mass spectrometry and database search. The sequence analysis of venom fractions revealed a highly complex venom proteome which counts a total of 76 proteins identified from database that can be assigned into 9 proteins families. We report the identification of: cobra venom factor (CVF), l-amino-acid oxidases (LAAO), acetylcholinesterase (AChE), snake venom metalloproteinases (SVMP), cysteine rich secretory proteins (CRISP), venom nerve growth factor (vNGF), phospholipases A2 (PLA2), vespryns, kunitz-type inhibitor, short neurotoxins, long neurotoxins, weak neurotoxins, neurotoxin like proteins, muscarinic toxins, cardiotoxins and cytotoxins. Comparison of these proteins showed high sequence homology with proteins from other African and Asian cobras. Further works are needed to assess the contribution of individual toxins in venom toxicity. Biological significance: Naja haje legionis is one of the medically important snakes implicated in the pathogenesis of snake bite in Morocco. The absence of information about venom composition and clinical manifestations of envenomation by this cobra represents an obstacle for the management of this environmental disease in the country. The elucidation of Moroccan cobra venom composition will provide a reasonable guidance for clinician to understand the pathophysiological conditions associated with cobra envenomation and the elaboration of better management strategies. [Copyright &y& Elsevier]
- Published
- 2014
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- View/download PDF
20. Structural consequences of dry heating on alpha-lactalbumin and beta-lactoglobulin at pH 6.5.
- Author
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Gulzar, Muhammad, Bouhallab, Saïd, Jardin, Julien, Briard-Bion, Valérie, and Croguennec, Thomas
- Subjects
- *
LACTALBUMIN , *HEATING , *LACTOGLOBULINS , *HYDROGEN-ion concentration , *WHEY proteins , *IMIDES , *MOLECULAR structure - Abstract
Abstract: In the present work, we investigated the structural modifications occurring during the dry heating of model whey proteins, β-lactoglobulin and α-lactalbumin. Samples were adjusted to pH 6.5, water activity aw =0.23 and dry heated at 100°C for up to 24h, and the structural modifications followed by gel permeation chromatography, reverse phase-HPLC, SDS PAGE and mass spectrometry (LC–MS/MS). The dry heating treatment traps a fraction of the proteins into covalently linked soluble aggregates. Moreover, a high proportion of non-aggregated α-lactalbumin (about 73%) was converted into non-native forms. The characteristic of those non-native species was the loss of one or two water molecules per α-lactalbumin molecules. Using tandem mass spectrometric peptide mapping, these chemical modifications were found to be attributed to (i) the formation of a pyroglutamic acid from the N-terminal glutamic acid and (ii) the formation of an internal cyclic imide at position Asp64. The non-native species were not favored in the case of β-lactoglobulin as they represented less than 18% of non-aggregated proteins. [Copyright &y& Elsevier]
- Published
- 2013
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21. Biochemical and pharmacological characterization of PhTX-I a new myotoxic phospholipase A2 isolated from Porthidium hyoprora snake venom
- Author
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Huancahuire-Vega, Salomón, Ponce-Soto, Luis Alberto, Martins-de-Souza, Daniel, and Marangoni, Sergio
- Subjects
- *
PHOSPHOLIPASE A2 , *SNAKE venom , *PHARMACOLOGY , *BIOCHEMISTRY , *CHROMATOGRAPHIC analysis , *NEUROTOXICOLOGY , *EDEMA - Abstract
Abstract: This paper reports the biochemical and pharmacological characterization of a new myotoxic PLA2 (EC 3.1.1.4) called PhTX-I, purified from Porthidium hyoprora venom by one step analytical chromatography reverse phase HPLC. The homogeneity of the PhTX-I fraction and its molecular mass were initially evaluated by SDS–PAGE and confirmed by MALDI-TOF spectrometry, indicating a molecular mass of 14.249Da and constituted of a single polipeptidic chain. Amino acid sequence was determined by “de novo sequencing,” in tandem mass spectrometry, belonging to D49-PLA2 enzyme class and exhibiting high identity (44–90%) with other myotoxics PLA2 from snake venoms. The enzymatic investigation showed maximal activity at pH 8 and 35–45°C. This activity was dependent on Ca2+, other cations (Mg2+, Mn2+, Cd2+ and Zn2+) reduced notably the enzymatic activity, suggesting that the arrangement of the catalytic site presents an exclusive structure for Ca2+. Ex vivo, whole venom and PhTX-I PLA2 caused blockade of the neuromuscular transmission in young chick biventer cervicis preparations similar to other isolated snake venom toxins from the Bothrops genus. In vivo, both induced local myotoxicity and systemic interleukin-6 response upon intramuscular injection, additionally, induced moderate footpad edema. In vitro, both induced low cytotoxicity in skeletal muscle myoblasts, however PhTX-I PLA2 was able to lyse myotubes. [Copyright &y& Elsevier]
- Published
- 2011
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22. Biological and biochemical characterization of two new PLA2 isoforms Cdc-9 and Cdc-10 from Crotalus durissus cumanensis snake venom
- Author
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Romero-Vargas, Frey Francisco, Ponce-Soto, Luis Alberto, Martins-de-Souza, Daniel, and Marangoni, Sergio
- Subjects
- *
CROTALUS , *SNAKE venom , *AMINO acid sequence , *NITROBENZENE , *FLUORIDES , *CREATINE kinase , *HIGH performance liquid chromatography - Abstract
Abstract: This work reports the purification, biological characterization and amino acid sequence of two new basic PLA2 isoforms, Cdc-9 and Cdc-10, purified from the Crotalus durissus cumanensis venom by one step analytical chromatography reverse phase HPLC. The molecular masses of the PLA2 were 14,175±2.7 Da for Cdc-9 and 14,228±3.5 Da for Cdc-10 both deduced by primary structure and confirmed by MALDI-TOF. The isoforms presented an amino acid sequence of 122 amino acid residues, being Cdc-9: SLVQFNKMIK FETRKSGLPF YAAYGCYCGW GGQRPKDATD RCCFVHDCCY GKVAKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLS TYKNEYMFYP DSRCREPPEY TC with pI value of 8.25 and Cdc-10: SLLQFNKMIK FETRKSGVPF YAAYGCYCGW GGRRPKDPTD RCCFVHDCCY GKLTKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLN TYKNEYMFYP DSRCRGPPEY TC with a pI value of 8.46, showing highly conserved Ca2+-binding and catalytic sites. The PLA2 activity decreased when the isoforms Cdc-9 and Cdc-10 were incubated with 4-bromophenacyl bromide (p-BPB), anhydrous acetic acid and p-nitrobenzene sulfonyl fluoride (NBSF) when compared with the activity of both native isoforms. In mice, the PLA2 isoforms Cdc-9 and Cdc-10 induced myonecrosis and edema. Myotoxic and edema activities were reduced after treatment of the isoforms with p-BPB; acetylation of the lysine residues and the treatment of PLA2 with NBSF have also induced edema reduction. However, p-BPB strongly diminishes the local and systemic myotoxic effects. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
- View/download PDF
23. Identification of large phosphopeptides from β-casein that characteristically accumulate during ripening of the semi-hard cheese Herrgård
- Author
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Ardö, Y., Lilbæk, H., Kristiansen, K.R., Zakora, M., and Otte, J.
- Subjects
- *
CHEESE , *ANIONS , *MASS spectrometry , *CHROMATOGRAPHIC analysis - Abstract
Abstract: The peptide composition of a cheese reflects its characteristic ripening process, and in this study, large hydrophobic phosphopeptides that accumulate in semi-hard cheese, Herrgård, were identified. Anion exchange chromatography, reverse phase (RP) HPLC, liquid chromatography mass spectrometry and N-terminal amino acid sequencing were used. Milk from homozygotic cows was used to prepare β-casein A1 and A2, and peptides produced from their hydrolysis by plasmin were analysed to support identification of the peptides in cheese. Eight large phosphopeptides released by plasmin hydrolysis of β-casein were identified in the semi-hard cheese, i.e., fractions (f29–105, f29–107, f1–105, f1–107) A1 and A2. Four other peptides that accumulated in the cheese, co-eluted on RP-HPLC with the large primary plasmin-derived phosphopeptides and contributed significantly to two characteristic large peaks, i.e., one peak for each of the two genetic variants A1 and A2 of two β-casein fractions, mainly (f29–93) but also (f30–93). [Copyright &y& Elsevier]
- Published
- 2007
- Full Text
- View/download PDF
24. SSGE and DEE, new peptides isolated from a soy protein hydrolysate that inhibit platelet aggregation
- Author
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Lee, Kyung-Ae and Kim, Seung-Ho
- Subjects
- *
PEPTIDES , *PROTEIN hydrolysates , *BLOOD platelet aggregation , *GEL permeation chromatography - Abstract
A soy protein hydrolysate was found to inhibit rat platelet aggregation induced by ADP, an aggregating agent. To find out its principal antiplatelet peptide(s), the soy protein hydrolysate was separated successively by gel filtration chromatography, reverse-phase HPLC, and cation exchange HPLC. During the course of separation, we observed that most fractions had antiplatelet effects, which suggests that most peptides have some degree of antiplatelet effect. Following the inhibitory fractions, we purified and identified two new peptides, SSGE and DEE, by LC–electrospray ionization MS and peptide sequencing. Both peptides were highly hydrophilic. The concentrations to obtain 50% inhibition (IC50) of the aggregation intensity were approximately 480 and 460 μM, respectively, for SSGE and DEE. [Copyright &y& Elsevier]
- Published
- 2005
- Full Text
- View/download PDF
25. Identification and characterization of major IgE binding of purified allergenic protein (11 kDa) from Buchanania lanzan.
- Author
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Kumar, Sachin, Khan, Shariqua, Verma, Ajay Kumar, and Dwivedi, Premendra D.
- Subjects
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HIGH performance liquid chromatography , *CARRIER proteins , *TRANSCRIPTION factors , *PROTEINS - Abstract
Tree nut along with peanut are among the most potent food allergens, responsible for frequently inducing the IgE-mediated hypersensitivity reaction. Our aim was identification, purification of Buchanania lanzan (Bl-11 kDa) protein along with characterization and assessment of allergenic potential of clinically relevant allergen. Further study was executed in clinical samples of sensitive patients, BALB/c mice, and in-vitro. A major IgE binding 11-kDa protein from Buchanania lanzan was purified by anion exchange chromatography, reverse phase high pressure liquid chromatography (RP-HPLC) and characterized using peptide mass fingerprinting (PMF). Buchanania lanzan (Bl-11 kDa) protein shows the pepsin resistance and depicts IgE interacting capacity to Buchanania lanzan allergic patient's sera as well as sensitized mice sera. It also showed increase in the allergic mediator's like IgE, IgG1, histamine levels in sensitized mice sera. Further study was carried out in-vitro (RBL-2H3 cells) and increased release mast cell degranulation mediators such as β-hexosaminidase, histamine, CysL and PGD2 in the culture supernatant was found. The activation of Th2 cytokines/transcription factors and expression of molecular markers in the downstream of mast cell signaling were up-regulated while the Th1 transcriptional factor (T-bet) was decreased in Bl-11 kDa protein treated mice. Conclusively, our study demonstrates Buchanania lanzan purified protein to be potential allergen that may generate an allergic reaction in sensitized individuals, and one of the most important IgE binding protein responsible for its allergenicity. Unlabelled Image • Bl mediated allergy is increasing due to its excessive usage in food preparations. • Bl-11 kDa protein shows the positive binding from Bl sensitized allergic patients. • Bl-11 kDa protein increased the levels of allergic parameters like IgE, IgG1, and Histamine etc. • Bl-11 kDa protein upregulated the Th2 mediated responses and activated the mast cell signaling resulting into degranulation. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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