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To develop an efficient method for the production of urocanic acid, optimal conditions for the production of microbial L-histidine ammonia lyase and for the conversion of L-histidine to urocanic acid by this enzyme were studied. A number of microorganisms were screened to test their ability to form and accumulate urocanic acid from L-histidine. Achromobacter liquidum was selected as the best organism. With this organism, enzyme activity as high as 2.0 units/ml could be produced by a shaking culture at 30 C in a medium containing glucose, urea, potassium phosphate, L-histidine, yeast extract, peptone, and inorganic salts. Appropriate addition of a surface-active agent to the reaction mixture shortened the time required for the conversion. A large amount of L-histidine was converted stoichiometrically to urocanic acid in 48 h at 40 C. Accumulated urocanic acid was readily isolated in pure form by ordinary procedures with isoelectric precipitation. Yields of isolated urocanic acid of over 92% from L-histidine were easily attainable. When the culture of Achromobacter liquidum was added to DL-histidine, D-histidine and urocanic acid were simultaneously obtained in high yields.

Reaction of 0.20M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M imidazole at pH 7.0 or 8.0 under drying conditions at 50 degree C for 6 days yields pyrophosphate and tripolyphosphate in the presence and absence of 0.10M divalent metal ion. The efficiency of utilization of N,S-diacetylcysteamine in the formation of pyrophosphate linkages ranges from 3 - 8% under the above conditions. The thioester, N,S-diacetylcysteamine, and imidazole are required for phosphoanhydride formation. Reaction of 0.40M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M imidazole at ambient temperature for 6 days yields phosphorylimidazole in the absence or presence of 0.50M MgCl2. Phosphorylimidazole and pyrophosphate are formed in the presence of 0.05M CaCl2; pyrophosphate and tripolyphosphate are formed with 0.15M CaCl2. The efficiency of utilization of N,S-diacetylcysteamine in the formation of pyrophosphate linkages is roughly 7% at 6 days of reaction with 0.15M CaCl2. The thioester, N,S-diacetylcysteamine and imidazole are required for the formation of phosphoanhydrides. The significance of these reactions to molecular evolution is discussed.

1. Serine reacts with N,N'-carbonyldiimidazole in aqueous solution at 0 degrees C to yield Nalpha-[imidazolyl-(1)-carbonyl]-L-serine. This compound slowly transforms to L-2-oxo-oxazolidine-5-carboxylic acid. We found that L-2-oxo-oxazolidine-5-carboxylic acid was stable to hydrolysis under a variety of conditions and did not oligomerize to yield peptides. Threonine was found to react in an analogous manner with N,N'-carbonyldiimidazole, yielding Nalpha-[imidazolyl-(1)-carbonyl]-L-threonine and L-(+)-trans-5-methyl-2-oxo-oxazolidine-5-carboxylic acid. 2. Histidine reacts with N,N'-carbonyldimidazole in aqueous solution at 0 degrees C to yield a variety of histidine-containing intermidiates. These slowly transform to give 7-carboxy-imidazole-[1,5cotetrahydropyrimidin-5-one in up to 90% yield. 3. The polymerization of 7-carboxy-imidazo-[1,5c]-tetrahydropyrimidin-5-one in imidazole buffer at 30 degrees gives excellent yields of oligohistidines.

Cell-free extracts of Escherichia coli were active in catalyzing the synthesis of a biotin vitamer from 7,8-diaminopelargonic acid. The vitamer was identified as desthiobiotin on the basis of its chromatographic and electrophoretic characteristics and its biotin activities for a variety of microorganisms. The reaction was stimulated five-fold by bicarbonate, suggesting that an "active CO(2)" was incorporated into the carbonyl carbon of desthiobiotin. The enzyme was demonstrable in a wild-type (K-12) and in all biotin mutants of E. coli that were tested, with the exception of a strain which was able to grow on desthiobiotin but not on diaminopelargonic acid. Furthermore, the enzyme was repressible by biotin in all of the strains tested. These results are consistent with the hypothesis that the biosynthesis of desthiobiotin from 7,8-diaminopelargonic acid is an obligatory step in the biosynthetic pathway of biotin in E. coli.

Intermediates formed during the microbial degradation of imidazole, namely 4(5)-imidazolone, formiminoglycine, and possibly glycine, are similar to those formed during metabolism of imidazole derivatives.

We report the design and characterization of a disposable light shielded paper–plastic microfluidic device that can detect nanomolar levels of H2O2 using a smartphone camera and a light sealed accessory. Chemiluminescence reaction of H2O2 with bis(2,4,6-trichlorophenyl)oxalate in the presence of rubrene and imidazole is confined to a paper reaction site where the individual reagents are delivered via plastic microfluidic channels. The net photon emission from the chemiluminescence reactions, detected by using a smartphone, is correlated with H2O2 concentrations. With a total reagent volume of 25 μL, the sensor system was able to detect H2O2 concentrations as low as 250 nM. The smartphone based chemiluminescence sensing system has great potential as a point of care diagnostic tool for monitoring nanomolar levels of H2O2 in biological samples. [ABSTRACT FROM AUTHOR]

The excess isentropic compressibilities of binary mixtures of 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide with ethyl acetate or methanol and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide with dimethyl sulfoxide or methanol were calculated based on thermodynamically rigorous ideal mixing rule. For the discussed mixtures, great differences between excess values of isentropic compressibilities and isentropic compressibility deviations from a simple mole fraction average of pure components isentropic compressibilities are observed. The usability and correctness of the Prigogine-Flory-Patterson (PFP) model for mixtures under test is discussed as well, because in constructing the PFP theory, hydrogen bonds and interactions of strong electrostatic nature are excluded [Fluid Phase Equilib. 233 (2005) 157]. [ABSTRACT FROM AUTHOR]

Background: Sofosbuvir (SOF)/daclatasvir (DCV) is the direct-acting antiviral regimen of choice in many low- and middle-income countries for curative treatment of chronic hepatitis C virus (HCV) infection in adults, but data on the use of DCV in children are lacking. We performed a population pharmacokinetic (PK) analysis to predict DCV exposure in children treated with available adult formulations., Methods: DCV concentration data from HCV-infected adolescents receiving SOF/DCV [400/60 mg, once daily (OD)] who participated in a PK study in Egypt were used for model development. PK parameters were estimated using a population approach. Monte Carlo simulations were run for virtual children weighing 10 to <35 kg receiving 60 or 30 mg OD, and DCV exposures were compared with adults ranges., Results: Seventeen HCV-infected adolescents (13 males) provided 151 DCV concentrations. Median (range) age was 14 (11-18) years and weight 50 (32-63) kg. In these adolescents receiving 60 mg DCV, median (interquartile range) DCV area under the concentration time curve 0 to 24 hours, maximum concentrations, and minimum concentrations were 11,130 (8140-14,690) ng·h/mL, 1030 (790-1220) ng/mL and 130 (110-220) ng/mL, respectively, compared with 10,343 (7661-14,095) ng·h/mL, 1132 (876-1518) ng/mL and 110 (55.7-192) ng/mL predicted in children 10 to <35 kg receiving 30 mg. The proportion of children with DCV exposures above the adult range rapidly increased for children <30 kg using 60 mg OD, similarly for children 10-14 kg using 30 mg., Conclusions: DCV 30 mg OD was predicted to achieve effective and safe exposures in children 14 to <35 kg, perhaps down to 10 kg. These results should be validated clinically. Low-cost available adult DCV formulations together with approved pediatric doses of SOF would expand global access to HCV treatment for children., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

A paper-based solid-phase assay is presented for transduction of nucleic acid hybridization using immobilized quantum dots (QDs) as donors in fluorescence resonance energy transfer (FRET). The surface of paper was modified with imidazole groups to immobilize QD-probe oligonucleotide conjugates that were assembled in solution. Green-emitting QDs (gQDs) were FRET-paired with Cy3 acceptor. Hybridization of Cy3-labeled oligonucleotide targets provided the proximity required for FRET-sensitized emission from Cy3, which served as an analytical signal. The assay exhibited rapid transduction of nucleic acid hybridization within minutes. Without any amplification steps, the limit of detection of the assay was found to be 300 fmol with the upper limit of the dynamic range at 5 pmol. The implementation of glutathione-coated QDs for the development of nucleic acid hybridization assay integrated on a paper-based platform exhibited excellent resistance to nonspecific adsorption of oligonucleotides and showed no reduction in the performance of the assay in the presence of large quantities of noncomplementary DNA. The selectivity of nucleic acid hybridization was demonstrated by single-nucleotide polymorphism (SNP) detection at a contrast ratio of 19 to 1. The reuse of paper over multiple cycles of hybridization and dehybridization was possible, with less than 20% reduction in the performance of the assay in five cycles. This work provides an important framework for the development of paper-based solid-phase QD-FRET nucleic acid hybridization assays that make use of a ratiometric approach for detection and analysis. [ABSTRACT FROM AUTHOR]

Shape complementarity is a biological craft for precisely binding substrates at protein-protein interfaces. An analogy to such a function can be drawn conceptually for crystalline porous solids; yet the manifested entities are rare in reticular chemistry. The bottleneck-shaped pores carved out of a metal-organic framework, Zn(MIBA) 2 (aka. MAF-stu-13), can perfectly accommodate benzene molecules. Remarkably, its framework adapts to the optimal guest binding-the enhanced host-guest interactions in the neck in turn minimize the guest-guest repulsion in the pore to the extent it turns into attraction-as demonstrated by the combined X-ray structural and DFT computational studies. This adaptive material can be used for liquid-phase production of ultrahigh-purity (≥99 %) cyclohexane, achieving a balance between uptake capacity and separation selectivity and surpassing the performances of other porous and nonporous crystals reported recently (e.g. product purity 99.4 % vs. 97.5 % to date)., (© 2021 Wiley-VCH GmbH.)