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Recent work has shed light on the abundance and diversity of D-amino acids in bacterial extracellular/ periplasmic molecules, bacterial cell culture, and bacteriarich environments.Within the extracellular/periplasmic space, D-amin...
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Recent work has shed light on the abundance and diversity of D-amino acids in bacterial extracellular/ periplasmic molecules, bacterial cell culture, and bacteriarich environments.Within the extracellular/periplasmic space, D-amino acids are necessary components of peptidoglycan, and disruption of their synthesis leads to cell death. As such, enzymes responsible for D-amino acid synthesis are promising targets for antibacterial compounds. Further, bacteria are shown to incorporate a diverse collection of D-amino acids into their peptidoglycan, and differences in D-amino acid incorporation may occur in response to differences in growth conditions. Certain D-amino acids can accumulate to millimolar levels in cell culture, and their synthesis is proposed to foretell movement from exponential growth phase into stationary phase. While enzymes responsible for synthesis of Damino acids necessary for peptidoglycan (D-alanine and Dglutamate) have been characterized froma number of different bacteria, the D-amino acid synthesis enzymes characterized to date cannot account for the diversity of D-amino acids identified in bacteria or bacteria-rich environments. Free D-amino acids are synthesized by racemization or epimerization at the α-carbon of the corresponding L-amino acid by amino acid racemase or amino acid epimerase enzymes. Additionally, Damino acids can be synthesized by stereospecific amination of α-ketoacids. Below, we review the roles of D-amino acids in bacterial physiology and biotechnology, and we describe the known mechanisms by which they are synthesized by bacteria.
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N-Acetyl-AA(amino acid)-NHtBu derivatives of all 20 naturally occurring amino acids have been synthesized. Syntheses were performed via solution-phase methodology with yields that allow for access to gram quantities of substrates,...
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N-Acetyl-AA(amino acid)-NHtBu derivatives of all 20 naturally occurring amino acids have been synthesized. Syntheses were performed via solution-phase methodology with yields that allow for access to gram quantities of substrates, in most cases. Syntheses include the coupling of a hindered amine,tert-butylamine, with each amino acid, either directly or in two steps using an activated ester isolated as an intermediate. The introduction of protecting groups was necessary in some cases. The development of synthetic sequences to access challenging substrates, such as the one derived from asparagine, are discussed.
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The considerable diversity of Conus peptides in the I sub(1)-superfamily provides a rare opportunity to define parameters important for the post-translational l- to d-isomerization of amino acids. This subtlest of post-translation...
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The considerable diversity of Conus peptides in the I sub(1)-superfamily provides a rare opportunity to define parameters important for the post-translational l- to d-isomerization of amino acids. This subtlest of post-translational modifications is not readily detectable by most techniques, and it would be a considerable advance if one could predict its potential occurrence purely from gene sequences. We previously described three I sub(1)-conotoxins, iota -RXIA (formerly designated r11a), r11b and r11c, each containing a d-amino acid at the third position from the C-terminus. In this work, we investigated two novel I sub(1)-superfamily members, r11d and ar11a, which we show have only l-amino acids. Based on these observations and an analysis of cDNA sequences of other group members, we suggest that there is a rule to predict d-amino acids in I sub(1)-superfamily peptides. Two factors are important: the residue to be modified should be three amino acids from the C-terminus of the precursor sequence, and it should be in a suitable sequence context. We apply the rule to other members of the I sub(1)-superfamily, to determine a priori which are probably modified.
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A practical and efficient two-step procedure is reported for the preparation of a variety of α-, β-, γ- and δ-amino acids from 2-pyridone, 2-pyrazinone or 2-hydroxypyrimidine and derivatives. The procedure is amenable to scale...
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A practical and efficient two-step procedure is reported for the preparation of a variety of α-, β-, γ- and δ-amino acids from 2-pyridone, 2-pyrazinone or 2-hydroxypyrimidine and derivatives. The procedure is amenable to scale-up and in most cases no chromatographic purification of the product is required. This approach is useful, especially in the synthesis of amino acids or deuterated amino acids that are not obtained by other methods.
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African bonytongue, Heterotis niloticus, is a river fish from the Central and West Africa basin. The species presents a great potential for fish farming and has been increasingly raised in Central and South Cameroon. The total ami...
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African bonytongue, Heterotis niloticus, is a river fish from the Central and West Africa basin. The species presents a great potential for fish farming and has been increasingly raised in Central and South Cameroon. The total amino acid and proximate composition of the whole body of egg, larva, juvenile, immature, and adult Heterotis were determined. Ash, moisture, whole-body protein, and lipid contents were significantly affected by size (P < 0.05). On the other hand, the amino acid composition of the whole-body tissue, when expressed as a percentage of dietary protein, was not significantly different among ontogenetic stages (ranging from 0.2 to 400 g mean body mass). The amino acid composition of the eggs was quite different to the one of whole-body tissue with lower levels of methionine, proline, and glycine, and higher levels of arginine, histidine, isoleucine, leucine, threonine, valine, serine, and alanine. The A/E ratios of adult Heterotis muscle tissue are similar to those obtained for other fish species, except for histidine and tryptophan. Based on whole-body or muscle tissue indispensable amino acids (IAA) to A/E ratios, the IAA requirement profiles for Heterotis (from larva to adult) were estimated and are similar to those of other omnivorous fish species, except for tryptophan and histidine.
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Fourier-transform infrared (FTIR) spectroscopy was used to monitor amino acids, organic acids, and changes during ripening. Twelve Cheddar cheese samples were ripened for 73 days and samples were drawn periodically. Water-soluble ...
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Fourier-transform infrared (FTIR) spectroscopy was used to monitor amino acids, organic acids, and changes during ripening. Twelve Cheddar cheese samples were ripened for 73 days and samples were drawn periodically. Water-soluble fractions of samples were analyzed by gas chromatography (20 amino acids), liquid chromatography (three organic acids), and FTIR spectroscopy (4000-700 cm-1). Spectra were correlated with chromatographic data and ripening events and analyzed by multivariate statistics to develop prediction and classification models. Most models showed a good fit (correlation coefficient >= 0.89) and could predict the levels of amino acids and organic acids and age of the cheese in less than 20 min. Lactic acid, leucine, glutamic acid, asparagine, phenylalanine, and valine were present in significantly high concentrations. Samples could be classified based on their age due to the differences in spectral region 1800-900 cm(-1). Some of the changes in the FTIR spectra of WSF during ripening were also characterized
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The aim of the present study was to test whether the dietary non-essential/conditionally essential amino acid composition has an effect on growth and protein utilisation and on delta C-13 of individual amino acids in rainbow trout...
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The aim of the present study was to test whether the dietary non-essential/conditionally essential amino acid composition has an effect on growth and protein utilisation and on delta C-13 of individual amino acids in rainbow trout (Oncorhynchus mykiss). Trout were reared on six purified diets containing only synthetic amino acids in place of protein. Diet 1 mimicked the amino acid composition of fishmeal, in diet 2, cysteine (Cys), glycine (Gly), proline (Pro) and tyrosine (Tyr) were isonitrogenously replaced by their precursor amino acids serine (Ser), glutamic acid (Glu) and phenylalanine (Phe), and in diet 3, alanine (Ala), asparagine and aspartate, Cys, Gly, Pro, Ser and Tyr were isonitrogenously replaced by Glu. Diets 4, 5 and 6 resembled diets 1, 2 and 3 except that Glu contained 0.1% C-13-enriched Glu. A control group was reared on a fishmeal-based diet. A total of forty-two trout (4.7 (SD 0.57) g) were fed one of the diets at a level of 3.5% body mass for 10 weeks in a flow-through system. Dietary non-essential amino acid composition significantly influenced protein gain (P<0.025) and delta C-13 of Ala, arginine (Arg), Gly, histidine (His), Phe and Tyr. Non-enriched Glu was predominantly found in trout fed C-13-enriched Glu, which is consistent with the fact that Glu has been shown to be used extensively in the gut as an energy source but is less consistent with the enrichment of Pro in fish fed diet 6 compared with fish fed diet 3. Further research is required to better understand the mechanisms that lead to the alteration of amino acid delta C-13 between diet and body tissues.
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The condensation reactions of sodium trimetaphosphate with single amino acids, namely glycine, L-alanine, β-alanine and γ-aminobutyric acid or pairs of these amino acids were reinvestigated by electrospray ion-trap mass spectrom...
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The condensation reactions of sodium trimetaphosphate with single amino acids, namely glycine, L-alanine, β-alanine and γ-aminobutyric acid or pairs of these amino acids were reinvestigated by electrospray ion-trap mass spectrometry and high performance liquid chromatography. It was found when mixtures were treated by sodium trimetaphosphate only in the presence of α-amino acid dipeptides were formed. Without addition of α-amino acids, the β-amino acid or γ-aminobutyric acid could not form peptide either by themselves or with their mixtures under the same conditions. From the data it is concluded that phosphate might select α-amino acids to produce the peptides being important precursors for the origin of life.
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alpha-Quaternary alpha-ethynyl alpha-amino acids are an important class of non-proteinogenic amino acids that play an important role in the development of peptides and peptidomimetics as therapeutic agents and in the inhibition of...
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alpha-Quaternary alpha-ethynyl alpha-amino acids are an important class of non-proteinogenic amino acids that play an important role in the development of peptides and peptidomimetics as therapeutic agents and in the inhibition of enzyme activities. This review provides an overview of the literature concerning synthesis and applications of alpha-quaternary alpha-ethynyl alpha-amino acids covering the period from 1977 to 2015.
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An improved synthesis of (2S, 4S)- and (2S, 4R)-2-amino-4-methyldecanoic acids was accomplished using a glutamate derivative as starting material and Evans' asymmetric alkylation as the decisive step. The NMR data of the two diast...
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An improved synthesis of (2S, 4S)- and (2S, 4R)-2-amino-4-methyldecanoic acids was accomplished using a glutamate derivative as starting material and Evans' asymmetric alkylation as the decisive step. The NMR data of the two diastereomers were measured and compared with those of the natural product. As a result, the stereochemistry of this novel amino acid unit in culicinins was assigned as (2S, 4R).
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