Glycine Equivalents Research Articles

Synthesis of 4,6‐Difluoro‐Tryptophan as a Probe for Protein 19F NMR

AbstractA scalable procedure for the synthesis of 4,6‐difluorotryptophan is reported based on a deaminative coupling of a 4,6‐difluorogramine with 2‐benzylthio‐1,5‐dihydro‐4H‐imidazolone as glycine equivalent. Thus prepared 4,6‐difluorotryptophan was incorporated into the C‐terminal domain of the HIV‐1 capsid protein (CA‐CTD), and 19F spectra of the 4,6‐difluoro Trp CA CTD were recorded and compared to the singly fluorinated counterparts.

Bi-objective optimization of nutrient intake and performance of broiler chickens using Gaussian process regression and genetic algorithm

This study investigated whether quantifying the trade-off between the maxima of two response traits increases the accuracy of diet formulation. To achieve this, average daily weight gain (ADG) and gain:feed ratio (G:F) responses of 7–21-day-old broiler chickens to the dietary supply of three nutrients (intake of digestible glycine equivalents, digestible threonine, and total choline) were modeled using a newly developed hybrid machine learning-based method of Gaussian process regression and genetic algorithm. The dataset comprised 90 data lines. Model-fit-criteria indicated a high model adjustment and no prediction bias of the models. The bi-objective optimization scenarios through Pareto front revealed the trade-off between maximized ADG and maximized G:F and provided information on the needed input of the three nutrients that interact with each other to achieve the trade-off scenarios. The trade-off scenarios followed a nonlinear pattern. This indicated that choosing target values intermediate to maximized ADG and G:F after single-objective optimization is less accurate than feed formulation after quantifying the trade-off. In conclusion, knowledge of the trade-off between maximized ADG and maximized G:F and the needed nutrient inputs will help feed formulators to optimize their feed with a more holistic approach.

Characterization and spoilage potential of Bacillus cereus isolated from farm environment and raw milk.

Bacillus cereus sensu lato (B. cereus sl) is important spoilage bacteria causing milk structure and flavor changes and is ubiquitous in the environment. This study addresses the biodiversity, toxicity, and proteolytic activity of B. cereus sl from 82 environmental samples and 18 raw bovine milk samples from a dairy farm in the region of Tianjin. In sum, 47 B. cereus sl isolates were characterized through biochemical tests, 16S rRNA gene sequencing, and panC gene analysis. Fourteen sequence types (STs) of B. cereus sl were found in raw bovine milk samples, and five new STs (ST2749, ST2750, ST2751, ST2752, and ST2753) were identified in this study. ST1150 was the dominant ST, associated with fecal, air, drinking water, teat skin, teat cup, and teat dip cup. The results of toxin gene analyses showed that 12.77% and 8.51% of isolates carried hblACD and nheABC operons, respectively. In addition, the detection rate of emetic cesB gene was 21.28%. B. cereus sl demonstrated high spoilage potentials even at 7°C, which has the proteolytic activity of 14.32 ± 1.96 μmol of glycine equivalents per ml. Proteolytic activities were significantly (p < 0.05) decreased after the heat treatment. The residual activity of protease produced at 7°C was significantly higher than that produced at 25°C and 37°C after treatment at 121°C for 10 s and 135°C for 5 s (p < 0.01). Together, the results provide insights into the characteristics of B. cereus sl from farm environment and raw bovine milk and revealed that B. cereus sl contamination should also be monitored in raw milk for ultra-high temperature (UHT) products. This knowledge illustrates that strict cleaning management should be implemented to control B. cereus sl and assure high-quality milk products.

Rapid and efficient syntheses of tryptophans using a continuous-flow quaternization-substitution reaction of gramines with a chiral nucleophilic glycine equivalent.

A continuous-flow quaternization reaction of gramines with MeI (<1 min) followed by a substitution reaction with a chiral nucleophilic glycine-derived Ni-complex (S)-2 (<1 min) has successfully been developed to afford the corresponding alkylated Ni-complexes 3 in good yields with excellent diastereoselectivity, based on the results of a one-pot quaternization-substitution reaction of gramines with (S)-2 in a batch process. The continuous-flow process allowed the safe and efficient scale-up synthesis of 3j (84% yield, 99% de, 540 g h-1) to give 7-azatryptophan derivative (S)-4j readily by an acid-catalyzed hydrolysis reaction followed by protection with an Fmoc group. The present method for the rapid and efficient syntheses of enantiopure unnatural tryptophan derivatives from various gramines and (S)-2 will be useful to further promote peptide and protein drug discovery and development research.

Synthesis of trifluoromethyl substituted nucleophilic glycine equivalents and the investigation of their potential for the preparation of α-amino acids

Abstract The synthetic preparation of several Ni(II) complexed Schiff Bases of glycine will be introduced, as well as investigations into their reactivity and utility. Key to these investigations is the incorporation of electron-withdrawing trifluoromethyl groups within the framework of the conjugated system that stabilizes the enolate derived from the glycine component. Reactivity was evaluated for each of the complexes under phase transfer catalyzed alkylations with hydroxide bases, as well as the DBU catalyzed Michael Additions of optically active 3′-substituted-2-oxazoladinone amides of unsaturated carboxylic acids. It was found that the trifluoromethyl containing nucleophilic glycine equivalents were more reactive than their non-trifluoromethyl analogues in both reaction types. Therefore, the application of these modified Ni(II) complexes of glycine Schiff Bases are useful for the preparation of α-amino acids through phase transfer catalyzed alkylation as well as the preparation of optically pure β-substituted pyroglutamic acid precursors.

Interactive Effects of Glycine Equivalent, Cysteine, and Choline on Growth Performance, Nitrogen Excretion Characteristics, and Plasma Metabolites of Broiler Chickens Using Neural Networks Optimized with Genetic Algorithms.

Simple SummaryThe negative effects of nitrogen emissions caused by animal husbandry on the environment can be reduced by lowering the crude protein content in the diets of broiler chickens. The nonessential amino acids glycine and serine, investigated together as glycine equivalent, can limit the growth of broiler chickens fed diets that are low in crude protein. The response of broiler chickens to dietary glycine equivalent is not constant and is affected by endogenous precursors of glycine equivalent and metabolic processes that dissipate glycine equivalent. Choline can be converted to glycine, and glycine equivalent is required to form cysteine from methionine. The present study investigated interactive effects among dietary glycine equivalent, cysteine, and choline in broiler chickens. The results showed that the gain:feed ratio increased with dietary glycine equivalent supplementation. The extent of interactive effects among glycine equivalent, cysteine, and choline on the gain:feed ratio was hardly pronounced. Very high nitrogen-utilization efficiency with low variation among treatments was found. The findings indicate that small differences in nitrogen-utilization efficiency caused low glycine equivalent dissipation for nitrogen excretion, likely resulting in small interactive effects among dietary glycine equivalent, cysteine, and choline. These results contribute to further dietary crude protein reduction in feed for broiler chickens.Responses of broiler chickens to dietary glycine equivalent (Glyequi) are affected by dietary cysteine and choline. Hence, this study investigated interactive effects among dietary Glyequi, cysteine, and choline on the growth of broiler chickens. Male Ross 308 broiler chickens were maintained in 105 metabolism units (10 birds/unit) from days 7 to 22. Excreta were collected in 12-h intervals from days 18 to 21. Blood was sampled on day 22 (1 bird/unit). Five levels each of Glyequi (9–21 g/kg), cysteine (2–5 g/kg), and choline (0.5–1.7 g/kg) were tested under 15 diets in 7 replicates each following a fractional central composite design. Another diet was provided to five metabolism units (15 birds/unit) to measure prececal amino acid digestibility. Data were evaluated using neural networks. The gain:feed ratio (G:F) increased with digestible Glyequi intake. Differences between low and high digestible cysteine intake were low. Effects of choline intake on G:F were low. Nitrogen-utilization efficiency (NUE) was high (≥77%), with low variation among treatments. Plasma metabolites varied among treatments and indicated that metabolism of Glyequi, cysteine, and choline was influenced. These findings showed that interactive effects of dietary Glyequi, cysteine, and choline on growth were small, possibly because NUE was barely influenced.

Glycine equivalent and threonine inclusions in reduced-crude protein, maize-based diets impact on growth performance, fat deposition, starch-protein digestive dynamics and amino acid metabolism in broiler chickens

Maize-based diets were formulated to contain 208, 193, 179 and 165 g/kg crude protein (CP) were prepared and the last diet was supplemented with 4.33 g/kg glycine equivalents and 1.10 g/kg threonine, individually and in combination, to provide seven dietary treatments. Each dietary treatment was offered to eight replicate cages (6 birds per cage) of off-sex, male Ross 308 chickens from 7 to 35 days post-hatch. The transition from 208 to 165 g/kg CP diets numerically compromised weight gain and feed conversion ratios (FCR) by 5.41% and 3.44%, respectively, and linearly increased relative fat-pad weights from 7.62 to 13.31 g/kg. The same transition linearly increased ileal starch:protein disappearance rate ratios from 2.01 to 3.23 (r = -0.823; P < 0.001) which were linearly related with relative fat-pad weights and quadratically related with FCR to significant extents across all seven dietary treatments. However, tandem inclusions of glycine equivalents and threonine in the 165 g/kg CP diet significantly decreased disappearance rate ratios from 3.23 to 2.64; moreover, this tandem inclusion increased weight gain from 1994 to 2150 g/bird, decreased relative fat-pad weights from 13.31 to 11.65 g/kg and numerically improved FCR from 1.562 to 1.520. Instructively, birds offered the 165 g/kg CP diet supplemented with glycine equivalents and threonine performed comparably to their 208 g/kg CP diet counterparts with numerical differences of 1.99% more weight gain, 3.03% higher feed intake and a 0.66% higher FCR. That tandem inclusions of glycine equivalents and threonine in the 165 g/kg CP diet condensed ileal starch:protein disappearance rate ratios diet largely stemmed from a 6.18% (0.842 versus 0.793; P < 0.005) increase in ileal protein (N) digestibility coefficients and an increase of 10.1% (21.39 versus 19.42 g/bird/day; P < 0.005) in ileal protein (N) disappearance rates. It is then relevant that the tandem inclusion increased mean apparent ileal amino acid digestibility coefficients by 7.99% (0.838 versus 0.776; P < 0.01) where increases in threonine, glycine and serine digestibilities were pronounced. The possible mechanisms whereby tandem inclusions of glycine equivalents and threonine in a reduced-CP diet increased ileal amino acid digestibilities, and ultimately condensed starch:protein disappearance rate ratios, are discussed and may stem from the up-regulation of relevant amino acid transport systems with over-lapping specificities.

Development of Hamari Ligands for Practical Asymmetric Synthesis of Tailor-Made Amino Acids.

Enantiomerically pure tailor-made amino acids are in extremely high demand in nearly every sector of the health-related industries. In particular, the rapidly growing number of amino-acid-based pharmaceuticals calls for the development of advanced synthetic approaches featuring practicality and commercial viability. Here we provide a brief summary of the development of axially chiral tridentate Hamari ligands and their application for general asymmetric synthesis of various structural types of amino acids. The methodological diversity includes: dynamic kinetic resolution and (S)-/(R)-interconversion of unprotected amino acids and homologation of nucleophilic glycine equivalents via alkyl halide alkylation reactions as well as multiple-step transformations allowing preparation of polyfunctional and cyclic derivatives. The practicality of these methods is critically discussed.

Chemical variation and antioxidant capacity of sumac (Rhus coriaria L.)

Sumac (Rhus coriaria L.) is a medicinal plant distributed worldwide for its health benefits and its culinary uses as a flavoring agent. The aim of the current study was to detect chemical characterization of Iranian sumac populations. A high degree of variation was found in the chemical characteristics and the results revealed significant differences among the accessions. Titratable acidity varied from 2.01 to 7.84%, while the pH ranged from 2.66 to 3.90. Ascorbic acid ranged from 10.00 to 45.00 mg per g of dry weight, while phenolic content varied from 77.54 to 389.30 mg gallic acid equivalents per g dry weight. In addition, flavonoid content ranged from 2.19 to 7.54 mg quercetin equivalents per g dry weight, while tannin content ranged from 52.00 to 189.80 mg gallic acid equivalents per g dry weight. Free amino acid content ranged from 25.01 to 166.38 mg glycine equivalents per g dry weight, while anthocyanin content varied from 3.57 to 66.14 mg cyanidin-3-glucoside equivalents per g dry weight. Furthermore, antioxidant capacity ranged from 1.55 to 11.09 mg ascorbic acid equivalents per g dry weight. Flavonoid content was positively correlated with pH (r = 0.56) and tannin content (r = 0.28). In addition, antioxidant capacity was positively correlated with flavonoid content (r = 0.45) and tannin content (r = 0.32). Cluster analysis revealed two separate clusters based on the chemical properties. In conclusion, antioxidant activities were found in the sumac fruit extracts, and thus this fruit might be useful as a raw material to generate natural antioxidants. Finally, 15 accessions showed high values in terms of chemical properties and antioxidant capacity and thus may be especially useful for breeding and industrial uses.

Convenient Asymmetric Synthesis of Fmoc-(S)-6,6,6-Trifluoro-Norleucine

In this work we report a convenient asymmetric synthesis of Fmoc-(S)-6,6,6-trifluoro-norleucine via alkylation reaction of chiral glycine equivalent. The target amino acid of 99% enantiomeric purity was prepared with 82.4% total yield (three steps).

Methods for the preparation of 1-Aminocyclopropanecarboxylic Acids

The derivatives of 1-aminocyclopropanecarboxylic acid (ACC) over recent decades have attracted close attention from synthetic chemists owing to their high physiological activity as plant growth regulators, conformationally rigid analogs of natural amino acids, and peptidomimetics. The present review considers contemporary approaches to the methods of preparation of amino acids of the ACC series, namely, the alkylation of glycine equivalents with 1,2-electrophiles, the intramolecular cyclization of γ-substituted amino acid derivatives, alkene cyclopropanation under the action of diazo compounds, ylides, and carbene intermediates, as well as other synthetic approaches.

Characterization of Pseudomonas spp. and Associated Proteolytic Properties in Raw Milk Stored at Low Temperatures.

Milk spoilage is caused by the presence of proteolytic enzymes produced by Pseudomonas spp. during storage at low temperatures. The aim of this study was to identify Pseudomonas spp. in raw milk and investigate their associated proteolytic properties at low temperatures. Raw milk samples (n = 87) were collected from 87 bulk tanks in Shaanxi Province in China. Pseudomonas spp. were identified using Pseudomonas specific 16S, universal 16S rRNA sequencing, and rpoB gene sequencing. The proteolytic properties of Pseudomonas spp. were examined using milk agar, quantitative trinitrobenzenesulfonic acid assay, and by the presence of alkaline metallopeptidase gene (aprX). A total 143 isolates from all 87 samples were confirmed as Pseudomonas, and were identified as belonging to 14 Pseudomonas species. Of these, 40 (28.0%) isolates revealed proteolysis on milk agar at 2°C, 74 (51.8%) at 4°C, 104 (72.7%) at 7°C, and 102 (71.3%) at 10°C. However, proteolytic activity of 45 (31.5%) isolates exceeded 2 μmol of glycine equivalents per mL at 7°C, followed by 43 (30.1%) at 10°C, 18 (12.6%) at 4°C, and 7 (4.9%) at 2°C. The results reveal proteolytic activity of Pseudomonas spp. present in milk and their spoilage potential at different temperatures.

Adverse effects of Plant Food Supplements and botanical preparation: Data collected during the EU project PlantLIBRA

Sumac (Rhus coriaria L.) is a medicinal plant distributed worldwide for its health benefits and its culinary uses as a flavoring agent. The aim of the current study was to detect chemical characterization of Iranian sumac populations. A high degree of variation was found in the chemical characteristics and the results revealed significant differences among the accessions. Titratable acidity varied from 2.01 to 7.84%, while the pH ranged from 2.66 to 3.90. Ascorbic acid ranged from 10.00 to 45.00 mg per g of dry weight, while phenolic content varied from 77.54 to 389.30 mg gallic acid equivalents per g dry weight. In addition, flavonoid content ranged from 2.19 to 7.54 mg quercetin equivalents per g dry weight, while tannin content ranged from 52.00 to 189.80 mg gallic acid equivalents per g dry weight. Free amino acid content ranged from 25.01 to 166.38 mg glycine equivalents per g dry weight, while anthocyanin content varied from 3.57 to 66.14 mg cyanidin-3-glucoside equivalents per g dry weight. Furthermore, antioxidant capacity ranged from 1.55 to 11.09 mg ascorbic acid equivalents per g dry weight. Flavonoid content was positively correlated with pH (r = 0.56) and tannin content (r = 0.28). In addition, antioxidant capacity was positively correlated with flavonoid content (r = 0.45) and tannin content (r = 0.32). Cluster analysis revealed two separate clusters based on the chemical properties. In conclusion, antioxidant activities were found in the sumac fruit extracts, and thus this fruit might be useful as a raw material to generate natural antioxidants. Finally, 15 accessions showed high values in terms of chemical properties and antioxidant capacity and thus may be especially useful for breeding and industrial uses.

ChemInform Abstract: Asymmetric Synthesis of Aromatic and Heteroaromatic α‐Amino Acids Using a Recyclable Axially Chiral Ligand.

AbstractA new chiral nucleophilic glycine equivalent containing a recyclable axially chiral ligand is prepared and its alkylation reactions with various alkyl bromides under unconventional conditions are described.

Asymmetric Synthesis of Aromatic and Heteroaromatic α‐Amino Acids Using a Recyclable Axially Chiral Ligand

AbstractIn this work, we introduce a new chiral nucleophilic glycine equivalent containing a recyclable axially chiral ligand. As the first synthetic application of this glycine reagent, we describe its alkylation reactions with various alkyl bromides, conducted under unconventional conditions using methanol as the reaction medium. The alkylation products were isolated in diastereomerically pure state in high &gt;80 % yields. The wide structural scope of this method and its limitations are convincingly demonstrated and critically discussed. The recyclable nature of the nonracemizable axially chiral ligands together with the generally excellent stereochemical outcome makes this a very valuable method for the practical preparation of enantiomerically pure aromatic tailor‐made α‐amino acids.

Advanced asymmetric synthesis of (1R,2S)-1-amino-2-vinylcyclopropanecarboxylic acid by alkylation/cyclization of newly designed axially chiral Ni(II) complex of glycine Schiff base.

Asymmetric synthesis of (1R,2S)-1-amino-2-vinylcyclopropanecarboxylic acid (vinyl-ACCA) is in extremely high demand due to the pharmaceutical importance of this tailor-made, sterically constrained α-amino acid. Here we report the development of an advanced procedure for preparation of the target amino acid via two-step SN2 and SN2' alkylation of novel axially chiral nucleophilic glycine equivalent. Excellent yields and diastereoselectivity coupled with reliable and easy scalability render this method of immediate use for practical synthesis of (1R,2S)-vinyl-ACCA.

A molecular modelling explanation of the unexpected stereochemistry observed in the alkylation of oxazinone-derived glycine equivalents using 4-chloromethyl-1,3,2-dioxathiolane-2-oxide

The (R)- and (S)-enantiomers of 4-chloromethyl-1,3,2-dioxathiolane-2-oxide were used as ‘epoxide-like’ synthons in the asymmetric alkylation of the enantiomers of oxazinone-derived glycine equivalents. The configurations of the obtained spiro compounds were easily determined using 2D nuclear Overhauser effect nuclear magnetic resonance experiments. Additionally, the mechanisms of the reactions performed were explained using molecular modelling. The spiro derivatives obtained can also be modified and hydrolysed to their corresponding amino acids, which are derivatives of 1-aminocyclopropane-1-carboxylic acids.

Cyclic sulfates as useful tools in the asymmetric synthesis of 1-aminocyclopropane-1-carboxylic acid derivatives

The enantiomers of 4-(2-methoxyethyl)-1,3,2-dioxathiolane-2,2-dioxide and 4-(methoxymethyl)-1,3,2-dioxathiolane-2,2-dioxide have been used as ‘epoxide-like’ synthons during the asymmetric alkylation of oxazinone-derived glycine equivalents. Using a fully stereoselective synthesis, eight stereoisomers of the spiro derivatives of the glycine equivalents were obtained. The relative configurations of the spiro compounds obtained were easily determined using nuclear magnetic resonance spectroscopy and two dimensional nuclear Overhauser effect experiments. Additionally, one of the spiro derivatives obtained was hydrolyzed to its corresponding amino acid, which was a derivative of 1-aminocyclopropano-1-carboxylic acid, a very important building block that is present in many compounds, which have interesting biological activity.

ChemInform Abstract: Adding a Functional Handle to Nature′s Building Blocks: The Asymmetric Synthesis of β‐Hydroxy‐α‐amino Acids

AbstractReview: [67 refs.

Asymmetric synthesis of all four stereoisomers of 1-amino-3-hydroxy-cyclopentane-1-carboxylic acid

An asymmetric synthesis of all four stereoisomers of 1-amino-3-hydroxy-cyclopentane-1-carboxylic acid based on a chiral glycine equivalent, oxazinone derivative is presented. The crucial point of the performed reactions is the alkylation of (S)- and (R)-glycine equivalent with the respective stereoisomers of 4-(2-iodoethyl)-1,3,2-dioxathiolan-2-oxide using phosphazenic base t-BuP4.