Dicarboxylic Amino Acids Research Articles

Glycine synthesis from nitrate and glyoxylate mediated by ferroan brucite: An integrated pathway for prebiotic amine synthesis

Amino acids are present in all known life, so identifying the environmental conditions under which they can be synthesized constrains where life on Earth might have formed and where life might be found on other planetary bodies. All known abiotic amino acid syntheses require ammonia, which is only produced in reducing and neutral atmospheres. Here, we demonstrate that the Fe-bearing hydroxide mineral ferroan brucite [Fe0.33,Mg0.67(OH)2] can mediate the reaction of nitrate and glyoxylate to form glycine, the simplest amino acid used in life. Up to 97% of this glycine was detected only after acid digestion of the mineral, demonstrating that it had been strongly partitioned to the mineral. The dicarboxylic amino acid 3-hydroxy aspartate was also detected, which suggests that reactants underwent a mechanism that simultaneously produced mono- and dicarboxylic amino acids. Nitrate can be produced in both neutral and oxidizing atmospheres, so reductive amination of nitrate and glyoxylate on a ferroan brucite surface expands origins of life scenarios. First, it expands the environmental conditions in which life's precursors could form to include oxidizing atmospheres. Second, it demonstrates the ability of ferroan brucite, an abundant, secondary mineral in serpentinizing systems where olivine is partly hydrated, to mediate reductive amination. Finally, the results demonstrate the need to consider mineral-bound products when analyzing samples for abiotic amino acid synthesis.

Two new clades recovered at high temperatures provide novel phylogenetic and genomic insights into Candidatus Accumulibacter.

Candidatus Accumulibacter, a key genus of polyphosphate-accumulating organisms, plays key roles in lab- and full-scale enhanced biological phosphorus removal (EBPR) systems. A total of 10 high-quality Ca. Accumulibacter genomes were recovered from EBPR systems operated at high temperatures, providing significantly updated phylogenetic and genomic insights into the Ca. Accumulibacter lineage. Among these genomes, clade IIF members SCELSE-3, SCELSE-4, and SCELSE-6 represent the to-date known genomes encoding a complete denitrification pathway, suggesting that Ca. Accumulibacter alone could achieve complete denitrification. Clade IIC members SSA1, SCUT-1, SCELCE-2, and SCELSE-8 lack the entire set of denitrifying genes, representing to-date known non-denitrifying Ca. Accumulibacter. A pan-genomic analysis with other Ca. Accumulibacter members suggested that all Ca. Accumulibacter likely has the potential to use dicarboxylic amino acids. Ca. Accumulibacter aalborgensis AALB and Ca. Accumulibacter affinis BAT3C720 seemed to be the only two members capable of using glucose for EBPR. A heat shock protein Hsp20 encoding gene was found exclusively in genomes recovered at high temperatures, which was absent in clades IA, IC, IG, IIA, IIB, IID, IIG, and II-I members. High transcription of this gene in clade IIC members SCUT-2 and SCUT-3 suggested its role in surviving high temperatures for Ca. Accumulibacter. Ambiguous clade identity was observed for newly recovered genomes (SCELSE-9 and SCELSE-10). Five machine learning models were developed using orthogroups as input features. Prediction results suggested that they belong to a new clade (IIK). The phylogeny of Ca. Accumulibacter was re-evaluated based on the laterally derived polyphosphokinase 2 gene, showing improved resolution in differentiating different clades.

Abstract PR008: The SLC1A1/EAAT3 dicarboxylic amino acid transporter: An actionable, HIF-independent, hub that links epigenetic dysregulation to nucleotide metabolism in kidney cancer

Abstract Significance: The clear cell renal cell carcinomas (ccRCCs), which harbor the hallmark inactivation of the von Hippel Lindau tumor suppressor protein (pVHL), represent the majority of adult kidney cancers. Although, early stage/localized ccRCC is effectively managed by surgery and surveillance, therapeutic options for advanced stage disease are limited, highlighting the unmet need for novel therapies. Chromatin dysregulation is routinely observed in ccRCC and our previous work identified a distinct histone modification signature associated with pVHL-deficient ccRCCs, versus the pVHL-proficient chromophobe and papillary sub-types, which included elevated levels of bulk Histone H3 K27 acetylation (H3K27ac). H3K27ac marks transcriptionally activated regions in the genome. We hypothesized that, as in other biological contexts, H3K27ac accumulation in pVHL-deficient ccRCCs drives the expression of key oncogenes. Here, we functionally probed this dysregulated epigenetic program to identify actionable targets in kidney cancer. Experimental Approach and Results: We identified genes marked by elevated H3K27ac (ChIP-Seq) and higher expression (RNA-Seq), specifically in pVHL-deficient cells and prioritized the top 100 genes that encoded druggable products. Using a library representing these ORFs, we did an in vivo ‘sufficiency’ screen, to identify candidates whose expression promoted tumor growth in otherwise poorly tumorigenic pVHL-proficient cells. Our screen (and downstream validation studies) identified SLC1A1, which encodes an Asp/Glu transporter named EAAT3, as an oncogenic driver in ccRCC. Results: SLC1A1 expression was elevated in pVHL-deficient cells – but in a HIF-independent manner. Inactivation of SLC1A1 (using CRISPR/Cas9) led to fitness defects in a panel of ccRCC cell lines, along with a notable depletion of nucleotide biosynthesis precursors, likely because of the importance of the Asp carbon skeleton in this pathway. Consistent with this, esterified-Asp rescued the fitness defects associated with SLC1A1 loss. Moreover, SLC1A1 upregulation (high Asp/Glu) diminished dependency on Glutaminase; whereas, SLC1A1 loss (low Asp/Glu) increased Glutaminase dependency and promoted sensitivity to Glutaminase blockade. Finally, using clinical cohorts and cell-based studies, we found that SLC1A1 can impact its own transcriptional expression, but also the expression of certain other metabolic transporters involved in Asp/Glu metabolism (e.g. SLC22A11) and nucleotide metabolism (e.g SLC28A1). We speculate, these transcriptional alterations are driven by the conversion of Glu into a-ketoglutarate, a key cofactor for KDMs. Our ongoing studies are addressing the mechanistic basis of this transcriptional regulation and exploring the feasibility of pharmacologically targeting SLC1A1 in ccRCC. Altogether, we show that ccRCCs hijack nutrient reabsorption mechanisms (e.g. SLC1A1) to drive oncogenic programs. SLC1A1 thus links epigenetic dysregulation to a HIF-independent metabolic program regulating nucleotide biosynthesis/uptake. Citation Format: Abhishek A. Chakraborty. The SLC1A1/EAAT3 dicarboxylic amino acid transporter: An actionable, HIF-independent, hub that links epigenetic dysregulation to nucleotide metabolism in kidney cancer [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr PR008.

The opportunities of using a natural adaptogen from the <i>Galleria mellonella</i> larvae in veterinary medicine

A comparative analysis of the adaptation effects of the Porsolt test of fractionated solutions obtained from the products of the larvae of the large wax moth (Galleria mellonella) on biological systems was performed. The method of X-ray photoelectron spectroscopy determined that in the obtained light fraction of the products of larval life there is a high-energy component of N1s spectra (~402.0 eV) and bond energy for carbon in the C-N bond (~286.0 eV), which indicates the presence of protonated amino groups in the samples. Absorption at 1700 cm-1 can be attributed to the presence of dicarboxylic amino acids (glutamic and aspartic) and other organic acids, which are much less in the heavy fraction. During oral administration of the studied extracts, their multidirectional effect on the intestines of laboratory mice was found. The negative effect of heavy fraction on the microbiocenosis of the intestine by the qualitative composition of the microflora was detected. When the light fraction is used, the intestinal microflora is close to the control. Analysis of the number of leukocytes of the small intestine when the fractions were injected reflected the local immune response of the body. The content of these cells on the mucosal plate of mice injected with the lung fraction was 67.2% higher than that of the control mice (p ≤ 0.05). The content of leukocytes on the own plate of the mucosa of mice injected with the heavy fraction was 2.7 times higher compared to the control, indicating an inflammatory reaction. The difference between the experimental groups is significant (p ≤ 0.001). The comparative effect of the fractions showed that their oral administration had a different effect on the swimming time compared to the control. After 20 days of the experiment, mice injected with the heavy fraction had significantly increased their swimming time compared to the first day (p ≤ 0.05). However, a negative adaptogenic effect compared to the control group is noticeable. A significant difference was found between the results on the 30th day between the experimental groups, which indicates a pronounced difference in the results obtained.

Amide group enhanced self-assembly and adsorption of dicarboxylic amino acid surfactants on a rhodochrosite surface through intermolecular weak interaction

Efficient recovery of fine mineral particles is challenging for minerals flotation due to a small particle mass and high specific surface area. This work innovatively applied a multifunctional surfactant 2-dodecanoylamino-pentanedioic acid (DPA) for achieving flocculation and recovery of fine rhodochrosite. Interestingly, the formation of larger aggregation induced by DPA, instead of sodium oleate (NaOL), was observed and the medium particle size (d50) was 2.29 times than that of NaOL, resulting in more strong collecting ability for fine rhodochrosite particles (with a recovery of 82.5% for 0.1 mmol/L DPA and 35.3% for 0.1 mmol/L NaOL). Analysis with EDLVO theory illustrated that the hydrophobicity force is one of the factors that induces hydrophobic flocculation, along with electrostatic repulsion, the Van der Waals force, and weak interaction. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations revealed the “weak-to-medium” hydrogen bond formation among the amide groups or amide and carboxyl functional groups in the DPA complex, further enhancing aggregation between rhodochrosite fine particles. These discoveries are beneficial for providing new insights into aggregation generation among fine particles in the presence of surfactants containing multiple functional groups.

Amino acid composition of proteins of meristem cells of maize roots under the combined action of lead, cadmium and nickel ions

Heavy metals are one of the main causes of plant damage. The main route of entry of metals into plants is their absorption by the root system from the soil. The accumulation of heavy metals in plants disrupts the flow of biochemical processes. Amino acid metabolism is one of the important factors that ensure biochemical adaptation of organisms to environmental changes. Therefore, the aim of the work was to study the content of protein amino acids in the generative tissues of the maize root under the combined action of lead, cadmium and nickel ions at the early stages of ontogenesis. To assess the impact of heavy metals, two-day-old corn seedlings were transplanted to solutions with heavy metal ions of various concentrations, both individually and in a mixture. The content of protein amino acids in the meristem was characterized by significant variation associated with both quantitative and qualitative changes in the composition of water-soluble proteins during germination. The level of accumulation of amino acids in the meristem cells of maize roots depended on the concentration of the xenobiotic and the germination period, and the general regularity of the influence of nickel ions was a decrease in the content of arginine, leucine, alanine and an increase in the content of histidine, cysteine, serine, proline, and valine. During the period of germination, the qualitative amino acid composition of plants did not change, while the quantitative content of individual amino acids varied greatly. Various increases in the content of dicarboxylic amino acids (glutamate and aspartate) testify to the intensification of metabolic processes under the influence of the studied substances. However, it cannot be excluded that the increase in the content of glutamic and aspartic acids is associated with a decrease in the speed of their utilization. In addition, heavy metals caused an increase in the content of amino acids of the ornithine cycle (arginine) and the end product of the cycle (proline) to varying degrees. Proline is an amino acid that has a stress-protective effect due to the binding of proline aggregates to surface hydrophobic residues of proteins, which prevents their denaturation. Perhaps a similar protective effect of proline occurs in the case, which is being considered.

Salt effects on the solubility of aromatic and dicarboxylic amino acids in water

The salt effect on the solubility of the amino acids l-aspartic acid, l-glutamic acid, l-tryptophan, and l-tyrosine, seldomly found in the literature, was studied at 298.2 K, in aqueous solutions of KCl and (NH4)2SO4, for salt concentrations up to 2.0 mol·kg−1. In this concentration range, both salts are salting-in agents for glutamic acid and aspartic acid, with a stronger effect induced by (NH4)2SO4. Regarding the two aromatic amino acids, a slight increase in the solubility was obtained at low salt concentrations, followed by a stronger salting-out effect, more pronounced by (NH4)2SO4 than by KCl. The relative solubility data obtained in this work were compared to literature data for other amino acids in the same electrolyte solutions to establish a relative solubility ranking connected to their structure.Finally, the solubility data were modeled using the electrolyte Perturbed-Chain Statistical Association Theory (ePC-SAFT). The modeling requires parameters for the amino acids and ions as well as melting properties of the amino acids. All these parameters and properties were obtained from previous works. To quantitatively describe the solubility of amino acids upon salt addition, binary interaction parameters (kij) between any amino acid and anions were determined, while between any amino acid and the cations were fixed to kij = 0.08. The kij parameters between amino acid and the inorganic anions show very similar values for amino acids of the same chemical class (e.g. kij between anion and amino acid with apolar side chains), which may be used to systematically reduce the number of adjustable parameters in future work.

Synthesis and Cyclooxygenase Enzyme Inhibitory Activity of Flurbiprofen Analogues: Simple Methodology of Their Nanoemulsion Systems

AbstractMost over‐the‐counter (OTC) and prescription NSAIDs have common side effects, especially gastrointestinal problems. Flurbiprofen, is an analogue of ibuprofen, that causes side effects and discomfort. This study was to synthesize flurbiprofen analogues, determine their NSAID activity using in vitro cyclooxygenase enzyme inhibitory assays and prepare their nanoemulsions. Six new flurbiprofen derivatives were synthesized via the reaction of acyl chloride (of flurbiprofen) and β‐amino alcohol, amino acid ester (or amino dicarboxylic acid ester). The masking of the free carboxylic acid functional group of flurbiprofen lowered the acidity by nearly two‐fold. The compounds, tested for their cyclooxygenase (COX‐1 and −2) enzyme inhibitory activity, showed analogues 3 d and 3 f could be of interest due to relatively higher COX‐2 enzyme inhibition. Nanoemulsions (NEs) of flurbiprofen analogues (3 d and 3 f) were developed using high energy emulsification technique and the results showed that the optimized nanoemulsions of 3 d presented a droplet size of 225 nm, polydispersity index of 0.568, and zeta potential of +29.60 mV.

Thermodynamics of complex formation between aspartic acid and 2,3,4-pyridinecarboxylic acids in aqueous solutions

The present work reports on molecular interactions of dicarboxylic amino acid, L-aspartic acid (Asp), with nicotinic acid, isonicotinic acid and picolinic acid in aqueous solutions at 298.15 K. Thermodynamic parameters of complex formation between the reagents were estimated using solution calorimetry method. It was found that strengthening of the stability of the Asp complexes follows the order nicotinic acid < isonicotinic acid < picolinic acid. The process of complex formation between Asp and the pyridinecarboxylic acids in water is entropically favorable. For zwitterionic forms of reagents, DFT theoretical calculations at B3LYP/6-31++G(d,p) level of theory have been performed. Analysis of natural bond orbitals (NBO) has been carried out for the most stable conformers of complexes formed. According to the quantum chemical calculations and thermodynamic data, the complexes between Asp and pyridinecarboxylic acids with 1:2 stoichiometry is mainly formed due to the electrostatic interactions and hydrogen bonding.

Bioelectrochemical processes of oxidation of dicarboxylic amino acids by strain Micrococcus luteus 1-I in a biofuel cell

A facultative anaerobic strain was isolated and studied from the activated sludge of the treatment facilities of a petrochemical enterprise. Its morphological and cultural, physiological and biochemical, tinctorial, molecular genetic characteristics have been investigated. Based on the data obtained, strain 1-I was assigned to the species Micrococcus luteus. The electrogenic activity of this bacterium in BFC was shown using dicarboxylic amino acids - glutamic and aspartic. The open-circuit voltage indices in the BFC with M. luteus 1-I increased in 6 days to 511.5 mV with the addition of aspartic acid, and 419 ± 38.5 mV with the addition of glutamic acid. In this case, the short-circuit current increased to 3.17 ± 0.12 and 1.6 ± 0.14 mA, respectively. The specific power of BFCs based on M. luteus 1-I was the highest with the addition of aspartic acid (40-50 mW / m2 at a current density of 0.15 to 0.4 A / m2). The indicated indicator in a similar BFC with glutamic acid was 26-32 mW / m2 (at a current density of 0.08 to 0.28 A / m2). The oxidation of these compounds by the studied bacterial strain was also confirmed by the methods of cyclic voltammetry.

Сравнительная характеристика аминокислотного состава и активности ферментов аминокислотного обмена в гемохориальной плаценте разных видов животных и человека

The amino acid composition and activity of the enzymes of the amino acid metabolism of placenta were studied. The objects of the study were guinea pigs (Cavia porcellus) and rhesus macaques (Macaca mulatta), which have a hemochoric placenta type, similar to humans. The study also included women with uncomplicated pregnancy and delivery on time (39-40 weeks). It was found that in the all tissues studied, the fetal part of the placenta is characterized by the highest content of free and bound amino acids. In the fetal part of the placenta, the maximal activity of amino acid metabolism enzymes (aminotransferases, deaminases, amino synthetases) was also found. Common to the placenta of guinea pigs, monkeys and humans is also a high level of dicarboxylic amino acids and glutamine. Along with the common features in the amino acid metabolism of the placenta of different species of animals and humans, some differences were revealed due to the evolutionary features of the development of the organ, the specifics of the existing maternal-fetal relationships. Interspecies differences of the same parts of the placenta relate to individual amino acids, the majority of which in the placenta of rodents exceeds similar indicators in primates. Between the placentas of humans and monkeys, the differences in the studied biochemical parameters are less pronounced. Another difference between guinea pig placenta and human and monkey placenta is the unequal non-covalent binding of amino acids to biopolymers, which modifies the state of the acceptor groups of proteins. Similar tissues of the afterbirth of different species of animals and humans differ in the activity of amino acid metabolism enzymes. There is a close correlation between the content of free amino acids and indicators of enzyme activity, showing their important role in the formation of the placental amino acid fund.

Specific properties of 3d-metal complexes with optical isomers of complexones derived from dicarboxylic amino acids

Methods for the synthesis of optical isomers of monoamine complexones derived from dicarboxylic amino acids and their complexes with 3d-metals are considered. The physicochemical properties of the compounds in question were studied and a number of specific properties of the complexes were revealed. An approach was proposed to the study of quantitative relationships between the chemical composition, structure, and properties of chemical substances.

Interactions of Amino Acids and Aminoxazole Derivatives: Cocrystal Formation and Prebiotic Implications Enabled by Computational Analysis.

In line with the postulated intermediacy of aminoxazoles derived from small sugars toward the direct assembly of nucleoside precursors, we show here a potential prebiotic scenario where aminoxazolines might have also played further roles as complexing and/or sequestering agents of other primeval blocks, namely amino acids. To this end, a bis-aminoxazoline derivative, generated from dihydroxyacetone and cyanamide, gives rise to stable co-crystal forms with dicarboxylic amino acids (Asp and Glu), while ionic interactions owing to proton transfer are inferred from spectroscopic data in aqueous solution. The structure of a 1:2 aminoxazoline: aspartic acid complex, discussed in detail, was elucidated by X-ray diffractometry. Optimized geometries of such ionic structures with bulk aqueous solvation were assessed by DFT calculations, which disclose preferential arrangements that validate the experimental data. Peripherally, we were able to detect in a few cases amino acid dimerization (i.e. dipeptide formation) after prolonged incubation with the bis-aminoxazole derivative. A mechanistic simulation aided by computation provides some predictive conclusions for future explorations and catalytic design.

Carriage of Shiga toxin phage profoundly affects Escherichia coli gene expression and carbon source utilization

BackgroundEnterohemorrhagic Escherichia coli (E. coli) are intestinal pathogenic bacteria that cause life-threatening disease in humans. Their cardinal virulence factor is Shiga toxin (Stx), which is encoded on lambdoid phages integrated in the chromosome. Stx phages can infect and lysogenize susceptible bacteria, thus either increasing the virulence of already pathogenic bacterial hosts or transforming commensal strains into potential pathogens. There is increasing evidence that Stx phage-encoded factors adaptively regulate bacterial host gene expression. Here, we investigated the effects of Stx phage carriage in E. coli K-12 strain MG1655. We compared the transcriptome and phenotype of naive MG1655 and two lysogens carrying closely related Stx2a phages: ϕO104 from the exceptionally pathogenic 2011 E. coli O104:H4 outbreak strain and ϕPA8 from an E. coli O157:H7 isolate.ResultsAnalysis of quantitative RNA sequencing results showed that, in comparison to naive MG1655, genes involved in mixed acid fermentation were upregulated, while genes encoding NADH dehydrogenase I, TCA cycle enzymes and proteins involved in the transport and assimilation of carbon sources were downregulated in MG1655::ϕO104 and MG1655::ϕPA8. The majority of the changes in gene expression were found associated with the corresponding phenotypes. Notably, the Stx2a phage lysogens displayed moderate to severe growth defects in minimal medium supplemented with single carbon sources, e.g. galactose, ribose, L-lactate. In addition, in phenotype microarray assays, the Stx2a phage lysogens were characterized by a significant decrease in the cell respiration with gluconeogenic substrates such as amino acids, nucleosides, carboxylic and dicarboxylic acids. In contrast, MG1655::ϕO104 and MG1655::ϕPA8 displayed enhanced respiration with several sugar components of the intestinal mucus, e.g. arabinose, fucose, N-acetyl-D-glucosamine. We also found that prophage-encoded factors distinct from CI and Cro were responsible for the carbon utilization phenotypes of the Stx2a phage lysogens.ConclusionsOur study reveals a profound impact of the Stx phage carriage on E. coli carbon source utilization. The Stx2a prophage appears to reprogram the carbon metabolism of its bacterial host by turning down aerobic metabolism in favour of mixed acid fermentation.

Manipulating selectivity of covalently-bonded hyperbranched anion exchangers toward organic acids. Part II: Effect of mono- and dicarboxylic amino acids in the internal part of the functional layer

Four covalently-bonded hyperbranched anion exchangers based on poly(styrene-divinylbenzene) (PS-DVB) substrate with different structure of the functional layer were prepared using mono- and dianionic amino acids such as glycine, β-alanine, aspartic acid, and glutamic acid in the internal part of the functional layer. Selectivity of all anion exchangers toward weakly retained organic acids was investigated at different temperatures in order to evaluate the effect of the number of carboxylic groups in the functional layer and its hydrophilicity on the separation. It was found that dianionic amino acids used in the first modification cycle of hyperbranching provide the best resolution for mono- and divalent organic acids, which makes the number of carboxylic groups in the structure of amino acid a key factor in the separation of such analytes with covalently-bonded hyperbranched anion exchangers, while the role of amino acid hydrophilicity is not that significant. Stationary phases prepared using aspartic and glutamic acids provided baseline resolution for quinic, glycolic, acetic, lactic, formic, and galacturonic acids, which are not resolved to baseline with modern commercially available anion exchangers; the increase of temperature was found to be favorable for improving the resolution even further.

Metabolic Activity of the Liver during Exercise—A Metabolomics Approach

The liver plays a pivotal role in substrate metabolism during fasting and exercise. Chances in the hepatic uptake or release of metabolites regulate the hepatic energy supply for other organs. Here we evaluated substrate flow over the hepato-splanchnic bed by assessing arterial-to-venous differences based on UPLC and CE-MS metabolomics analysis at rest and during exercise. Catheterized healthy young male subjects (n = 10) performed 2 h of ergometer cycling followed by 4 h of recovery. In response to exercise there was pronounced hepatic uptake of lactate, pyruvate, various amino acids and dicarboxylic acids, indicating high demand for gluconeogenic substrates and increase in anaplerotic reactions of the citric acid cycle. Medium chain fatty acids e.g., caproic acid showed a clear hepatic uptake during exercise, underlining their potential role as regulators of gluconeogenesis and mitochondrial substrate oxidation. While most long chain fatty acids showed increased hepatic uptake, saturated fatty acids with carbon chain &amp;gt; 18 were released. In contrast to other amino acids, branched chain amino acids were not taken up or released from the liver at any time point. Notably, the hepato-splanchnic bed showed pronounced uptake of oxygen and release of CO2 during exercise indicating up-regulation of energy consuming metabolic processes. In conclusion, the data provide novel insight in the regulation of hepatic metabolism at rest and during exercise. Disclosure P. Plomgaard: None. C. Hu: None. J.S. Hansen: Employee; Self; Novo Nordisk A/S. X. Zhao: None. M. Hoene: None. X. Wang: None. N. Secher: None. H. Haering: None. R. Lehmann: None. G. Xu: None. C. Weigert: None.

Revisiting the Mechanism of Hydrolysis of Betanin.

Betanin (betanidin 5-O-β-D-glucoside) is a water-soluble plant pigment used as a color additive in food, drugs and cosmetic products. Despite its sensitivity to light and heat, betanin maintains appreciable tinctorial strength in low acidic and neutral conditions, where the color of other plant pigments, such as anthocyanins, quickly fades. However, betanin is an iminium natural product that experiences acid- and base-catalyzed hydrolysis to form the fairly stable betalamic acid and cyclo-DOPA-5-O-β-D-glucoside. Here, we show that the decomposition of betanin in aqueous phosphate solution pH 2-11 is subject to general base catalysis by hydrogen phosphate ion and intramolecular general acid and base catalysis, providing new insights on the mechanism of betanin hydrolysis. UV/Vis absorption spectrophotometry, 1 H NMR spectroscopy and mass spectrometry were used to investigate product formation. Furthermore, theoretical calculations support the hypothesis that the nitrogen atom of the tetrahydropyridine ring of betanin is doubly protonated, as observed for structurally simpler amino dicarboxylic acids. Our results contribute to the study of betanin and other pigments belonging to the class of betalains and to deepen the knowledge on the chemical properties of imino acids as well as on iminium-catalyzed modifications of carbonyl compounds in water.

Influence of amino acid imbalance in maternal and fetal organisms on the development of placental insufficiency and the course of the neonatal period.

The content of amino acids in maternal serum and umbilical cord blood during physiological pregnancy and placental insufficiency (PI) was estimated using ion-exchange chromatography. It was found that that the content of arginine, serine, glutamine, alanine, cysteine, methionine, tryptophan, leucine, phenylalanine and proline, which are involved in many metabolic processes necessary to maintain the normal functioning of the mother-placenta-fetus system, was decreases in maternal serum at PI. Opposite deviations have dicarboxylic amino acids, lysine, histidine, glycine, tyrosine and threonine, the number of which increases, strengthening the nitrogen imbalance. In the blood serum of the umbilical cord for most amino acids, was a similar direction of changes, but the degree of it is more pronounced. The opposite direction of changes is found for glycine, threonine, tyrosine, the content of which is reduced. The results of the study make it possible to broaden the understanding of the mechanisms of PI development and to offer informative tests for predicting the state of newborns.

PH and reduction sensitive bio-based polyamides derived from renewable dicarboxylic acid monomers and cystine amino acid

ABSTRACTNew reduction biodegradable and pH-sensitive linear nonpeptidic polyamides were synthesized by interfacial polycondensation of diamines and cystine amino acid with dicarbonyl dichlorides derived from renewable dicarboxylic acids. The polymer degradability by glutathione is enhanced by the introduction of disulfide linkages, and the response to pH change is enhanced by introducing pendant carboxylic acid functions. The results of pH sensitivity tests indicated that protonation–deprotonation of the carboxylic acid group at about pH of 4.1 with cation exchange capacity 4.5 meq g−1 and the disulfide bonds in polyamides were effectively cleaved.

Noncovalent interactions underlying binary mixtures of amino acid based ionic liquids: insights from theory

Mixtures of ionic liquids formed by blending a common 1-methyl-3-butylimidazolium [Bmim] cation with the dicarboxylic amino acid anions viz., aspartic acid [Asp], asparagine [Asn], glutamic acid [Glu], and glutamine [Gln], have been investigated by employing dispersion corrected density functional theory. Binary mixtures of [Bmim]2[Asp][Asn] and [Bmim]2[Glu][Gln] ionic liquids emerge with distinct structural patterns. Competition between the constituting anions towards cationic binding sites in acidic and basic (polar) amino acid binary mixtures engenders diverse noncovalent interactions, viz., C-HO hydrogen bonding, π-π stacking, and lpπ and CHπ interactions, which impart local liquid structure to these systems governing the structural and physicochemical properties of such double salt ionic liquids (DSILs). The DSIL conformers reveal distinct structural features arising from the middle, normal and front arrangements of anions combined with parallel, antiparallel, rotated or displaced orientations of the cations. The inclusion of dispersion corrections through the D3 method affects their binding energies significantly bringing forth alteration in their energy rank order. Molecular insights accompanying the ion aggregates provide directives for the use of DSILs with improved performance in tribological applications.