Amino Acid L-arginine Research Articles

Abstract 7660: L-Arginine metabolism is of prognostic relevance in women with breast cancer, but varies considerably between subtypes in vitro - A bedside-to-bench translational approach

Abstract Availability of the semi-essential amino acid L-arginine (L-arg) is limiting for proliferation in highly proliferative tissues. L-Arg is also a substrate for nitric oxide synthases (NOS) and arginases (ARG) 1 and 2. Methylation of L-arg residues within proteins by protein L-arg methyltransferases (PRMTs) leads to asymmetric (ADMA) and symmetric dimethylarginine (SDMA). Protein L-arg methylation is an important post-translational mechanism to regulate gene expression and cell cycle control. We measured L-arg and its metabolites in a prospective cohort of patients with primary breast cancer (BC). We further measured these metabolites and expression of genes involved in L-arg metabolic pathways in cell lines representing intrinsic BC subtypes. Plasma L-arg-related metabolite concentrations from 243 women with primary BC were associated with total mortality and disease recurrence during a median follow-up of 88 (IQR, 82-93) months. MCF-7, BT-474, SK-BR-3, and MDA-MB-468 cells representing ER-positive, HER2-positive, and triple negative BC were cultured in standard conditions and compared to MCF-12A normal breast epithelial cells. The plasma (in vivo) and intracellular concentrations (in vitro) of L-arg, L-ornithine (L-orn), L-citrulline (L-cit), ADMA, and SDMA were measured by UPLC-MS/MS. mRNA expression was quantified by qRT-PCR and protein expression was analyzed by Western Blot. In vivo, the plasma concentrations of all L-arg metabolites differed significantly between BC patients and healthy controls. L-Arg and ADMA were significantly higher in patients with recurrent disease and in those who died during follow up. ADMA was significantly associated with total mortality and recurrent disease in Luminal A patients; low L-orn/L-arg ratio was associated with survival in HER2+ BC patients, and low L-cit was associated with survival in triple negative BC. With the exception of MCF-7 cells, DDAH1 and DDAH2 mRNA concentrations in vitro were significantly higher in BC cells than in MCF-12A cells (DDAH1: 32-44 fold, DDAH2: 1.7-4.2 fold; p<0.05). These differences were mirrored by DDAH1 and DDAH2 protein concentrations. By contrast, MCF-7 cells were characterized by low DDAH1 and DDAH2, but high PRMT4 and PRMT6 mRNA expression and high L-arg content. BT-474 cells showed high ARG2 expression and high L-arg and L-orn concentrations, and MDA-MB-468 cells had the highest L-cit/L-arg ratio. In conclusion, regulation of L-arg metabolic pathways shows a complex and differential pattern between intrinsic BC subtypes, which is mirrored in representative cell lines in vitro. ADMA is a prognostic biomarker in Luminal A breast cancer patients; its metabolizing enzyme, DDAH, is highly overexpressed in BC cells in vitro. Thus, fingerprinting of L-arg metabolism may offer novel personalized treatment options within intrinsic BC subtypes. Citation Format: Juliane Hannemann, Leticia Oliveira Ferrer, Antonia Röglin, Fiona Kleinsang, Volkmar Müller, Isabell Witzel, Rainer Böger. L-Arginine metabolism is of prognostic relevance in women with breast cancer, but varies considerably between subtypes in vitro - A bedside-to-bench translational approach [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7660.

Antiproliferative and Antimigratory Activity of Poly-gallic Acid in Cancer Cell Lines.

Enzyme-mediated grafting of poly (gallic acid) (PGAL) and L-arginine and a-L-lysine onto PGAL produces reactive oxygen species (ROS)-suppressor multiradical molecules with low cytotoxicity, high thermostability and water solubility with cancer treatment potential. This study examined the anticancer effects of these molecules in hepatic (HepG2, ATCC HB-8065), breast (MCF7, ATCC HTB-22), and prostate (PC-3, ATCC CRL-1435 and DU 145, ATCC HTB-81) cancer cell lines, as well as in fibroblasts from healthy human skin as control cells. PGAL was synthesized by the oxidative polymerization of the naturally abundant GA using laccase from Trametes versicolor. Insertions of amino acids L-arginine and α-L-lysine on the PGAL chain were carried out by microwave. The cells of dermal fibroblast (Fb) were obtained from primary skin cultures and isolated from skin biopsies. The cancer cells lines of hepatic (HepG2), breast (MCF7), and prostate (PC-3, DU 145) were obtained from ATCC. The viability of the cancer cells and the primary culture was obtained by the MTT assay. Proliferation was demonstrated by crystal violet assay. Cell migration was determined by Wound healing assay. Finally, cell cycle analysis was carried out with cells. The results show that 200 μg/ml of PGAL cultured in vitro with prostate cancer cells decreased viability, proliferation, and migration, as well as arrested cells in the G1 and S phases of the cell cycle. In contrast, the dermal fibroblasts and the hepatic line remained unaffected. The random grafting of L-Arg and a-L-Lys onto the PGAL chain also decreased the viability of prostate cancer cells. PGAL and PGAL-grafted amino acids are potential adjuvants for prostate cancer treatment, with improved physicochemical characteristics compared to GA.

Analysis of heterologous expression of phaCBA promotes the acetoin stress response mechanism in Bacillus subtilis using transcriptomics and metabolomics approaches.

Acetoin, a versatile platform chemical and popular food additive, poses a challenge to the biosafety strain Bacillus subtilis when produced in high concentrations due to its intrinsic toxicity. Incorporating the PHB synthesis pathway into Bacillus subtilis 168 has been shown to significantly enhance the strain's acetoin tolerance. This study aims to elucidate the molecular mechanisms underlying the response of B. subtilis 168-phaCBA to acetoin stress, employing transcriptomic and metabolomic analyses. Acetoin stress induces fatty acid degradation and disrupts amino acid synthesis. In response, B. subtilis 168-phaCBA down-regulates genes associated with flagellum assembly and bacterial chemotaxis, while up-regulating genes related to the ABC transport system encoding amino acid transport proteins. Notably, genes coding for cysteine and D-methionine transport proteins (tcyB, tcyC and metQ) and the biotin transporter protein bioY, are up-regulated, enhancing cellular tolerance. Our findings highlight that the expression of phaCBA significantly increases the ratio of long-chain unsaturated fatty acids and modulates intracellular concentrations of amino acids, including L-tryptophan, L-tyrosine, L-leucine, L-threonine, L-methionine, L-glutamic acid, L-proline, D-phenylalanine, L-arginine, and membrane fatty acids, thereby imparting acetoin tolerance. Furthermore, the supplementation with specific exogenous amino acids (L-alanine, L-proline, L-cysteine, L-arginine, L-glutamic acid, and L-isoleucine) alleviates acetoin's detrimental effects on the bacterium. Simultaneously, the introduction of phaCBA into the acetoin-producing strain BS03 addressed the issue of insufficient intracellular cofactors in the fermentation strain, resulting in the successful production of 70.14g/L of acetoin through fed-batch fermentation. This study enhances our understanding of Bacillus's cellular response to acetoin-induced stress and provides valuable insights for the development of acetoin-resistant Bacillus strains.

The effect of L-Arginine from Giant Snake Head fish (Channa micropeltes) on neuroinflammation and neuron damage in traumatic brain injury in rats

Backgrounds: Traumatic brain injury has high mortality and morbidity. The involvement of neuroinflammatory responses and neuronal damage in traumatic brain injury is the basis for the development of renewable neuroprotective agents, one of which is the amino acid L-Arginine. The amino acid L-Arginine which can be found in Giant Snake Head fish (Channa micropeltes) is thought to inhibit anti-inflammatory effects through the Arg-1 signaling pathway. Aims: To prove and analyze the effect of giving L-Arginine Giant Snake Head fish on neuroinflammation and neuronal damage in a rat model of traumatic brain injury. Methods: This randomized controlled trial (RCT) study used a posttest-only control group design. Thirty-five male rats (Rattus norvegicus) with the Wistar strain were randomly divided into five treatment groups, namely the normal control group (N), negative control (KN), and 3 treatment groups (A-C). The KN and A-C groups were modeled after traumatic brain injury and given L-Arginine at a dose of 0.5; 1.5; and 3 g/kgBW/day for 7 days specifically A-C. Brain tissue samples were used for the examination of TLR4, TNF-α, GSDMD, Caspase-3, and histopathological features. All data were analyzed using the Kruskall-Wallis test, except for GSDMD expression with a significance <0.05. Results: The mean TLR4 expression in A (15.7 ± 5.35), B (12.9 ± 5.67), and C (11.4 ± 6.27) were lower and significant compared to KN, but higher and significant compared to N. The same pattern appears in the decrease in TNF-α expression, Caspase-3 expression, and histopathology of brain tissue damage. The mean relative expression of GSDMD to N in A (1.3 ± 0.53), B (1.2 ± 0.52), and C (1.2 ± 0.60) was higher than in KN, but not significant. Relative expression of GSDMD to Beta Actin, A and B have the same higher expression than C, KN, and N. Conclusion: Expression of TLR-4, TNF-α, Caspase-3 and histopathology of brain tissue damage in traumatic brain injury model rats given Giant Snake Head fish L-Arginine were lower than without L-Arginine. Meanwhile, the expression of GSDMD in traumatic brain injury model rats when given Giant Snake Head fish L-Arginine was slightly higher than without L-Arginine.

Green synthesis approach using deep eutectic solvents to enhance the surface functional groups on porous carbon for CO2 capture

This study explores the potential of green solvents using amino acids-based deep eutectic solvents to alter surface functionality of activated carbon thus enhancing the carbon dioxide (CO2) adsorption capacity. Green solvent is prepared by mixing an amino acid (L-Arginine) with ethylene glycol to form amino acid-based deep eutectic solvents. Amino acid-based deep eutectic solvents were used to modify the surface functionalities of activated carbon derived from palm shell waste. The change in surface functional groups and surface morphology of the modified activated carbon samples were characterized by Fourier-transform infrared spectroscopy and Scanning electron microscopy-energy dispersive X-ray analysis. Then, CO2 removal performance was performed using a packed-bed CO2 adsorption reactor to evaluate CO2 breakthrough time and adsorption capacity. CO2 adsorption experiments were measured at a certain temperature (25–45°C), at a fixed feed flow rate and CO2 concentration of 200 mL/min and 15%. It was observed that modified activated carbon showed the highest breakthrough time (15.2 min) compared to raw palm shell (5.2 min) at an adsorption temperature of 25°C. CO2 breakthrough times significantly decreased with increasing adsorption temperature because of physical adsorption.

Potential Use of L-Arginine Amino Acids towards Proliferation and Migratory Speed Rate of Human Dental Pulp Stem Cells.

L-arginine is a semi-essential amino acid produced by the body which has an important role in the process of stem cell regeneration. However, under inflammatory conditions, denaturation of pulp amino acids and proteins occurr resulting in a decrease in the ability of stem cells to self-renew. Therefore, in this study, L-arginine was added in vitro to the culture media Dulbecco's Modified Eagle Medium - (DMEM) of human dental pulp stem cells (hDPSCs) to analyse the potential of L-arginine on migration and proliferation by comparing between 3 concentrations, namely 300, 400, 500 μmol/L and control group (DMEM), to obtain the most optimal concentration for proliferation and migration. Serum-starved hDPSCs were divided into four groups: control: hDPSCs in DMEM; hDPSCs in 300 μmol/L of the L-Arginine based culture media group; hDPSCs in 400 μmol/L of the L-Arginine based culture media group; and hDPSCs in 500 μmol/L of the L-Arginine based culture media group, which were added in two separate 24-well-plates (5×104 cell/well) for proliferation and migration evaluation. The proliferation of all groups was measured by using a cell count test (haemacytometer and manual checker) after 24 h. The migratory speed rate of all groups was measured by using cell migration assay (scratch wound assay) after 24 h. Cell characteristics were evaluated under microscope that was then evaluated using image-J® interpretation. This image J represented the measurement of migratory speed rate (nm/h) data. Statistical analysis was conducted using one-way ANOVA and post hoc Bonferroni (p<0.05) for proliferation and post hoc LSD (p<0.05) for migration. There was a statistically significant difference in hDPSCs proliferation among various concentration groups of the L-Arginine based solution (300, 400 and 500 μmol/L) compared to the control group (p<0.05). There was a statistically significant difference in the migratory speed rate of hDPSCs at 500 μmol/L of the L-Arginine based solution group compared to lower concentrations and control group (p<0.05). All three concentrations of L-arginine can induce proliferation of hDPSCs. L-arginine at 500 μmol/L can induce higher hDPSCs proliferation and faster migration at 24 hours compared to lower concen-trations and control.

Ammonium nanochelators in conjunction with arginine-specific enzymes in amperometric biosensors for arginine assay

Amino acid L-arginine (Arg), usually presented in food products and biological liquids, can serve both as a useful indicator of food quality and an important biomarker in medicine. The biosensors based on Arg-selective enzymes are the most promising devices for Arg assay. In this research, three types of amperometric biosensors have been fabricated. They exploit arginine oxidase (ArgO), recombinant arginase I (ARG)/urease, and arginine deiminase (ADI) coupled with the ammonium-chelating redox-active nanoparticles. Cadmium-copper nanoparticles (nCdCu) as the most effective nanochelators were used for the development of ammonium chemosensors and enzyme-coupled Arg biosensors. The fabricated enzyme/nCdCu-containing bioelectrodes show wide linear ranges (up to 200 µM), satisfactory storage stabilities (14 days), and high sensitivities (A⋅M−1⋅m−2) to Arg: 1650, 1700, and 4500 for ADI-, ArgO- and ARG/urease-based sensors, respectively. All biosensors have been exploited to estimate Arg content in commercial juices. The obtained data correlate well with the values obtained by the reference method. A hypothetic scheme for mechanism of action of ammonium nanochelators in electron transfer reaction on the arginine-sensing electrodes has been proposed.Graphical abstract

Solution-processed graphene films for electrochemical monitoring of extracellular nitric oxide released by breast cancer cells

Nitric oxide (NO) plays an important role in cardiovascular function, immune response, and intercellular signaling. However, due to its short lifetime, real-time detection of NO is challenging. Herein, an electrochemical sensor based on fibronectin-modified, solution-processed graphene ink for NO detection is developed using a facile fabrication method involving spin-coating and hot-plate annealing. The sensor is first electrochemically characterized with a NO donor, spermine NONOate, exhibiting a dynamic range of 10–1000 μM. The fibronectin-functionalized graphene supports the attachment and growth of MDA-MB-231 breast cancer cells, as confirmed by optical microscopy. Extracellular NO production is stimulated using the amino acid L-arginine. NO production results in morphological changes to the adhered cells, which are reversible upon the addition of the NO synthase antagonist Nω-nitro-L-arginine methyl ester. The production of NO is also confirmed using real-time amperometric measurements with the fibronectin-functionalized graphene sensors. While this work focuses on NO detection, this potentially scalable platform could be extended to other cell types with envisioned applications including the high-throughput evaluation of therapeutics and biocompatible coatings.

Growth and improved properties of single crystal α-LiIO3 doped with amino acids

In this study, the effect of doping the amino acids L-arginine and L-nitroarginine on α-LiIO3 single crystal were presented. Bulk crystals were grown both from solutions doped with L-arginine and L-nitroarginine and from pure solution of α-LiIO3.When doped with L-arginine and L-nitroarginine the optical quality of the crystals was improved and growth rate was increased. These grown crystals were studied by single-crystal X-ray diffraction, IR and UV–Vis spectroscopy, Vickers microhardness, diffuse reflection, and second harmonic generation methods. Studies of microhardness and nonlinear optical activity showed that the properties of α-LiIO3 crystals were improved in the presence of L-arginine and L-nitroarginine. UV–Vis transmittance was improved in the presence of L-arginine (range 370–800 nm) and L-nitroarginine (range 290–370 nm). The second harmonic generation activity of the crystals α-LiIO3 grown with L-arginine (1.16 times) and L-nitroarginine (1.18 times) dopants is higher than that of pure α-LiIO3. The energy of the band gap increases by 1.2 times in the case of arginine dopants, and it decreases by 1.37 times in the case of the nitroarginine dopants, compared to that for the pure α-LiIO3.

Interaction of anti-inflammatory drug naproxen with essential amino acids: Quantitative thermodynamic insights

A combination of ultrasensitive isothermal titration calorimetry and uv–visible spectroscopy has been employed to unravel interaction of anti-inflammatory drug naproxen with five essential amino acids L-arginine, L-lysine, L-phenylalanine, L-valine and L-tryptophan. The nature of interaction in each case has been examined based on standard molar enthalpy of interaction ΔHmo and changes in the spectral properties. The values and sign of ΔHmo have been related with the nature of interacting groups and solvent reorganization as a result of drug-amino acid association. Exothermic standard molar enthalpy of interaction of naproxen with L-arginine indicated significant of polar interactions, and endothermic heat effects with all other amino acids suggested dominance of hydrophobic effect and desolvation penalty in the association process. The overall value of enthalpy of interaction for all the studied amino acids is less than 2 kJmol-1 suggesting that these interactions are not very strong. The uv–visible results provided support to ITC results in obtaining mechanistic insights into the nature of interactions. The results derive significance from the fact that sometimes anti-inflammatory drug naproxen may be administrated along with supplements of essential amino acids. In case there is a strong drug-amino acids interaction, efficacy of each one may be affected.

Basic amino acids treatment prior to spray drying improved the functional properties and flavor attributes of soy protein isolate

This work investigated the effect of treatment of soy protein isolate (SPI) with basic amino acids (BAA) (l-Arginine, l-Histidine, and l-Lysine) at different concentrations prior to spray drying on the beany-flavor and functional properties. The results illustrated that the BAA prominently improved the solubility and emulsifying properties of SPI, and reduced the its release of beany-flavor compounds. Additionally, l-Arginine was more effective in increasing the solubility and emulsifying properties of the SPI than l-Histidine and l-Lysine. Notably, 0.3% l-Arginine improved the solubility, emulsifying activity index, emulsifying stability index of the SPI by 43.5%, 64.2% and 45.3% respectively. Through the headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS), the 0.3% BAA showed the better mitigation effect on the beany flavor of SPI among three addition concentrations. The increased ζ-potential showed that BAA enhanced the electrostatic repulsion of the SPI, facilitating its dissolution and formation of a more stable emulsion system. Surface hydrophobicity and fluorescence spectral results revealed that BAA enhance the exposure of hydrophobic groups, enhancing the stability of oil-water interface and promoting the interaction between beany-flavor compounds and SPI. These findings lay the theoretical groundwork for further research and application of soy protein.

Enhancing the antifouling and chlorine resistance capabilities of thin-film composite reverse osmosis via surface grafting of dipeptide

There has been constant progress in the development of innovative polyamide (PA) thin-film composite (TFC) reverse osmosis (RO) membranes to address limitations in fouling potential, chlorine resistance, salt rejection and water flux trade-offs. In this work, dipeptide of zwitterionic amino acid L-arginine, i.e., arginyl-arginine (Arg-Arg), was grafted on the surface of PA TFC RO membrane in order to simultaneously improve the antifouling properties, chlorine resistance, and separation performance. The interactions between the Arg-Arg dipeptide and PA layer were evidenced by Fourier transforms infrared spectroscopy and nuclear magnetic resonance spectroscopy, which have indicated the distinguished chemical grafting of Arg-Arg dipeptide on the RO membrane surface. The grafting of Arg-Arg dipeptide led to a thinner, smoother, more hydrophilic, and less negatively charged PA surface. The surface-modified membranes simultaneously exhibited enhanced desalination performances, antifouling and chlorine resistance properties. Compared to the neat TFC membrane, the water flux of Arg-Arg dipeptide-modified membrane was improved by 26.19%. The salt rejection also slightly increased from 96.25% to 98%. The roles of Arg-Arg dipeptide in altering the surface chemistry and the structure of the membranes are discussed to highlight the potential of surface-modified membranes in heightening the desalination performances of RO TFC membranes.

L-Arginine sulfate reduces irreversible protein binding in immobilized metal affinity chromatography

Immobilized metal affinity chromatography (IMAC) is a powerful technique for capture and purification of relevant biopharmaceuticals in complex biological matrices. However, protein recovery can be drastically compromised due to surface induced spreading and unfolding of the analyte, leading to fouling of the stationary phase. Here, we report on the kinetics of irreversible adsorption of a protease on an IMAC resin in a time span ranging from minutes to several hours. This trend correlated with the thermal data measured by nano differential scanning calorimetry, and showed a time-dependent change in protein unfolding temperature. Our results highlight that ‘soft’ proteins show a strong time dependent increase in irreversible adsorption. Furthermore, commonly used co-solvents for preservation of the native protein conformation are tested for their ability to reduce fouling. Thermal data suggests that the amino acid l-arginine is beneficial in preventing unfolding, which was confirmed in batch adsorption experiments. The choice of counter-ions has to be considered when using this amino acid. These results show that l-arginine sulfate decelerates the irreversible adsorption kinetics of proteins on the IMAC stationary phase to a greater extent than l-arginine chloride.

Amino acid promoted single-step carbon dioxide capture and mineralization integrated with polymer-mediated crystallization of carbonates

Integrated CO2 capture and mineralization is a promising technology for cutting CO2 emissions and associated environmental impacts. Two major challenges in CO2 mineralization in aqueous media are (1) the lack of green and energy-efficient processes and (2) limited applications of the produced carbonates. Here, we present a very efficient, environmentally friendly, and convenient integrated CO2 capture and mineralization method to produce functional calcium carbonate (CaCO3) particles. We use a gas diffuser reaction setup to bubble CO2 in liquid media containing reagents such as amino acid as CO2 absorption promotor, water-soluble polymers as crystal growth modifiers, and Ca2+ ions. Different concentrations of amino acid L-arginine with a fixed CO2 bubbling rate were investigated for Ca2+ conversion. At the optimized conditions, more than 90% Ca2+ was converted to CaCO3 within 5 min of CO2 bubbling at a nominal rate. Additionally, functional carbonates that could be used as dye, heavy metals adsorbents, and functional composite fillers are produced using crystal growth modifiers. The method is simple, efficient, eco-friendly, and could be used for CO2/Ca2+-rich industrial waste valorization.

Crystal Structure and Functional Characterization of Acetylornithine Aminotransferase from Corynebacterium glutamicum.

The amino acids l-arginine and l-ornithine are widely used in animal feed and as health supplements and pharmaceutical compounds. In arginine biosynthesis, acetylornithine aminotransferase (AcOAT) uses pyridoxal-5'-phosphate (PLP) as a cofactor for amino group transfer. Here, we determined the crystal structures of the apo and PLP complex forms of AcOAT from Corynebacterium glutamicum (CgAcOAT). Our structural observations revealed that CgAcOAT undergoes an order-to-disorder conformational change upon binding with PLP. Additionally, we observed that unlike other AcOATs, CgAcOAT exists as a tetramer. Subsequently, we identified the key residues involved in PLP and substrate binding based on structural analysis and site-directed mutagenesis. This study might provide structural insights on CgAcOAT, which can be utilized for the development of improved l-arginine production enzymes.

GC-MS Studies on Nitric Oxide Autoxidation and S-Nitrosothiol Hydrolysis to Nitrite in pH-Neutral Aqueous Buffers: Definite Results Using 15N and 18O Isotopes.

Nitrite (O=N-O-, NO2-) and nitrate (O=N(O)-O-, NO3-) are ubiquitous in nature. In aerated aqueous solutions, nitrite is considered the major autoxidation product of nitric oxide (●NO). ●NO is an environmental gas but is also endogenously produced from the amino acid L-arginine by the catalytic action of ●NO synthases. It is considered that the autoxidation of ●NO in aqueous solutions and in O2-containing gas phase proceeds via different neutral (e.g., O=N-O-N=O) and radical (e.g., ONOO●) intermediates. In aqueous buffers, endogenous S-nitrosothiols (thionitrites, RSNO) from thiols (RSH) such as L-cysteine (i.e., S-nitroso-L-cysteine, CysSNO) and cysteine-containing peptides such as glutathione (GSH) (i.e., S-nitrosoglutathione, GSNO) may be formed during the autoxidation of ●NO in the presence of thiols and dioxygen (e.g., GSH + O=N-O-N=O → GSNO + O=N-O- + H+; pKaHONO, 3.24). The reaction products of thionitrites in aerated aqueous solutions may be different from those of ●NO. This work describes in vitro GC-MS studies on the reactions of unlabeled (14NO2-) and labeled nitrite (15NO2-) and RSNO (RS15NO, RS15N18O) performed in pH-neutral aqueous buffers of phosphate or tris(hydroxyethylamine) prepared in unlabeled (H216O) or labeled H2O (H218O). Unlabeled and stable-isotope-labeled nitrite and nitrate species were measured by gas chromatography-mass spectrometry (GC-MS) after derivatization with pentafluorobenzyl bromide and negative-ion chemical ionization. The study provides strong indication for the formation of O=N-O-N=O as an intermediate of ●NO autoxidation in pH-neutral aqueous buffers. In high molar excess, HgCl2 accelerates and increases RSNO hydrolysis to nitrite, thereby incorporating 18O from H218O into the SNO group. In aqueous buffers prepared in H218O, synthetic peroxynitrite (ONOO-) decomposes to nitrite without 18O incorporation, indicating water-independent decomposition of peroxynitrite to nitrite. Use of RS15NO and H218O in combination with GC-MS allows generation of definite results and elucidation of reaction mechanisms of oxidation of ●NO and hydrolysis of RSNO.

A green amino acid-based solvent blended with diethanolamine solution for CO2 capture using micro-contactor

The current research aims at developing an amino acid-based green technology containing a secondary alkanolamine (DEA) and L-arginine amino acid (ARG) for CO2 capture process from a gas stream in a T-type micro-contactor. To strengthen the understanding of the mass transfer of biodegradable green ARG in the micro-reactor, the mass transfer performance of CO2 absorption has been experimentally assessed under liquid flow rate (QL: 3.0–9.0 ml/min), gas flow rate (QG: 120.0–300.0 ml/min) at a constant temperature of 45 °C, and atmospheric pressure. The aqueous composition of the blended solution was DEA-ARG (35–0 wt%), DEA-ARG (31–4 wt%), DEA-ARG (27–8 wt%), and DEA-ARG (23–12 wt%). It was found that an increase in the solvent flow rate from 3.0 to 9.0 ml/min enhanced the CO2 absorption efficiency (θ), volumetric gas-phase mass transfer coefficient (KGaV), and volumetric molar flux (NGaV) by 2.5, 12.8, and 2.6%, respectively. However, an increase in the gas flow rate from 120.0 to 300.0 ml/min reduces the efficiency by 6% but improves the KGaV and NGaV by 88% and 225%, respectively. Additionally, the KGaV values followed a declining trend as the contribution of the DEA in the blended solution increased. Employing response surface methodology (RSM), the optimized values for CO2 absorption efficiency and KGaV were attained 92.93% and 69.40 kmol/m3 h kPa for QL of 9.0 ml/min, QG of 263.4 ml/min, and DEA-ARG concentration, CDEA-ARG of (23–12 wt%). Comparing the gas–liquid mass transfer characteristics of the aqueous DEA-ARG mixture with the traditional aqueous amine solutions, it was illustrated that the presence of L-arginine amino acid with high composition of 12 wt%, as a substitute organic promoter in aqueous DEA 35 wt%, can boost the performance of CO2 absorption process.

Mechanistic insights into the lignin dissolution behavior in amino acid based deep eutectic solvents

Deep eutectic solvents (DESs) composed by amino acids (L-arginine, L-proline, L-alanine) as the hydrogen bond acceptors (HBAs) and carboxylic acids (formic acid, acetic acid, lactic acid, levulinic acid) as hydrogen bond donors (HBDs) were prepared and used for the dissolution of dealkaline lignin (DAL). The mechanism of lignin dissolution in DESs was explored at molecular level by combining the analysis of Kamlet-Taft (K-T) solvatochromic parameters, FTIR spectrum and density functional theory (DFT) calculations of DESs. Firstly, it was found that the formation of new hydrogen bonds between lignin and DESs mainly drove the dissolution of lignin, which were accompanied by the erosion of hydrogen bond networks in both lignin and DESs. The nature of hydrogen bond network within DESs was fundamentally determined by the type and number of functional groups in both HBA and HBD, which affected its ability to form hydrogen bond with lignin. One hydroxyl group and carboxyl group in HBDs provided active protons, which facilitated proton-catalyzed cleavage of β-O-4, thus enhancing the dissolution of DESs. The superfluous functional group resulted in more extensive and stronger hydrogen bond network in the DESs, thus decreasing the lignin dissolving ability. Moreover, it was found that lignin solubility had a closed positive correlation with the subtraction value of α and β (net hydrogen donating ability) of DESs. Among all the investigated DESs, L-alanine/formic acid (1:3) with the strong hydrogen-bond donating ability (acidity), weak hydrogen-bond accepting ability (basicity) and small steric-hindrance effect showed the best lignin dissolving ability (23.99 wt%, 60 °C). On top of that, the value of α and β of L-proline/carboxylic acids DESs showed some positive correlation with the global electrostatic potential (ESP) maxima and minima of the corresponding DESs respectively, indicating the analysis of ESP quantitative distributions of DESs could be an effective tool for DESs screening and design for lignin dissolution as well as other applications.

The Effectiveness of L-arginine in Clinical Conditions Associated with Hypoxia.

The review summarises the data of the last 50 years on the effectiveness of the amino acid L-arginine in therapeutic practice in conditions accompanied by different-origin hypoxia. The aim of this review was to analyse the literature and our research data on the role of nitric oxide in the modulation of individual physiological reactivity to hypoxia. The review considers the possibility of eliminating methodological conflicts in the case of L-arginine, which can be solved by taking into account individual physiological reactivity (or the hypoxia resistance factor). Considerable attention is paid to genetic and epigenetic mechanisms of adaptation to hypoxia and conditions of adaptation in different models. The article presents data on the clinical effectiveness of L-arginine in cardiovascular system diseases (hypertension, atherosclerosis, coronary heart disease, etc.) and stress disorders associated with these diseases. The review presents a generalised analysis of techniques, data on L-arginine use by athletes, and the ambiguous role of NO in the physiology and pathology of hypoxic states shown via nitric oxide synthesis. Data on the protective effects of adaptation in the formation of individual high reactivity in sportsmen are demonstrated. The review demonstrates a favourable effect of supplementation with L-arginine and its application depending on mitochondrial oxidative phosphorylation processes and biochemical indices in groups of individuals with low and high capacity of adaptation to hypoxia. In individuals with high initial anti-hypoxic reserves, these favourable effects are achieved by the blockade of NO-dependent biosynthesis pathways. Therefore, the methodological tasks of physiological experiments and the therapeutic consequences of treatment should include a component depending on the basic level of physiological reactivity.

Metabolic Profiles of Clinical Isolates of Drug-Susceptible and Multidrug-Resistant Mycobacterium tuberculosis: A Metabolomics-Based Study.

Mycobacterium tuberculosis (MTB) is a global and highly deleterious pathogen that creates an enormous pressure on global public health. Although several effective drugs have been used to treat tuberculosis, the emergence of multidrug-resistant Mycobacterium tuberculosis (MDR-MTB) has further increased the public health burden. The aim of this study was to describe in depth the metabolic changes in clinical isolates of drug-susceptible Mycobacterium tuberculosis (DS-MTB) and MDR-MTB and to provide clues to the mechanisms of drug resistance based on metabolic pathways. Based on the minimum inhibition concentration (MIC) of multiple anti-tuberculosis drugs, two clinical isolates were selected, one DS-MTB isolate (isoniazid MIC=0.06 mg/L, rifampin MIC=0.25 mg/L) and one MDR-MTB isolate (isoniazid MIC=4 mg/L, rifampin MIC=8 mg/L). Through high-throughput metabolomics, the metabolic profiles of the DS-MTB isolate and the MDR-MTB isolate and their cultured supernatants were revealed. Compared with the DS-MTB isolate, 128 metabolites were significantly altered in the MDR-MTB isolate and 66 metabolites were significantly altered in the cultured supernatant. The differential metabolites were significantly enriched in pyrimidine metabolism, purine metabolism, nicotinate and nicotinamide metabolism, arginine acid metabolism, and phenylalanine metabolism. Furthermore, metabolomics analysis of the bacterial cultured supernatants showed a significant increase in 10 amino acids (L-citrulline, L-glutamic acid, L-aspartic acid, L-norleucine, L-phenylalanine, L-methionine, L-tyrosine, D-tryptophan, valylproline, and D-methionine) and a significant decrease in 2 amino acids (L-lysine and L-arginine) in MDR-MTB isolate. The present study provided a metabolite alteration profile as well as a cultured supernatant metabolite alteration profile of MDR-MTB clinical isolate, providing clues to the potential metabolic pathways and mechanisms of multidrug resistance.