Amino Acids In Aqueous Solutions Research Articles

Detection of amino acid with metamaterial perfect absorbers in the terahertz band

At present, most amino acid detection techniques have the shortcomings of laborious equipment operation procedures, long detection periods, and low accuracy, which cannot meet the requirements of high-standard amino acid identification in the food industry. Based on the related literature, some amino acids are readily soluble in water. Therefore, a novel detection and identification method can be designed based on the different refractive indices of aqueous amino acid solutions. We introduce a terahertz metamaterial perfect absorber which component successively are a Si buffer layer, a solid metallic Au reflecting layer, a SiO2 depletion layer, a main structure array layer, and a cover layer from bottom to top. The main structure array layer composed of graphene four-opening square ring structure and a golden hemisphere. The absorber achieves perfect absorption based on the principle of impedance matching. It is innovatively applied for the detection of aqueous amino acid additives solution. The absorber has two modes with absorptivity of 99.86% and 99.99% at 5.9 THz and 8.1 THz, respectively. The sensing sensitivity of both modes can reaches 1.1 THz/RIU and 1.5 THz/RIU, respectively, which has obvious advantages in other reported sensors. Experimental results show that the proposed sensor can accurately identify the four amino acids selected by 100% in this study. The research presented this paper provides an essential reference for further development of metamaterial sensors.

Role of Charged Amino Acids in Sullying the Fluorescence of Tryptophan or Conjugated Dansyl Probe in Monomeric Proteins.

When Trp/dansyl probe conjugated to a monomeric protein is photoexcited, it is assumed that all emitted fluorescence originates solely from them. In this work, we show that hidden unconventional intrinsic chromophores (called ProCharTS) that originate from confined charge clusters in the protein can contaminate Trp/dansyl emission. Previous work has shown that charge recombination among charge-separated excited states of monomeric proteins, rich in charged residues, can emit weak luminescence (300-700 nm) overlapping with ProCharTS absorption (250-800 nm) and Trp (300-400 nm) and dansyl (400-600 nm) emission. We examine how this overlap taints the fluorescence arising from Trp/dansyl. We compared the effect of dense aqueous solutions of amino acids, Lys/Glu/Asp/Arg/His, on the fluorescence intensity decay/spectrum of N-acetyl-l-tryptophan amide (NATA). Significant broadening on the red side of Trp emission spectrum was observed solely in the presence of lysine, which appeared to be the most potent in altering the mono-exponential fluorescence decay of NATA. Interestingly, NATA in the presence of proteins α3C and dehydrin (DHN1), which are rich in Lys residues, showed substantial deviation from mono-exponential fluorescence decay in contrast to PEST wt and Symfoil-4P pv2, which lack Lys residues. Remarkably, Trp emission spectra among charge-rich proteins like α3W, PEST M1, and DHN1 CW1 were altered on the red side of Trp emission. Emission spectrum of dansyl-labeled human serum albumin (HuSA) was broadened and its fluorescence quenched with gradual addition of excess unlabeled HuSA, which displays bountiful ProCharTS luminescence. Our results unveil the additive influence of ProCharTS luminescence on Trp/dansyl emission with no measurable evidence of energy transfer.

Modeling the Distribution of Organic Carbon and Nitrogen in Impact Crater Melt on Titan

Abstract Titan is a chemically rich world that provides a natural laboratory for the study of the origin of life. Titan’s atmospherically derived C x H y N z molecules have been shown to form amino acids when mixed with liquid water, but the transition from prebiotic chemistry to the origin of life is not well understood. Investigating this prebiotic environment on Titan is one of the primary motivations behind NASA’s Dragonfly mission. One of its objectives is to visit the 80 km diameter Selk crater, where a melt sheet of liquid water would have formed during the impact cratering process. Organic molecules on Titan’s surface could have mixed with this water, forming molecules of prebiotic interest. Constraining how this material becomes trapped in the refreezing ice is necessary for Dragonfly to effectively target and interpret the samples it aims to acquire. In this work, we adapt the planetary ice model of Buffo et al. to Titan conditions to track how organic molecules will become trapped within the ice of the freezing melt sheet. We use HCN as a model impurity because of its abundance on Titan and its propensity to form amino acids in aqueous solutions. We show that without hydrolysis, HCN will be concentrated in the upper and middle portions of the resolidified melt sheet. In a closed system like Selk crater, the highest concentration of HCN appears 75% of the way into the frozen melt pond (relative to the surface), but HCN should be accessible at high concentrations nearer the surface as well.

Hydrogenation of CO2 to formic acid in biphasic systems using aqueous solutions of amino acids as the product phase

The catalytic hydrogenation of CO2 in a biphasic reaction system results in formic acid/amino acid solutions with potential use in agricultural applications such as cattle feed, avoiding energy demanding separation for decentralized BECCU concepts.

ДИНАМИКА РОСТА И ПОКАЗАТЕЛИ ФУНКЦИОНАЛЬНОГО ГОМЕОСТАЗА У МОЛОДНЯКА КРУПНОГО РОГАТОГО СКОТА ПРИ ВВЕДЕНИИ В РАЦИОН БИОКОМПЛЕКСА СВОБОДНЫХ L-АМИНОКИСЛОТ

The most complete realization of the genetic potential is possible only in healthy animals with healthy offspring. At the same time, as practice shows, a significant part of newborn calves have various pathologies associated with genetically determined disorders, the procedure of calving, drinking the first portion of colostrum, etc. The situation is complicated by the fact that in the first weeks and months of life, due to violations of the technology of cultivation and management at the complex, calves show clinical signs associated with bacterial and viral damage to the body against a background of weak immunity. Therefore, the cultivation of healthy young animals is one of the most pressing problems in dairy farming. The effect of a biocomplex of free L-amino acids in the form of an aqueous amino acid solution NOMAR148-R on the dynamics of live weight and indicators of functional homeostasis of heifers of a black-and-white Holstein breed was studied. The positive effect of this feed additive on the dynamics of the average daily increase in live weight of calves up to 6 months of age, protein metabolism and indicators of functional homeostasis has been established, which is confirmed by the results of studying the activity of indicator enzymes of transamination.The use of water-amino acid solution NOMAR148-R in the rearing of young cattle under the age of 2 months contributes to an increase in the rate of absolute increase in live weight of calves by an average of 11.1 %, while the average daily increase increases by an average of 24.2 %; when using the feed additive «ZEO-AMINO» at the age of 2 to 4 months, an increase in the rate of absolute live weight gain was established by an average of 15.4 %, the average daily increase in heifers increased by an average of 13.3 %; at the age of 4 to 6 months, an increase in the rate of absolute live weight gain was established by an average of 17.2 %, the average daily increase in heifers increased by an average of 5.7 %. The study of the processes of growth and development of animals, the metabolism of proteins, carbohydrates and lipids, as well as the activity of indicator enzymes of transamination allows us to testify that the use of the feed supplement «ZEO-AMINO» in the cultivation of young cattle contributes to an increase in the use of feed proteins, activates a number of vital functions associated with the participation of globulins in the transport of lipids, including cholesterol, steroid hormones, vitamins, as well as the performance of transport and protective functions by globulins, being factors of specific and nonspecific immunity in the normal course of physiological processes and ensuring functional homeostasis.

A Spectrophotometric Study of the Complexation of Magnesium(II) with a Number of Amino Acids in Aqueous Solutions

A Spectrophotometric Study of the Complexation of Magnesium(II) with a Number of Amino Acids in Aqueous Solutions

Sulfur dioxide absorption characteristics of aqueous amino acid solutions

The SO2 absorption/desorption performances of 14 aqueous amino acid solutions were evaluated to identify efficient absorbents to remove SO2 from coal-powered plant emissions. SO2 absorption/desorption experiments were conducted at 298.15 and 373.15 K, respectively, using 600 ppmv SO2 (N2 balance) and N2 purging. Thereafter, the absorption/desorption loadings and rates of the solutions, as well as their net cyclic capacities, were compared. The SO2 absorption mechanisms were explored via 13C NMR, 1H NMR, and UV–Vis analyses, and the relationship between the pKa values and absorption performances of the 14 aqueous amino acid solutions was investigated. Furthermore, the effects of absorption temperature, absorbent concentration, and inlet SO2 concentration on the SO2 absorption performances of the solutions were explored. 5-Aminovaleric acid, 4-aminobutyric acid, β-alanine, and histidine were identified as suitable SO2 absorbents based on their absorption/desorption performances and their net cyclic capacities. Furthermore, the net cyclic capacities of these four absorbents were similar or superior to those of previously reported deep eutectic solvents and ionic liquids. The results of this study provide a strategy for preparing eco-friendly SO2 absorbents.

Observation of intra- and intermolecular vibrational coherences of the aqueous tryptophan radical induced by photodetachment.

The study of the photodetachment of amino acids in aqueous solution is pertinent to the understanding of elementary processes that follow the interaction of ionizing radiation with biological matter. In the case of tryptophan, the tryptophan radical that is produced by electron ejection also plays an important role in numerous redox reactions in biology, although studies of its ultrafast molecular dynamics are limited. Here, we employ femtosecond optical pump-probe spectroscopy to elucidate the ultrafast structural rearrangement dynamics that accompany the photodetachment of the aqueous tryptophan anion by intense, ∼5-fs laser pulses. The observed vibrational wave packet dynamics, in conjunction with density functional theory calculations, identify the vibrational modes of the tryptophan radical, which participate in structural rearrangement upon photodetachment. Aside from intramolecular vibrational modes, our results also pointto the involvement of intermolecular modes that drive solvent reorganization about the N-H moiety of the indole sidechain. Our study offers new insight into the ultrafast molecular dynamics of ionized biomolecules and suggests that the present experimental approach can be extended to investigate the photoionization- or photodetachment-induced structural dynamics of larger biomolecules.

Biomimetic crosslinking of collagen gels by energetic electrons: The role of L-lysine

Energetic electrons have recently evolved as a powerful tool for crosslinking bio-derived hydrogels without the need for adding potentially hazardous reagents. Application of this approach allows for synthesis of biomimetic collagen-derived networks of highly tunable properties and functionalization. Yet, the underlying reaction kinetics are still not sufficiently established at this point. While hydroxyl radicals are generated by energetic electron-induced hydrolysis of water and play a key role in introducing covalent bonds between network fibers, a detailed mechanistic understanding would significantly increase applicability. We present a comprehensive analysis of central aspects of the reactivity between the hydroxyl radical (•OH) and collagen, elastin, glycine (Gly) and l-lysine (Lys). Pulse radiolysis (PR), solid state nuclear magnetic resonance (NMR), ultraviolet-visible absorption spectroscopy (UV/VIS) and electron spray ionization mass spectrometry (ESI-MS) shine light on distinct features of the crosslinking process. These highlight retained protein backbone integrity in collagen and elastin whilst Lys's ability to form several imine bonded Lys-Lys-species suggests striking similarities to crosslinking via lysyl oxidase catalysis in vivo. Thus, energetic electron based crosslinking opens the venue for customized hybrid gels of outstanding biomimicry and –compatibility. Statement of significanceEnergetic electron beam treatment constitutes a highly attractive approach to establish chemical bonds between (bio) molecules. Although a convincing number of publications showed the versatility regarding crosslinking of bioderived hydrogels, insights into the underlying chemistry are still unestablished at this point. The present work unravels the mechanistics of energetic electron induced processes in collagen and elastin hydrogels as well as several abundant amino acids in aqueous solution. As key finding we demonstrate, that i) the connection between polymer chains is dominated by amino acid side chain interaction and ii) two single l-lysine molecules form an imine bond between the terminal amino group of one molecule and the delta carbon of the second molecule. We also consider the formation of H-bonds as a second crosslinking pathway. These findings open up for advanced, optionally spatially resolved biomaterials design.

Theoretical electronic circular dichroism investigations of chiral amino acids and development of separation and identification methods independent of standards

Through an appropriate computational protocol and environmental simulation, a satisfactory fit was observed for the theoretical electronic circular dichroism (ECD) spectra of 19 chiral amino acids (AAs), which correspondeds to the forms of the AAs in aqueous solution. Methods for enantioseparation of these chiral AAs by capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) were developed. Combining ECD with chromatographic separation methods, enantiomers were identified and quantified independent of a single enantiomer standard.

Physicochemical study on molecular interactions of the active pharmaceutical ingredient ionic liquid domiphen salicylate with amino acids at different temperatures

The molecular interactions between the active pharmaceutical ingredient ionic liquid domiphen salicylate ([Dom][Sal]) and some amino acids (glycine, L-alanine, L-valine, L-leucine) in aqueous solution were studied. In order to accomplish this objective, the volume, conductivity and UV–vis spectroscopy of ternary systems were measured at different temperatures. The infinite dilution apparent molar volume, V2,φ0, transfer volume, ΔtV0, hydration number, nH and infinite dilution apparent molar expansibility, Eφ0 of amino acids in aqueous [Dom][Sal] solution were derived from the measured density data. Side chain contributions to V2,φ0 have been estimated. Critical micelle concentration, cmc, and thermodynamic properties of micellization (ΔGm0, ΔHm0,ΔSm0) for [Dom][Sal] in aqueous amino acids solutions were calculated using electrical conductivity data. The binding constant Kb of the amino acid with [Dom][Sal] was estimated based on the maximum absorbance data of the UV–vis spectroscopy. The impacts of temperature, concentration and the length of aliphatic chain of amino acids on these parameters were discussed. The mentioned parameters was employed to unveil the solute–solvent interactions in ternary systems.

Semiquantitative Visual Chiral Assay with a Pseudoenantiomeric Fluorescent Sensor Pair.

A new red-light-emitting fluorescent probe (R)-5 was synthesized. In the presence of Zn2+, this compound was found to exhibit good enantioselective fluorescence enhancement at λ = 655 nm when treated with a variety of amino acids in aqueous solution. This probe in combination with a green-light-emitting probe (S)-4 that has enantioselective fluorescence enhancement at λ = 505 nm has formed a pseudoenantiomeric sensor pair because of their opposite enantioselectivities. This sensor pair can simultaneously detect both enantiomers of a chiral amino acid at two very different wavelengths (Δ = 150 nm). It was used to visually and semiquantitatively determine the enantiomeric compositions of amino acids. For example, when a 1:1 mixture of (R)-5 and (S)-4 was treated with Zn(OAc)2 and histidine samples of 0-100% [d-His], the color of the mixtures changed from green to yellow, orange, and red under a UV lamp (365 nm), which allowed a quick quantification of [d-His]%. This is the first example of using fluorescence to visually quantify the enantiomeric composition of chiral compounds.

A Simple Method to Reduce the Optimized Parameters of Aqueous Amino Acid Solutions Using Association EOSs

Bringing up dissociation/ association equilibria, four new correlated equations are suggested for fixing the parameters of less investigated amino acid systems in a given value for two association models including PC-SAFT and CPA EOSs. Correlated parameters including co-volume parameter, association volumes, and the number of segments are dependent on the molecular weight of amino acids and have derived optimizing and fitting the parameters of the much-used aqueous amino acid solution. Moreover, to indicate the applicability of offered new equations, these formulas are utilized to reduce the number of optimized parameters from six to four for less investigated amino acid solutions. In the case of PC-SAFT EOS, the number of segments and association volume are fixed in a specified value and used to adjust four other parameters of PC-SAFT EOS including the segment of diameter, association energy, dispersion energy, and binary interaction parameter for less investigated amino acid solutions. In the case of CPA model, the correlated parameters are co-volume parameter and association volume, and these two parameters are applied to optimize four other parameters of CPA model such as temperature-dependent energy parameter containing a0 and c1, association energy, and binary interaction parameter. Also, the solubility of studied systems is predicted at different temperatures for aqueous binary solutions. Furthermore, osmotic coefficients and water activity of these less investigated systems are evaluated. In the case of PC-SAFT model, the calculated AADs for liquid density, activity coefficient, water activity, osmotic coefficient, and solubility are 0.0032, 0.0864, 0.0058, 0.051, and 4.46*10-4, respectively. For CPA model, the AADs of these thermodynamic properties are 0.0117, 0.075, 0.0023, 0.16, and 2.79*10-4, respectively. Both models can reproduce the literature data as well, and though the CPA model is a semi-empirical EOS, it doesn’t have irrelevant answers.

Analyzing the driving forces of insulin stability in the basic amino acid solutions: A perspective from hydration dynamics.

Amino acids having basic side chains, as additives, are known to increase the stability of native-folded state of proteins, but their relative efficiency and the molecular mechanism are still controversial and obscure as well. In the present work, extensive atomistic molecular dynamics simulations were performed to investigate the hydration properties of aqueous solutions of concentrated arginine, histidine, and lysine and their comparative efficiency on regulating the conformational stability of the insulin monomer. We identified that in the aqueous solutions of the free amino acids, the nonuniform relaxation of amino acid-water hydrogen bonds was due to the entrapment of water molecules within the amino acid clusters formed in solutions. Insulin, when tested with these solutions, was found to show rigid conformations, relative to that in pure water. We observed that while the salt bridges formed by the lysine as an additive contributed more toward the direct interactions with insulin, the cation-π was more prominent for the insulin-arginine interactions. Importantly, it was observed that the preferentially more excluded arginine, compared to histidine and lysine from the insulin surface, enriches the hydration layer of the protein. Our study reveals that the loss of configurational entropy of insulin in arginine solution, as compared to that in pure water, is more as compared to the entropy loss in the other two amino acid solutions, which, moreover, was found to be due to the presence of motionally bound less entropic hydration water of insulin in arginine solution than in histidine or lysine solution.

Terahertz spectral nondestructive detection of amino acid molecules in aqueous solution

Only in liquid environment can most biomolecules maintain their biological activity, the realization of terahertz (THz) spectrum detection of water-bearing biomolecules has an important application value for the research of the function and structure of active biomolecules and non-invasive biomedical detection. In this paper, by using the THz radiation source generated by LiNbO3 light rectification, and combing with the local electric field enhancement effect of the flared gradient parallel flat waveguide, we have built a THz time domain spectral measurement system that can detect the trace amounts of living cells and aqueous biomolecules, which can implement THz spectral detection of 4-aminobenzoic acid and glutamic acid in solution. The results show that 4-aminobenzoic acid and glutamic acid in aqueous solution have obvious and unique characteristic absorption peaks in the frequency band of 0.1–2.0 THz when the effect of water on THz wave absorption is removed. The acquisition of characteristic absorption spectrum of amino acid aqueous solution in THz frequency band lays a foundation for the detection of active biological macromolecules or tissues.

Dielectric dispersion, relaxation processes and interaction investigation by time domain reflectometry, thermal analysis and spectral implications on aromatic amino acid in aqueous solution

A first characterization and its signal analysis of various low molecular weight aromatic amino acid(L-Tryptophan and L-Tyrosine) over a broad frequency region. Our present principle researches focused on aqueous solutions to amino acids over 10MHz to 50GHz (0.01MHz≤ν ≤50GHz) using Time Domain Reflectometry(TDR). The molecular dynamics and dielectric relaxation significance of aromatic amino acid on different mole fraction and temperature were determined. From our obtained signal analysis various dielectric parameters, dispersed relaxation times, thermodynamic parameters, correlation factors are revealed. Correlation between heat flow with relaxation time and fragility through thermal analysis-Differential Scanning Calorimetry(DSC) are well described. Thermal analysis incites the dependency on glass transition temperature, dielectric strength and temperature. Confirmation of inter and intra molecular interaction and its mixture groups by FT-IR, FT-Raman and NMR analysis.

Physico-chemical Characteristics of Amino Acids in Aqueous Solution of Amikacin Sulphate

Physico-chemical Characteristics of Amino Acids in Aqueous Solution of Amikacin Sulphate

Equilibria Studies on Nickel(II) Complexes with 1,10-Phenanthroline Derivatives and Some Amino Acids in Aqueous Solution

In recent years, an increase in the biological applications of metal complexes of biologically active ligands has been observed due to their key role in clinical treatments. A potentiometric titration technique has been used to determine the protonation constants of biologically active ligands {glycine (gly), leucine (leu), methionine (met), phenylalanine (phe), tryptophan (trp), asparagine (asn), glutamine (gln), 1,10-phenanthroline (phen), 4-methyl-phenanthroline (4-mphen), 5-methyl-phenanthroline (5-mphen), 3,4,7,8-tetramethyl-1,10-phenanthroline (3,4,7,8-tmphen), 5-nitro-phenanthroline (5-nphen)} and the stability constants of their (1:1) and (1:1:1) complexes with Ni(II) ion (I = 0.100 mol·L–1 KCl and T = 298.15 K). The protonation constants of the biologically active ligands and the stability constants of the (1:1) and (1:1:1) complexes of Ni(II) with the biologically active ligands have been computed by using the BEST program. Moreover, the SPE program has been used to determine the distribution of the species that occurred in the aqueous solution medium. The relative stabilities of the (1:1:1) Ni(II) complexes are compared with those of the corresponding (1:1) Ni(II) complexes in terms of Δlog10K values. The effect of phenanthroline substituents (4-methyl, 5-methyl, 3,4,7,8-tetramethyl, 5-nitro) on the nature of the Ni(II) complexes is evaluated.

Extraction of Histidine, Proline, and Methionine and Their Mixtures Using Systems Based on N-VinylFormamide

Methods are proposed for the extraction of amino acids histidine, methionine, and proline from aqueous media with water-soluble polymers for their subsequent determination by capillary electrophoresis. Regularities of the interphase distribution of analytes in water–salt extraction systems based on poly-N-vinyl formamide and its copolymer with N-vinylimidazole are revealed and their efficiency is proved. The rate of formation of a two-phase system water-soluble polymer–aqueous salt solution of amino acid is substantially affected by the molecular weight and intrinsic viscosity of the extractant. The effect of the volume ratio of water and organic phases on the efficiency of extraction of histidine, methionine, and proline is studied, also on their simultaneous presence; quantitative characteristics of the process are calculated. Homo- and copolymers of N-vinylformamide are used for the efficient extraction and extraction separation of a histidine−methionine mixture. Partition coefficients and the recoveries of amino acids are specified in the systems containing poly-N-vinylformamide and its copolymer with N-vinylimidazole in the presence of an ammonium sulfate salting-out agent. The conditions for the electrophoretic determination of amino acids are optimized, i.e., the composition of the buffer solution and the type and concentration of the micelle-forming agent. The developed method for the electrophoretic separate determination of amino acids with the preliminary extraction of the target components with water-soluble polymers can be recommended for routine analyses in determining the safety of foodstuffs, energy drinks, and pharmaceuticals.

Carbon Dioxide Capture by Chemical Solvents Based on Amino Acids: Absorption and Regeneration

AbstractThe use of sodium salts of aqueous solutions of different amino acids (glycinate and prolinate) for carbon dioxide (CO2) separation by chemical absorption is analyzed in a bubble‐column reactor under different experimental conditions of solvent concentration and gas flow rate. The differences in absorption rate and reaction mechanism caused by the presence of carboxylic groups in comparison to the case without (monoethanolamine and pirrolidine) are evaluated. Glycinate solvent reaches a similar behavior than monoethanolamine aqueous solutions but with a higher destabilization of carbamate that allows to increase CO2 loading. Prolinate exhibits a similar behavior than pirrolidine at low CO2 loadings. Both solvents show a significant reduction in absorption capacity when stripping regeneration is carried out.