Amino Acids In Aqueous Solutions Research Articles

The primary photo-dissociation dynamics of amino acids in aqueous solution: breaking the Cα-bond.

We report a study of the primary photo-dissociation dynamics of aqueous alanine, isoleucine and proline by 200 nm UV pump-IR probe transient absorption spectroscopy. Photo-dissociation of the three amino acids predominantly results in decarboxylation, and 38 ± 7% of the excited alanine, 35 ± 10% of the excited isoleucine and 47 ± 10% of the excited proline zwitterions remain dissociated 100 picoseconds after the excitation. The decarboxylation occurs from a transient intermediate with a lifetime of ∼20 picoseconds to which we assign the excited state of the amino acids based on comparison of the measured and calculated IR spectra, and calculated excited state energy surfaces.

Effect of the Conformation of Poly(L-lactide-co-glycolide) Molecules in Organic Solvents on Nanoparticle Size.

Controlling the size of nanoparticles is important for drug delivery methods such as pulmonary administration, transdermal administration, and intravenous administration. In this study, we have investigated the effect of polymer conformation in organic solvents on the size of the nanoparticles. Poly(L-lactide-co-glycolide) (PLLGA), a promising nanoparticle carrier, was used as the polymer. A mixed solution of dichloromethane, which is a good solvent, and a lower alcohol (methanol, ethanol, and 1-propanol), which is a poor solvent, was used as the solvent for dissolving PLLGA. An oil-in-water emulsion was prepared by sonication using the mixed solution of organic solvents in which PLLGA was dissolved as a dispersed phase and an amino acid aqueous solution as a continuous phase. Nanocomposite particles were prepared from the emulsion using a spray dryer and redispersed in purified water to obtain the PLLGA nanoparticles. The conformation of PLLGA molecules in the organic solvents was evaluated by analyzing the results of the viscosity measurements. The polymer coil radius and the volume per polymer coil were observed to decrease with the increase in the ratio of the lower alcohol in the solvent, whereas these values tended to decrease with the use of more hydrophilic lower alcohols. In addition, based on the results of the calculated entanglement index, it was found that when the hydrophobicity of the dispersed phase is reduced, the polymers were hardly entangled with each other. These results were significant, specifically when the ratio of the lower alcohol in the solvent was low. Estimation of the Pearson's correlation coefficients indicated that there were positive correlations between these indices and the mean volume diameter of PLLGA nanoparticles. This study shows that changing the composition of the dispersed phase, in which the PLLGA is dissolved, can change the conformation of the PLLGA molecules and control the size of the PLLGA nanoparticles.

Drug Delivery Properties of Nanocomposite Particles for Inhalation: Comparison of Drug Concentrations in Lungs and Blood.

Nanocomposite particles are suitable for inhalation; however, their systemic migration has not been confirmed. The aim of this study was to compare drug concentrations in lungs and blood after inhalation of nanocomposite particles. Rifampicin (RFP) was used as a model drug. Nanocomposite particles were prepared from dichloromethane with RFP and poly(DL-lactic acid-co-glycolic acid) (PLGA) dissolved in an amino acid aqueous solution using a spray dryer. Measurement of RFP concentrations in lung and blood of mice was performed by in vivo tests. Compared with the oral administration group as a control, the RFP concentration in the lungs was significantly higher in the inhalation group. In addition, studies with a fluorescent substance suggested sustained release of drugs from nanocomposite particles in the lungs. Nanocomposite particles deliver pulmonary drug in an efficient and sustained manner.

The Effect of Different Amino Acids on the Development of Cucumber (Cucumis sativus L.) Plant Species growing in Düzce Region

Abstract: While amino acids balance the metabolic pathway in plants and soil by activating / inhibiting enzymes, they also produce protein-rich foods to meet the needs of the body and provides resistance to stress conditions such as high temperature, low humidity, frost, insect damage, hail damage and flood which reduce the quality and quantity of the product and has a negative impact on plant metabolism. In addition, the application of amino acids before, during and after the occurrence of stress conditions has the effect of preventing and improving problems in stress physiology. In this context, aqueous solutions of amino acids in different concentrations were prepared in research by using phenylalanine, tyrosine, arginine and methionine as amino acid types and applications were made on cucumber (Cucumis sativus L.) plants grown in ecological conditions of Düzce region. These studies were carried out under greenhouse and controlled conditions (temperature, humidity, light). After growing plants, macro and micro nutrients obtained from leaves and soil samples were examined. IR analysis was performed to determine the general content of the samples taken from the plants. As a result of the research, transportation of anionic and cationic plant nutrients from soil to plant or from plant to soil by means of amino acids was achieved. However, since the amino acids are in dipolar structure and provide the possibility to carry both anionic and cationic plant nutrients simultaneously, development process of plants shortened and their effects on the agricultural properties of plants were found to be positive. It was seen that protein content can be increased significantly by the application of amino acid, which is the building block of protein and that its effects on agricultural properties of plants can be positive.

Effect of cosolvents in the preferential binding affinity of water in aqueous solutions of amino acids and amides

Effects of two naturally occurring osmolytes, urea and trimethylamine-N-oxide (TMAO) on the solvation structure of hydrophobic moiety of alanine, glycine, N-methylacetamide and acetamide are investigated by classical molecular dynamics simulations. Our results are analysed in terms of site-site radial distribution functions (RDF), spatial distribution functions (SDF), number of hydrogen bonds, orientation profile, KB integrals, preferential binding coefficient and hydrogen bond dynamics. RDF and SDF showed presence of an extra hydration shell near the hydrophobic unit when TMAO is present in the solution. This hydration shell mainly consists of broken hydrogen bonds. In urea-water solution, intramolecular association is favoured compared to intermolecular association: which is in contrast to the TMAO-water solution. Alanine, glycine, NMA and acetamide showed preferred interactions with the water molecules in presence of TMAO compared to urea. Urea and TMAO both are found to be excluded from the alanine, glycine, NMA and acetamide surface but presence of urea was slightly favoured at higher distances in case of NMA and acetamide. The strong hydrogen bond between TMAO-water increases the hydrogen bond lifetime of other hydrogen bonds in the system. The preferential binding affinity of water with the protein molecules and strong hydrogen bonds are found to be the key reasons for stability in presence of TMAO.

Studies on the constituents of Helleborus purpurascens: use of derivatives from calix[6]arene, homooxacalix[3]arene and homoazacalix[3]arene as extractant agents for amino acids from the aqueous extract.

The task of this work was to investigate the extraction capacity of various calixarenes for free and esterified amino acids from aqueous acid phases. Furthermore, this method was applied to aqueous extracts of Helleborus purpurascens. Generally, it is known that calixarenes can be used as extractants for ammonium compounds due to π-cation and lone pair cation interactions. As first, tert-Butyl-calix[6]arene and derivatives thereof were used. They had already proven their worth in previous investigations. In addition, tert-Butyl-hexahomooxa-calix[3]arene was used also, which can also enter into lone pair cation interactions. In addition to these well-known calixarenes, new calixarenes were produced and tested. Based on the tert-Butyl-hexahomooxa-calix[3]arene, a phosphor(III)bridged derivative was prepared, combining the three aromatic hydroxyl groups to a phosphite. As a seldom-described class of calixarenes, tert-Butyl-hexahomoaza-calix[3]arene derivatives were used. The nitrogen analogues of tert-Butyl-hexahomooxa-calix[3]arene could be produced as N-benzyl derivatives. The structure of the esterified carboxymethylated derivative of N,N',N″-Tribenzyl-tert-Butyl-hexahomoaza-calix[3]arene could be verified by X-ray structure analysis. It crystallized as a partial cone. The extraction capacity of the described calixarenes was investigated for amino acids from aqueous acidic solutions into an organic phase. For the testing were chosen asparagine, aspartic acid, tyrosine, tryptophane, phenylalanine and pipecolinic acid and their methyl esters. The amino acids and their methyl esters were dissolved in water at different pH values. The calixarenes were dissolved in dichloromethane (DCM) or chloroform. After this preparation, the aqueous acidic amino acid solutions were mixed with the solutions and shaken intensively. In addition, blank values were determined by extracting the aqueous stock solutions of the amino acids and their methyl esters with pure solvents. To determine the extraction rate, the phases were separated and each analysed using GC-FID, partially GC-MS(EI). The evaluation is performed in two ways. On the one hand the depletion in the aqueous phase and on the other hand the content in the organic phase was determined.

Dissolution-enhanced emission of 1,3,6,8-Tetrakis(p-benzoic acid)pyrene for detecting arginine and lysine amino acids

Since the aggregation-induced emission (AIE) of fluorescent probe was reported, it has been widely considered as a universal phenomenon for fluorescent sensing, imaging and detection in chemistry, biology and medicine fields. In this work, we for the first time report the dissolution-enhanced emission (DEE) of 1,3,6,8-Tetrakis(p-benzoic acid)pyrene (TBAPy) as a turn-on fluorescent probe for detecting amino acids. The TBAPy probe shows not only extremely high selectivity with high luminescence enhancement (>220 times), but also high sensitivity and anti-interference abilities for selectively detecting arginine (Arg) and lysine (Lys) amino acids in aqueous solutions. The DEE mechanism is proposed to reveal the fluorescence turn-on phenomenon, which is confirmed by 1H NMR spectra and UV–vis absorption spectra of TBAPy suspension before and after adding Arg and Lys. The DEE mechanism provides a new universal strategy for designing turn-on fluorescent probes, and would yield potentially significant applications such as detecting small organic compounds, peptides, proteins and biologic imaging.

Volumetric Properties of Amino Acids in Aqueous Solutions of Glucosamine Hydrochloride at T = 293.15–313.15 K

The densities (ρ) of glycine, L-alanine, L-serine, and L-threonine solutions in 0.05, 0.10, 0.15, 0.20, and 0.30 mol kg–1 aqueous solutions of D-glucosamine hydrochloride have been measured at T = 293.15, 298.15, 303.15, 308.15, and 313.15 K. The apparent molar volumes (Vϕ), limiting partial molar volumes ($$V_{\phi }^{0}$$) of the amino acids have been calculated from the density data. Transfer partial molar volumes (∆tr$$V_{\phi }^{0}$$) and hydration numbers from water to the aqueous solutions of D-glucosamine hydrochloride were also obtained. These parameters of volumetric properties can help to understand the mixing effects and interactions between amino acids and D-glucosamine hydrochloride aqueous solution.

Thermo-mechanical properties of epoxy nanocomposites incorporating amino acid and acid functionalized multi-walled carbon nanotubes

In this study, multi-walled carbon nanotubes (MWCNTs) were functionalized by both sulfuric/nitric acids and amino acids to form COOH and NH2/COOH/OH groups on their surface, respectively. The functionalized MWCNTs were characterized by Fourier Transform Infrared Spectroscopy, titration test, thermal gravimetric analysis, and solvent stability test. The results revealed that in each method, the functional groups were successfully attached to the surface of nanotubes. Acid treatment grafted more oxygen-containing groups compared to commercial carboxylated MWCNTs. The amino acid functionalized MWCNTs indicated improved stability in different solvents compared to raw and acid treated MWCNTs. These functionalized MWCNTs were incorporated into epoxy resin and the properties of the nanocomposites were evaluated by scanning electron microscopy, tensile test, dynamic mechanical thermal analysis, differential scanning calorimetry, and thermogravimetric analysis. The morphology of the nanocomposites revealed that acid and amino acid treated samples had better interaction with the epoxy resin. Compared to epoxy sample contained raw MWCNT (control) and commercial carboxylated MWCNTs, the addition of functionalized MWCNTs to the epoxy resin improved the tensile strength by 39% and 25% (for acid treated) and 46% and 33% (for amino acid treated), respectively. The best tensile properties for acid and amino acid treated samples were reached by MWCNTs acid treated at 110℃ for 15 min and MWCNTs treated in a 50 g/L aqueous solution of amino acid, respectively. Storage modulus of the epoxy samples which contained acid and amino acid treated MWCNTs were 1560 and 1900 MPa, respectively. The glass rubber transition temperature ( Tg) of the epoxy samples containing acid and amino acid treated nanotubes were increased by 1.1℃ and 5.9℃, respectively, compared to the control sample. Therefore, based on these mechanical properties, the epoxy samples containing nanotubes functionalized by amino acid exhibited the highest performance in the epoxy nanocomposite. Incorporating acid and amino acid treated MWCNTs accelerated the curing process of epoxy where the curing temperature decreased by 9.1℃ and 13.3℃, respectively. Because of the reaction between amine groups grafted on MWCNTs in the amino acid treatment and epoxide groups of the epoxy resin, this acceleration was more significant in the case of amino acid sample. Note that addition of functionalized MWCNTs to epoxy resin did not lead to increased thermal stability.

Surface Tension of Aqueous Solutions of Small-Chain Amino and Organic Acids

Surface tension was measured for aqueous solutions of dl-malic acid, l-glutamine, l-serine, l-proline, l-methionine, l-valine, and l-lactic acid as a function of concentration using a Du Nouy ring ...

Carbon dioxide absorption into aqueous potassium salt solutions of glutamine amino acid

Amino acid salts (AAS) are mentioned as potential solvents for the separation and capture of carbon dioxide (CO2). This study investigates the aqueous solution of Potassium Glutaminate (K-Glu) solvent from different viewpoints including equilibrium solubility of carbon dioxide varying the concentration and absorption temperature at different pressures, reaction kinetics and mechanism between K-Glu and CO2, heat of absorption and cyclic absorption and regeneration efficiency. The reaction rate was calculated using the obtained experimental data and quasi first order overall reaction rate is proposed. The successive absorption-desorption preliminary tests showed a negligible drop in CO2 capture capacity over consecutive cycles through regeneration at 343.15 K. The proposed solvent has the advantages of high absorption rate and capacity (compared with monoethanolamine and N-methyldiethanolamine) with interesting aspects such as lower corrosion rate, environmental biening and high resistance against thermal and oxidative degradation covering the shortcomings of conventional amines, which considers it as a potential new solvent.

Temperature dependent volumetric and acoustic properties of some amino acids in aqueous solutions of an antidepression drug

The interactions of amino acids (histidine, valine and glycine) with drug amitriptyline as a subordinate of temperature have been perused by combination of volumetric and acoustic methods. Densities and speeds of sound of histidine, valine and glycine in aqueous solutions of amitriptyline have been measured at T = (305.15, 310.15 and 315.15) K. Apparent molar volume Vφ, apparent molar isentropic compression kφ, s, of amino acids (solute) in binary aqueous solutions of (0.0006, 0.001, 0.002 and 0.004) mol. kg−1 amitriptyline (solvent) have been designated at reported temperatures. The mentioned parameters are used to construct the solute–solvent interactions in ternary systems. The dependency of these parameters on concentration, temperature and hydrocarbon chain length of the amino acids clearly suggest the roles of amino acids in solute-solvent interactions.

Fluorescence Spectral Studies on the Interaction of Alanine and Valine with Resorcinol-Based Acridinedione Dyes in Aqueous Solution: A Comparative Study with Glycine.

Photophysical studies were carried out for simple amino acids like alanine and valine with resorcinol-based aqueous acridinedione (ADDR) dyes. ADDR dyes exhibit interesting excited-state characteristics on altering the substituents at the 9th and 10th sites (Scheme 1). The longest-wavelength absorption maxima remain the same on adding the amino acids to the fluorophore, whereas the excited-state behavior varies significantly mostly based on the nature of the substituent at the 9th position. The absence of fluorescence enhancement was observed with addition of β-alanine, l-alanine, and l-valine to ADDR1 dye (photoinduced electron transfer, PET), whereas addition of glycine exhibits enhancement accompanied with a shift toward a longer-wavelength region. Interestingly, the addition of amino acids to non-PET dyes results in a fluorescence quenching accompanied with a larger shift toward the shorter-wavelength region. The properties of fluorophore and nonfluorophore dyes in the presence of alanine or valine are found to be entirely different from those of glycine. The interaction of alanine with ADDR dyes is predominantly through H-bonding, but the structural aspects of H-bonding interactions of alanine and water are completely different from those of glycine and water. The time-correlated single-photon counting method portrays the existence of fluorophore in two distinguishable microenvironments in the presence of amino acids. The fluorescence spectral technique used as a tool in elucidating the mode of interaction of dye with neutral amino acids in aqueous solution is illustrated in the present study.

Simultaneous Determination of Concentration and Enantiomeric Composition of Amino Acids in Aqueous Solution by Using a Tetrabromobinaphthyl Dialdehyde Probe.

3,3'-Diformyl-1,1'-bi-2-naphthol or its methoxymethyl-protected derivative is found to undergo a highly selective reaction with excess bromine in CH2 Cl2 at reflux to give the novel 5,5',6,6'-tetrabrominated product (S)- or (R)-2. The observed electrophilic substitution at the 5,5'-positons of an optically active binaphthyl compound is unprecedented. Unlike unbrominated 3,3'-diformyl-1,1'-bi-2-naphthol, which is not suitable for fluorescent recognition in water, compound (S)-2, in combination with Zn2+ , exhibits a highly enantioselective fluorescent response toward amino acids in aqueous solution (HEPES buffer, pH 7.4). It is further found that the condensation product of (R)-2 with tryptophan, (R)-3, shows dual-responsive emissions toward amino acids; the short wavelength (λ1 =350 nm) emission is sensitive to the concentration of the substrate regardless of the chiral configuration and the long wavelength (λ2 >500 nm) emission is highly enantioselective. Thus, the use of (R)-3 allows the simultaneous determination of the concentration and enantiomeric composition of an amino acid sample from one fluorescence measurement.

High gas barrier coating using non-toxic nanosheet dispersions for flexible food packaging film

One of the major challenges in the circular economy relating to food packaging is the elimination of metallised film which is currently the industry standard approach to achieve the necessary gas barrier performance. Here, we report the synthesis of high aspect ratio 2D non-toxic layered double hydroxide (LDH) nanosheet dispersions using a non-toxic exfoliation method in aqueous amino acid solution. High O2 and water vapour barrier coating films can be prepared using food safe liquid dispersions through a bar coating process. The oxygen transmission rate (OTR) of 12 μm PET coated film can be reduced from 133.5 cc·m−2·day−1 to below the instrument detection limit (<0.005 cc·m−2·day−1). The water vapour transmission rate (WVTR) of the PET film can be reduced from 8.99 g·m−2·day−1 to 0.04 g·m−2·day−1 after coating. Most importantly, these coated films are also transparent and mechanically robust, making them suitable for flexible food packing while also offering new recycling opportunities.

Molecular interactions between some amino acids and a pharmaceutically active ionic liquid domiphen DL-mandelic acid in aqueous medium at temperatures from 293.15 K to 313.15 K

Molecular interactions between some amino acids (glycine, l-alanine, l-valine and l-leucine) and a pharmaceutically active ionic liquid domiphen DL-mandelic acid ([DOM][MAN]) in aqueous solution at various temperatures have been studied by means of volumetric, conductivity and spectroscopy measurements. Density data were used to derive standard partial molar volume, V2,φ0 standard partial molar expansibility, Eφ0, standard transfer volume, ΔtV0, isobaric thermal expansion coefficient, α0 and hydration number, nH of amino acids. On the basis of the experimental conductivity and fluorescence spectroscopy data, the aggregation behaviour of [DOM][MAN] in aqueous amino acid solutions was investigated. Critical micelle concentration, cmc, aggregation number, Nagg, some thermodynamic functions, ΔGm0, ΔHm0, ΔSm0 and ΔCp0 of micellization for [DOM][MAN] have been obtained. Effect of concentration and temperature on the obtained parameters has been discussed. Binding constant Kb for amino acid-[DOM][MAN] complex estimated using the UV–vis spectroscopic data approved that the solute-solvent interactions were strengthened by elevating the size of alkyl part of amino acids.

Assessment of carbon dioxide capture by precipitating potassium taurate solvent

One of the most mature technologies for removal of carbon dioxide from gaseous streams is chemical absorption. Among these, aqueous solutions of amino acids have been considered because of the advantages associated with their being precipitating solvents. This paper presents detailed analyses of the performance of the potassium taurate absorption system by means of a rigorous simulation in a commercial process software (ASPEN Plus®). The profiles of temperature, heat transfer, compositions, and molar flows of carbon dioxide and water have been examined. The operating line and the equilibrium curve for different lean loadings of the solvent are reported and show that the minimium reboiler duty occurs at a lean loading of 0.27. Examination of the influence of the solid-liquid separator on the reboiler duty shows that a recycle split fraction of 0.2 results in the lowest reboiler duty. Different minimum temperature approaches in the lean-rich cross heat exchanger have also been investigated.

THE METHOD OF DETECTION OF BIOMOLECULES FOR THE CREATION OF SENSORS BASED ON NANO-STRUCTURED Si.

In the work, the modification of photoluminescence spectra in the processing of porous silicon in aqueous solutions with different oxygen contents and aqueous solutions of amino acids was studied in order to further create a sensor sensitive to chemically active oxygen near the surface of porous silicon in the presence of various amino acids. he growth of the photoluminescence intensity at the processing of porous silicon in distilled water and the sensitivity of the intensity of photoluminescence to the oxygen content in water are revealed. It is proposed to use a change in the intensity of luminescence to study the properties of biomolecules, namely the determination of the amount of chemically active oxygen near the surface of porous silicon in the presence of various amino acids. Changing the sizes of nanocrystals is the main reason for increasing the intensity of photoluminescence when processing porous silicon in aqueous solutions. After applying to the surface of samples of porous silicon aqueous solutions of glycine, alanine, phenylalanine, the intensity of photoluminescence varies for all samples. Changing the sizes of nanocrystals is the main reason for increasing the intensity of photoluminescence when processing porous silicon in aqueous solutions. After applying to the surface of samples of porous silicon aqueous solutions of glycine, alanine, phenylalanine, the intensity of photoluminescence varies for all samples. Key words: photoluminescence, nanostructured porous silicon, biosensors.

Decomposition and oxidation of methionine and tryptophan following irradiation with a nonequilibrium plasma jet and applications for killing cancer cells

We present evidence for the decomposition and oxidation of amino acids in aqueous solution following irradiation with a nonequilibrium plasma jet. Of 15 amino acids tested in cell culture medium, plasma irradiation induced a marked chemical change in methionine and tryptophan due to the effective production of reactive oxygen species by plasma-water interaction. We also report that plasma-treated methionine and tryptophan aqueous solutions can kill cancer cells, greatly decreasing the viability of human endometrial carcinoma (HEC-1) cancer cells due to the presence of decomposition or oxidation products generated from the amino acid. Plasma-treated methionine and tryptophan aqueous solutions also induced an anti-cancer effect on cancer-initiating cells.

Decomposition of amino acids in water with application to in-situ measurements of Enceladus, Europa and other hydrothermally active icy ocean worlds

To test the potential of using amino acid abundances as a biosignature at icy ocean worlds, we investigate whether primordial amino acids (accreted or formed by early aqueous processes) could persist until the present time. By examining the decomposition kinetics of amino acids in aqueous solution based on existing laboratory rate data, we find that all fourteen proteinogenic amino acids considered in this study decompose to a very large extent (>99.9%) over relatively short lengths of time in hydrothermally active oceans. Therefore, as a rule of thumb, we suggest that if amino acids are detected at Enceladus, Europa, or other hydrothermally active ocean worlds above a concentration of 1 nM, they should have been formed recently and not be relicts of early processes. In particular, the detection of aspartic acid (Asp) and threonine (Thr) would strongly suggest active production within the ocean, as these amino acids cannot persist beyond 1 billion years even at the freezing point temperature of 273 K. Identifying amino acids from the oceans of icy worlds can provide key insight into their history of organic chemistry.