Amino Acids In Aqueous Solutions Research Articles

A cucurbit[8]uril-based supramolecular phosphorescent assembly: cell imaging and sensing of amino acids in aqueous solution

A cucurbit[8]uril-based supramolecular phosphorescent assembly: cell imaging and sensing of amino acids in aqueous solution

Physiochemical study of 1-methyl imidazole trifluoro methane sulfonate ionic liquid in aqueous and aqueous amino acid solutions at different temperatures

The experimental density and speed of sound of 1-methyl imidazole trifluoro methane sulfonate ionic liquid in aqueous binary ([MIm][OTf]+H2O) solution and aqueous ternary ([MIm][OTf] + 0.05 mol.kg−1 aqueous glycine) solution are reported in the dilute concentration range (0.06 to 0.16 mol.kg−1) at the temperature between 288.15 and 318.15 K with 5K interval and at atmospheric pressure. These density (ρ) and speed of sound (u) data are utilized to derive various significant thermophysical parameters namely apparent molar volume of solute (Vϕ), isentropic compressibility of solution (κs) and apparent molar isentropic compressibility of solute (KS,ϕ). The limiting apparent molar volume (Vϕ0) and limiting apparent molar isentropic compressibility (KS,ϕ0) of [MIm][OTf] are estimated by extrapolation methods. By using Vϕ0and KS,ϕ0data of the studied binary and ternary systems, the values of transfer volumes i.e. volume changes due to transfer (ΔtrVϕ0)and transfer compressibility i.e. compressibility changes due to transfer(ΔtrKsϕ0) from aqueous to aqueous amino acid solution are estimated. The observed ΔtrVϕ0and ΔtrKsϕ0values are temperature dependent. The outcomes of this investigation are framed within the context of solute-solute and solute-solvent interactions.

Development of an Activity Coefficient Model for the Aqueous Amino Acid Solution

AbstractThe enthalpy and solubility of aqueous amino acid solutions are essential thermodynamic properties for the modeling of heat and mass balance, and these properties can be estimated by considering the activity coefficient in thermodynamic calculations. In this study, the parameters of a non‐random two‐liquid model were identified using heat capacity and solubility data together to calculate the acceptable activity coefficient for an aqueous amino acid system. As a result, a highly accurate activity coefficient model of an aqueous amino acid solution was developed, and inaccurate alternative solutions regressed with heat capacity or solubility only can be avoided.

Techno-Economic Assessment for the Best Flexible Operation of the CO2 Removal Section by Potassium Taurate Solvent in a Coal-Fired Power Plant

Alternative solvents based on aqueous solutions of amino acids have been recently developed as possible substitutes for Mono Ethanol Amine (MEA) for CO2 removal from flue gas streams. The potassium taurate solvent has the advantages of degradation resistance, low toxicity and low energy requirements for its regeneration. With any type of solvent, CO2 removal applied to a power production plant decreases the revenues obtained from selling electricity because of the energy requirements. Operating the CO2 removal section in flexible mode avoids significant effects on the profits of the power plant, while accomplishing environmental regulations. This work is the first journal paper focusing on the application in flexible mode of the potassium taurate system for treating a flue gas stream from a 500 MW coal-fired power plant. Techno-economic evaluations are performed to determine the best operating conditions considering the variation in the electricity demand and its price, and different values of carbon tax. In the summer period, with high electricity prices and demands, carbon tax values between 45 EUR/tCO2 and 60 EUR/tCO2 favor CO2 absorption in the flexible mode, without periods of full CO2 emissions during the day.

Consistent Analytical Second Derivatives of the Kohn-Sham DFT Energy in the Framework of the Conductor-Like Screening Model through Gaussian Charge Distributions.

The use of implicit solvation models such as the conductor-like screening model (COSMO) in quantum chemical calculations is very common, as both a rough estimate of solvation effects as well as a general tool for stabilizing ionic molecular structures. In order to generate a smooth potential energy surface as well as consistent gradients, it is necessary to apply the Gaussian charge model (GCM) for the COSMO charges. This work introduces an efficient implementation for consistent analytical second derivatives of the electronic energy with COSMO-GCM in the framework of the Kohn-Sham density functional theory. This is used to investigate the infrared spectroscopy of amino acids in aqueous solution, where the impact of pH on the molecular structure and vibrational spectra is examined. Furthermore, the structure and stability of selected all-metal aromatic cluster ions are assessed.

Physicochemical studies of some bioactive molecules in aqueous solution of tetrabutylammonium methanesulphonate (TBAMS) to investigate assorted molecular interaction at different temperatures simultaneously optimized by computational approach

Aqueous tetrabutylammonium methanesulphonate (TBAMS) solvent was used to solubilize the simplest stable amino acid (AA) Glycine and protein maker amino acid (AA) L-Alanine, and their solution behaviour has been meticulously examined to explore how they interact under various temperature conditions, using parameters like density (ρ), viscosity (η), surface tension (σ), and electrolytic conductivity. 1H NMR was also performed to verify further the mode of interactions prevailing in the solution, which is further supported by the DFT study. This research primarily aims to understand the interactions between biologically significant TBAMS and important amino acids in aqueous solutions, with potential implications for the pharmaceutical field. These results are anticipated to contribute crucial foundational knowledge for grasping the influence of sugar alcohols on the stability of protein structures.

Study of Cryostructuring of Polymer System. 65. Features of Changes in the Physicochemical Properties of Poly(vinyl alcohol) Cryogels Caused by the Action of Aqueous Solutions of Amino Acids of General Formula H2N–(CH2)n–COOH

Study of Cryostructuring of Polymer System. 65. Features of Changes in the Physicochemical Properties of Poly(vinyl alcohol) Cryogels Caused by the Action of Aqueous Solutions of Amino Acids of General Formula H2N–(CH2)n–COOH

Temperature dependent micellar study of streptomycin sulfate in aqueous amino acid solutions: physicochemical approach

Temperature dependent micellar study of streptomycin sulfate in aqueous amino acid solutions: physicochemical approach

Amino acid and acetone fluorescence sensors based on a stable light-emitting Cd(II) metal-organic framework with derivatives of isonicotinic acid

As one of the most promising category of functional materials, luminescent metal–organic frameworks (LMOFs) have been widely investigated as fluorescence chemical sensors which can offer a reliable diagnostic tools in biomedical research. Herein, a luminescent Cd-MOF [Cd2(L)2(H2O)]n (Cd-MOF) (H2L = 3-(3-carboxylphenyl) isonicotinic acid), was synthesized by and characterized in detail. Single-crystal structure determination reveals that Cd-MOF crystalizes in the monoclinic crystal system with C2/c space group. Experimental results show that Cd-MOF is a highly selective and sensitive luminescent sensor for rapidly detecting acetone, l-Tryptophane (L-Trp) and l- Aspartic acid (L-Asp) in water. It can significantly test acetone in common solvents, selectively identify l-Trp-and l-Asp-in 12 amino acid aqueous solutions, and enhance the fluorescence signal of Tryptophan and quench l-Asp-with the detection limit of 17.6 μM and 68.8 μM respectively. However, upon the interaction with electron rich amino acid (L-Trp), the Cd-MOF shows the selective “Turn-On” behavior, which may also be supported by the DFT studies.

VLE determination and microscopic properties of amino acid aqueous solutions

The vapor–liquid equilibrium (VLE) data of amino acids holds immense importance in chemical engineering. The VLE data of L-Alanine + H2O, DL-Valine + H2O and DL-Methionine + H2O were measured experimentally. The feasibility of VLE data is studied by using NRTL-Xu model, and the parameters of these systems were given. Furthermore, the Fourier Transform Infrared (FTIR) spectroscopy technique was used to study the microscopic properties of the amino acid solutions. Finally, the total mean interaction energy of water in the systems was studied by COSMOthermX. The results show that the vapor pressure increases with increasing temperature in the system, the vapor pressure of the higher solubility system is lower than the low solubility system and the pure solvent. From the FTIR results, it can be seen that the greater the solubility of amino acids in water, the stronger the hydrogen bond interaction with water. Meanwhile, the results of COSMOthermX show that the total mean interaction energy in the systems is least affected by the concentration. The structure–activity relationship between macroscopic properties (VLE) and microscopic interactions (hydrogen bonds) was established.

Site-Specific Charge Regulation Model for Amino Acids in Aqueous Solutions

Site-Specific Charge Regulation Model for Amino Acids in Aqueous Solutions

A Method of Water COD Retrieval Based on 1D CNN and 2D Gabor Transform for Absorption-Fluorescence Spectra.

Chemical Oxygen Demand (COD) is one of the indicators of organic pollution in water bodies. The rapid and accurate detection of COD is of great significance to environmental protection. To address the problem of COD retrieval errors in the absorption spectrum method for fluorescent organic matter solutions, a rapid synchronous COD retrieval method for the absorption-fluorescence spectrum is proposed. Based on a one-dimensional convolutional neural network and 2D Gabor transform, an absorption-fluorescence spectrum fusion neural network algorithm is developed to improve the accuracy of water COD retrieval. Results show that the RRMSEP of the absorption-fluorescence COD retrieval method is 0.32% in amino acid aqueous solution, which is 84% lower than that of the single absorption spectrum method. The accuracy of COD retrieval is 98%, which is 15.3% higher than that of the single absorption spectrum method. The test results on the actual sampled water spectral dataset demonstrate that the fusion network outperformed the absorption spectrum CNN network in measuring COD accuracy, with the RRMSEP improving from 5.09% to 1.15%.

Design of the process of CO2 removal in NGCC by potassium taurate solvent

One of the most mature technologies for removal of carbon dioxide from gaseous streams is chemical absorption and aqueous solutions of alkanolamines are employed, with Monoethanolamine (MEA) considered the benchmark solvent. However, its volatility and toxicity and the need for a lot of energy for regeneration made research focus on possible solvents that can perform the desired treatment of gaseous streams while reducing production and operating costs and the environmental impact, to be considered as substitutes. The process based on amino acid aqueous solutions, one type of these new solvents, has the advantage of an improved sustainability and, as the one employing aqueous solutions of potassium taurate, can also benefit of the enhancement due to the reaction of precipitation. In this work a rigorous rate-based model, built in the commercial process simulator ASPEN Plus®, properly customized for the representation of the system, is used to carry out a detailed process design for the CO2 removal section of a NGCC plant by an aqueous solutions of potassium taurate, for which no previous papers on the topics have been found in the literature. The scheme is optimized and the performances of the process are evaluated for different targets of CO2 removal.

PEP-FOLD4: a pH-dependent force field for peptide structure prediction in aqueous solution.

Accurate and fast structure prediction of peptides of less 40 amino acids in aqueous solution has many biological applications, but their conformations are pH- and salt concentration-dependent. In this work, we present PEP-FOLD4 which goes one step beyond many machine-learning approaches, such as AlphaFold2, TrRosetta and RaptorX. Adding the Debye-Hueckel formalism for charged-charged side chain interactions to a Mie formalism for all intramolecular (backbone and side chain) interactions, PEP-FOLD4, based on a coarse-grained representation of the peptides, performs as well as machine-learning methods on well-structured peptides, but displays significant improvements for poly-charged peptides. PEP-FOLD4 is available at http://bioserv.rpbs.univ-paris-diderot.fr/services/PEP-FOLD4. This server is free and there is no login requirement.

Spectrophotometric Study of Palladium(II) Complexation with Elementary Amino Acids in Aqueous Solution

Spectrophotometric Study of Palladium(II) Complexation with Elementary Amino Acids in Aqueous Solution

Determination of osmotic coefficients and activity coefficients of calcium d-pantothenate, cefazolin sodium, and ceftriaxone sodium drugs in aqueous solutions of amino acids by using vapor pressure osmometry at 310.15 K

Fundamental and serious efforts have been made over the past years to improve the drug acts, which leads to the discovery of novel drug preparations and delivery systems. The optimal design of such processes requires a molecular-level understanding of the interactions between drug molecules and biomolecules such as proteins. The thermodynamic investigation provides deep insight and knowledge of solute-solvent interactions and selection of appropriate production compounds in pharmaceutical fields. Particularly, the study of drug + biomolecule in aqueous media is the central issue in many types of research. The osmotic coefficient data for aqueous solutions containing the drugs (calcium d-pantothenate (CDP), cefazolin sodium (CFZ.Na), ceftriaxone sodium (CFT.Na)) with simple amino acid, l-alanine, glycine and l-leucine are obtained at 310.15 K using vapor pressure osmometry. Activity coefficients of both components in mixture were estimated using experimental osmotic coefficients. According to the results, the values of osmotic coefficients for the ternary system (drug + water + l-leucine) with a concentration of 0.04 mol∙kg−1 are higher than those values in other systems. The concentration dependence of osmotic coefficients indicates ion-pair formation between the ions of the drugs. Finally, Lin et al. and ECA models were used to correlate the water activity data in the presence of the amino acids obtained for the aqueous solution (drug + water + amino acid).

Impact of an Ionic Liquid on Amino Acid Side Chains: A Perspective from Molecular Simulation Studies.

Ionic liquids (ILs) are known to modify the structural stability of proteins. The modification of the protein conformation is associated with the accumulation of ILs around the amino acid (AA) side chains and the nature of interactions between them. To understand the microscopic picture of the structural arrangements of ILs around the AA side chains, room temperature molecular dynamics (MD) simulations have been carried out in this work with a series of hydrophobic, polar and charged AAs in aqueous solutions containing the IL 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) at 2 M concentration. The calculations revealed distinctly nonuniform distribution of the IL components around different AAs. In particular, it is demonstrated that the BMIM+ cations preferentially interact with the aromatic AAs through favorable stacking interactions between the cation imidazolium head groups and the aromatic AA side chains. This results in preferential parallel alignments and enhanced population of the cations around the aromatic AAs. The potential of mean force (PMF) calculations revealed that such favorable stacking interactions provide greater stability to the contact pairs (CPs) formed between the aromatic AAs and the IL cations as compared to the other AAs. It is further quantified that for most of the AAs (except the cationic ones), a favorable enthalpy contribution more than compensates for the entropy cost to form stable CPs with the IL cations. These findings are likely to provide valuable fundamental information toward understanding the effects of ILs on protein conformational stability.

Study of Thermodynamic Properties of l-Serine and l-Threonine in Aqueous Solutions of 1-(2-Carboxyethyl)-3-methylimidazolium Chloride [HOOCEMIM][Cl

The stability of amino acids in solutions containing electrolytes and the effect of ambient pH on their biological activity is an important research area. In this research work, the volumetric and transport properties of ionic liquid (IL) aqueous solution with special performance of 1-(2-carboxyethyl)-3-methylimidazolium chloride ([HOOCEMIM][Cl]) were studied. The selected IL acts as an electrolyte and allows the study of systems containing amino acids at acidic pH. In this work, the density, speed of sound and viscosity of binary and ternary solutions of IL in aqueous solution of amino acids in the structure of proteins, namely l-serine and l-threonine within IL molality range of (0.05, 0.07 and 0.09 mol·kg−1) were measured at 298.15 K. From these quantities, apparent molar volume, limiting apparent molar volume, apparent molar isentropic compression, limiting apparent molar isentropic compression, transfer standard volumes for amino acids from water to the aqueous IL solutions and viscosity B-coefficients were calculated using the equations of Redlich–Meyer and Jones–Dole. Close examination of literature indicates that there is no data for water activity for solution of l-serine + H2O at 308.15 and 318.15 K. In this way water activity, osmotic coefficient and vapor pressure were measured and using the interaction parameters of Wilson, NRTL, NRF-NRTL and UNIQUAC models, activity coefficient values of l-serine calculated.

Development of Thermophysical Property Models for Aqueous Amino Acid Solutions

AbstractModels for the calculation of density, heat capacity, viscosity, and thermal conductivity of amino acid aqueous solutions were proposed. Density, heat capacity, viscosity, and thermal conductivity of pure amino acid liquids were predicted by the Rackett model, Watson model, Heu‐Sheu‐Tu group contribution method, and Sato‐Riedel model, respectively. Mixing rule equations required for the prediction of density, heat capacity, viscosity, and thermal conductivity of amino acid aqueous solutions were suggested. Density, heat capacity, viscosity, and thermal conductivity data of 930, 975, 450, and 167 data points, respectively, for 20 amino acid aqueous solution systems were regressed to determine the most appropriate mixing rule parameters.

Evidence of excited-state lifetime enhancement in dimyristoyl-phosphocholine nanodiscs by ultraviolet absorption spectroscopy

Ultraviolet absorption spectroscopy is an analytical tool that is commonly utilized to determine protein concentrations, primarily due to characteristic absorption of tryptophan and tyrosine at 280 nm. Accurate concentration determination is essential to the accuracy of many biophysical techniques, and ultraviolet absorption provides a convenient and rapid method to assess protein concentration. However, the widespread usage of this method assumes that ultraviolet absorption is the same for individual amino acids in aqueous solution (where the molar extinction coefficient was measured) as for the amino acid in the conformational environment of the protein of interest. We demonstrate that additional considerations may be necessary for the membrane scaffold protein in dimyristoyl-phosphocholine nanodiscs through ultraviolet absorption spectroscopy of nanodiscs, liposomes, the membrane scaffold protein, and a mixture of liposomes and the non-nanodisc-associated protein. The aromatic amino acids of the membrane scaffold protein absorb significantly less light at 280 nm when associated with lipids in a lipoprotein assembly, which we plausibly attribute to an enhancement of chromophore excited-state lifetimes due to reduced intramolecular motion in the nanodisc. We caution that using the molar absorptivity of the membrane scaffold protein alone to determine nanodisc concentrations may not yield accurate results. Instead, the molar absorptivity of each nanodisc formulation should be explored independently to account for the unique conformational environment of each nanodisc.