جستجوی مقالات مرتبط با کلیدواژه « amino acid » در نشریات گروه « شیمی »

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.

Corona is a result of biological molecules and nanoparticles tend to each other and mainly refers to the case of proteins. The formation of the non-protein corona, i.e. carbohydrate and amino acids, and identifying the variations in their biological behavior were the purposes of this paper. The current study focused on silver nanoparticles (AgNPs), (20 and 120 nm), interaction with model small biomolecules, monosaccharides (glucose and fructose), and amino acids (histidine, cysteine, and tryptophan). The study considered the formation and composition of the corona as well as the characteristics and variations of carbohydrates/amino acids affected by AgNPs. Coronas were synthesized using the chemical reduction method, and their interactions with small biomolecules were monitored using response surface methodology (RSM). The results showed that treating glucose with smaller nanoparticles (20 nm) caused an increase in their size, agglomeration and aggregation, and a decrease in their homogeneity range. In the case of larger nanoparticles (120 nm), the glucose treatment caused the size to increase to ≥1 µm. Unlike glucose, fructose treatment had no influence on the size or stability of AgNPs.

This paper reports density and speed of sound data for solutions of the ionic liquids (ILs) [C4mim]Cl and [C4mim][CF3SO3] in aqueous solution of 0.05 w/w amino acids of alanine, serine and proline at T = (288.15, 298.15, 308.15 and 318.15) K. From the experimental data measured, the apparent molar volume (Vϕ), isentropic compressibility ( ), and apparent molar isentropic compression ( ) have been calculated. The Vϕ values of [C4mim]Cl and [C4mim][CF3SO3] in the investigated aqueous amino acid solutions decreased by increasing the hydrophobicity of the amino acid and follow the order: serine alanine proline. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated ILs in the aqueous amino acid solutions and their variations with temperature have been determined. The infinite dilution apparent molar volume and adiabatic compressibility for transfer of the studied ILs from water to aqueous solutions of the amino acids have been calculated and the results were discussed in terms of different interactions existing in these solutions.

In this research, investigation of the adsorption isotherms and the effect of solution conditions such as pH and concentration of complexation of some amino acids with cobalt(II) nitrate six-hydrate upon multi-wall type carbon nanotube (CNT) were done. The adsorption capacity of complexation of amino acids onto the surface of carbon nanotube increased with the pH from acidic to alkaline. At pH = 9 the affinity order of the complexation of amino acids towards carbon nanotube is L-arginine > L-phenylalanine > L-asparagine > L-methionine > L-cysteine > glycine > L-alanine > L-valine > L-histidine. The curves have an important role in the design and optimization of the unit operations such as preservation, drying storing packaging and mixing. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir and Temkin models, but the Freundlich model is better than other models because is does not assume the surface as homogeneous with respect to adsorption energies and also the r2 value indicates the goodness of fit between the data and the isotherm.