Amino acid/water interactions study: a new amino acid scale

Abstract

Partition ratios of 8 free l-amino acids (Gln, Glu, His, Lys, Met, Ser, Thr, and Tyr) were measured in 10 different polymer/polymer aqueous two-phase systems containing 0.15 M NaCl in 0.01 M phosphate buffer, pH 7.4. The solute-specific coefficients representing the solute dipole/dipole, hydrogen-bonding and electrostatic interactions with the aqueous environment of the amino acids were determined by multiple linear regression analysis using a modified linear solvation energy relationship. The solute-specific coefficients determined in this study together with the solute-specific coefficients reported previously for amino acids with non-polar side-chains where used in a Quantitative Structure/Property Relationship analysis. It is shown that linear combinations of these solute-specific coefficients are correlated well with various physicochemical, structural, and biological properties of amino acids.

Analyzing the effects of protecting osmolytes on solute–water interactions by solvatochromic comparison method: I. Small organic compounds

“…The solute-specific coefficients for organic compounds differ from those reported previously 26,[29][30][31][32] for the same compounds in 0.15M NaCl in 0.01 M NaPB, pH 7.4. It has been reported 27 for proteins that different solute-specific coefficients for different proteins are linearly interrelated.…”

“…There is a clear interfacial boundary separating two distinct aqueous-based phases, each preferentially rich in one of the polymers, with the aqueous solvent in both phases providing conditions suitable for biological products. 27,[29][30][31][32] The partition coefficient K of a solute is defined as the ratio of the solute concentrations in the two phases. [26][27][28][29][30][31][32] Differences in solute-solvent interactions in the two phases lead to uneven solute distribution which is readily quantified by the partition coefficient, designated as K, and may be exploited for sensitive detection of changes in the solute structure.…”

“…The partition coefficient of a solute in an ATPS can be described as: 27,[29][30][31][32] logK i = S s ∆π* i + B s ∆α i + A s ∆β i + C s c i (1) where K is the solute partition coefficient; Δπ* is the difference between the solvent dipolarity/ polarizability of the two phases, Δα is the difference between the solvent HBD acidity of the two phases, Δβ is the difference between the solvent HBA basicity of the two phases; c is the difference between the electrostatic properties of the two phases; S s , A s , B s , and C s are constants (solute specific coefficients) quantifying the complementary interactions of the solute with the solvent media in the coexisting phases and representing the relative contributions of these interactions into partition coefficient of the solute; the subscript s designates the solute; the subscript i denotes the ATPS used; the difference for each solvent property is determined as the one between the upper and lower phases. The solute specific coefficients may be determined for a given compound (including proteins) by the analysis of partition coefficients of this compound in multiple ATPSs with different polymer but same ionic composition with established solvent properties of the phases.…”

Cooperativity between various types of polar solute–solvent interactions in aqueous media

“…It has been shown recently that the solute specific coefficients may be determined for a given compound (including proteins) by analysis of partition coefficients of the compound in multiple ATPS with different polymers but the same ionic composition [4][5][6][15][16][17]. Once , ˛, ˇ, and c parameters in multiple ATPS are determined, the solute specific coefficients can be calculated by multiple linear regression analysis.…”

“…The solute preferential distribution between the aqueous phases is mainly driven by different solute-solvent interactions [13][14][15][16][17] and it can be described as [4][5][6][15][16][17]:…”