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

Abstract

Solvent properties of water (dipolarity/polarizability, hydrogen bond donor (HBD) acidity, and hydrogen bond acceptor (HBA) basicity) in aqueous solutions of osmolytes (sorbitol, sucrose, trehalose, and trimethylamine N-oxide (TMAO)) were studied at different osmolytes concentrations using solvatochromic comparison method. The solvent properties of aqueous media in the coexisting phases of aqueous dextran-PEG-sodium/potassium phosphate buffer (0.01 M K/NaPB, pH7.4) two-phase system (ATPS) containing 0.5 M osmolyte additive (sorbitol, sucrose, trehalose, TMAO) and osmolytefree ATPS were characterized. Partitioning of 30 low molecular weight polar organic compounds was examined in aqueous dextran-PEG-0.01M K/NaPB ATPS containing 0.5 M sorbitol. The solute-specific coefficients for the compounds examined were determined from the data obtained here and those reported previously. The results obtained demonstrate that the osmolytes examined affect the partition behavior of organic compounds in ATPS by influencing solvent properties of the media and not by direct association with the compounds. 23 ATPSs are formed in aqueous mixtures of different polymers or a single polymer and a specific salt. 24,25 When two certain polymers, for example, dextran and Ficoll, are mixed in water above certain concentrations, the mixture separates into two

Analysis of partitioning of organic compounds and proteins in aqueous polyethylene glycol-sodium sulfate aqueous two-phase systems in terms of solute–solvent interactions

“…Partitioning of six proteins was examined in all aforementioned ATPSs and the corresponding partition coefficients are listed in Table 2. Tables 1 and 2 shows that the so-called Collander solvent regression equation (see, e.g., in [22,[32][33][34][35]) holds for all compounds (including proteins) in the PEG-8000-Na 2 SO 4 and PEG-10000-Na 2 SO 4 ATPSs as shown in Fig. 2a Partition coefficients for all compounds in ATPS containing 0.5 M trehalose and 0.5 M sucrose fit the Collander relationship very well (see Fig.…”

“…It has been shown previously [32][33][34][35] that the osmolytes additives change the solvent properties of the phases under fixed salt composition of the system, while not being engaged in direct interactions with compounds (including proteins) being partitioned. Therefore these additives enable one to vary solvent properties of the polymer-salt ATPS without changing overall polymer and salt composition of the particular system.…”

Effects of sodium chloride and sodium perchlorate on properties and partition behavior of solutes in aqueous dextran-polyethylene glycol and polyethylene glycol-sodium sulfate two-phase systems

“…Aqueous two-phase systems were prepared as described previously [20,21]. Stock solutions of PEG 8000 (50 wt.%), PEG-10000 (50 wt.%) and Na 2 SO 4 (20.3 wt.%) were prepared in water.…”

“…All solvatochromic measurements in the phases of ATPSs used were performed as described previously [20,21]. The detailed description of the protocols used is provided in SI B.…”

“…Partitioning of the homologous series of Na-salts of dinitrophenylated (DNP-) amino acids was examined in order to estimate the difference between the relative hydrophobic and electrostatic properties of the phases as described previously [5,20,21]. Partition coefficients of Na-salts of DNP-amino acids with the aliphatic alkyl side-chains of the increasing length (alanine, norvaline, norleucine, and ␣-amino-n-octanoic acid) in the ATPS under study are listed below in Tables 1-3 and Tables A1-A3 and shown graphically as functions of the equivalent number of methylene groups representing the length of the alkyl side-chain in Fig.…”