Physico-chemical factors governing partition behaviour of solutes and particles in aqueous polymeric biphasic systems. III. Features of solutes and biological particles detected by the partition technique

The partition behaviour of human serum albumin and oxyhaemoglobin and several amino acids and small peptides was studied in the aqueous Ficoll-dextran biphasic system as a function of the ionic composition and pH. The partition coefficients of the solutes were expressed in terms of the equivalent number of CH2 groups, nCH2, and the equivalent number of carboxyl groups, m. The physical meaning of these two parameters and of the relationships found between them and pH for the proteins examined are discussed. A correlation was established between the difference in the relative hydrophobicities of the individual phases of various water-organic solvent systems and the interfacial tension, gamma 12, of the systems. It is argued that a relation of a similar type exists for the aqueous polymeric biphasic systems. The possibility of estimating the relative intensity of Van der Waals and hydration interactions of a solute and particle surface by examination of their partitioning in a biphasic system calibrated for the hydrophobic and hydration properties of the phases is discussed.     

Computational prediction of ionic liquid 1-octanol/water partition coefficients

Wet 1-octanol/water partition coefficients (log?K(ow)) predicted for imidazolium-based ionic liquids using adaptive bias force-molecular dynamics (ABF-MD) simulations lie in excellent agreement with experimental values. These encouraging results suggest prospects for this computational tool in the a priori prediction of log?K(ow) values of ionic liquids broadly with possible screening implications as well (e.g., prediction of CO(2)-philic ionic liquids).     

Limiting diffusion coefficients of ionic liquids in water and methanol: a combined experimental and molecular dynamics study

Mutual diffusion coefficients D(12) of the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(2)MIM][NTf(2)]) and [C(4)MIM][NTf(2)] in highly diluted solutions of water and methanol have been measured at different temperatures between 288 K and 313 K using the Taylor dispersion technique. Tracer diffusion coefficients of the two cations [C(2)MIM](+) and [C(4)MIM](+) as well as the anion [NTf(2)](-) in these solutions have been obtained by molecular dynamics (MD) simulations. For our simulations we used well established force fields for the solvents water and methanol and a recently developed force field for imidazolium-based ionic liquid [C(n)MIM][NTf(2)]. Mutual diffusion coefficients D(12) have been calculated from the tracer diffusion coefficients using the Nernst-Hartley equation strictly valid only at low ionic concentration. The agreement between the diffusion coefficients reported in the literature, the experimental data obtained in this work and the MD results is excellent.     

Estimation of partition coefficients by MEKC part 2: anthocyanins

The octanol-water partition coefficients of seven anthocyanins (in neutral form, pH = 7.0) were measured by means of MEKC. A new iterative method for the estimation of migration time of electroosmotic flow (EOF) and micelles in MEKC is presented. This calculation is based on Gauss-Newton linearization of the dependence between migration indices and migration times of a set of suitable standards and the application of an advanced statistical evaluation procedure. The values of partition coefficients obtained with the aid of an iterative process are compared with values obtained on use of EOF and micelle markers.     

Interactions between hydrophobic and ionic solutes in aqueous guanidinium chloride and urea solutions: lessons for protein denaturation mechanism

In order to clarify the mechanism of denaturant-induced unfolding of proteins we have calculated the interactions between hydrophobic and ionic species in aqueous guanidinium chloride and urea solutions using molecular dynamics simulations. Hydrophobic association is not significantly changed in urea or guanidinium chloride solutions. The strength of interaction between ion pairs is greatly diminished by the guanidinium ion. Although the changes in electrostatic interactions in urea are small, examination of structures, using appropriate pair functions, of urea and water around the solutes show strong hydrogen bonding between urea's carbonyl oxygen and the positively charged solute. Our results strongly suggest protein denaturation occurs by the direct interaction model according to which the most commonly used denaturants unfold proteins by altering electrostatic interactions either by solvating the charged residues or by engaging in hydrogen bonds with the protein backbone. To further validate the direct interaction model we show that, in urea and guanidinium chloride solutions, unfolding of an unusually stable helix (H1) from mouse PrPC (residues 144-153) occurs by hydrogen bonding of denaturants to charged side chains and backbone carbonyl groups.     

Parallel synthesis and study of fluorous biphasic partition coefficients of 1H,1H,2H,2H-perfluoroalkylsilyl derivatives of triphenylphosphine: a statistical approach

A library of fluorous, (1H,1H,2H,2H-perfluoroalkyl)silyl-substituted derivatives of triphenylphosphine, Ph(3-a)P[C(6)H(5-y)[SiMe(3-b)(CH(2)CH(2)C(x)F(2x+1))(b)](y)-pos](a) [a = 1-3; b = 1-3; x = 4, 6, 8, or 10; pos = 3, 4 (y = 1) or 3,5 (y = 2)], was prepared using parallel synthetic techniques. Upon variation of these four parameters, a total of 108 different fluorous phosphines can be synthesized. Using factorial design, 37 phosphines were selected and their partition coefficients in the typical fluorous biphasic solvent system PFMCH/toluene (PFMCH = perfluoromethylcyclohexane) determined. By fitting of the partition coefficient data to linear functions of the parameters a, b, and x, the partition coefficients of the remaining 71 fluorous phosphines, which were not prepared, could be predicted. Using this approach, some unexpected trends in the dependence of the partition coefficient on variations of the four parameters became clear, resulting in a better understanding of the optimum fluorous substitution pattern for obtaining the highest partition coefficient (P). In this way, the partition coefficient was increased by 2 orders of magnitude, i.e., from the initial value P = 7.8 for 1(3, 2, 6, C4) to P > 238 for 1(2, 3, 6, C3C5). Para- and 3,5-substituted phosphines showed irregular behavior in the sense that elongation or increase of the number of perfluoroalkyl tails did not necessarily lead to higher partition coefficients. Particularly high values were found for phosphines containing a total of 72 fluorinated carbon atoms on the meta position(s) of the aryl rings. Linear relationships were found between the predicted log P of 1(a, b, x, C4) and the experimentally determined log P values of fluorous diphosphines [CH(2)P[C(6)H(4)(SiMe(3-b)(CH(2)CH(2)C(6)F(13))(b))-4](2)](2) and monophosphines Ph(3-a)P(C(6)H(4)(CH(2)CH(2)C(6)F(13))-4)(a). One of the most fluorophilic phosphines, i.e., 1(3, 1, 8, C3C5), was applied and efficiently recycled in rhodium-catalyzed, fluorous hydrosilylation of 1-hexene by HSiMe(2)Ph using PFMCH as the fluorous phase and the substrates as the organic phase. It was demonstrated that a higher partition coefficient of the ligand in PFMCH/toluene at 0 degrees C indeed resulted in less leaching of both the catalyst and the free ligand during phase separation.     

CO2 hydrogenation in ionic liquids: Recent update

The suppression of CO₂ emission is an important global issue. Therefore, CO₂ hydrogenation is a hopeful method for capturing and recycling of CO₂. Ionic liquids have been known to have a high affinity with CO₂, indicative of the expectation for the enhancement of CO₂ hydrogenation in case used as reaction medium. In this article, progress of this area in 2018–2021 is mainly reviewed, namely, formic acid, hydrocarbons, methanol formation, hydroformylation, enzymatic methanol formation, and electro-reduction of CO₂ (CO₂RR). Various products are obtained with coupling of catalysts and ILs with changing properties. It is convincing that promising methodologies are growing for the sustainable society.     

Generalization of ionic partition diagrams to lipophilic compounds and to biphasic systems with variable phase volume ratios.

The ionic partition diagram methodology has been generalized to address both hydrophilic and lipophilic compounds and to consider biphasic systems with variable phase volume ratios. With this generalized approach electrochemical measurements of ion transfer potentials afford the determination of the standard partition coefficients of all forms of ionizable molecules, including the neutral form, as well as the evaluation of the dissociation constant of monoprotic substances. An interesting consequence of this approach is the definition of an extraction pK(a,ext) which is the apparent pK(a) of neutral acids and bases when dissolved in the organic phase.     

Tandem isomerisation-metathesis catalytic processes of linear olefins in ionic liquid biphasic system

trans-3-Hexene is converted to heavier linear olefins by a tandem Ru-catalysed biphasic isomerisation/metathesis sequence. The difference in olefin metathesis and isomerisation rates is modulated by keeping the ionophilic metathesis catalyst in an ionic phase whilst the isomerisation catalyst is in another organic non-polar phase.     

Effect of salt additives on partition of nonionic solutes in aqueous PEG-sodium sulfate two-phase system

Partition of 12 nonionic organic compounds in aqueous PEG-8000-Na(2)SO(4) two-phase system was examined. Effects of four salt additives (NaCl, NaSCN, NaClO(4), and NaH(2)PO(4)) in the concentration range from 0.027 up to ca. 1.9 M on binodal curve of PEG-sulfate two-phase system and solute partitioning were explored. It was found that different salt additives at the relatively high concentrations display different effects on both phase separation and partition of various nonionic solutes. Analysis of the results indicates that the PEG-Na(2)SO(4) ATPS with the up to 0.215 M NaCl concentration may be viewed as similar to the ATPS without NaCl in terms of the Collander equation's predictive ability of the partitioning behavior of nonionic compounds. All ATPS with each of the salt additive used at the concentration of 0.027 M may be viewed as similar to each other as the Collander equation holds for partition coefficients of nonionic solutes in these ATPS. Collander equation is valid also for the compounds examined in the ATPS with additives of NaSCN and NaClO(4) at the concentrations up to 0.215 M. The observed similarity between these ATPS might be explained by the similar effects of these two salts on the water structure. At concentrations of the salt additives exceeding the aforementioned values, different effects of salt additives on partitioning of various nonionic solutes are displayed. In order to explain these effects of salt additives it is necessary to examine the intensities of different solute-solvent interactions in these ATPS within the framework of the so-called Linear Solvation Energy Relationship (LSER) model.     

Equilibrium partition coefficients of ZnCl2, CdCl2, and PbCl2 in NaCl

Conclusions The equilibrium partition coefficients of ZnCl₂, CdCl₂, and PbCl₂ in NaCl were determined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, p. 2321, October, 1971.     

Chromato-mass-spectrometric identification using partition coefficients in the system of hexane-2,2,2-trifluoroethanol

An additional characteristic of organic compounds, the partition coefficients in the heterophase solvent system n-hexane-2,2,2-trifluoroethanol, is shown to be useful for refining the results of chromatographic and gas chromatography-mass spectrometric identification. This opportunity is the most important for compounds that were not yet characterized by either mass spectra or chromatographic retention indices.