Can Jones-Dole's B-Coefficient be a Consistent Structure-Making/Breaking Marker? Rigorous Molecular-Based Analysis and Critical Assessment of Its Marker Uniqueness

On the Elusive Links between Solution Microstructure, Dynamics, and Solvation Thermodynamics: Demystifying the Path through a Bridge over Troubled Conjectures and Misinterpretations

We build a fundamentally based bridge between the solute-induced microstructural perturbation of the species environment and the dynamic as well as thermodynamic responses of the fluid system, regardless of the state conditions, composition, nature of the solvent, and either the magnitude or the type of solute-solvent intermolecular-interaction asymmetries. For that purpose, we advance a fluctuation-based solvation formalism of fluid mixtures to provide meaningful descriptors of solvation phenomena, the microstructural signatures of their solute-solvent intermolecular interaction asymmetry, and the thermodynamic manifestations linked to the solution nonideality. The rigorous foundations afford us to address some crucial issues frequently invoked in the literature including the microstructural perturbation domain, its proper identification and molecular-based meaning toward the interpretation of the solvation process, and the potential impact of the local differential behavior between anions and cations on the actual salt-induced perturbation of the solvent microstructure. Indeed, we link the precisely characterized species solvation behavior to fundamental thermodynamic residual-property relations, and the dynamics associated with either the viscous flow or diffusive behavior of the solvent, to finally illustrate their outcome with experimental data of aqueous electrolyte solutions from the available literature. Ultimately, this effort provides a highly desirable unambiguous identification of the cause-effect connections between the microstructurally perturbed domains and the experimentally measured macroscopic solvation properties, including their effect on the dynamics of the solvent environment. More importantly, it lends a well-established solvation framework to bridge rigorously the microstructural details of the mixture, its dynamics, and its solvation thermodynamics to enhance our understanding of well-defined ranked Hofmeister series, i.e., by avoiding ad hoc conjectures and unsupported microscopic interpretations of solvation phenomena.

Guidelines for an optimized differential centrifugation of cells

Literature reviews reveal a significant deficiency in conceptual comprehension concerning centrifugation, a crucial step in both medical and research protocols. The arbitrary fluctuations in centrifugal forces present a potential threat to the reproducibility of results. To address this, we propose concise guidelines that integrate key factors such as temperature, osmolarity, fluid volume, and viscosity. These guidelines aim to enhance comprehension of optimal sedimentation conditions for cell suspensions. Additionally, we introduce a standardized protocol for determining the optimal RCF and centrifugation time. The goal is to maximize sedimentation efficiency while minimizing cell damage, contributing to a universally applicable and reproducible method in centrifugation practices.

Gigahertz elastic modulus and OH stretching frequency correlate with Jones-Dole's B-coefficient in aqueous solutions of the Hofmeister series

The ability of salts to change the macroscopic viscosity of their aqueous solutions is described by the Jones-Dole equation with B-coefficient for the linear concentration term. The sign and value of this coefficient are often considered as a measure of the salt's structure-making/breaking ability, while the validity of this assignment is still under discussion. Here, by applying Raman and Brillouin scattering spectroscopy to various salts from the Hofmeister series, we studied a possible relation between macroscopic Jones-Dole's B-coefficient and the microscopic dynamic response. Raman spectroscopy provides information about molecular vibrations and Brillouin spectroscopy about acoustic phonons with wavelengths of hundreds of nanometers. It has been found that Jones-Dole's B-coefficient correlates linearly with the coefficients, describing the concentration dependences of the average OH stretching frequency, real and imaginary parts of gigahertz elastic modulus. These relationships have been interpreted to mean that the OH stretching frequency is a measure of the ion-induced changes in the water network that cause changes in both viscosity and gigahertz relaxation. Depolarized inelastic light scattering revealed that the addition of structure-making ions not only changes the frequency of the relaxation peak but also increases the low-frequency part of the relaxation susceptibility. It was shown that the ion-induced increase in the gigahertz elastic modulus can be described by changes in the relaxational susceptibility without a noticeable change in the instantaneous elastic modulus. The isotropic Raman contribution associated with the tetrahedral-like environment of H₂O molecule does not correlate with Jones-Dole's B-coefficient, suggesting a minor influence of these tetrahedral-like configurations on viscosity.