Ergodic Algorithmic Model (EAM), with Water as Implicit Solvent, in Chemical, Biochemical, and Biological Processes

For many years, we have devoted our research to the study of the thermodynamic properties of hydrophobic hydration processes in water, and we have proposed the Ergodic Algorithmic Model (EAM) for maintaining the thermodynamic properties of any hydrophobic hydration reaction at a constant pressure from the experimental determination of an equilibrium constant (or other potential functions) as a function of temperature. The model has been successfully validated by the statistical analysis of the information elements provided by the EAM model for about fifty compounds. The binding functions are convoluted functions, RlnKeq = {f(1/T)* g(T)} and RTlnKeq = {f(T)* g(lnT)}, where the primary linear functions f(1/T) and f(T) are modified and transformed into parabolic curves by the secondary functions g(T) and g(lnT), respectively. Convoluted functions are consistent with biphasic dual-structure partition function, {DS-PF} = {M-PF} ∙ {T-PF} ∙ {ζw}, composed by ({M-PF} (Density Entropy), {T-PF}) (Intensity Entropy), and {ζw} (implicit solvent). In the present paper, after recalling the essential aspects of the model, we outline the importance of considering the solvent as “implicit” in chemical and biochemical reactions. Moreover, we compare the information obtained by computer simulations using the models till now proposed with “explicit” solvent, showing the mess of information lost without considering the experimental approach of the EAM model.

Understanding Hydrophobic Effects: Insights from Water Density Fluctuations

The aversion of hydrophobic solutes for water drives diverse interactions and assemblies across materials science, biology, and beyond. Here, we review the theoretical, computational, and experimental developments that underpin a contemporary understanding of hydrophobic effects. We discuss how an understanding of density fluctuations in bulk water can shed light on the fundamental differences in the hydration of molecular and macroscopic solutes; these differences, in turn, explain why hydrophobic interactions become stronger upon increasing temperature. We also illustrate the sensitive dependence of surface hydrophobicity on the chemical and topographical patterns the surface displays, which makes the use of approximate approaches for estimating hydrophobicity particularly challenging. Importantly, the hydrophobicity of complex surfaces, such as those of proteins, which display nanoscale heterogeneity, can nevertheless be characterized using interfacial water density fluctuations; such a characterization also informs protein regions that mediate their interactions. Finally, we build upon an understanding of hydrophobic hydration and the ability to characterize hydrophobicity to inform the context-dependent thermodynamic forces that drive hydrophobic interactions and the desolvation barriers that impede them. Expected final online publication date for the Annual Review of Condensed Matter Physics, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Microwave heating of water–ethanol mixtures

A simple measure of the susceptibility of a substance to microwaves (MW) is the resulting heating rate that depends on its heat capacity, density, starting temperature, MW extinction coefficient at the used MW frequency and distance from the irradiated surface. Water, that is ubiquitous in many products, currently treated with MW, shows a large susceptibility at 2450 MHz MW. This is why water is a suitable reference to rank the MW susceptibility of other compounds. Aqueous solutions are the simplest systems to investigate how the presence of extra compounds can modify (normally, reduce) this property. The present work provides a very simple evidence of a peculiar MW susceptibility of the water–ethanol mixture with azeotropic composition, XEtOH = 0.90 mol fraction, at temperatures rather below the respective boiling point at ambient pressure. The available literature reports a number of experimental and theoretical investigations that suggest the formation of (EtOH)n·(H2O)m ring clusters that change the hydrogen bond network and/or favor intermolecular hydrophobic hydration. The decamer, (EtOH)9·H2O, could be responsible for the peculiar MW susceptibility of the azeotropic mixture.