title: On the effect of low concentrations of alcohols on the conformational stability of globular proteins.
abstract: Low concentrations of alcohols have proven to be able to enlarge the stability curve of globular proteins, by decreasing the cold denaturation temperature and increasing the hot denaturation temperature [S. R. Martin, V. Esposito, P. De Los Rios, A. Pastore and P. A. Temussi, J. Am. Chem. Soc., 2008, 130, 9963-9970]. In order to try to explain these data, I have considered that: (1) an aqueous 2 M MeOH solution can be treated as a uniform liquid, constituted by water molecules, whose density, above the temperature of maximum density, has the same values of neat water, simply shifted by 2 °C toward lower temperatures, whereas, below the temperature of maximum density, it decreases to a slightly lesser extent than the density of neat water; (2) the ΔE(a)(2 M MeOH) quantity, a balance between intra-protein energetic attractions and those with the surrounding solvent molecules, both water and methanol, assumes a constant positive value. These physically-based assumptions, when inserted into the theoretical model developed to rationalize the occurrence of cold denaturation in neat water [G. Graziano, Phys. Chem. Chem. Phys., 2010, 12, 14245-14252], reproduce in a qualitatively correct manner the effect of low concentrations of alcohols.
authors.affiliation: Dipartimento di Scienze per la Biologia, la Geologia e l'Ambiente, Università del Sannio, Via Port'Arsa 11, 82100 Benevento, Italy. graziano@unisannio.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Graziano
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D013696:Temperature
chemical_list: D000438:Alcohols; D011506:Proteins