Data for: The effect of water structure on proton transfer: an EPR approach to solving a classic problem

The mechanism of proton transfer (PT), and how it is affected by water structure, is a fundamental issue in numerous chemical and biological processes. Formulated more than 200 years ago a possible model for PT in aqueous media was proposed by Grotthuss, which continues to be actively studied and debated. In this study, we present a novel experimental approach to investigate PT in aqueous solutions. Our method employs pH-sensitive stable nitroxyl radicals, and makes use of photolysis of 2-nitrobenzaldehyde to generate protons in the sub-nanosecond timescale. The proposed method was used to study the effect of classical chaotropic compounds on PT as studied in various aqueous solutions, i.e. 8 M urea, 6 M guanidine hydrochloride (Gdn·HCl), and potassium chloride (KCl). Our findings reveal significant impacts on PT rates. For instance, in 6 M Gdn·HCl, PT occurred 40-fold slower than in water. The method’s sensitivity to water structure is demonstrated, highlighting its potential for monitoring the kinetics of PT in ice and in proteins.

Journal - Scientific Reports