Relationship Between Cryoprotectant Potential and Protein Hydration in Aqueous Zwitterionic Solutions

Abstract

The cryoprotectant potential of 3‐(1‐(2‐(2‐methoxyethoxy)ethyl)imidazol‐3‐io)butane‐1‐carboxylate (OE2imC3C) for proteins necessitates assessment to elucidate its relationship with protein hydration. To reveal this relationship, we assessed the protein stability (pre‐freezing and post‐thawing) and melting behavior in dilute aqueous protein–OE2imC3C solutions containing varying mole fractions (x) of OE2imC3C (x = 0, 7.7 × 10−3, and 1.7 × 10−2) using Fourier‐transform infrared (FTIR) and near‐UV circular dichroism (near‐UV CD) spectroscopy and differential scanning calorimetry (DSC) techniques. Following freezing/thawing using a deep freezer, protein stability in aqueous OE2imC3C solutions (x = 1.7 × 10−2) preserved the folded state owing to the protein–OE2imC3C interaction, whereas stability at x = 7.7 × 10−3 was reduced. These results indicate that the protein cryoprotectant potential in aqueous OE2imC3C solutions at x = 1.7 × 10−2 is higher than that at x = 7.7 × 10−3, owing to the preferential binding of OE2imC3C with proteins.