Table of Contents
International Scholarly Research Notices
Volume 2014, Article ID 834189, 6 pages
http://dx.doi.org/10.1155/2014/834189
Research Article

Notable Stabilization of α-Chymotrypsin by the Protic Ionic Additive, [ch][dhp]: Calorimetric Evidence for a Fine Enthalpy/Entropy Balance

1Department of Biophysics, I. Beritashvili Center of Experimental Biomedicine, Gotua 14, 0160 Tbilisi, Georgia
2Institute for Biophysics and Bionanosciences at the Department of Physics, I. Javakhishvili Tbilisi State University, I. Chavchavadze Avenue 3, 0128 Tbilisi, Georgia
3Department of Chemistry and Pharmacy, Friedrich-Alexander University of Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany

Received 3 March 2014; Accepted 23 June 2014; Published 7 September 2014

Academic Editor: Monir Moniruzzaman

Copyright © 2014 Sophio Uchaneishvili et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An impact of 0.5 to 3 M choline dihydrogen phosphate, [ch][dhp], the biotechnologically relevant ionic substance, on the thermal stability of a model globular protein, α-chymotrypsin (α-CT), has been studied exploiting the highly sensitive differential scanning calorimetry (DSC) technique. The notable overall stabilizing effect of  K regarding the thermal transition (melting) temperature, , has been detected. For this kind of series, for the first time, the calorimetric melting enthalpy and transition entropy parameters have been determined simultaneously throughout. The first analysis indicated a two-phase impact implying (a) the initial, dramatic drop in both and , obviously connected to specific, direct interaction between the [ch][dhp] components and α-CT’s charged groups (within 0 to 1 mol/L [ch][dhp]), leading to the essential rearrangement of the interfacial hydrogen-bonded (HB) network; and (b) the follow-up (within 1 to 3.0 mol/L [ch][dhp]), modest changes in and lack of changes in , seemingly connected with a subsequent steady strengthening of already reformed HB network, respectively. These changes, presumably, are primarily facilitated by Coulombic interactions between the [dhp] anions and solvent-exposed positively charged amino groups of α-CT.