Separate contributions of large- and small-scale dynamics to the heat capacity of proteins. A new viscosity approach.
We present here a theoretical description and experimental verification of a novel method of separating large-scale (LS) and small-scale (SS) dynamics contributions to the heat capacities of proteins in solution by using viscosity dependences. It was assumed that the LS dynamics, related to the thermal fluctuations of domains and subunits, is dependent on solvent viscosity within a sucrose concentration of 0-15% w/v, in contrast with the SS dynamics, which are related to fluctuations of atoms and amino acid residues. The results obtained with immunoglobulin G, hemoglobin and cytochrome c were in reasonable accordance with the previous data achieved by a spin-label method: the LS dynamics decrease, whereas the SS dynamics increase within the temperature elevation. The changes are dependent on the stage of the active sites of the proteins. The internal compensation of molecular dynamics between the LS and SS fluctuations may be an important factor in the design of thermostable enzymes and proteins. A new phenomenon concerning the ability of macromolecules to increase free volume in water as a result of ice-like clusters stabilization is revealed.
Käiväräinen
A
A
Finnish-Russian Joint Biotechnology Laboratory, Department of Biochemistry, University of Turku.
Fradkova
L
L
Korpela
T
T
D006358:Hot Temperature; D011506:Proteins / Q000737:chemistry*; D014783:Viscosity
D011506:Proteins