Intrinsic volumetric properties of trialanine isomers in aqueous solution.

The intrinsic volume and the intrinsic coefficient of thermal expansion of alanine tripeptides of different chirality are obtained from densimetric and pressure-perturbation calorimetric measurements by using the volumetric properties of water of hydration obtained from computer simulations. The aim of this study is to provide better understanding of the different contributions to the volumetric properties of peptides in solution. Water of hydration makes a major contribution to the volumetric properties measured experimentally.

Towards a quantitative understanding of protein hydration and volumetric properties.

Herein, we probe by pressure perturbation calorimetry (PPC) the coefficient of thermal expansion, the volumetric and the hydration properties of variants of a hyperstable variant of staphylococcal nuclease (SNase), Delta+PHS. The temperature-dependent volumetric properties of the folded and unfolded states of the wild-type protein are calculated with previously published data. The present PPC results are used to interpret the volume diagram and expansivity at a molecular level.

Pressure perturbation calorimetric studies of the solvation properties and the thermal unfolding of proteins in solution--experiments and theoretical interpretation.

We used pressure perturbation calorimetry (PPC), a relatively new and efficient technique, to study the solvation and volumetric properties of amino acids and peptides as well as of proteins in their native and unfolded state. In PPC, the coefficient of thermal expansion of the partial volume of the protein is deduced from the heat consumed or produced after small isothermal pressure jumps, which strongly depends on the interaction of the protein with the solvent or cosolvent at the protein-solvent interface. Furthermore, the effects of various chaotropic and kosmotropic cosolvents on the volume and expansivity changes of proteins were measured over a wide concentration range with high precision.