The 'Janus' nature of proteins: systems at the verge of the microscopic and macroscopic world.
Direct measurement of the heat capacity of proteins by microcalorimetry has had a decisive impact on understanding the behaviour of these biopolymers. Statistical mechanics allow a straightforward calculation and prediction of the enthalpy and heat capacity curves from the partition function. We show that these predictions can differ from the more intuitive models used so far for the description of the thermodynamic behaviour of proteins if the transition involves a stoichiometry other than 1:1. Furthermore, we delineate that the characteristics of protein unfolding are governed by the fluctuations associated with the small size of these molecules. Therefore it may be necessary to modify the picture of the unfolding of small proteins in the light of statistical physics, while for very large proteins the current view may be maintained as a useful limiting approximation.
Rösgen
J
J
Institut für Physikalische Chemie der Westfälischen Wilhelms-Universität Münster, Germany.
Hallerbach
B
B
Hinz
H J
HJ