A simple quantitative relationship
between the molecular conformational
changes and the corresponding changes in the free energy is presented.
The change in free energy is the sum of that part of the enthalpic
change that is due to the externally applied work (perturbation) and
of that part of the entropic change, termed dissipative entropy, that
is related to the conformational changes. The dissipative entropy
is equivalent to the relative entropy, a concept from information
theory, between the distributions of the conformations in the initial
and the final states. The remaining change in entropy (nondissipative)
cancels exactly with the remaining enthalpic change. The calculation
of the dissipative entropy is demonstrated to pose the main difficulty
in free energy computation. The straightforward decomposition of the
dissipative entropy into contributions from different parts of the
system promises to improve the understanding of the role of conformational
changes in biochemical reactions
