Entropy is a state function that is often erroneously referred to as the 'state of disorder' of a system. Qualitatively, entropy is simply a measure how much the energy of atoms and molecules become more spread out in a process and can be defined in terms of statistical probabilities of a system or in terms of the other thermodynamic quantities. Entropy is also the subject of the Second and Third laws of thermodynamics, which describe the changes in entropy of the universe with respect to the system and surroundings, and the entropy of substances, respectively.
The idea that entropic effects play a major role in enzyme catalysis has been invoked frequently. In order to quantify this possibility we developed a restraint release (RR) approach for the evaluation of activation entropies in enzymes and solution reactions.   The RR approach appears to be a particularly powerful strategy overcoming the major problems of most current approach, including the inherent unreliability of quasi harmonic and related approaches.
Our initial studies indicated that the entropic contributions to catalysis are much less important than previously thought. We have continued in exploring entropic effects to binding  and catalysis   using the RR approach will also explored entropic contributions to enantioselectivity. We continue to push the frontiers in developing and using efficient and reliable ways for calculations entropy in proteins.