Calculating the local solvent chemical potential in crystal hydrates

Determining solvation patterns in biological systems is crucial in investig ating the functional role water may play in structural stabilization and mo lecular recognition. Determining whether a particular position would be occ upied by a solvent molecule requires the local thermodynamics to be known. In this work we introduce a simple and inexpensive approach based on grand canonical molecular simulations to determine the occupancy factors of the c avities. The method is applied to the test case of the sodium salt of hyalu ronic acid. The results agree very well with experimental results and demon strate the success of the method.