sesA: A Program for the Analytic Computation of Solvent-Excluded Surface Areas.

The surface area of a molecule, an inherent geometric property of its structure, plays important roles in its solvation and functioning. Here we present an accurate and robust program, sesA, for the analytic computation of solvent-excluded surface (SES) areas. The accuracy and robustness are achieved through the analytic computations of all the solvent-accessible surface (SAS) regions for a surface atom and probe-probe intersections. The detailed comparisons of the areas for a large set of protein structures by sesA and msms, a de-facto standard for analytic SAS and SES computations, confirm sesA's accuracy to a good extent and in the same time reveal significant differences between them. The unprecedented accuracy and robustness of sesA make it possible to analyze in great detail the surface areas of any molecules in general and biomolecules in particular.