Fast approximations for accessible surface area and molecular volume of protein segments

Equations are presented that approximate the accessible surface area of a continuous protein segment using the surface area of an inertial ellipsoid and that approximate the molecular volume from the number of non‐hydrogen atoms in the segment. These approximations, which are appropriate for segments of four or more residues in length, are much faster to calculate than the exact solutions, yet suffer only a 3–8% error. Included in an appendix are FORTRAN subroutines that calculate the surface area of an ellipsoid from its three principal moments of inertia.