Segment of a BPTI molecule and its associated Hessian entries. Here, for illustration, a block is defined by one residue. Each residue corresponds to a Hessian block containing all of the forces within the residue, denoted ‘Full’. Adjacent residues have a corresponding electrostatic block denoted ‘Elec.’, e.g. Elec. 13-14. Physically local residues within the cutoff distance have a corresponding electrostatic block, e.g. Elec. 13-38. Bonds connecting non-adjacent residues, such as the disulfide bonds shown, correspond to small 3×3 blocks in the Hessian.