The change in the solvent-accessible surface area (SASA) is calculated for 10 hydrophobic core amino acids, Tyr555, Ile574, His575, Ala576, Val577,Phe591, Val593, Leu631, Val636, and Phe639, and plotted versus time. Within 450 ps, the SASA increases by 60%. Therefore, these amino acids are significantly exposed on force activation of repeat 4 of the rod domain.