Change in fixed-charge in the thick filament lattice of Limulus striated muscle with sarcomere shortening.

A highly significant increase in fixed-charge occurs in the A-bands of Limulus striated muscle following activation and sarcomere shortening. This is in striking contrast to vertebrate striated muscle. Treatment with either papain or alkaline phosphatase reduces this fixed-charge. The increase in charge may serve as a motive force in thick filament shortening.