recently we reported preliminary mechanical experiments on freshly skinned rabbit psoas fibers that suggested that while almost all of the cross-bridges are attached to actin in the presence of 4 mm adenyl-5'-yl-imidodiphosphate ( amp-pnp ) ( ionic strength , 0.13 m ) , there is an equilibrium between the attached and detached states , so that , in the presence of 4 mm amp-pnp , fibers should not be able to maintain tension ( schoenberg , et al. , 1984 , in contractile mechanisms in muscle , pollack and sugi , editors. , plenum publishing corp. , ny ) .
C0001271
actin
C0026820
contractile