Intensification of the first actin layer-line during contraction of frog skeletal muscle.

The peak position of the first myosin layer-line in frog skeletal muscle shifts towards the higher angle during contraction. An analysis showed that the observed axial intensity profile of the first myosin layer-line is fitted well by summation of two layer-lines at 1/43.0 and 1/36.0 nm-1. The former corresponds to the first myosin layer-line, and the latter to the first actin layer-line whose intensity the analysis shows to increase in 0.03-0.08 nm-1 but to decrease in 0.08-0.14 nm-1 during contraction.