Studies on the Formation and Physical Chemical Properties of Synthetic Myosin Filaments

Abstract

Myosin forms at physiological KCl concentration, filaments which resemble native thick filaments of a sarcomere. An extensive survey on filament length changing various conditions was carried out by both flow birefringence and electron microscopy. The most effective condition on filament length was the speed of lowering of KCl concentration, whereas protein concentration was not effective. The change of turbidity caused by association reaction was measured with a stopped flow apparatus, and the early reaction fitted with an exponential curve. The apparent half time was inversely proportional to the square of protein concentration. The width of the filament calculated from the length in electron micrographs and was s°₂₀, _w was 125 Å and independent of length when the length was longer than 0.61μ. The degree of association was about 200 per 1μ. It is difficult to explain the mechanism of asso-ciation using a usual nucleation-and-growth model without modification.