Separation of thick and thin myofilaments

Abstract

Methods have been developed for separating the thin myofilaments from the thick ones in two molluscan muscles, the opaque adductor of the oyster, and the crossstriated adductor of Pecten. The thick filaments of these muscles have also been obtained with only a small contamination by thin ones. The media used in all procedures were designed to keep the filaments intact. Either differential centrifugation or zone velocity sedimentation on sucrose or glycerol density-gradients may be used; the latter method promises to be more generally useful. The sedimentation coefficients of these natural myofilaments (as measured under the conditions of the experiments) are: $ ̃ 34 s and $ ̃ 50 s for the thin filaments from the oyster muscle; $ ̃ 33 s for the thin filaments and $ ̃ 300 s for the thick filaments from the Pecten muscle. The S-value for the thick filaments from the oyster muscle is too large to be measured. Both myosin and paramyosin were found in the thick filaments of the oyster muscle and the Pecten muscle. Attempts to separate the thick and thin filaments of glycerol-extracted rabbit psoas muscle are also described; the problems involved are discussed.