Myofilaments in Frozen-etched Muscle


THE myosin molecule is a slender rod about 1550 Å long and 20 Å in diameter with a globular thickening at one end1–5. Huxley has shown2 that these molecules can combine in vitro to form rod-shaped aggregates with a smooth central section and regions at each end which bear numerous lateral projections, and has pointed out the similarity of this structure to that of the thick filaments of striated muscle. He has suggested that thick filaments are formed by interaction between the longitudinally oriented tails of the component molecules, while the globular heads project to form cross bridges to the thin filaments. The head ends are all directed away from the centres which lie in the M bands so that the two halves of the filament have opposite structural polarity. This communication reports a new demonstration of this dipolar structure of the thick filament which is fundamental to the sliding filament theory of muscular contraction2.

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BERTAUD, W., RAYNS, D. & SIMPSON, F. Myofilaments in Frozen-etched Muscle. Nature 220, 381–382 (1968).

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