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Dynamic Characteristics of Muscle Thin Filaments <I>In Vivo</I>

1979; Physical Society of Japan; Volume: 19; Issue: 2 Linguagem: Inglês

10.2142/biophys.19.73

1347-4219

S. Yoshino, Y. Umazume, S. Fujime,

Micro and Nano Robotics

Muscle contraction occurs as a result of the interaction between thin and thick filaments in the presence of free Ca2+ and MgATP. It is thus very important to investigate the dynamic properties of thin filaments in the elementary process of muscle contraction, especially to correlate the tension development with the flexibility of the thin filament due to fluctuations of the imtermolecular bond-strength of actin, tropomyosin and/or troponin.When a striated muslce fiber is overstretched or ATP is removed from the myofibrillar space, the fiber can not contract on electric stimulation. The intensities of optical diffraction lines of such a fiber increase when an electric field is applied along the fiber axis. From this electro-optical effect, we have studied the flexural rigidity of thin filaments in vivo and its dependence on concentrations of free Ca2+. The flexural rigidity steeply changed from 3·10-17 dyn cmcm2 at free [Ca2+] above 3μM to 2·10-16 dyn cmcm2 at free [Ca2+] below 0.5μM.In this article we review the story of our study on this effect from its finding (Umazume & Fujime, 1975) to the recent progress (Fujime & Yoshino, 1978; Yoshino, Umazume, atori, Fujime & Chiba, 1978).