1972 年 71 巻 4 号 p. 607-614
Rabbit skeletal tropomyosin was conjugated with fluorescein isothiocyanate at neutral pH and the depolarization of the fluorescence was measured as a function of tem-perature. Rotational relaxation times determined from isothermal experiment at room temperature were from 30 to 45 nanoseconds varing with preparation. Since the rotational relaxation time of a sphere equivalent to tropomyosin monomer is of the order of 120 nanosecond, the above value indicates a flexibility or a segmental motion of tropomyosin. When temperature was raised, a remarkable depolarization was observed around 33°C (at pH 7.5) and the rotational relaxation time reduced to the order of 10-20 nanoseconds. Concomitant with the depolarization, the intrinsic viscosity changed from 0.45dl/g to 0.04dl/g indicating a gross conformational change. This conformational state of low intrinsic viscosity was stable up to 45°C and was completely reversed when temperature was lowered again.
