Myosin sedimentation constant

The existence of a true myosin in fish muscle has, however, been unequivocally established by the ultracentrifugation of carp actomyosin in presence of ATP (Hamoir, 1951b, 1955). The actomyosin peak disappears completely under these conditions and a new one sedimenting much more slowly becomes visible. Its sedimentation-concentration curve extrapolated to zero concentration gives a sedimentation constant of 6.55 (Fig. 26). The figure of 6.9 previously published (Hamoir, 1951b) has been corrected according to a new calibration of the rotor temperature. In the... 

The diffusion constant of L-myosin is difficult to measure, because this determination, unlike that of sedimentation constant, is spoiled by the denaturation products. These arise very easily in the purification of L-myosin (c/. Section III, 66), and, most important, spontaneously, even in completely homogeneous preparations kept at 0°, from about... 

However large may be before the addition of ATP—whether it is too large to be measured (the gel-like component of Snellman and Erdos (1949) and of Johnson and Landolt (1950), or 280, or approximately 90 (Portzehl et al., 1950)—after the addition there appears consistently only the component with = 7.1 (H. H. Weber, 1947 Portzehl et al., 1950 Snellman and Erdos, 1949 confirmed also by Mommaerts, 1951c) and 7.1 is the sedimentation constant of pure L-myosin. Snellman and Erdos (1949) mention that they have sometimes found also the F-actin peak, which is much more difficult to observe. 

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