Fig. 3.

Radioautograph of myosin extracted from primary muscle culture during differentiation, after step B of purification. Cultures were labeled with [³⁵S]methionine for 1 h. Myosin was extracted as described in Table 1 and analyzed on SDS-polyacrylamide gels. The numbers below the gels indicate the time in S medium (hours) when the 1-h labeling ended. The number of cultures used to extract myosin at each time point is listed in Figure 2. The samples loaded on the gels at 12, 15½, 18½, 22, 25, 28, 40 and 64 h were the equivalents of 1.8, 1.47, 1.39, 1.49, 1.59, 0.44, 0.31 and 0.08 cultures, respectively. Counts per min on gels at each time point were 4,740; 7,810; 10,160; 14,375; 32,410; 17,240; 17,860; and 26,721, respectively. The gel was exposed to the X-ray film for 3 days