Fig.3. (A) Electrophoretic separation of I. emarginata extensor muscle fibres on a 15% SDS gel. The positions of molecular mass standards (kDa) are indicated. (B) Effect of proctolin (1µmoll^-1) on serine phosphorylation of I. emarginata extensor muscle proteins. The 30kDa protein band of the proctolin-treated sample (arrow) shows an increased phosphorylation signal compared to the 30kDa protein band of the untreated sample. Molecular mass standards are indicated by arrowheads. Although differences in phosphorylation of a 31kDa, 35kDa and a 36kDa protein are seen in this experiment, these effects do not occur consistently as an effect of proctolin incubation. (C) Densitometric analysis of B. The 30kDa protein band is marked (arrow).