Fig. 6. Kinetic analyses of Bak activation and cytochrome c efflux at two [tBid]. (A) The immunoblots show mitochondrial cytochrome c and trypsin-resistant Bak following the addition of either 15 or 0.5 nM tBid to mitochondria at zero time. (B) The blots were used to determine the time courses of Bak conformation change (black symbols) and cytochrome c release (white symbols). Circles, 15 nM tBid; triangles, 0.5 nM tBid. The Bak data were best-fitted according to equation 1 (see Materials and Methods) by the curves shown, yielding the c and f values given (C; f values constrained equal). These values were then used to derive the best fits for the cytochrome c data according to equation 2 (see Materials and Methods) to yield the curves shown and the a values given.