FIG. 6.

The dependence of fusion kinetics on sphingolipid structure. Experimental conditions were the same as for Fig. 1 except that SM was replaced with the indicated sphingolipid. Waiting-time distributions were generated (see Materials and Methods). (A) SM and ceramide-PE yielded faster kinetics of fusion than did the ceramides. Lyso-SM supported fusion with kinetics comparable to those of the ceramides. (B) The kinetics of fusion for ceramides or cerobrosides in the planar bilayer membrane were similar. Neither the precise head group of the cerobroside nor the length of the amide-linked acyl chain on the ceramide strongly affected kinetics.