In eq. 1, membrane fusion is induced using a spanning cylinder composed of N sf slices (see fig. ). N sf (p) accounts for the number of tail beads (C4A, C4B or C5A) within slice s inside the fusion cylinder. δ sf is a continuous function in the interval [0 1] (δ sf =0 for no beads in slice s and δ sf =1 for 1 or more beads in slice s). In eq. 2, fusion pore nucleation is achieved with a different cylinder (composed of N sn slices, see fig. ) now applied to an also different group, containing lipid heads (PO4), dynamically defined intra-organelle (W)