Fig. 4. Poisson analysis. Proteolytic loss of SNAREs with increasing trypsin concentrations (1 hour) does not correlate with either the observed decrease in fusion or the derived number of active fusion complexes () at 1 mM [Ca²⁺]_free. Protein proteolysis data are from five separate experiments; the fusion curve and data are from 26 experiments. Proteolytic loss of SNAREs with increasing papain concentrations (1 hour) does not correlate with a loss in fusion. Protein proteolysis and fusion data are from three experiments, except for 2000 units/ml papain, which are the averaged data of 10-14 experiments.