Unbiased Rare Event Sampling in Spatial Stochastic Systems Biology Models Using a Weighted Ensemble of Trajectories
Fig 11
Enhanced sampling of the first fusion time distribution in the NMJ Model in low calcium conditions.
Shown are measurements of the first fusion (i.e., first passage) time distribution for calcium concentrations of 0.5 mM (left), and 0.3 mM (right). In both plots, weighted ensemble estimate of the distribution of first fusion times for the NMJ model (blue), are compared to brute-force estimates (red) made using the same computational power as the weighted ensemble estimate. Points at the bottom of the plot indicate no fusion events in that time period. Single points with no error bars indicate only one sample, yielding no ability to estimate uncertainties. Brute-force sampling sees very few events, and gives a poor estimate of the shape of the distribution and yields poor confidence intervals (it is unable to exclude zero from any time point at one standard error). Weighted ensemble is able to capture the shape of the fusion time distribution, as well as providing good estimates in the uncertainty of the measured values.