As a consequence, this imbalanced lateral pressure distribution can induce spontaneous curvature of the membrane, as indicated by our continuum mechanics calculation and other recent studies. There were two experimental results regarding the effect of Ca 2+ on the membrane's bending: one suggests a negative curvature, i.e., bending away from the Ca 2+ , while the other suggests the opposite. Our simulation results are in line with Graber et al.'s experimental observation that Ca 2+ can induce a negative curvature of membranes. We suspect that the observation of the positive curvature was due to the different experimental setup, which may introduce other factors that were not accounted for in simulations.