Therefore, the imbalanced stress across membranes and the resulting membrane curvature induced by Ca 2+ might provide an additional regulatory mechanism for the activation of mechanosensitive channels. The addition of Ca 2+ ions to vesicles containing negatively charged lipids may provide a straightforward way to manipulate membrane curvature, which can be useful for regulating many membrane-involved biological, chemical, and nanoscale processes, such as membrane fusion, drug delivery, and even capturing the activated structures of mechanosensitive ion channels. In addition, Ca 2+ may also have indirect effects on membrane structures, for example through calcium-activated scramblases. When those proteins are activated by Ca 2+ , PS lipids would lip from the inner lealet to the outer lealet, which might also change the membrane structures.