All living cells have a plasma membrane (PM) that separates cytoplasmic space from the extracellular world. This membrane has two lipid layers (or leaflets) which have long been known to be highly asymmetric in their lipid composition. PM asymmetry is a universal and fundamental feature of eukaryotic cells and can be transiently released during biological processes, yet how interleaflet (re)organization of lipids affects bilayer structure and dynamics remains poorly understood. We recently found that in addition to lipid composition, the two leaflets can also differ in their relative total phospholipid abundance (or number). Molecular dynamics (MD) simulations indicate that, similar to compositional asymmetry, such lipid number asymmetry can profoundly alter the biophysical profile of the membrane and its interactions with proteins, however, technical challenges are hindering detailed investigation of these effects in vitro. Our group is working at the forefront of these efforts, using MD simulations to guide the design and interpretation of experiments aimed at unraveling molecular mechanisms driving the observed effects. In this project we will apply MD simulations to: 1) examine a possible experimental handle for studying the properties of number-asymmetric bilayers by using elastically stressed symmetric membranes, which are much easier to prepare and analyze in vitro, and 2) identify the direct and allosteric interactions between leaflets that determine the effects of compositional and number asymmetries.