Modeling Relaxation Timescales of Coupled Membrane/Protein Systems

Biological membranes are essential players in the biggest and most complex biological processes. Therefore, when modeling such systems, it is critical to accurately capture the relevant physics. We use a continuum description of the membrane combined with a simple particle model to investigate the coupled dynamics of the systems with the aim to accurately reproduce the present relaxation timescales. These timescales can provide structural information as well as make critical distinctions between mechanisms. How the particles are attached to the membrane is an important distinction when trying to reproduce accurate dynamics and ensembles. For particles that are tightly bound to the membrane lipids, we consider that “diffusion in” the membrane is not equivalent to particles that are bound generally to the membrane, which we designate “diffusion on” the membrane surface. Dif- fusion on the surface acts as a negative tension on the membrane. However, diffusion in the surface does not have the same contribution and when embedding a lipid-like particle into a continuum membrane, effectively replacing an implicit lipid, it is critical not to “double count” contributions to mechanical properties. In this work we consider two important consequences of dynamics on membrane surfaces. First, we characterize the effect of the dynamics of curvature-sensitive particles on relaxation timescales. Second, we examine the circumstances in which membrane-attached proteins can exhibit an effective negative tension, supporting tubulation and membrane bending