Grant: Discovery Grants Program - Individual

My long-term aim is the development of accurate computational models to describe the molecular interactions between membrane components and the use of these models to solve fundamental problems in the area of the biophysics and biochemistry of lipid bilayers and monolayers. Computer simulations of lipids and more generally membrane models have grown significantly in the past five years and are now a widely used technique to study the physical chemistry and biophysics of lipids, both by themselves and in combination with experiment. My group has contributed to this area since its inception in the 1990s, when computer power was ca. 5 orders of magnitude less than today and the models much less sophisticated. In the past five years we have made significant progress in improving lipid models, increasing the complexity of our models, and moving closer towards the complexity of biological systems while continuing our work on well-controlled model systems including simple lipid mixtures, micelles and bicelles. We use primarily molecular dynamics simulations and free energy calculations, based on atomistic and coarse-grained descriptions of lipids and other molecules, supplemented by other methods such as electronic structure calculations and continuum electrostatics calculations where required. We co-develop Martini, currently the most popular coarse-grained model for molecular simulation. We will pursue two major directions in our research program. The first is aimed at expanding our computational toolkit to model complex membranes and includes the further development of Martini, computational methods to more efficiently sample mixing of lipid mixtures using a combined molecular dynamics/Monte Carlo method, and the use of virtual reality software in visualization and analysis of membrane simulations. The second direction is driven by fundamental questions about membrane structure and the role of the many components of biological membranes. We will investigate the complex properties of lipid mixtures as a function of composition, including model membranes that, like biological membranes, have a different composition in each of the two leaflets that form their basic bilayer structure. Related to this problem is how cholesterol, a major component of most cell membranes, redistributes within the membrane and interacts with other components, and how lipid distributions and protein conformation are coupled to each other through membrane curvature. These two directions are interrelated as improved computational tools are essential to answer the fundamental questions and to more closely link experiment and simulations. The systems used to study fundamental questions typically are also useful to develop, test, and validate models and new methods. The program will result in improved computational tools that can be used in a broad range of future studies, as well as insight in the fundamental building blocks of biological membranes.