Benchmarks for Membrane Biophysics

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This project addresses fundamental gaps in our understanding of lipids and proteins in biological membranes. Biological function is governed by the molecular properties of proteins and other biomolecules that operate within the membrane micro-environment provided by and for living cells. As biological understanding progresses, computational methods are becoming increasingly important for predicting the properties of cell membranes. At the same time, the computational methods need to be checked and validated by means of experimental measurements that can serve as benchmarks for the calculations. This project provides such an experimental framework to serve as a basis for advancing the predictive power of computational biophysics. The overarching goal is to understand the operational diversity of membrane proteins for the performance and regulation of biological function. This project will sustain community outreach, dialogue, and early involvement of undergraduate students in cutting-edge research. This proposal will also expose young people to science and recruit them to engage in research through the "Science Café" program. This project addresses central issues in predictive membrane biophysics, including molecular orientation, dynamic properties and the ionization states of designated functional side chains of His, Lys, Glu, Asp and Arg in membrane proteins. The key methods involve peptide synthesis, stable isotope labeling, circular dichroism spectroscopy, solid-state magnetic resonance (NMR) measurements, and collaborations with computational biophysicists. The experimental approaches employ a novel "host" peptide design, developed by the investigators, in which minimal numbers of interfacial aromatic amino-acid residues serve to position a tilted transmembrane helix near a "tipping point" in lipid bilayer membranes. Within this context, the systematic incorporation of specific "guest" residues provides important insights concerning ionization behavior and protein-lipid molecular interactions that are essential for the biological functions of many classes of membrane proteins. The experimental results from this project are expected to establish fundamental benchmarks to aid the development and validation of computational methods for addressing the molecular mechanisms that govern the functioning of specific membrane proteins such as potassium channels, acetylcholine receptors or growth factor receptors, amongst others. This project is supported by the Molecular Biophysics Cluster of the Molecular and Cellular Biosciences Division in the Directorate for Biological Sciences.