Biological Physics is an exciting frontier in physics. It combines the principles of physics and the methods of mathematical analysis to understand how biological systems work. In our group, we specifically investigate the mechanisms by which complex biological molecules and assemblies operate. At the same time, bio-related phenomena offer us physicists unique opportunities to learn new physics on elegant, complex systems.
Problems currently under study at Carnegie Mellon include the structure of lipid bilayers, the physics of viruses, the folding of proteins and the three-dimensional structure of cells. More applied studies are focusing on drug delivery in the lung and the toxicology of nanomaterials. In these studies, we use the entire spectrum of tools from experimental over theoretical to computational, including: x-ray and neutron scattering, optical microscopy and single-molecule spectroscopy, statistical thermodynamics, field theory, differential geometry, and Monte Carlo and molecular dynamics simulations.
A more detailed description of the field and its history can be found HERE.
Markus Deserno uses theoretical and computational approaches – continuum elasticity theory and field thory as well as coarse-grained simulations – to study molecular-scale and mesoscale phenomena in biophysics. This allows him to study larger systems on longer time scales than in atomistic simulations and access a new arena for physical questions, many of which have biological significance. Specifically, Deserno investigates lipid membranes, proteins, viruses, or DNA on length scales larger than atomic resolution but smaller than a typical cell. On these scales, many fundamental physical concepts make a big impact on biology – among them thermal fluctuations, cooperativity, self-assembly, or elasticity. For instance, due to their surfactant-like nature individual lipid molecules in an aqueous environment spontaneously aggregate into membranes, which are laterally many orders of magnitude larger than their thickness. These quasi-two-dimensional fluid surfaces resist bending, a continuum elastic concept, but since the associated moduli are only about one order of magnitude bigger than thermal energy, membranes exhibit large thermal undulations that affect their properties.
Mathias Lösche's research focuses on the functional, structural and dynamic characterization of biomimetic membranes – that is, artifical and lipid bilayer systems that are simpler than complex biological membranes but capture their fundamental Physics aspects. For example, we use surface-sensitive x-ray and neutron scattering alongside with electrochemical and advanced optical techniques to identify, characterize, and optimize membrane models in which we study the association of proteins with lipid bilayers, such as the one shown here. Microscopy techniques are used to assess the in-plane fluidity, dynamics, and 2D morphology of such systems. With this set of tools, we investigate experimentally the physical principles of membrane self-assembly and functionality. We also study the molecular origins of disease, through quantification of the membrane interactions of proteins and peptides, such as neurotransmitters, toxins or tumor suppressor proteins. These studies contribute to a deeper understanding of disease mechanisms, and help characterize cellular attack through pathogens and the self-assembly of viral particles, such as HIV, in affected cells.
John F. Nagle is a research-active emeritus professor, well-known for his ground-breaking experimental and theoretical work on lipid bilayers, which form the structural basis of biomembranes. His studies use x-ray scattering in combination with theoretical modeling, statistical mechanical calculations and simulations, as well as volume measurements. Nagle's long-term focus has been to obtain reliable data for basic structural properties of bilayers and to elucidate the interactions between them. For biologically relevant fluid phase lipid bilayers, both issues involve measuring nanoscale fluctuations, which the group achieves using synchrotron x-rays. A longer-range goal is to understand how the molecular interactions bear out in the observed structure and the fluctuations.