Statistical mechanics of polymer systems and lipid bilayer membranes

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My research focuses on the structural and dynamical properties of complex fluids, including single-chain polymer systems, Langmuir monolayers, and lipid bilayer membranes.  These polymeric systems have practical applications in thin-film technology and have environmental applications, such as employing biofilms in soil remediation processes (which links well with UPEI's expertise in ecotoxicology).  Additionally, this research has vital biomedical implications.  For example, studies on the coil-globule and globule-solid transitions for isolated polymers in solution are essential to obtain insight into some of the key features that dominate the protein folding process.  In my proposed research, I will use discontinuous molecular dynamics (DMD) simulations to examine the effects of varying different parameters, including the monomer/solvent size ratio, on both the collapse and freezing transitions for homopolymer and heteropolymer systems.     Langmuir monolayers consist of a single layer of surfactants deposited at an air/water interface.  When a monolayer is compressed beyond the equilibrium spreading pressure, the monolayer can collapse through a number of different mechanisms.  In this proposal, I will study how the structure of the solvent affects the stability of the monolayer and attempt to elucidate the driving mechanisms responsible for particular types of collapse phenomena.  These studies are important in understanding the function of lung surfactant monolayers, since this could shed light into the mechanisms responsible for Respiratory Distress Syndrome, a condition occurring in pre-mature infants where there is insufficient surfactant lining the alveoli in the lungs.   Lipid rafts are cholesterol rich domains which form in model lipid bilayer and cell membranes due to lateral phase separation.  Studies on raft formation are relevant for understanding processes such as intracellular trafficking, immune response, and synaptic transmission. In this research project, I will investigate how differences in lipid composition affect the shape, size, and the number of domains for binary lipid-lipid/lipid-cholesterol and ternary lipid-lipid-cholesterol systems.