2005-2006 Young Musicians Competition - Winds, Brass, and Percussion

Sponsored by Jim and Bette Cumpton Competition Coordinator Marc Reese, Lynn University Conservatory of Music Jury Christina Burr, Artist Faculty David Cole, Artist Faculty Michael Ellerthttps://spiral.lynn.edu/conservatory_other-competitions/1003/thumbnail.jp

Lattice Simulations Of Phase Morphology In Model Membrane Systems

Model membrane systems are a useful tool for studying the role of lateral phase separation in relation to the lipid rafts on living cells. One key aspect of the phase separation observed in both living and model systems is phase morphology, the size and shape of phase domains. For many lipid systems the phase morphology tends towards a single large round (macroscopic) domain to minimize the perimeter to area ratio. By contrast, several lipid systems have been found to have nanoscopic (nanodomains) or modulated (periodic and thermodynamically stable) phase domains. The explanation for the large excess in phase boundary present in these mixtures requires the use of a competing interactions model, in which line tension (energy per unit length) competes with curvature and/or electrostatics to stabilize non-trivial phase morphologies. To study these interactions in a way that accurately represents the membrane shape we present and implement a lattice model for use in computer simulations of phase morphology. These simulations show that on a spherical surface, curvature can compete with line tension to produce modulated phases that closely match the size and characteristics observed on giant unilamellar vesicles (GUV). The model is extended to include electrostatic repulsion, which is found to break up macroscopic domains on large unilamellar vesicles (LUV) into irregular clusters with correlation lengths consistent with size measurements of nanodomains

Control of a Nanoscopic-to-Macroscopic Transition: Modulated Phases in Four-Component DSPC/DOPC/POPC/Chol Giant Unilamellar Vesicles

We have found modulated phase morphology in a particular region of composition within the liquid-ordered + liquid-disordered coexistence region in the four-component lipid bilayer mixture DSPC/DOPC/POPC/Chol. By controlling lipid composition, we could see distinct types of modulated liquid-liquid phase morphologies, including linear, irregular, and angular features in giant unilamellar vesicles. We used a combination of confocal, two-photon, wide-field fluorescence, and differential interference contrast microscopies, and used stringent controls to minimize light-induced artifacts. These studies establish that both the size and morphology of membrane rafts can be controlled by the concentration and the type of low-melting lipid in mixtures with cholesterol and a high-melting lipid