W0144

Atomic Force Microscopy of Cholesterol Crystal Growth. Jennifer Swift, Richard Abendan, Crina Frincu, Chemistry, Georgetown University, 37th and O Streets, Washington, DC 20057-1227 USA.

The unregulated deposition of cholesterol in vivo is associated with undesirable conditions such as cardiovascular disease and the formation of gallstones. Supersaturation is a prerequisite for crystal nucleation and growth, but the precise mechanism(s) of cholesterol crystallization have not been firmly established. Our recent efforts have focused on elucidating the molecular-level surface structure(s) and growth mechanism(s) of cholesterol crystals under simplified model conditions that simulate those found in vivo.

Epitaxial relationships between the surfaces of inorganic and bio-organic crystals is known to be a potentially important factor in crystal nucleation and growth processes in a variety of biological environments. A modeling algorithm (based on simple geometric lattice matching parameters) was initially used to identify those naturally abundant mineral surfaces that might serve as epitaxial substrates for cholesterol nucleation and growth. The best calculated “fit” was found to arise from (1004) calcite. In situ Atomic Force Microscopy revealed that cholesterol from model bile systems does nucleate and grow epitaxially on such calcite surfaces in orientations predicted by calculations. Using chemical force microscopy techniques, the chemical composition of (001) crystal surfaces has also been established under different solution environments. Through these studies of the nanoscale surface structure and defects, crystal growth mechanisms and epitaxial relationships with other crystalline species, we hope to gain fundamental molecular-level insight into these important pathological crystallization processes.