M.Sc Thesis

M.Sc StudentHaimovich-Caspi Lilac
SubjectPhase Transitions, Nucleation and Crystallization in Mixed-
Lipid Model Bile Systems
DepartmentDepartment of Chemical Engineering
Supervisor PROFESSOR EMERITUS Yeshayahu Talmon


We combined transmission electron microscopy at cryogenic temperatures (cryo-TEM) with digital light microscopy (DLM) to visualize and analyze microstructures in two self-aggregation biological systems. In addition, we used cryo-electron diffraction to characterize the crystals growing in solution. We also used freeze-fracture-replication (FFR), to examine microstructures that are too big for direct-imaging cryo-TEM and too small for DLM.

We studied the effects of the addition of a crystallization inhibitor to physiological model bile and to native bile. From our work it appears that its effects on the system are not simply physical. Addition of the inhibitor induced formation of cholesterol monohydrate crystals faster than in the pure model, but crystal size and growth were similar. We believe that the effects of the crystal inhibitor are mainly metabolic, not a direct effect on the cholesterol crystals.

In the second part of our work, we examined the effect of different temperatures and preparation methods on two lung surfactants. We showed the effect of sonication on the size and morphology of the formed vesicles. We also showed the effect of salt on the size of the nanostructure, by changing the solute from water to buffer. In addition, we examined the microstructures below and above the chain melting transition temperature of one of the lipids, dipalmitoylphosphatidylcholine (DPPC).

 Some of the experiments of the lung surfactants were conducted in order to support previous results of indirect measurements for the same samples. The cryo-TEM results matched DLS and SAXS results.