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Dissertation Information for Kevin Lawrence Caran

NAME:
- Kevin Lawrence Caran

DEGREE:
- Ph.D.

DISCIPLINE:
- Chemistry

SCHOOL:
- Emory University (USA) (2001)

ADVISORS:
- Fred M. Menger

COMMITTEE MEMBERS:
- Lanny S. Liebeskind
- David Goldsmith

MPACT Status: Fully Complete

Title: I. L-Cystine-derived thermoreversible aqueous gelators. II. Morphological and chemical studies on large and giant vesicles

Abstract: "A family of compounds based on dibenzoyl-L-cystine ( 1 ), a colloidal gelator, has been synthesized in an effort to gain a greater understanding of aqueous physical gels. Eight of the 14 derivatives studied were found to immobilize aqueous media containing DMSO, three of which formed stable gels at less than 1 mM concentration. Gels from all of the new successful gelators formed faster, could be prepared at lower concentrations, and had higher shear storage moduli (G ' ) than 1 . Rheological measurements were analyzed by comparing G ' values of gels across a range of concentrations for each gelator. Thermal stability of gels was studied using temperature-sweep oscillation rheology, the ""ball-drop"" method, differential scanning calorimetry (DSC), and variable temperature (VT) NMR. The thermally induced transition between gel and sol was found to be gradual and non-precipitous. Additional modes of study included X-ray crystallography, light microscopy and scanning electron microscopy (conventional and cryo-HRSEM) which, along with VT NMR, provide evidence for polymorphic fibrous aggregated as the solid-like framework supporting these gels.

Vesicles are important colloidal aggregates which can range in size from approximately 20 nanometers to hundreds of micrometers. High-resolution images of extruded large vesicles have been recorded using two modern low temperature electron microscopy techniques: cryo-high-resolution scanning electron microscopy (cryo-HRSEM) and cryo-scanning transmission electron microscopy (cryo-STEM). Both methods allow the direct observation of fully hydrated vesicles without prior fixation and removal of water required for conventional EM techniques. Giant vesicles have been used to coat microscopically visible polystyrene latex beads. Epi-fluorescence microscopy reveals that a fluorescent lipid probe is able to travel quickly from one shell to another within a double-coated bead. Vesicles containing surface-bound mannose-6-phosphonate were incubated with human breast cancer cells, which possess an abnormally high number of mannose-6-phosphate receptors on their surface. Both phase-contrast and epi-fluorescence microscopy give evidence that the sugar-steroid conjugate may serve as a chemical adhesive between the vesicles and cells. Finally, a membrane-bound non-fluorescent quinolinium derivative has been synthesized. Deprotection of this compound (either by hydrolysis or nucleophilic attack) liberates a membrane-bound fluorescent dye. This ongoing work provides us with a powerful tool to study inter-membrane interactions."

MPACT Scores for Kevin Lawrence Caran

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2008-04-07 07:55:40

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