MODIFICATION OF THE GANGLIOSIDE GM1 TO FACILITATE IMAGING AND FUNCTIONAL STUDIES.
Abstract: Since 1997, the lipid rafts model has been proposed to describe the
structure and functions of cell membranes. Many efforts have been made to visualize the
lipid rafts in living cells using various techniques, and revealed the lipid rafts have
small size (20-200 nm) and short lifetime (<1 s). Nonetheless, the direct evidence
remains lacking due to limitation of available techniques. ... read moreWe have designed a new detecting
system using fluorinated ganglioside GM1 to probe lipid rafts by nanoSIMS imaging. We have
synthesized a series of fluorinated ganglioside GM1 analogues (F-GM1s) by modification of
natural GM1 that derived from bovine brain tissues using fluorinated fatty acid
substitution on the lipid tails. (Chapter 2) Mono- and tri-fluorinated GM1 analogues have
been obtained with fluorine atoms at different positions of the lipid tail. Higher order
fluorination (-C6F13) of GM1 has also been accomplished either on the fatty acid chain or
both the fatty acid (C6F13-GM1) and the sphingosine chains (Di-C6F13-GM1). This is the
first report of modification of the sphingosine chain on ganglioside analogues. We have
evaluated the biophysical properties of F-GM1s using multiple techniques, including FACS,
AFM and calcium signaling assay. (Chapter 3) As a result, the terminal mono-fluorinated
version (18-F-GM1) exhibited the highest similarity to the native GM1 and could be
potentially used as a probe to study its behaviors in membranes. The mono-fluorinated GM1
analogues have been employed to study phase behaviors in a quaternary mixture of supported
lipid bilayers using SIMS imaging. By isotopic labeling, domains rich in F-GM1 and
cholesterol have been observed. Additionally, 18-F-GM1 formed larger domains than 12-F-GM1
in bilayers, which was attributed to their different phase transition temperature revealed
by a DSC assay. We have designed and synthesized a NBD labeled GM1 analogue to study its
endocytic pathway in cells. The GM1 analogue was incorporated in Hela cells and analyzed by
confocal fluorescence microscopy. The fluorescently labeld GM1 was found accumulated in
lysosomes, Golgi, and ER, thus provided a potential method for drug delivery and functional
Thesis (Ph.D.)--Tufts University, 2012.
Submitted to the Dept. of Chemistry.
Advisor: Krishna Kumar.
Committee: Clay Bennett, Elena Rybak-Akimova, and Jianmin Gao.
Keywords: Chemistry, and Organic chemistry.read less