title: FTIR study of the monosialoganglioside GM1 in perdeuterated dimyristoylglycerophosphocholine (DMPCd54) multilamellar bilayers: spectroscopic evidence of a significant interaction between Ca2+ ions and the sialic acid moiety of GM1.
abstract: Fourier transform infrared (FTIR) spectroscopy was employed to study bovine brain GM1 and perdeuterated dimyristoylglycerophosphocholine (DMPCd54) multilamellar dispersions (mole fractions of GM1 in DMPCd54: 0.12, 0.15, 0.19, 0.26, 0.34, 0.41, and 0.58), in the absence and presence of 10 mM CaCl2. GM1 micelles did not display a thermal phase transition in the temperature range 5-60 degrees C. Moreover, the ceramide moiety of GM1 inserted into the hydrophobic core of DMPCd54 bilayers and was capable of undergoing a single, cooperative phase transition (Tm = 22-28 degrees C, depending on GM1 content) in a bilayer system. This suggested that the mixed bilayers consisted of a homogeneous mixture and that GM1 was uniformly dispersed in the bilayer plane rather than segregated into regions of relative enrichment. The coexistence of GM1 and DMPCd54 in a bilayer environment induced a rearrangement of the interfacial hydrogen bonding network of the amide I and ester C=O groups, relative to GM1 micelles and DMPCd54 bilayers, respectively. The modifications induced by GM1 might ultimately modulate surface events such as lipid-lipid and/or lipid-protein interactions. The spectroscopic results also suggested that the glycolipid's headgroup surface location and conformation in bilayers allow GM1 to act as a receptor for Ca2+ via its sialic acid moiety.
authors.affiliation: Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada, K1H 8M5.
authors.forename: M
authors.initials: M
authors.lastname: Bou Khalil
authors.forename: M
authors.initials: M
authors.lastname: Kates
authors.forename: D
authors.initials: D
authors.lastname: Carrier
mesh_terms: D000577:Amides; D000818:Animals; D002118:Calcium / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D002417:Cattle; D003903:Deuterium; D017666:Deuterium Oxide; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D005677:G(M1) Ganglioside / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry*; D008823:Micelles; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D000577:Amides; D002264:Carboxylic Acids; D008051:Lipid Bilayers; D008823:Micelles; D010710:Phosphates; D010715:Phosphatidylglycerols; D005677:G(M1) Ganglioside; D003903:Deuterium; C002773:dimyristoylphosphatidylglycerol; D019158:N-Acetylneuraminic Acid; D017666:Deuterium Oxide; D002118:Calcium; D004134:Dimyristoylphosphatidylcholine