title: Electrochemical and PM-IRRAS studies of the effect of cholesterol on the structure of a DMPC bilayer supported at an Au (111) electrode surface, part 1: properties of the acyl chains.
abstract: Charge density measurements and polarization modulation infrared reflection absorption spectroscopy were employed to investigate the spreading of small unilamellar vesicles of a dimyristoylphosphatidylcholine (DMPC)/cholesterol (7:3 molar ratio) mixture onto an Au (111) electrode surface. The electrochemical experiments demonstrated that vesicles fuse and spread onto the Au (111) electrode surface, forming a bilayer, at rational potentials -0.4 V < (E - Epzc) < 0.4 V or field strength <6 x 10(7) V m(-1). Polarization modulation infrared reflection absorption spectroscopy experiments provided information concerning the conformation and orientation of the acyl chains of DMPC molecules. Deuterated DMPC was used to subtract the contribution of C-H stretching bands of cholesterol and of the polar head region of DMPC from spectra in the C-H stretching region. The absorption spectra of the C-H stretch bands in the acyl chains were determined in this way. The properties of the DMPC/cholesterol bilayer have been compared with the properties of a pure DMPC bilayer. The presence of 30% cholesterol gives a thicker and more fluid bilayer characterized by a lower capacity and lower tilt angle of the acyl chains.
authors.affiliation: Department of Chemistry, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Bin
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Horswell
authors.forename: Jacek
authors.initials: J
authors.lastname: Lipkowski
mesh_terms: D002244:Carbon / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry*; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry; D008560:Membrane Fluidity; D010455:Peptides / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D008051:Lipid Bilayers; D008055:Lipids; D010455:Peptides; D010713:Phosphatidylcholines; D002244:Carbon; D006046:Gold; D006859:Hydrogen; D002784:Cholesterol; D004134:Dimyristoylphosphatidylcholine