Effects of cholesterol on conformational disorder in dipalmitoylphosphatidylcholine bilayers. A quantitative IR study of the depth dependence
- Rutgers Univ., NJ (USA)
A method originally proposed by Snyder and Poore as a specific probe of trans-gauche isomerization in hydrocarbon chains and recently applied to the quantitative determination of phospholipid acyl chain conformational order is utilized to monitor the effects of cholesterol at various depths in dipalmitoylphosphatidylcholine (DPPC) bilayers. The method is based on the observation that the CD2 rocking modes from the acyl chains of specifically deuterated phospholipids occur at frequencies in the Fourier transform infrared spectrum which depend upon the local geometry (trans or gauche) of the C-C-C skeleton surrounding a central CD2 group. Three specifically deuterated derivatives of DPPC, namely, 4,4,4',4'-d4 DPPC (4-d4 DPPC), 6,6,6',6'-d4 DPPC (6-d4 DPPC), and 12,12,12',12'-d4 DPPC (12-d4 DPPC), have been synthesized, and the effects of cholesterol addition at 2:1 DPPC/cholesterol (mol:mol) on acyl chain order at various temperatures have been determined. At 48 degrees C, cholesterol inhibits gauche rotamer formation by factors of approximately 9 and approximately 6 at positions 6 and 4, respectively, of the acyl chains, thus demonstrating a strong ordering effect in regions of the bilayer where the sterol rings are presumed to insert parallel to the DPPC acyl chains. In contrast, the ability of the sterol to order the acyl chains is much reduced at the 12-position. The sterol demonstrates only a slight disordering of phospholipid gel phases. Finally, the contributions of different classes of gauche conformers to the spectra have been determined.
- OSTI ID:
- 6709185
- Journal Information:
- Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:18; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMICAL REACTION KINETICS
CHOLESTEROL
DEUTERIUM
ESTERS
FOURIER TRANSFORMATION
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
INFRARED SPECTRA
INTEGRAL TRANSFORMATIONS
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
LIPIDS
MOLECULAR STRUCTURE
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
PHOSPHOLIPIDS
REACTION KINETICS
SPECTRA
SPECTROPHOTOMETRY
STABLE ISOTOPES
STEROIDS
STEROLS
TRACER TECHNIQUES
TRANSFORMATIONS