Effects of halothane on dipalmitoylphosphatidylcholine liposomes: a Raman spectroscopic study
Raman spectroscopy has been to monitor the concentration of halothane (1-bromo-1-chloro-2,2,2-trifluoroethane) in 20% aqueous dispersions of dipalmitoylphosphatidylcholine (DPPC) as well as to follow changes in the acyl chain order within the hydrocarbon interior of the liposomes. Temperature profiles for the gel to liquid-crystalline phase transitions for the liposomes were constructed from changes in peak height intensity ratios in the C-H stretching mode and C-C stretching mode regions. Halothane present at the clinical level produces a change of -0.5/sup 0/C in the phase transition temperature. A limiting transition temperature of about 21/sup 0/C and saturation of the gel phase occur when the molar ratio of halothane to DPPC reaches about 1.25. At molar ratios above 2.1, the liquid-crystalline phase is also saturated with halothane. Calculations of the distribution of halothane between the various phases in the system are presented and used to interpret literature data as well as the present experiments. Ideal solution theory accounts rather well for the depression in the transition temperature over most of the mole ratio range, an outcome which implies that halothane is excluded from the hydrocarbon interior but not the head-group region in the gel phase. The role of halothane in the head-group region is discussed.
- Research Organization:
- National Institutes of Health, Bethesda, MD
- OSTI ID:
- 5833083
- Journal Information:
- Biochemistry; (United States), Vol. 26:9
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
HALOGENATED ALIPHATIC HYDROCARBONS
BIOLOGICAL EFFECTS
RAMAN SPECTROSCOPY
LIPOSOMES
TRANSITION TEMPERATURE
AQUEOUS SOLUTIONS
PHASE TRANSFORMATIONS
PHOSPHOLIPIDS
CELL CONSTITUENTS
DISPERSIONS
ESTERS
LASER SPECTROSCOPY
LIPIDS
MIXTURES
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANOIDS
PHYSICAL PROPERTIES
SOLUTIONS
SPECTROSCOPY
THERMODYNAMIC PROPERTIES
560300* - Chemicals Metabolism & Toxicology