Effect of cholesterol on the solubilization site and the photoionization efficiency of chlorophyll a in dipalmitoylphosphatidylcholine vesicle solutions as studied by electron spin resonance and optical absorption spectroscopies

Journal Article · Wed Jul 22 04:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00249a012· OSTI ID:6181220

Hiromitsu, I; Kevan, L

Electron spin resonance (ESR) and optical absorption studies are carried out to investigate the solubilization site and the photoionization efficiency of chlorophyll a (Chla) in DL-..cap alpha..-dipalmitoylphosphatidylcholine (DPPC) vesicles due to varying concentration of cholesterol. With an increase in the cholesterol concentration, the optical absorption intensity of Chla decreases in liquid vesicle solutions, indicating that the local light intensity inside the vesicle decreases. Photoionization efficiencies of Chla in frozen vesicle solutions with and without potassium ferricyanide, a lipophobic electron scavenger, decrease with the cholesterol addition, while no effect of added cholesterol is seen in electron-transfer efficiency from photoexcited Chla to p-benzoquinone, a lipophilic electron scavenger, in liquid vesicle solution. Paramagnetic dipolar interaction between photoproduced Chla cation and added ferricyanide ion becomes weaker with cholesterol addition in frozen vesicle solutions. It is concluded that both Chla and p-benzoquinone move deeper into the vesicle bilayer when cholesterol is added because of an increase in the internal fluidity or alkyl chain straightening of the bilayer.

• Research Organization: Univ. of Houston, Texas
• OSTI ID: 6181220
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:15; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
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& Thermochemical Conversion-- (1980-)
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
CARBOXYLIC ACIDS
CHEMISTRY
CHLOROPHYLL
CHOLESTEROL
DATA
EFFICIENCY
ELECTRON SPIN RESONANCE
EXPERIMENTAL DATA
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY COMPOUNDS
INFORMATION
IONIZATION
MAGNETIC RESONANCE
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOTOCHEMISTRY
PHOTOIONIZATION
PHYTOCHROMES
PIGMENTS
PORPHYRINS
PROTEINS
QUANTITY RATIO
RESONANCE
SOLUBILITY
SPECTROSCOPY
STEROIDS
STEROLS