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Dark interaction of 5-methoxypsoralen and 8-methoxypsoralen with erythrocyte ghosts: a fluorescence and circular
1Laboratoire de Physique et Chimie Biomoléculaire (CNRS URA 198), Paris, France.
Abstract:
The dark interaction of 5-methoxypsoralen (5-MOP) and 8-methoxypsoralen (8-MOP) with plasma membranes was studied using human erythrocyte ghosts as a model. In the presence of ghosts, modifications of the fluorescence characteristics of 5-MOP were observed, together with a quenching of the fluorescence of the tryptophan (Trp) residues of membrane proteins (up to 25%). Moreover, the appearance of an induced circular dichroism indicates that 5-MOP is located in a chiral environment. In contrast, only slight effects were observed in the case of 8-MOP. It is concluded that 5-MOP molecules are located partly within chiral protein sites of the membrane in such a way that a Förster energy transfer can occur from the Trp residues to the psoralen molecules.
Insights
5-methoxypsoralen (5-MOP) interacts with human erythrocyte membranes, altering fluorescence and protein tryptophan residues. This suggests 5-MOP binds within chiral protein sites, enabling energy transfer.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Photochemistry
Background:
- Psoralens are photoreactive compounds with potential therapeutic applications.
- Understanding psoralen interaction with biological membranes is crucial for their application.
- Human erythrocyte ghosts provide a model system for studying membrane interactions.
Purpose of the Study:
- To investigate the interaction of 5-methoxypsoralen (5-MOP) and 8-methoxypsoralen (8-MOP) with plasma membranes.
- To elucidate the localization and molecular environment of 5-MOP within the membrane.
- To explore potential energy transfer mechanisms between membrane components and psoralens.
Main Methods:
- Utilized human erythrocyte ghosts as a model membrane system.
- Monitored fluorescence characteristics of 5-MOP and tryptophan (Trp) residues.
- Measured induced circular dichroism (CD) to assess molecular environment.
- Compared the effects of 5-MOP and 8-MOP.
Main Results:
- Observed significant modifications in 5-MOP fluorescence in the presence of erythrocyte ghosts.
- Detected quenching of tryptophan fluorescence in membrane proteins by up to 25%.
- Induced circular dichroism indicated 5-MOP resides in a chiral environment.
- 8-MOP showed only minor effects on membrane properties.
Conclusions:
- 5-methoxypsoralen (5-MOP) interacts specifically with human erythrocyte membranes.
- 5-MOP molecules are localized within chiral protein sites of the membrane.
- A Förster resonance energy transfer (FRET) likely occurs from tryptophan residues to 5-MOP.
- 8-MOP exhibits a weaker interaction with the erythrocyte membrane compared to 5-MOP.