Electric Field Dependence of Protein Conformation and Channel Function in Lipid Membranes of Different Compositions

The project concentrated on the effect of cross membrane and tangential electric fields on the conformation and on the motion of membrane components. Cross membrane electric fields were shown by circular dichroism CD to have a pronounced effect on the conformation of bacteriorodopsin and of alamethicin incorporated into lipid bilayer membrane. We tried to confirm the CD results with FTIR but membrane potentials could not be maintained at the high polypeptide concentrations required in the lipid vesicles. No effect of electric field could be observed on the vibrational spectra of the different phospholipid groups. Measurable albeit not very large effects on the spectra were induced by added cholesterol. Permeability of lipid vesicular membranes induced by alamethicin, melittin and by complexes of cholera toxin with ganglioside GM1 was measured polarographically. It is influenced by membrane potential. Lateral mobility of photosystem I PSI induced by tangential electric field was determined by measurement of time dependent change in electrophotoluminescence. Potential dependent interaction of alamethicin, melittin protein kinase C PKC with phospholipid monolayers and of cholera toxin and tetratoxin with lipid monolayers containing the gangliosides GM1 and GT1 were investigated on the polarized mercury electrode surface. Keywords Alamethicin, Melittin, Interaction lipid monolayer, Bilayer structure, Permeability conformation.