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Biophys J, May 2000, p. 2572-2580, Vol. 78, No. 5

Photosensitizer Binding to Lipid Bilayers as a Precondition for the Photoinactivation of Membrane Channels

Tatyana I. Rokitskaya,* Michael Block,dagger Yuri N. Antonenko,* Elena A. Kotova,* and Peter Pohldagger

 *A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia, and  dagger Martin-Luther-Universität, Medizinische Fakultät, Institut für Medizinische Physik und Biophysik, 06097 Halle, Germany

The photodynamic activity of sulfonated aluminum phthalocyanines (AlPcSn, 1 <=  n <=  4) was found to correlate with their affinity for membrane lipids. Adsorbing to the surface of large unilamellar vesicles (LUVs), aluminum phthalocyanine disulfonate induced the highest changes in their electrophoretic mobility. AlPcS2 was also most efficient in mediating photoinactivation of gramicidin channels, as revealed by measurements of the electric current across planar lipid bilayers. The increase in the degree of sulfonation of phthalocyanine progressively reduced its affinity for the lipid bilayer as well as its potency of sensitizing gramicidin channel photoinactivation. The portion of photoinactivated gramicidin channels, alpha , increased with rising photosensitizer concentration up to some optimum. The concentration at which alpha  was at half-maximum amounted to 80 nM, 30 nM, 200 nM, and 2 µM for AlPcS1, AlPcS2, AlPcS3, and AlPcS4, respectively. At high concentrations alpha  was found to decrease, which was attributed to quenching of reactive oxygen species and self-quenching of the photosensitizer triplet state by its ground state. Fluoride anions were observed to inhibit both AlPcSn (2 <=  n <=  4) binding to LUVs and sensitized photoinactivation of gramicidin channels. It is concluded that photosensitizer binding to membrane lipids is a prerequisite for the photodynamic inactivation of gramicidin channels.

Biophys J, May 2000, p. 2572-2580, Vol. 78, No. 5
© 2000 by the Biophysical Society   0006-3495/00/05/2572/09  $2.00


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T. I. Rokitskaya, E. A. Kotova, and Y. N. Antonenko
Tandem Gramicidin Channels Cross-linked by Streptavidin
J. Gen. Physiol., April 28, 2003; 121(5): 463 - 476.
[Abstract] [Full Text] [PDF]


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