Photodynamic Inactivation of Gramicidin Channels in Bilayer Lipid Membranes: Protective Efficacy of Singlet Oxygen Quenchers Depends on Photosensitizer Location

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T. I. Rokitskaya^*, A. M. Firsov, E. A. Kotova, and Y. N. Antonenko

Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, 119991 Moscow, Russia; fax: +7 (495) 939-3181; E-mail: rokitskaya@genebee.msu.ru

^* To whom correspondence should be addressed.

Received December 23, 2014; Revision received February 27, 2015

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The impact of double bonds in fatty acyl tails of unsaturated lipids on the photodynamic inactivation of ion channels formed by the pentadecapeptide gramicidin A in a planar bilayer lipid membrane was studied. The presence of unsaturated acyl tails protected gramicidin A against photodynamic inactivation, with efficacy depending on the depth of a photosensitizer in the membrane. The protective effect of double bonds was maximal with membrane-embedded chlorin e₆-monoethylenediamine monoamide dimethyl ester, and minimal – in the case of water-soluble tri-sulfonated aluminum phthalocyanine (AlPcS₃) known to reside at the membrane surface. By contrast, the protective effect of the hydrophilic singlet oxygen scavenger ascorbate was maximal for AlPcS₃ and minimal for amide of chlorin e₆ dimethyl ester. The depth of photosensitizer position in the lipid bilayer was estimated from the quenching of photosensitizer fluorescence by iodide. Thus, the protective effect of a singlet oxygen scavenger against photodynamic inactivation of the membrane-inserted peptide is enhanced upon location of the photosensitizer and scavenger molecules in close vicinity to each other.

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KEY WORDS: photodynamic action, gramicidin A, photosensitizer, unsaturated lipids, ascorbate, singlet oxygen, bilayer lipid membrane

DOI: 10.1134/S0006297915060097

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