Depth of immersion of fluorescent chromophores in biomembranes studied by quenching with nitroxide radical

A novel method has been developed for measuring depth of immersion of a flu orescent chromophore in biological matrices, such as biomembranes. The meth od is based on dynamic quenching of chromophore fluorescence by a nitroxide probe freely diffused in solution. Theoretical considerations and experime ntal evidences relating to the method are discussed. The proposed method wa s applied to investigation of lecithin liposomes and membranes from Bacillu s subtilis modified by the photochrome-fluorescent probe 4,4'-dimethylamino cyanostilbene. (C) 2001 Elsevier Science B.V. All rights reserved.