[Evaluation of the degree of tryptophan residue immersion into the lipid phase of low density serum lipoproteins].
Based on the theory of inductive resonance energy transfer, it was demonstrated that in a two-phase waterlipid system the efficiency of the transfer from the donor to the acceptor, which is evenly distributed in the lipid phase, depends on the donor localization with respect to the interface. The inductive resonance energy transfer from the tryptophane residues of protein of low density serum lipoproteins (LDL) to the pyrene fluorescent probe distributed in the lipid phase of LDL was studied. The degree of immersion of the tryptophane residues with respect to the LDL surface is 11,6 +/- 2,6 A. Among the existing models of LDL where the proteins are localized at 20--80 A above the particle surface or are arranged in a monolayer on the particle surface, the first one does not coincide with the experimental data, whereas the second one agrees well with them.