Li. Horvath et al., SPIN LABEL SATURATION TRANSFER EPR DETERMINATIONS OF THE STOICHIOMETRY AND SELECTIVITY OF LIPID PROTEIN INTERACTIONS IN THE GEL PHASE, Biochimica et biophysica acta, 1147(2), 1993, pp. 277-280
Lipid-protein interactions with the myelin proteolipid protein incorpo
rated in the gel phase of dimyristoylphosphatidylcholine bilayers have
been studied by saturation transfer EPR spectroscopy of spin-labelled
phospholipids. The integrated intensities of the saturation transfer
EPR spectra from spin-labelled phosphatidylcholine are linearly depend
ent on the protein/lipid ratio, and correspond to a fixed stoichiometr
y of approximately 11 lipids per monomer associated with the protein i
n the gel phase. The normalized saturation transfer intensities of spi
n-labelled phosphatidic acid, on the other hand, display a non-linear
dependence on the protein/lipid ratio that can be described well by a
selectivity for interaction with the protein in the gel phase with an
average association constant relative to phosphatidylcholine of approx
. 5.2. These values for the stoichiometry and selectivity of lipid-pro
tein interaction in the lipid gel phase obtained from saturation trans
fer EPR spectroscopy are comparable to those found previously in fluid
phase lipids by conventional EPR spectroscopy.