| Abstract
| - We have developed a fluorescence quenching method using peptides containing 3,5-dibromotryrosine to measure oligomerization of model transmembrane α-helices in lipid bilayers. Peptidesof the type Ac-LysLysGlyLeumXLeunLysLysAla-amide where X is tryptophan or 3,5-dibromotyrosinewere found to form heterodimers in bilayers of phosphatidylcholine in the liquid-crystalline phase. Thefree energy of dimer formation changed little with increasing number of Leu residues from 16 to 22 butincreased with increasing phospholipid fatty acyl chain length, with a slope of about 0.5 kJ mol-1 perfatty acyl chain carbon. Peptides were excluded from lipid in the gel phase, resulting in increased levelsof oligomerization. Addition of cholesterol to form the liquid-ordered state led to increased dimerizationbut without phase separation. The presence of phosphatidylethanolamine had little effect on dimerization.
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