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Temperature-dependent Fourier transform infrared spectra of phospholipid bilayers: melittin- and cholesterol-induced effects on molecular organization.

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  • Sevim Akyüz
  • J. Eric D. Davies
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<mark>Journal publication date</mark>14/01/1993
<mark>Journal</mark>Vibrational Spectroscopy
Issue number2
Volume4
Number of pages8
Pages (from-to)199-206
Publication StatusPublished
<mark>Original language</mark>English

Abstract

The perturbations induced by melittin and cholesterol on the molecular organization of dimyristoyl- -α-phosphatidylcholine (DMPC) bilayers, depending on the temperature and concentrations of both melittin and cholesterol, were studied using FT-IR spectrometry. Analysis of the amide I and amide II bands of melittin indicates that melittin exists as a monomer at all temperatures in the DMPC-melittin system (lipid:protein molar ratio R = 14:1) and in DMPC-cholesterol-melittin dispersions (R = 14 and 25) for low cholesterol concentrations (10 mol%). However in the DMPC-cholesterol-melittin systems with high cholesterol (20 mol%) and high melittin (R = 14) concentrations, melittin is found to be in a tetrameric form at T > Tm. The melittin-induced effects in DMPC bilayers containing a low melittin concentration (R = 25) are found to decrease on addition of cholesterol (10 or 20 mol%). Cholesterol, however, has the opposite effect in DMPC-cholesterol-melittin systems containing high cholesterol (20 mol%) and high melittin concentrations (R = 14), i.e., and increased lipid-protein interaction. Cholesterol- and melittin-induced effects on the spectral features of the phospholipid are discussed.