The effects of various peptides on the thermotropic properties of phosphatidylcholine bilayers |
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Authors: | Richard M Epand Julian M Sturtevant |
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Institution: | 1. Department of Biochemistry, McMaster University Health Sciences Center, Hamilton, Ontario L8N 3Z5, Canada;2. Department of Chemistry and Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA |
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Abstract: | The effects of an amino acid derivative (N-benzoyl-l-argininamide), four small peptides (Phe-Gly-Phe-Gly, gastrin-related peptide (Trp-Met-Arg-Phe-NH2), tetragastrin (Trp-Met-Asp-Phe-NH2), pentagastrin (Boc-βAla-Trp-Met-Asp-Phe-NH2)) and one medium-sized peptide. glucagon (29 residues), on the gel-to-liquid crystalline transition of a multilamellar suspension of dimyristoylphosphatidylcholine have been studied by means of high-sensitivity differential scanning calorimetry. At low concentrations of added solutes, the temperature at which the excess apparent specific heat in the gel-to-liquid crystalline phase transition of the lipid is maximal is lowered by an amount proportional to the total concentration of the peptide, with proportionality constants ranging from ?0.018 K mM?1 for Phe-Gly-Phe-Gly to ?3.1 K mM?1 for the gastrin-related peptide. The lipid mixtures involving the first two solutes listed above exhibited approximately symmetrical curves of excess apparent specific heat vs. temperature. The curves for the other solutes were asymmetric, and could be well represented as the sum of either two or three two-state curves. The asymmetry, which was especially pronounced in the cases of pentagastrin and glucagon, thus appeared to be due to the presence of components having lower and/or higher transition temperatures than that of the lipid. Pentagastrin and glucagon (R.M. Epand and J.M. Sturtevant, Biochemistry 20 (1981) 4603) have much smaller effects on the gel-to-liquid crystalline phase transition of dipalmitoylphosphatidylcholine than on that of the dimyristoyl analog. |
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Keywords: | Glucagon: Pentagastrin Lipid bilayer Phase transition Peptide -lipid interaction DMPC di-myristoylphosphatidylcholine DPPC dipalmitoylphosphati-dylcholine DSC differential scanning calorimeter(ry) |
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