title: Spin label and 2H-NMR studies on the interaction of melanotropic peptides with lipid bilayers.
abstract: The interaction of the cationic tridecapeptide alpha-melanocyte stimulating hormone (alpha-MSH) and the biologically more active analog [Nle4, DPhe7]-alpha-MSH with lipid membranes was investigated by means of ESR of spin probes incorporated in the bilayer, and NMR of deuterated lipids. All spin labels used here, stearic acid and phospholipid derivatives labeled at the 5th and 12th position of the hydrocarbon chain, and the cholestane label, incorporated into anionic vesicles of DMPG (1,2-dimyristoyl-sn-glycero-3-phosphoglycerol) in the liquid-crystalline phase, indicated that both peptides decrease the motional freedom of the acyl chains. No peptide effect was detected with neutral lipid bilayers. Changes in the alpha-deuteron quadrupolar splittings and spin lattice relaxation time of DMPG deuterated at the glycerol headgroup paralleled the results obtained with ESR, showing that the peptides cause a better packing both at the headgroup and at the acyl chain bilayer regions. The stronger effect caused by the more potent analog in the membrane structure, when compared to the native hormone, is discussed in terms of its larger lipid association constant and/or its deeper penetration into the bilayer.
authors.affiliation: Instituto de Física, Universidade de São Paulo, Brasil.
authors.forename: M H
authors.initials: MH
authors.lastname: Biaggi
authors.forename: T J
authors.initials: TJ
authors.lastname: Pinheiro
authors.forename: A
authors.initials: A
authors.lastname: Watts
authors.forename: M T
authors.initials: MT
authors.lastname: Lamy-Freund
mesh_terms: D000595:Amino Acid Sequence; D002776:Cholestanes; D004578:Electron Spin Resonance Spectroscopy; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D008969:Molecular Sequence Data; D010455:Peptides / Q000032:analysis; D010715:Phosphatidylglycerols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D013113:Spin Labels; D013229:Stearic Acids / Q000737:chemistry; D013696:Temperature; D000521:alpha-MSH / Q000031:analogs & derivatives* / Q000032:analysis
chemical_list: D002776:Cholestanes; D008051:Lipid Bilayers; D010455:Peptides; D010715:Phosphatidylglycerols; D010743:Phospholipids; D013113:Spin Labels; D013229:Stearic Acids; D000521:alpha-MSH; C027756:MSH, 4-Nle-7-Phe-alpha-; C002773:dimyristoylphosphatidylglycerol