Soares Macêdo Z, Furquim T A, Ito A S
Instituto de Física, Universidade de São Paulo, Brazil.
Biophys Chem. 1996 Mar 7;59(1-2):193-202. doi: 10.1016/0301-4622(95)00136-0.
The interaction of alpha-melanocyte stimulating hormone (alpha-MSH) and its analogs [Nle4,D-Phe7]-alpha-MSH (MSH-I) and [Nle4,Asp5,D-Phe7,Lys10]-alpha-MSH(4-10) (MSH-II) with vesicles of dimyristoylphosphatidylglycerol (DMPG) was studied by steady-state fluorescence spectroscopy. The association constants for the interaction were obtained from binding isotherms. Electrostatic effects on the interaction were taken into account through calculation of Gouy-Chapman potentials. The quenching of fluorescence of the peptides by acrylamide and nitroxide labeled lipids demonstrated that insertion of the peptides into the lipid phase of the vesicles causes the changes in the hormone's fluorescence in the presence of DMPG. The parallax method was employed for the estimation of an average depth of penetration of the peptides in the DMPG vesicles. It was found that the Trp residue in alpha-MSH and in MSH-II is positioned around the carbons 6 and 8 of the aliphatic chain. The analog MSH-I goes deeper into the bilayer compared to the others peptides, and the Trp residue locates between carbons 10 and 11 of the acyl chain. The average depth of penetration shows correlation with the number of lipid molecules that interact with one molecule of peptide. There is no direct correlation between the association constants for the lipid-peptide interactions and the depth of penetration of the hormone.
通过稳态荧光光谱法研究了α-黑素细胞刺激素（α-MSH）及其类似物[Nle4，D-Phe7]-α-MSH（MSH-I）和[Nle4，Asp5，D-Phe7，Lys10]-α-MSH(4-10)（MSH-II）与二肉豆蔻酰磷脂酰甘油（DMPG）囊泡的相互作用。从结合等温线获得相互作用的缔合常数。通过计算 Gouy-Chapman 电位来考虑静电对相互作用的影响。丙烯酰胺和氮氧化物标记的脂质对肽荧光的猝灭表明，在 DMPG 存在下，肽插入囊泡的脂质相会导致激素荧光的变化。采用视差法估计肽在 DMPG 囊泡中的平均穿透深度。发现α-MSH 和 MSH-II 中的色氨酸残基位于脂肪链的碳 6 和 8 周围。与其他肽相比，类似物 MSH-I 进入双层更深，色氨酸残基位于酰基链的碳 10 和 11 之间。平均穿透深度与与一个肽分子相互作用的脂质分子数量相关。脂质-肽相互作用的缔合常数与激素的穿透深度之间没有直接相关性。
