Effect of n-Alkanols on Lipid Bilayer Hydration
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- 作者：Cojen Ho and Christopher D. Stubbs
- 刊名：Biochemistry
- 出版年：1997
- 出版时间：September 2, 1997
- 年：1997
- 卷：36
- 期：35
- 页码：10630 - 10637
- 全文大小：219K
- 年卷期：v.36,no.35(September 2, 1997)
- ISSN：1520-4995
文摘
The effect of a homologous series of aliphaticn-alkanols on the presence of water within thehead group and acyl chain region of lipid bilayers was investigatedusing time-resolved fluorescencespectroscopy according to a previously published approach [Ho, C.,Slater, S. J., & Stubbs, C. D. (1995)Biochemistry 34, 6188-6195]. Upon addition ofn-alkanols to phosphatidylcholine bilayers thefluorescencelifetime ofN-[5-(dimethylamino)naphthalene-1-sulfonyl]dipalmitoylphosphatidylethanolamine(dansyl-PE) decreased, indicative of an increased water content within the headgroup region, the effect being alinear function of n-alkanol chain length (C1-C8), basedon the total n-alkanol concentration. Thefluorescence lifetimes of1-palmitoyl-2-[[2-[4-(6-phenyl-trans-1,3,5-hexatrienyl)phenyl]ethyl]carbonyl]-3-sn-phosphatidylcholine (DPH-PC) andN-[[4-(6-phenyl-1,3,5-hexatrienyl)phenyl]propyl]trimethylammoniump-toluenesulfonate (TMAP-DPH), and the fluorescenceintensity ratio of the latter in D2O comparedtothat in H2O, were used to probe the level of water in theacyl chain region. There was a decrease in thelifetime and an increase in the D2O/H2Ofluorescence intensity ratio upon addition of short-chainn-alkanols(C1-C3), suggestive of increased water content. By contrast,long-chain n-alkanols (C4-C8) increasedthe lifetime and decreased the ratio, suggestive of decreased watercontent. Acyl chain order, determinedfrom DPH-PC fluorescence anisotropy, was decreased by alln-alkanols, indicating that the effects werenot probe-dependent. The effects of short- and long-chainn-alkanols on the fluorescence lifetime of thetryptophans of gramicidin, incorporated into phosphatidylcholinebilayers as a model membrane protein,were similar to those obtained with TMAP-DPH and DPH-PC; ethanoldecreased and hexanol increasedthe lifetime. Thus the effect of n-alkanols and generalanesthetics on changes in the amount of water thatmay be accommodated within the acyl chain region of the bilayer is notpredictable on the basis of themagnitude of effects on head group region or acyl chainorder/fluidity.