A calorimetric and spectroscopic comparison of the effects of ergosterol and cholesterol on the thermotropic phase behavior and organization of dipalmitoylphosphatidylcholine bilayer membranes
A calorimetric and spectroscopic comparison of the effects of ergosterol and cholesterol on the thermotropic phase behavior and organization of dipalmitoylphosphatidylcholine bilayer membranes
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DOI：
10.1016/j.bbamem.2009.09.002
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发表时间：
2010-03-01
影响因子：
3.4
通讯作者：
McElhaney, Ronald N.
中科院分区：
文献类型：
--
作者：
Mannock, David A.;Lewis, Ruthven N. A. H.;McElhaney, Ronald N.
我们进行了比较DSC和FTIR光谱测量胆固醇（Chol）和麦角甾醇（Erg）的热致相行为和组织的DPPC双层的影响。麦角甾醇是酵母、真菌和许多原生动物生物膜中的主要甾醇。它与Chol的不同之处在于有两个额外的双键，一个在C7-8的类固醇核中，另一个在C22-23的烷基链中。Erg还在C24的烷基链中具有额外的甲基。我们的DSC研究表明，Erg的掺入比Chol更有效地降低预转变的焓。在较低的浓度下，Erg在减少主相变的尖锐和宽分量的不确定性方面也比Chol更有效。然而，在甾醇浓度为30至50摩尔%时，Erg在降低宽组分的焓方面通常不太有效，并且在50摩尔%时不能完全消除协同烃链熔融相变，Chol也是如此。然而，在该较高的麦角固醇浓度范围内，没有证据表明麦角固醇微晶形成。我们的FTIR光谱研究表明，Erg掺入产生类似的液晶DPPC双层的排序一样胆固醇，但增加的程度的氢键的脂肪酰基羰基基团的DPPC双层的甘油主链区域。这些和其他结果表明，Erg在较高浓度下在DPPC双层中的混溶性低于Chol。最后，我们提供了一个尝试性的分子解释Erg和胆固醇磷脂双层的比较实验和计算结果，强调这两个甾醇之间的动态构象差异。(C)2009 Elsevier B. V.保留所有权利。
We performed comparative DSC and FTIR spectroscopic measurements of the effects of cholesterol (Chol) and ergosterol (Erg) on the thermotropic phase behavior and organization of DPPC bilayers. Ergosterol is the major sterol in the biological membranes of yeasts, fungi and many protozoa. It differs from Chol in having two additional double bonds, one in the steroid nucleus at C7-8 and another in the alkyl chain at C22-23. Erg also has an additional methyl group in the alkyl chain at C24. Our DSC studies indicate that the incorporation of Erg is more effective than Chol is in reducing the enthalpy of the pretransition. At lower concentrations Erg is also more effective than Chol in reducing the enthalpies of both the sharp and broad components of main phase transition. However, at sterol concentrations from 30 to 50 mol%, Erg is generally less effective at reducing the enthalpy of the broad components and does not completely abolish the cooperative hydrocarbon chain-melting phase transition at 50 mol%, as does Chol. Nevertheless, in this higher ergosterol concentration range, there is no evidence of the formation of ergosterol crystallites. Our FTIR spectroscopic studies demonstrate that Erg incorporation produces a similar ordering of liquid-crystalline DPPC bilayers as does Chol, but an increased degree of hydrogen bonding of the fatty acyl carbonyl groups in the glycerol backbone region of the DPPC bilayer. These and other results indicate that Erg is less miscible in DPPC bilayers at higher concentrations than is Chol. Finally, we provide a tentative molecular explanation for the comparative experimental and computation results obtained for Erg and Chol in phospholipid bilayers, emphasizing the dynamic conformational differences between these two sterols. (C) 2009 Elsevier B.V. All rights reserved.