Jaikishan Shishir, Björkbom Anders, Slotte J Peter
Biochemistry, Department of biosciences, Abo Akademi University, 20520 Turku, Finland.
Biochim Biophys Acta. 2010 Aug;1798(8):1615-22. doi: 10.1016/j.bbamem.2010.03.022. Epub 2010 Mar 30.
In this study, we have examined the membrane properties and sterol interactions of phosphatidyl alcohols varying in the size of the alcohol head group coupled to the sn-3-linked phosphate. Phosphatidyl alcohols of interest were dipalmitoyl derivatives with methanol (DPPMe), ethanol (DPPEt), propanol (DPPPr), or butanol (DPPBu) head groups. The Phosphatidyl alcohols are biologically relevant, because they can be formed in membranes by the phospholipase D reaction in the presence of alcohol. The melting behavior of pure phosphatidyl alcohols and mixtures with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or cholesterol was assessed using high sensitivity differential scanning calorimetry (DSC). DPPMe had the highest melting temperature ( approximately 49 degrees C), whereas the other phosphatidyl alcohols had similar melting temperatures as DPPC ( approximately 40-41 degrees C). All phosphatidyl alcohols, except DPPMe, also showed good miscibility with DPPC. The effects of cholesterol on the melting behavior and membrane order in multilamellar bilayer vesicles were assessed using steady-state anisotropy of 1,6-diphenyl-1,3,5-hexatriene (DPH) and DSC. The ordering effect of cholesterol in the fluid phase was lower for all phosphatidyl alcohols as compared to DPPC and decreased with increasing head group size. The formation of ordered domains containing the phosphatidyl alcohols in complex bilayer membranes was determined using fluorescence quenching of DPH or the sterol analogue cholesta-5,7,(11)-trien-3-beta-ol (CTL). The phosphatidyl alcohols did not appear to form sterol-enriched ordered domains, whereas DPPMe, DPPEt appeared to form ordered domains in the temperature window examined (10-50 degrees C). The partitioning of CTL into bilayer membranes containing phosphatidyl alcohols was to a small extent increased for DPPMe and DPPEt, but in general, sterol interactions were weak or unfavorable for the phosphatidyl alcohols. Our results show that the biophysical and sterol interacting properties of phosphatidyl alcohols, having identical acyl chain structures, are markedly dependent on the size of the head group.
在本研究中，我们检测了与sn-3连接的磷酸基团相连的醇头基大小各异的磷脂醇的膜性质和甾醇相互作用。感兴趣的磷脂醇是具有甲醇（DPPMe）、乙醇（DPPEt）、丙醇（DPPPr）或丁醇（DPPBu）头基的二棕榈酰衍生物。磷脂醇具有生物学相关性，因为它们可在醇存在的情况下通过磷脂酶D反应在膜中形成。使用高灵敏度差示扫描量热法（DSC）评估了纯磷脂醇以及与1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）或胆固醇的混合物的熔化行为。DPPMe具有最高的熔化温度（约49℃），而其他磷脂醇的熔化温度与DPPC相似（约40 - 41℃）。除DPPMe外，所有磷脂醇与DPPC也表现出良好的混溶性。使用1,6-二苯基-1,3,5-己三烯（DPH）的稳态各向异性和DSC评估了胆固醇对多层双层囊泡中熔化行为和膜有序性的影响。与DPPC相比，所有磷脂醇在流体相中胆固醇的有序化作用均较低，且随头基尺寸增加而降低。使用DPH的荧光猝灭或甾醇类似物胆甾-5,7,(11)-三烯-3-β-醇（CTL）确定了复合双层膜中含磷脂醇的有序域的形成。磷脂醇似乎未形成富含甾醇的有序域，而DPPMe、DPPEt在检测的温度范围（10 - 50℃）内似乎形成了有序域。对于DPPMe和DPPEt，CTL在含磷脂醇的双层膜中的分配略有增加，但总体而言，磷脂醇的甾醇相互作用较弱或不利。我们的结果表明，具有相同酰基链结构的磷脂醇的生物物理和甾醇相互作用特性明显取决于头基的大小。
