Multiple orientation of melittin inside a single lipid bilayer determined by combined vibrational spectroscopic studies
Multiple orientation of melittin inside a single lipid bilayer determined by combined vibrational spectroscopic studies
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DOI：
10.1021/ja067446l
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发表时间：
2007-02-07
影响因子：
15
通讯作者：
Chen, Zhan
中科院分区：
文献类型：
--
作者：
Chen, Xiaoyun;Wang, Jie;Chen, Zhan
尽管有几种成熟的蛋白质结构测定技术，但测定细胞膜或生物材料表面的界面蛋白质的结构和取向信息仍然是一个难题。我们将和频产生（SFG）振动光谱与衰减全反射-傅里叶变换红外光谱（ATR-FTIR）相结合，研究了在底物支撑的脂质双层中重组的α -螺旋肽的取向。蜂蜂素被选为α -螺旋肽的模型，并研究了其与支撑的1,2-双棕榈酰- asn -甘油-3-磷酸甘油（DPPG）双分子层相互作用时的取向。通过对SFG和ATR-FTIR测量得到的酰胺I信号进行极化分析，利用几个试验分布函数推导出了DPPG双分子层内蜂蜂素的取向分布。Melittin模型要么是一个理想的螺旋，要么是一个弯曲结构的螺旋。发现简单的分布函数如δ分布或高斯分布不足以描述DPPG双分子层内蜂窝素的取向分布。相反，两个蜂窝蜂素群体，对应于两个蜂窝蜂素-双层结合状态，可以用来解释实验观察到的结果。本研究中采用的方法证明了在没有外源标记的情况下，使用振动光谱技术的组合在原位获得更准确的肽/蛋白质取向分布的可行性。
Despite the availability of several mature structure determination techniques for bulk proteins, determination of structural and orientational information of interfacial proteins, e.g., in cell membranes or on biomaterial surfaces, remains a difficult problem. We combine sum frequency generation (SFG) vibrational spectroscopy with attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) to investigate the orientation of alpha-helical peptides reconstituted in substrate supported lipid bilayers. Melittin was chosen as a model for alpha-helical peptides, and its orientation when interacting with a supported 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) bilayer has been examined. Through polarization analysis using amide I signals obtained from both SFG and ATR-FTIR measurements, the orientation distribution of melittin inside a DPPG bilayer was deduced using several trial distribution functions. Melittin was modeled as either an ideal helix or a helix with a bent structure. It was found that a simple distribution function such as a delta-distribution or a Gaussian distribution was not adequate to describe the melittin orientation distribution inside a DPPG bilayer. Instead, two populations of melittin, corresponding to two melittin-bilayer association states, could be used to interpret the experimentally observed result. The method employed in this study demonstrates the feasibility of acquiring a more accurate orientation distribution of peptides/proteins in situ using a combination of vibrational spectroscopic techniques without exogenous labeling.