Probing the conformational features of a phage display polypeptide sequence directed against single-walled carbon nanohorn surfaces
Probing the conformational features of a phage display polypeptide sequence directed against single-walled carbon nanohorn surfaces
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DOI：
10.1021/la050961x
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发表时间：
2005-12-06
期刊：
影响因子：
3.9
通讯作者：
Evans, JS
中科院分区：
文献类型：
--
作者：
Kulp, JL;Shiba, K;Evans, JS
单壁碳纳米角（SWNHs）是一种有趣的碳纳米结构，具有科学和技术应用。使用M13噬菌体展示技术，已经出于许多纳米技术和制药目的产生了再次定向于SWNH表面的多肽，但多肽序列相互作用和与SWNH表面结合的分子机制尚不清楚。最近，我们鉴定了线性12-AA M13噬菌体pIII序列NH-12-5-2（DYFSSPYYEQLF），其以高亲和力结合SWNH表面。为了进一步探测该pIII尾部多肽的结构，我们研究了代表12 AA NH-12-5-2序列的模型肽的构象。在中性pH值下，NH-12-5-2模型多肽在构象上不稳定，并表现出涉及D1-S5 N末端片段的两态构象交换。与这种构象交换过程同时进行的是观察到P6残基表现出亚氨基环构象变化。在存在的结构稳定溶剂，TFE，或在pH 2.5，交换过程和Pro环运动现象消失，表明该肽序列的结构可以稳定的外在因素。有趣的是，我们观察到NH-12-5-2在90% v/v TFE中的NMR参数（ROE，（3）J偶合常数）与部分螺旋结构的存在一致，与我们早期CD实验中在低pH下观察到的相似。我们得出结论，NH-12-5-2模型多肽序列具有涉及D1-S5序列区段和P6残基的固有构象不稳定性，但是这种不稳定性可以被外在因素（例如，电荷中和、亚氨基环互变和疏水-疏水相互作用）。这些非键合相互作用可能在识别和结合该噬菌体序列区域SWNH表面中发挥作用。
Single-walled carbon nanohorns (SWNHs) are interesting carbon nanostructures that have applications to science and technology. Using M13 phage display technology, polypeptides directed again SWNHs surfaces have been created for a number of nanotechnology and pharmaceutical purposes, yet the molecular mechanism of polypeptide sequence interaction and binding to SWNHs surfaces is not known. Recently, we identified a linear 12-AA M13 phage pIII sequence, NH-12-5-2 (DYFSSPYYEQLF), that binds with high affinity to SWNHs surfaces. To probe the structure of this pIII tail polypeptide further, we investigated the conformation of a model peptide representing the 12 AA NH-12-5-2 sequence. At neutral pH, the NH-12-5-2 model polypeptide is conformationally labile and exhibits two-state conformational exchange involving the D1-S5 N-terminal segment. Simultaneous with this conformational exchange process is the observation that the P6 residue exhibits imido ring conformational variation. In the presence of the structure-stabilizing solvent, TFE, or at pH 2.5, both the exchange process and Pro ring motion phenomena disappear, indicating that the structure of this peptide sequence can be stabilized by extrinsic factors. Interestingly, we observe NMR parameters (ROEs, (3)J coupling constants) for NH-12-5-2 in 90% v/v TFE that are consistent with the presence of a partial helical structure, similar to what was observed at low pH in our earlier CD experiments. We conclude that the NH-12-5-2 model polypeptide sequence possesses an inherent conformational instability that involves the D1-S5 sequence segment and the P6 residue but that this instability can be offset by extrinsic factors (e.g., charge neutralization, imido ring interconversion, and hydrophobic- hydrophobic interactions). These nonbonding interactions may play a role in the recognition and binding of this phage sequence region to SWNHs surfaces.