H-Exchange Rates and Hydrogen Bonding of Individual Peptide NH Protons in Alpha-Helices

鲍德温博士建议首次测量单个孤立的α-螺旋中单个多肽NH质子的交换率。将使用核磁共振技术，基于一维质子谱的15N谱编辑。通过化学合成将单肽NH标记为15N，并使用15N自旋回波差分光谱给出单肽NH的1H谱。最后进行了一次试验，验证了该方法的可行性。新方法将被用来检验螺旋-随机卷曲转变理论的基本假设，并提供关于单个α-螺旋中酰胺质子交换率的背景信息，用于解释蛋白质折叠中间体的数据。提出的实验将为获得短肽的结构信息提供一种新的技术，例如，当短肽与特定的受体络合时。目前，无论是在生物技术领域还是在生物医学科学领域，都对“多肽库”产生了广泛的兴趣。已经开发出用于合成天文数字的不同短肽序列，然后用于选择少量能够与信号转导途径中的受体特异性结合的序列的方法。这种方法将为表征多肽-受体复合体中的多肽结构提供一个重要的工具。如上所述，该方法还可直接应用于表征蛋白质折叠途径上的动力学中间体的结构问题。

Dr. Baldwin proposes to measure, for the first time, exchange rates of individual peptide NH protons within single, isolated alpha- helices. A nuclear magnetic resonance (NMR) technique will be used, based on 15N spectral editing of the one-dimensional proton spectrum. A single peptide NH will be 15N-labeled by chemical synthesis of the peptide, and 15N spin echo difference spectroscopy will be used to give the 1H spectrum of the single 15N-labeled peptide NH. A trial experiment demonstrating the feasibility of this approach has been made. The new method will be used to test the basic assumptions of helix-random coil transition theory, and also to provide background information about exchange rates of amide protons in single alpha-helices, for use in interpreting data on protein folding intermediates. %%% The proposed experiments will provide a new technique for obtaining structural information about short peptides, for example, when the peptide is complexed with a specific receptor. Currently there is wide interest in " peptide libraries", both in the biotechnology field and in biomedical science generally. Methodologies have been developed for synthesizing astronomical numbers of different short peptide sequences and then for selecting a small number of sequences that can bind specifically to a receptor in a signal transduction pathway. This method will provide an important tool for characterizing the structure of a peptide in a peptide-receptor complex. As pointed out above, the method also has direct application to the problem of characterizing structures of kinetic intermediates on the pathway of protein folding.