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

Baldwin博士首次提出测量单个、孤立的α -螺旋内单个肽NH质子的交换速率。将使用核磁共振（NMR）技术，对一维质子谱进行15N谱编辑。通过化学合成将单个肽NH进行15N标记，利用15N自旋回波差谱法得到单个15N标记肽NH的1H谱。通过实验验证了该方法的可行性。新方法将用于测试螺旋-随机线圈过渡理论的基本假设，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。所提出的实验将提供一种获取短肽结构信息的新技术，例如，当肽与特定受体络合时。目前，无论是在生物技术领域还是在生物医学领域，“肽库”都引起了广泛的兴趣。人们已经开发出了合成天文数字的不同短肽序列的方法，然后选择少量可以在信号转导途径中特异性结合受体的序列。这种方法将为多肽-受体复合物中多肽结构的表征提供重要工具。如上所述，该方法也可以直接应用于表征蛋白质折叠途径上的动力学中间体结构的问题。

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.