Accurate quantitation of water-amide proton exchange rates using the Phase-Modulated CLEAN chemical EXchange (CLEANEX-PM) approach with a Fast-HSQC (FHSQC) detection scheme
Accurate quantitation of water-amide proton exchange rates using the Phase-Modulated CLEAN chemical EXchange (CLEANEX-PM) approach with a Fast-HSQC (FHSQC) detection scheme
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DOI：
10.1023/a:1008276004875
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发表时间：
1998-02-01
影响因子：
2.7
通讯作者：
Mori, S
中科院分区：
文献类型：
--
作者：
Hwang, TL;van Zijl, PCM;Mori, S
通过磁化转移方法测量水和NH质子之间的交换率通常因人为因素而复杂化，例如分子内NOE和/或来自与水频率一致的C-α质子的TOCSY转移，或来自快速交换羟基或胺质子的交换中继NOE。通过在混合期间应用相位调制清洁化学交换（CLEANEX-PM）自旋锁定序列，135度（x）120度（-x）110度（-x）110度（-x）120度（x）135”（-x），可以消除这些伪影，从而显示明确的水-NH交换光谱。在本文中，CLEANEX-PM混合方案与快速HSQC（FHSQC）检测相结合，并用于获得准确的化学交换率从初始斜率分析的N-15标记的葡萄球菌核酸酶样品。将结果与使用水交换过滤器（WEX）II-FHSQC和自旋回波过滤WEX II-FHSQC测量获得的速率进行比较，并清楚地识别交换系统中的杂散NOE贡献。
Measurement of exchange rates between water and NH protons by magnetization transfer methods is often complicated by artifacts, such as intramolecular NOEs, and/or TOCSY transfer from C-alpha protons coincident with the water frequency, or exchange-relayed NOEs from fast exchanging hydroxyl or amine protons. By applying the Phase-Modulated CLEAN chemical EXchange (CLEANEX-PM) spin-locking sequence, 135 degrees(x) 120 degrees(-x) 110 degrees(x) 110 degrees(-x) 120 degrees(x) 135"(-x) during the mixing period, these artifacts can be eliminated, revealing an unambiguous water-NH exchange spectrum. In this paper, the CLEANEX-PM mixing scheme is combined with Fast-HSQC (FHSQC) detection and used to obtain accurate chemical exchange rates from the initial slope analysis for a sample of N-15 labeled staphylococcal nuclease. The results are compared to rates obtained using Water EXchange filter (WEX) II-FHSQC, and spin-echo-filtered WEX II-FHSQC measurements, and clearly identify the spurious NOE contributions in the exchange system.