Marinetti T D, Snyder G H, Sykes B D
Biochemistry. 1977 Feb 22;16(4):647-53. doi: 10.1021/bi00623a015.
The interactions of Pr(III) and Eu(III) with specifically nitrated derivatives of the basic bovine pancreatic trypsin inhibitor have been studied using optical spectroscopy and nuclear magnetic resonance (NMR) at 250 and 270 MHz. Stability constants for proton and metal binding to nitrotyrosines 10 and 21 determined optically are in good agreement with those from NMR. Observations of the Eu(III)-induced NMR shifts of the ring protons of nitrotyrosine 21 allowed calibration of the magnetic interactions for this binding site. The Pr(III)-induced shifts for several resolved nonexchangeable backbone proton resonances were compared with calculated shifts using the known x-ray structure. With several simplifying assumptions, the Pr(III)-induced shifts were used to assign one alpha-CH and five NH protons to compatible sets of backbone positions which are consistent with the known pH dependence and resistance to exchange with solvent D2O. Some of the more general aspects of lanthanide-induced shifts are discussed with reference to their use in proteins. Due to the complexities of the analysis of the shift data, the most straightforward use of this technique is in conjunction with the relaxation probe Gd(III) for measurement of intramolecular distances.
利用光学光谱法以及在250和270兆赫下的核磁共振（NMR）技术，研究了Pr(III)和Eu(III)与碱性牛胰蛋白酶抑制剂的特定硝化衍生物之间的相互作用。通过光学方法测定的质子和金属与硝基酪氨酸10和21结合的稳定常数，与核磁共振得出的结果高度一致。对Eu(III)诱导的硝基酪氨酸21环质子的核磁共振位移的观察，使得能够校准该结合位点的磁相互作用。将Pr(III)诱导的几个已解析的非交换主链质子共振的位移，与使用已知x射线结构计算出的位移进行了比较。在做出几个简化假设的情况下，Pr(III)诱导的位移被用于将一个α-CH和五个NH质子分配到与已知pH依赖性和对溶剂D2O交换的抗性相一致的主链位置兼容组中。结合镧系元素诱导位移在蛋白质中的应用，讨论了其一些更普遍的方面。由于位移数据分析的复杂性，该技术最直接的用途是与弛豫探针Gd(III)结合使用，以测量分子内距离。
