Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
J Chem Phys. 2011 Aug 7;135(5):055106. doi: 10.1063/1.3623418.
Mid-IR active analogs of enzyme cofactors have the potential to be important spectroscopic reporters of enzyme active site dynamics. Azido-nicotinamide adenine dinucleotide (NAD(+)), which has been recently synthesized in our laboratory, is a mid-IR active analog of NAD(+), a ubiquitous redox cofactor in biology. In this study, we measure the frequency-frequency time correlation function for the antisymmetric stretching vibration of the azido group of azido-NAD(+) in water. Our results are consistent with previous studies of pseudohalides in water. We conclude that azido-NAD(+) is sensitive to local environmental fluctuations, which, in water, are dominated by hydrogen-bond dynamics of the water molecules around the probe. Our results demonstrate the potential of azido-NAD(+) as a vibrational probe and illustrate the potential of substituted NAD(+)-analogs as reporters of local structural dynamics that could be used for studies of protein dynamics in NAD-dependent enzymes.
中红外活性酶辅因子类似物有可能成为酶活性位点动力学的重要光谱报告物。我们实验室最近合成的叠氮烟酰胺腺嘌呤二核苷酸（NAD(+))是 NAD(+)的中红外活性类似物，NAD(+)是生物学中普遍存在的氧化还原辅因子。在这项研究中，我们测量了叠氮-NAD(+)中叠氮基团的反对称伸缩振动的频率-频率时间相关函数在水中的情况。我们的结果与以前对水中拟卤化物的研究一致。我们得出结论，叠氮-NAD(+)对局部环境波动敏感，而在水中，这种波动主要由探针周围水分子的氢键动力学决定。我们的结果表明叠氮-NAD(+)作为振动探针的潜力，并说明了取代的 NAD(+)-类似物作为局部结构动力学报告物的潜力，可用于研究 NAD 依赖性酶中的蛋白质动力学。
