Dalosto Sergio D, Vanderkooi Jane M, Sharp Kim A
Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
J Phys Chem B. 2004 May 20;108(20):6450-7. doi: 10.1021/jp0310697.
Changes in the matrix electric field in a protein, due for example to mutations or structural fluctuations, can be correlated with changes in the vibrational transition frequencies of suitable chromophores measured by IR spectroscopy through the Stark tuning rate. To make this correlation, the Stark tuning rate must be known from experiment or theory. In this paper, density functional theory at the B3LYP/TZV level of theory is used to compute the Stark tuning rate of adducts of heme porphyrin, namely, -CO, -CN, and -NO+ compounds. The results are compared with the corresponding vibrational frequencies-field dependencies from vibrational Stark spectroscopy of heme-proteins. The zero-field computed Stark tuning rate of 1.3 cm-1/MV/cm for heme-CO is in agreement with experiment, where typically the rate is 2.4/f cm-1/MV/cm for myoglobin, where f is a local field correction between 1.1 and 1.4. Several small nitrile, carbonyl, and dinitrile molecules were studied to rationalize the findings for the heme-adducted models. Here, the higher B3LYP/6-311++G(2d,2p) level of theory could be used so the agreement with recent experimental results is even better than for heme-adducted groups.
蛋白质中基质电场的变化，例如由于突变或结构波动引起的变化，可以通过斯塔克调谐速率与红外光谱测量的合适发色团的振动跃迁频率变化相关联。为了建立这种关联，必须从实验或理论中得知斯塔克调谐速率。在本文中，使用B3LYP/TZV理论水平的密度泛函理论来计算血红素卟啉加合物，即-CO、-CN和-NO+化合物的斯塔克调谐速率。将结果与来自血红素蛋白振动斯塔克光谱的相应振动频率-场依赖性进行比较。血红素-CO的零场计算斯塔克调谐速率为1.3 cm-1/MV/cm，与实验结果一致，其中肌红蛋白的典型速率为2.4/f cm-1/MV/cm，其中f是介于1.1和1.4之间的局部场校正。研究了几种小的腈、羰基和二腈分子，以合理化血红素加合模型的研究结果。在这里，可以使用更高的B3LYP/6-311++G(2d,2p)理论水平，因此与最近实验结果的一致性甚至比血红素加合基团更好。
