Garner W H, Spector A, Schleich T, Kaptein R
Curr Eye Res. 1984 Jan;3(1):127-35. doi: 10.3109/02713688408997194.
The surface or solvent accessibility of certain individual aromatic residues of calf-gamma II crystallin in solution (1 mM) were measured by the dramatic intensity enhancements of NMR lines generated by the interactions of cyclic radical pair formation of the 3-N-carboxymethyl lumiflavin (flavin I) dye excited (488nm) by an argon laser (5 watts) with the protein. This effect is called photo-chemically induced dynamic nuclear polarization: photo-CIDNP. The "light" and "dark" NMR spectra were taken in alternating scans in the pulsed Fourier transform mode on a Bruker 360 MHz instrument. Subtraction results in the photo-CIDNP difference spectrum containing lines of the polarized residues. With flavin dyes only tyrosine, histidine, and tryptophan can be polarized. The respective theoretical static accessibility of these residues based upon van der Waal's contact radii have been calculated from the atomic coordinates and provide a basis for evaluating the dynamic NMR photo-CIDNP results and for assigning the resonances. These results suggest that while the four tryptophan residues are completely buried, His-113 and His-14 of the five histidines; and Tyr-165 and Tyr-62 of the fifteen tyrosines are sufficiently exposed to elicit a photo-CIDNP effect. These results confirm and extend the observations previously obtained with theoretical electrostatic programs and FT-NMR measurements.
通过用氩离子激光（5瓦，488纳米）激发的3-N-羧甲基黄素（黄素I）染料与蛋白质形成环状自由基对的相互作用所产生的核磁共振谱线强度的显著增强，来测量溶液（1毫摩尔）中小牛γII晶状体蛋白某些单个芳香族残基的表面或溶剂可及性。这种效应被称为光化学诱导动态核极化：光CIDNP。在布鲁克360兆赫仪器上，以脉冲傅里叶变换模式交替扫描获取“亮”和“暗”核磁共振谱。相减得到包含极化残基谱线的光CIDNP差异谱。使用黄素染料时，只有酪氨酸、组氨酸和色氨酸可以被极化。根据范德华接触半径，从原子坐标计算出这些残基各自的理论静态可及性，为评估动态核磁共振光CIDNP结果和指定共振提供了基础。这些结果表明，虽然四个色氨酸残基完全被掩埋，但五个组氨酸中的His-113和His-14；以及十五个酪氨酸中的Tyr-165和Tyr-62充分暴露，从而引发光CIDNP效应。这些结果证实并扩展了先前通过理论静电程序和傅里叶变换核磁共振测量获得的观察结果。
