Yagi K, Ohishi N, Nishimoto K, Choi J D, Song P S
Biochemistry. 1980 Apr 15;19(8):1553-7. doi: 10.1021/bi00549a003.
Riboflavin tetrabutyrate undergoes characteristic spectral changes, in both the first and second absorption band regions, upon hydrogen bonding with trichloroacetic acid of trifluoroacetic acid. On the basis of the calculated electron densities, hydrogen bonding at the heteroatoms of the isoalloxazine nucleus is considered to occur with increasing concentrations of the proton donor, first at N(1), then at O(12), O(14), and N(3)H, and finally at N(5). The idea that the major effect of the hydrogen bonding at the N(1), N(3)H, and oxygen atoms of the flavin nucleus is to facilitate the electrophilicity of the N(5) position, which was predicted by molecular orbital calculations, was supported by the observation that the hydrogen-bonded flavin in its triplet state abstracts hydrogen from the donor N-benzyl-n,n'-dimethylethylenediamine at a faster rate than do the non-hydrogen-bonded species in CCI4. The implications of the present study in the spectroscopic and catalytic properties of flavoproteins are briefly discussed.
核黄素四丁酸酯与三氯乙酸或三氟乙酸形成氢键时，在第一和第二吸收带区域都会发生特征光谱变化。根据计算出的电子密度，异咯嗪核杂原子处的氢键被认为会随着质子供体浓度的增加而形成，首先在N(1)处，然后在O(12)、O(14)和N(3)H处，最后在N(5)处。黄素核中N(1)、N(3)H和氧原子处的氢键主要作用是促进N(5)位的亲电性，这一观点是通过分子轨道计算预测得出的，且得到了如下观察结果的支持：处于三重态的氢键结合黄素从供体N-苄基-n,n'-二甲基乙二胺中提取氢的速率比在CCl4中的非氢键结合物种更快。本文简要讨论了本研究对黄素蛋白光谱和催化性质的影响。
