胆红素与胆汁酸盐作用时的构象变化

CONFORMATION CHANGE OF BILIRUBIN AS THE ACTION OF IT ON BILE SALTS

利用PPP-SCF-CI-DV量子化学程序拟合胆红素以及胆汁酸盐-胆红素水溶液的UV和CD谱,借以研究胆红素及其与胆汁酸盐复合物的构象性质。发现胆红素与胆汁酸盐作用时,两个双吡咯生色团的扭角由104°变成112°,仍保持形成分子内氢键的状态,其UV及CD谱两个吸收峰间隔的增宽,主要是胆红素的一侧双吡咯生色团与胆汁酸盐呈疏水性结合的原故;二羟基和三羟基胆汁酸盐所形成的二元复合物园二色谱的差别,是胆红素的对映选择性结合造成的。

In this paper, UV and CD spectra of bilirubin and bile salts-bilirubin in aqueous solution have been simulated by. means of 'PPP-SCF-CI-DV', quantum chemical programme, in order to clarify the conformations of bilirubin and its complexes with bilesalts. The torsional angles between two dipyrrole chromophores of bilirubin were pos-tulated changing from 104° to 112°, after binding with bile salts and the intramole-cularly hydrogen bonded states of bilirubin still are kept; the separation betweentwo absorption peaks in both UV and CD spectrum increases in presence of bile salts,it is interpreted by that one dipyrrole chromophores of bilirubin are combined withbile salts mainly; the difference of CD spectrum which are produced by dihydroxyand trihydroxy bile salts may be explained by enantio-selective binding.