长链脂肪酸影响胆红素-人血清蛋白复合物的激发态分化

胆红素与人血清白蛋白结合后会发生光异构和光诱导环化反应，其中后一反应将最终形成一种名为光红素的产物，这些光诱导化学反应是临床上治疗新生儿黄疸的基本原理. 据前人研究报道，长链脂肪酸的加入有利于光红素的生成，但其背后的机理，特别是其激发态动力学尚不明确. 本文利用飞秒瞬态吸收和飞秒荧光转换技术，探究了棕榈酸对胆红素在血清蛋白中的光化学反应的影响. 研究表明，随着棕榈酸的加入，光激发后的胆红素更倾向于通过4 ps的衰减通道返回热基态，而不是通过固有的超快激发态衰减途径(小于1 ps). 这一效应促进了热基态的胆红素发生由Z-Z到E-Z构型的异构化，从而提高了光红素的产率. 这是首次利用飞秒时间分辨光谱技术对长链脂肪酸在光疗过程中的作用进行表征，其结果可为相关临床研究提供有利的信息.

Long Chain Fatty Acid Affects Excited State Branching in Bilirubin-Human Serum Protein Complex

After binding to human serum albumin, biliru-bin could undergo photo-isomerization and photo-induced cyclization pro-cess. The latter process would result the forma-tion of a product, named as lumirubin. These photo induced behaviors are the fundamental of clinical therapy for neonatal jaundice. Previous studies have reported that the addition of long chain fatty acids is beneficial to the generation of lumirubin, yet no kinetic study has revealed the mechanism behind. In this study, how palmitic acid affects the photochemical reaction process of bilirubin in Human serum albumin (HSA) is studied by using femtosec-ond transient absorption and fluorescence up-conversion techniques. With the addition of palmitic acid, the excited population of bilirubin prefers to return to its hot ground state (S0) through a 4 ps decay channel rather than the intrinsic ultrafast decay pathways (<1 ps). This effect prompts the Z-Z to E-Z isomerization at the S0 state and then further increases the production yield of lumirubin. This is the first time to characterize the promoting effect of long chain fatty acid in the process of phototherapy with femtosecond time resolution spectroscopy and the results can provide useful information to benefit the relevant clinical study.