Fast repair of dAMP hydroxyl radical adduct by verbascoside via electron transfer

DNA damaged by oxygen radicals has been implicated as a causative event in a number of degenerative diseases, including cancer and aging. So it is very impotant to look for ways in which either oxygen radicals are scavenged prior to DNA damage or damaged DNA is repaired to supplement the cells' inadequate repair capacity. The repair activity and its mechanism of verbaseoside, isolated from Pedicularis species, towards dAMP-OH·was studied with pulse radiolytic technique. On pulse irradiation of nitrous oxide saturated 2 mmol/L dAMP aqueous solution containing verbascoside, the transient absorption spectrum of the hydroxyl adduct of dAMP decayed with the formation of that of the phenoxyl radical of verbascoside well under 100 microseconds after electron pulse irradiation. The result indicated that dAMP hydroxyl adducts can be repaired by verbascoside. The rate constants of the repair reaction was deduced to be 5.9×10~8 dm~3·mol~(-1)·s~(-1). A deeper understanding of this new repair mechanism will undo     

核黄素光敏损伤DNA的凝胶电泳

以琼脂糖凝胶电泳研究了波长为427~457nm可见光照射下核黄素(VB₂)光敏诱导的质粒DNA损伤,结果发现DNA光敏损伤主要与照光量、核黄素和DNA浓度比、溶液中的氧气等有关.在无氧条件下光敏损伤更为显著,证明VB₂光敏损伤DNA主要是通过VB₂激发三重态与DNA碱基组分间发生电荷转移导致其产生氧化性损伤实现的.表明核黄素光敏损伤DNA时最佳浓度比为bp∶VB₂ = 3.5∶1.对照结果表明,单链DNA(ssDNA)比双链DNA(dsDNA)的碱基更易被核黄素敏化发生损伤,这可能是由于ssDNA中碱基暴露的原因.     

毛蕊花甙快速修复dAMP羟自由基加合物

活性氧造成的DNA损伤被认为是许多退行性疾病(包括癌症和衰老)的诱发事件.因此,探索清除活性氧和修复被活性氧损伤的DNA是非常重要的.利用脉冲辐解技术研究了从中药马先蒿中提取的毛蕊花甙对dAMP羟基加合物的修复能力与机制.脉冲辐照由氧化亚氮饱和的并含有毛蕊花甙的dAMP水溶液,发现伴随着dAMP羟基加合物瞬态吸收谱的衰减,生成了毛蕊花甙酚氧自由基瞬态吸收谱,表明毛蕊花甙可修复dAMP羟基加合物.修复反应的速率常数为5.9×108dm3·mol-1·s-1.对这一新的修复机制的深入了解有助于探讨新型防治药物.