Photochemical reduction of 5-bromouracil by cysteine derivatives and coupling of 5-bromouracil to cystine derivatives.
Photochemical reduction of 5-bromouracil by cysteine derivatives and coupling of 5-bromouracil to cystine derivatives.
复制标题
半胱氨酸衍生物对 5-溴尿嘧啶的光化学还原以及 5-溴尿嘧啶与胱氨酸衍生物的偶联。
DOI：
10.1111/j.1751-1097.1989.tb04085.x
复制
发表时间：
1989
影响因子：
3.3
通讯作者：
Koch,TH
中科院分区：
文献类型：
--
作者：
Dietz,TM;Koch,TH
在存在半胱氨酸肽样衍生物的情况下，使用XeCl准分子激光器在308 nm处照射pH 7的5-溴尿嘧啶（BU）水溶液，仅产生尿嘧啶（U）和相应的胱氨酸衍生物的初始形成。继续辐照产生S-尿嘧啶基半胱氨酸加合物以及额外的U和胱氨酸衍生物。对BU和胱氨酸衍生物的溶液进行类似的照射，产生了U和S-尿嘧啶半胱氨酸加合物的初始形成。在用254 nm光照射相应溶液后，观察到这些产物以及尿嘧啶光化学的次级产物的形成。在308 nm激光激发下，U-Cys加合物的形成和BU还原为U的过程是通过胱氨酸衍生物的二硫化物向三重态BU的初始电子转移进行的。在胱氨酸衍生物存在下，308 nm激发下BU破坏的量子产率为1.1 × 10 - 3。三联体BU与半胱氨酸衍生物的反应不产生U-Cys加合物，而是产生U和胱氨酸衍生物。蛋白质BU-DNA复合物中的半胱氨酰残基将三联体BU还原为U的可能副产物是磺基溴，其可能通过DNA中的亲核位点对硫进行亲核取代而产生蛋白质-DNA交联。
Irradiation of pH 7, aqueous solutions of 5‐bromouracil (BU) in the presence of cysteine peptide‐like derivatives at 308 nm using a XeCl excimer laser yielded initial formation of only uracil (U) and the corresponding cystine derivative. Continued irradiation yielded an S‐uracilylcysteinyl adduct as well as additional U and cystine derivative. Similar irradiation of a solution of BU and a cystine derivative yielded initial formation of U and the S‐uracilylcysteinyl adduct. Formation of these products as well as secondary products of uracil photochemistry was observed upon irradiation of the respective solutions with 254 nm light. With 308 nm laser excitation, U‐Cys adduct formation and reduction of BU to U are proposed to occur via initial electron transfer from the disulfide of the cystine derivative to triplet BU. The quantum yield of BU destruction with 308 nm excitation in the presence of cystine derivative is 1.1 × 10‐3. Reaction of triplet BU with the cysteine derivative does not yield U‐Cys adduct but U and cystine derivative. A possible byproduct of reduction of triplet BU to U by a cysteinyl residue in a protein BU‐DNA complex is a sulphenyl bromide which might yield a protein‐DNA crosslinkvianucleophilic substitution on sulfur by a nucleophilic site in DNA.