PHOTOCHEMICAL COUPLING OF 5-BROMOURACIL (BU) TO A PEPTIDE LINKAGE - A MODEL FOR BU-DNA PROTEIN PHOTO-CROSS-LINKING
PHOTOCHEMICAL COUPLING OF 5-BROMOURACIL (BU) TO A PEPTIDE LINKAGE - A MODEL FOR BU-DNA PROTEIN PHOTO-CROSS-LINKING
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DOI：
10.1021/ja00240a032
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发表时间：
1987-03-18
影响因子：
15
通讯作者：
KOCH, TH
中科院分区：
文献类型：
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作者：
DIETZ, TM;VONTREBRA, RJ;KOCH, TH
含有5-溴尿嘧啶（BU）的DNA的光交联取代了一些胸腺嘧啶的相关蛋白质有可能研究蛋白质核酸相互作用。与模型化合物的实验进行了描述，这表明一些电子和分子的交联的细节。早期的实验表明，BU发色团在其π，. π *单重态可能通过C-Br键的均裂作用导致BU-DNA单链断裂，三重态可能通过初始电子转移导致BU-DNA与相关蛋白的交联。以前只观察到BU与半胱氨酸、谷胱甘肽、色氨酸和色氨酸衍生物的分子间偶联。这里建立的重要结论是（1）BU发色团具有差分辨的，可能是n-π *（2）BU发色团的光化学显著地依赖于波长，（3）1 n，π *态可以用XeCl受激准分子激光器或用单色器隔离的313-nm汞带选择性地填充，（4）1 n，π *三重态不经历C-Br键均裂，与系统间交叉竞争到三重态歧管，和（5）三重态偶联到邻近的肽连接，与HBr的损失。通过研究BU在2-丙醇-d中的光还原以及（5-溴-6-尿嘧啶基）-N-乙基乙酰胺（1）和N-[（5-溴-6-尿嘧啶基）乙酰基]-D，L-苏氨酸N-乙基酰胺（2）在缓冲水中的光环化成呋喃3和6（两者均为波长的函数），确立了这些结论。
Photocrosslinking of DNA containing 5-bromouracil (BU) in place of some of the thymine to an associated protein has potential for studying protein nucleic acid interactions. Experiments with model compounds are described which indicate some of the electronic and molecular details of the crosslinking. Earlier experiments suggested that the BU chromophore in its .pi., .pi.* single state reacted by C-Br bond homolysis probably leading to BU-DNA single strand breaks and that the triplet state was responsible for crosslinking of BU-DNA to associated proteins probably via initial electron transfer. Only intermolecular coupling of BU to cysteine, glutathione, tryptophan, and tryptophan derivatives had been observed previously. The important conclusions established here are (1) that the BU chromophore has a poorly resolved, possibly n-.pi.* transition in the region of 308 nm, (2) that the photochemistry of the BU chromophore is significantly wavelength dependent, (3) that the 1n,.pi.* state can be selectively populated with a XeCl excimer laser or the 313-nm mercury band isolated with a monochromator, (4) that the 1n,.pi.* state does not undergo C-Br bond homolysis in competition with intersystem crossing to the triplet manifold, and (5) that the triplet state couples to a peptide linkage in proximity with loss of HBr. These conclusions were established by studying the photoreduction of BU in 2-propanol-d and the photocyclization of (5-bromo-6-uracilyl)-N-ethylacetamide (1) and N-[(5-bromo-6-uracilyl)acetyl]-D,L-threonine N-ethylamide (2) to furans 3 and 6 in buffered water, both as a function of wavelength.