Kodama Tetsuya, Greenberg Marc M
Department of Chemistry, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, USA.
J Org Chem. 2005 Nov 25;70(24):9916-24. doi: 10.1021/jo051666k.
[reaction: see text] Hydrogen atom abstraction from the C5'-position of nucleotides in DNA results in direct strand scission. The newly formed 5'-termini of the cleaved DNA consists of alkali-labile fragments of the oxidized nucleotide. One terminus contains a 5'-aldehyde as part of an otherwise undamaged nucleotide (T-al). A second more structurally distinct product that is produced in lower yields results from cleavage of the C4'-C5' carbon-carbon bond. The 1,4-dioxo-2-phosphorylbutane (DOB) is a precursor of the alkylating agent but-2-ene-1,4-dial. To facilitate studies on these lesions, methods for synthesizing oligodeoxynucleotides containing DOB or T-al at their 5'-termini were developed. The effects of these lesions on the UV-melting temperatures of duplex DNA, and their cleavage labilities were determined. T-al cleaves very slowly (t(1/2) = 100.7 h), whereas DOB has a half-life at 37 degrees C (pH 7.2) of less than 11 h. In addition, DOB forms a stable adduct very efficiently with Tris, which protects the abasic site against cleavage.
[反应：见正文] 从DNA中核苷酸的C5'-位夺取氢原子会导致直接链断裂。断裂DNA新形成的5'-末端由氧化核苷酸的碱不稳定片段组成。一个末端含有5'-醛，作为一个未受损核苷酸（T-al）的一部分。另一种产量较低、结构上更独特的产物是由C4'-C5'碳-碳键断裂产生的。1,4-二氧代-2-磷酰基丁烷（DOB）是烷基化剂2-丁烯-1,4-二醛的前体。为了便于对这些损伤进行研究，开发了在其5'-末端合成含有DOB或T-al的寡脱氧核苷酸的方法。测定了这些损伤对双链DNA紫外熔解温度的影响及其切割稳定性。T-al切割非常缓慢（t(1/2) = 100.7小时），而DOB在37℃（pH 7.2）下的半衰期小于11小时。此外，DOB与Tris非常有效地形成稳定加合物，保护无碱基位点不被切割。
