Tabaczynski W A, Lemaire D G, Ruzsicska B P, Alderfer J L
Molecular and Cellular Biophysics Department, Roswell Park Cancer Institute, Buffalo, NY 14263-0001, USA.
Biopolymers. 1999 Aug;50(2):185-91. doi: 10.1002/(SICI)1097-0282(199908)50:2<185::AID-BIP7>3.0.CO;2-N.
Both trans-syn cyclobutane-type photodimers of 2'-deoxyuridylyl (3'-5') thymidine (dUpdT) were formed by deamination of the corresponding trans-syn cyclobutane photodimers of 2'-deoxycytidylyl (3'-5') thymidine (dCpdT) and were examined by 1H-, 13C-, and 31P-nmr spectroscopy. One- and two-dimensional nmr experiments provided a nearly complete assignment of the 1H, 13C, and 31P resonances. Scalar and nuclear Overhauser effect contacts were used to determine the conformation of the deoxyribose rings, exocyclic bonds, cyclobutane rings, and glycosidic linkages. Isomer I (S-type class; CB-; SYN-ANTI) and isomer II (N-type class; CB+; ANTI-SYN) exhibit markedly different conformational features. 31P chemical shifts show that the relative flexibility is dUpdT > isomer II > isomer I. The conformations of these species are very similar to those of other previously examined trans-syn photodimers. Among bipyrimidine photodimers of a given diastereomeric form (i.e., trans-syn I or II), the nmr-derived conformational parameters are nearly invariant, regardless of base substitution pattern. This contrasts with the substituent-dependent variation of cyclobutane ring conformation observed by Kim et al. (Biopolymers, 1993, Vol. 33, pp. 713-721) for an analogous series of cis-syn photodimers. Steric crowding of cyclobutane ring substituents is offered as an explanation for the difference in substituent effects between the families of cis-syn and trans-syn photodimers.
2'-脱氧尿苷酰基（3'-5'）胸苷（dUpdT）的两种反式-顺式环丁烷型光二聚体均由相应的2'-脱氧胞苷酰基（3'-5'）胸苷（dCpdT）的反式-顺式环丁烷光二聚体脱氨形成，并通过1H-、13C-和31P-核磁共振光谱进行了研究。一维和二维核磁共振实验几乎完全确定了1H、13C和31P共振峰。利用标量和核Overhauser效应接触来确定脱氧核糖环、环外键、环丁烷环和糖苷键的构象。异构体I（S型类别；CB-；SYN-ANTI）和异构体II（N型类别；CB+；ANTI-SYN）表现出明显不同的构象特征。31P化学位移表明相对灵活性为dUpdT>异构体II>异构体I。这些物种的构象与其他先前研究的反式-顺式光二聚体的构象非常相似。在给定非对映体形式（即反式-顺式I或II）的双嘧啶光二聚体中，核磁共振衍生的构象参数几乎不变，与碱基取代模式无关。这与Kim等人（《生物聚合物》，1993年，第33卷，第713 - 721页）观察到的类似系列顺式-顺式光二聚体中环丁烷环构象的取代基依赖性变化形成对比。环丁烷环取代基的空间拥挤被认为是顺式-顺式和反式-顺式光二聚体家族之间取代基效应差异的解释。
