圆二色谱法研究碱基错配对G-quadruplex稳定性的影响  

CIRCULAR DICHROISM STUDY ON THE STABILITY OF MISMATCHED G-QUADRUPLEX

作　　者：王文星[1] 柳华杰[2] 王一丁[1] 杨洋[2] 刘冬生[2] 

机构地区：[1]四川师范大学生命科学学院,成都610068 [2]国家纳米科学中心,北京100080

出　　处：《高分子学报》2008年第1期55-61,共7页Acta Polymerica Sinica

基　　金：国家自然科学基金(基金号20573027,30670218,50625312);国家重点基础研究发展计划(973计划,项目号2005CB724701,2006CB705601)资助项目

摘　　要：通过将参与形成四链结构G-quadruplex的G(鸟嘌呤)碱基分别替换为T(胸腺嘧啶),C(胞嘧啶)和A(腺嘌呤),用圆二色光谱系统地研究了不同位置的G对G-quadruplex结构稳定性的贡献.结果表明,(1)替换G-quadruplex结构中间层的G对其稳定性的影响最大;(2)该序列及其错配序列大多数情况下在钾离子溶液中比钠离子溶液中稳定;(3)某些特定位置的G被替换为C或A后序列的熔点与原始序列接近甚至高于原始序列.It is well reported that human telomeric DNA sequence [AGGG（TTAGGG）3 ] can form a well-definedquadruplex structure with the hydrogen bonds between guanine bases in the appearance of K^＋ and Na^＋ . It was reported that the formation and stability of the structure was meaningful for both gene regulation and apoptosis. In this study, the replacement of guanine bases in this sequence with thymine, adenine and cytosine at different position was cariied out respectively. Their ability to form G-quadruplex as well as the G-quadruplex stability has been studied by circular dichroism （CD） spectroscopy. All oligonucleotides were synthesized and purified by Saibaisheng company. The concentrations of the oligonucleotides, expressed in singlestrand molarity, were determined by UV absorption at 260 nm using a‘nearestneighbor＇ approximation. Circular dichroism experiments were performed on a JASCO model J-810 circular dichroism spectrapolarimeter equipped with a Peltier temperature controller. All samples （10 μmol/L in 10 mmol/L tris-HC1 buffer containing 100 mmol/L NaCl at pH 7 ） were preheated to 95℃ for 5 min and slowly cooled to room temperature prior to measurements. A 1 mm path length cell was used for all measurements, and each spectrum was an average of five scans at 5℃. The G-quadruplex solutions were recorded in the 5℃ to 95℃ temperature range, using a scan rate of 0.5 K min^-1 and following the variation of CD absorption at its peak around 295 nm. Analysis of the thermal curves was performed by using the software origin. Van＇t Hoff thermodynamic analysis was cariied out for the intramolecular G-quadruplex oligonucleotides. Their thermal reversibility （superimposable heating and cooling profiles） allowed the calculation of the value of the equilibrium constant （K） assuming a two- state model. Application of the Van＇t Hoff equation （lnK= -△H/RT ＋ △S/R） yielded to the determination of the enthalpy （△H） and entropy （△S ） of the process, as described els

关 键 词：G-qudruplex 圆二色谱 端粒 DNA 

分 类 号：O657.7[理学—分析化学] Q523[理学—化学]