MELTING AND PREMELTING TRANSITIONS OF AN OLIGOMER MEASURED BY DNA-BASE FLUORESCENCE AND ABSORPTION

被引:132
作者
XU, DG [1 ]
EVANS, KO [1 ]
NORDLUND, TM [1 ]
机构
[1] UNIV ALABAMA,DEPT PHYS,BIRMINGHAM,AL 35294
关键词
D O I
10.1021/bi00198a027
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Incorporation of 2-aminopurine (2AP) in place of adenine gives an optical probe of local and global DNA conformation. The temperature dependence of the absorption of the duplex d[CTGA(2AP)-TTCAG](2) DNA decamer shows that the helix has approximately an all-or-none melting transition. Absorbance at wavelengths of 260 and 330 nm monitors the average normal base conformation and the 2AP base local conformation, respectively. From this measure, the 2AP base melts less than 1 degrees C below the other bases. Temperature-dependent lifetime measurements of 2AP also mirror the melting transition. Absorption spectra show that below T-m most 2AP's are H-bonded. Fluorescence intensity and excitation spectra measurements show, on the other hand, that the most highly-fluorescent states correspond to nonH-bonded 2AP's which sense conformational changes of the helix. The temperature dependence of the fluorescence spectral shift shows the conformation and/or dynamics of the 2AP base changes 10 degrees C or more below T-m. The data suggest a premelting transition which is purely dynamic in nature-transient exposure of most 2AP's to water increases, while the average conformation remains B-helical.
引用
收藏
页码:9592 / 9599
页数:8
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