Ulanovsky L, Bodner M, Trifonov E N, Choder M
Proc Natl Acad Sci U S A. 1986 Feb;83(4):862-6. doi: 10.1073/pnas.83.4.862.
Curved DNA molecules and unusually small circles have been obtained by ligation of synthetic 21-base precursors: (sequence in text). The ligation resulted in the formation of double-stranded oligo-(precursor)s possessing a strong 10.5-base-pair (bp) periodicity of the runs of adenines. Two-dimensional polyacrylamide gel electrophoresis of the ligation products showed two distinct families of spots: (i) noncircular oligo(precursor)s of 21 to 231 bp (1- to 11-mers) and (ii) four circles from 105 to 168 bp (eluted and analyzed by denaturing gel electrophoresis). The noncircular oligomers exhibited anomalously slow migration, as if they were as much as three times longer than they actually are. The amount of circular products peaked sharply at approximately equal to 126 bp, near which size the circles have been estimated to be nonconstrained both torsionally and in terms of bending. The nonconstrained circularization provides a technique for the direct measurement of the inherent curvature of DNA in solution. From the size of the circles, an estimate of 8.7 degrees is obtained for the absolute value of the AA X TT wedge angle (roll and tilt combined).
通过合成的21个碱基的前体进行连接，已获得了弯曲的DNA分子和异常小的环状物：（文中序列）。连接导致形成了具有腺嘌呤排列强烈的10.5碱基对（bp）周期性的双链寡聚（前体）。连接产物的二维聚丙烯酰胺凝胶电泳显示出两个不同的斑点家族：（i）21至231 bp（1至11聚体）的非环状寡聚（前体），以及（ii）四个105至168 bp的环状物（通过变性凝胶电泳洗脱并分析）。非环状寡聚物表现出异常缓慢的迁移，就好像它们比实际长度长多达三倍。环状产物的量在大约等于126 bp处急剧达到峰值，据估计在此大小附近，环状物在扭转和弯曲方面均不受限制。这种不受限制的环化提供了一种直接测量溶液中DNA固有曲率的技术。根据环状物的大小，获得了AA×TT楔形角（滚动和倾斜合并）绝对值的估计值为8.7度。
