A-DNA
A-DNA又称A型DNA，为DNA双螺旋的一种形式，拥有与较普遍的B-DNA相似的右旋结构，但其螺旋较短较紧密。A-DNA是三种具有生物活性的DNA双螺旋结构，另两种则为B-DNA及Z-DNA。一般只有脱水的DNA样本中才会出现，可用来作晶体学实验。此外当DNA与RNA混合配对时，也可能出现A-DNA形式的螺旋。
结构
A-DNA与B-DNA相似，有大小凹陷处之分。但其每一转的螺旋中具有较多的碱基对，因而产生较深的大凹陷处与较浅的小凹陷处。
A-DNA的预测
B-DNA具有转变成为A-DNA的倾向，此种推测是由俄勒冈州立大学的Beth Basham、Gary Schroth与P. Shing Ho所发展[1]。
他们在摘要中如此形容：
The ability to predict macromolecular conformations from sequence and thermodynamic principles has long been coveted but generally has not been achieved. We show that differences in the hydration of DNA surfaces can be used to distinguish between sequences that form A- and B-DNA. From this, a "triplet code" of A-DNA propensities was derived as energetic rules for predicting A-DNA formation. This code correctly predicted > 90% of A- and B-DNA sequences in crystals and correlates with A-DNA formation in solution. Thus, with our previous studies on Z-DNA, we now have a single method to predict the relative stability of sequences in the three standard DNA duplex conformations.[1]
参考文献
- ^ 1.0 1.1 Basham B, Schroth GP, Ho PS. An A-DNA triplet code: thermodynamic rules for predicting A- and B-DNA. Proc Natl Acad Sci USA. 1995, 92 (14): 6464–6468. PMID 7604014.