炭疽芽孢DNA适配子结构与长度对亲和力的影响

目的 研究炭疽芽孢适配子结构与长度变化对其与芽孢之间亲和力的影响。方法 人工合成f77-1适配子序列，并构建在其7条突变体序列，将这些寡核苷酸序列分别与炭疽芽孢结合，利用TMB显色系统判断读取吸光度A值，确定各序列与芽孢间亲和力大小；同时通过核酸序列分析软件包模拟各序列的二级结构，推断适配子的结构与亲和力之间的关系。结果 适配子f77-1与突变体中的f77-3与芽孢亲和力较好，约是突变体中f77-4亲和力的11倍，二级结构显示：f77-1,f77-3都具有茎环或发卡结构，且3'端都有连续3个G。结论 适配子5'端的茎环结构和发卡结构是这些寡核苷酸序列与芽孢结合的结构基础，3'端的连续3个G可能对提高亲和力起着重要的作用。

Relationship between the secondary structure of an aptamer and its binding affinity to Bacillus anthracis spores

AIM To determine the effects of aptamers length and structure on its binding affinity to spores of Bacillus anthracis vaccine strain A.16R. METHODS An oligonucleotide aptamer f77 1 and its seven mutants were synthesized. Binding of oligonucleotides to spores was visualized by biotin streptavidin horseradish peroxides system. All theoretical secondary structures were caculated using the Fold subroutine of the DNASIS v2.5 software package based on a free energy minimization algorithm. RESULTS Affinities of the aptamer f77 1 and mutant f77 3 were 11 times higher than that of mutant f77 4. And the theoretical secondary structures calculated showed that they had stem loop or hairpin at 5' end of the aptamer and mutant and GGG sequences at 3' end of the structures. CONCLUSION Stem loop and hairpin at 5' end of the aptamer work as main motif in the interaction between oligonucleotides and spores. Meanwhile, GGG sequences at 3' end of the aptamer play an important role in determining its binding capacity.