Molecular self-assembly of stable and small branched DNA nanostructures: Higher than a helical turn is enough for hybridization.

The Watson-Crick base pairing property of DNA is widely used for fabricating DNA nanostructures with well-defined geometry. Moreover, DNA nanostructures can be easily modified in terms of shape, size and function at the nanoscale level. Therefore, investigation on smaller and stable branched DNA (bDNA) is of critical significance for biomedical applications. In the present communication, we report smaller and stable branched DNA (bDNA) which is of critical significance for biomedical applications. In this study, a novel strategy has been used in identifying stable bDNA nanostructures with a minimum number of Watson-Crick base pairings. The importance of hybridizing regions and helical twists between multiple oligonucleotides has been explored using various biophysical techniques. The electrophoretic analysis demonstrated that hybridizing regions with ≥12 nt nucleotides can form stable bDNA structures. Substantial negative enthalpic contributions determine the significance of base stacking and the length of oligonucleotides in the hybridization process. Finally, thermal melting investigations confirmed the creation of bDNA nanostructures with ≥12 nt long hybridizing regions. In general, our findings indicate that bDNA oligonucleotides do not undergo hybridization if the number of base pairs is lesser for a single helical turn. Furthermore, the yield and stability of smaller bDNA nanostructures in physiological conditions are comparable with the earlier reported higher-order structures. Hence, smaller bDNAs are more stable which may be preferred over conventional bDNA nanostructures for advanced biomedical applications.