Freezing-directed Stretching and Alignment of DNA Oligonucleotides

Most single-stranded DNA oligonucleotides are random coils with a persistence length of below 1 nm. So far, no good methods are available to stretch oligonucleotides. Herein, it is shown that freezing can stretch DNA, as confirmed using fluorescence resonance energy transfer, thiazole-orange staining, and surface-enhanced Raman spectroscopy. Lateral inter-strand interactions are critical, and the stretched DNA oligonucleotides are aligned. This work also provides a set of methods for studying frozen oligonucleotides. Upon freezing, DNA oligonucleotides are readily adsorbed onto various nanomaterials, including gold nanoparticles, graphene oxide, iron oxide, and WS ₂ via the most thermodynamically stable conformation, leading to more stable conjugates.