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 WS2 via the most thermodynamically stable conformation, leading to more stable conjugates.