Fig. 2: Nucleic acid-based storage units.
From: Advances and challenges in non-canonical nucleic acids data storage
a Sequence-encoded strategies. i Canonical 4-letter DNA encodes 2 bits per nucleotide. ii Unnatural base pairs (UBPs), such as the 12-letter AEGIS system, increase the theoretical storage capacity to 3.58 bits per nucleotide according to log2 (N). iii The relationship between alphabet size (N) and coding capacity is shown. iv Sugar-modified nucleic acids (e.g., TNA) improve biochemical stability and data integrity. v Mirror-image (L-) nucleic acids offer high bio-orthogonality and have been explored for steganographic applications, and epigenetic modifications enable multi-layered coding and parallelized storage. b Nanostructure-encoded strategies. Static DNA structures: i DNA hairpins, ii DNA origami, and iii DNA tile arrays provide robust and addressable frameworks. Dynamic DNA structures: iv temperature-responsive structures, v pH-responsive structures, and vi light-responsive azobenzene-modified systems enable reversible signal switching between distinctive bit states. In this figure (a) (vi, “Epigenetic modification”) is reproduced with permission from Zhang, C. et al., Nature 634, 824–832 (2024). © 2024 Springer Nature. All graphical elements in this figure were originally created by the authors using Adobe Illustrator.
