Self-Assembly of Perylenediimide-Single-Strand-DNA Conjugates: Employing Hydrophobic Interactions and DNA...

The self-assembly behavior of DNA conjugates possessing a perylenediimide (PDI) head group and an N-oligonucleotide tail has been investigated using a combination of optical spectroscopy and cryogenic transmission electron microscopy (cryo-TEM) imaging. To obtain insight into the interplay between PDI hydrophobic interactions and DNA base-pairing we employed systematic variation in the length and composition of the oligo tails. Conjugates with short (TA)_n or (CG)_n oligo tails (n≤3) form helical or nonhelical fibers constructed from π-stacked PDI head groups with pendent oligo tails in aqueous solution. Conjugates with longer (TA)_n oligo tails also form stacks of PDI head groups, which are further aggregated by base-pairing between their oligo tails, leading to fiber bundling and formation of bilayers. The longer (CG)_n conjugates form PDI end-capped duplexes, which further assemble into PDI-stacked arrays of duplexes leading to large scale ordered assemblies. Cryo-TEM imaging reveals that (CG)₃ gives rise to both fibers and large assemblies, whereas (CG)₅ assembles preferentially into large ordered structures.