Using the principle of self-assembly, a fluorescence-based photonic network is constructed with one input and two spatially and spectrally distinct outputs. A hexagonal DNA nanoassembly is used as a scaffold to host both the input and output dyes. The use of DNA to host functional groups enables spatial resolution on the level of single base pairs, well below the wavelength of light. Communication between the input and output dyes is achieved through excitation energy transfer. Output selection is achieved by the addition of a mediator dye intercalating between the DNA base pairs transferring the excitation energy from input to output through energy hopping. This creates a tool for selective excitation energy transfer on the nanometer scale with spectral and spatial control. The ability to direct excitation energy in a controlled way on the nanometer scale is important for the incorporation of photochemical processes in nanotechnology.

We demonstrate a new method to reversibly cross-link DNA-nanoparticle dimers, trimers, and tetramers using light as an external stimulus. A DNA interstrand photo-cross-linking reaction is possible via ligation of a cyano-vinyl carbazole nucleoside with an opposite thymine when irradiated at 365 nm. This reaction results in nanoparticle assemblies that are not susceptible to DNA dehybridization conditions. The chemical bond between the two complementary DNA strands can be reversibly broken upon light irradiation at 312 nm. This is the first example of reversible ligation in DNA-nanoparticle assemblies using light and enables new developments in the field of programmed nanoparticle organization.

We present a novel nanoparticle building block system based on the interactions between short synthetic oligonucleotides and peptides. Gold nanoparticles coated with DNA-binding peptides can be attached to self-organized oligonucleotide templates to formulate well-ordered structures of nanoparticles. By regulating the amount of DNA-binding peptide attached to the nanoparticle surface and using specifically designed oligonucleotides, the nanoparticle assembly can be controlled to form dimers, trimers, and adjustable-length nanoparticle chains as well as more complex structures.

The efficiencies of DNA-templated acyl transfer reactions between a thioester modified oligonucleotide and a series of amine and thiol based nucleophiles are directly compared. The reactivity of the nucleophile, reaction conditions (solvent, buffer, pH) and linker length all play important roles in determining the efficiency of the transfer reaction. Careful optimisation of the system enables the use of DNA-templated synthesis to form stable peptide-like bonds under mild aqueous conditions close to neutral pH.

3-Aminophenyl-modified analogues of the bicyclic nucleoside N-methyl-3H-pyrrolo[2,3-d]pyrimidin-2(7H)-one were synthesised and incorporated directly into triplex-forming oligonucleotides in order to utilise their extended hydrogen bonding motif for recognition of the CG base pair. All analogues demonstrated strong binding affinity and very good selectivity for CG from pH 6.2 to 7.0; a marked improvement on previous modifications.