One-Dimensional Multichromophor Arrays Based on DNA: From Self-Assembly to Light-Harvesting

Abstract

Light-harvesting complexes collect light energy and deliver it by a cascade of energy and electron transfer processes to the reaction center where charge separation leads to storage as chemical energy. The design of artificial light-harvesting assemblies faces enormous challenges because several antenna chromophores need to be kept in close proximity but self-quenching needs to be avoided. Double stranded DNA as a supramolecular scaffold plays a promising role due to its characteristic structural properties. Automated DNA synthesis allows incorporation of artificial chromophore-modified building blocks, and sequence design allows precise control of the distances and orientations between the chromophores. The helical twist between the chromophores, which is induced by the DNA framework, controls energy and electron transfer and thereby reduces the self-quenching that is typically observed in chromophore aggregates. This Account summarizes covalently multichromophore-modified DNA and describes how such multichromophore arrays were achieved by Watson-Crick-specific and DNA-templated self-assembly. The covalent DNA systems were prepared by incorporation of chromophores as DNA base substitutions (either as C-nucleosides or with acyclic linkers as substitutes for the 2'-deoxyribofuranoside) and as DNA base modifications. Studies with DNA base substitutions revealed that distances but more importantly relative orientations of the chromophores govern the energy transfer efficiencies and thereby the light-harvesting properties. With DNA base substitutions, duplex stabilization was faced and could be overcome, for instance, by zipper-like placement of the chromophores in both strands. For both principal structural approaches, DNA-based light-harvesting antenna could be realized. The major disadvantages, however, for covalent multichromophore DNA conjugates are the poor yields of synthesis and the solubility issues for oligonucleotides with more than 5-10 chromophore modifications in a row. A logical alternative approach is to leave out the phosphodiester bridges between the chromophores and let chromophore-nucleoside conjugates self-assemble specifically along single stranded DNA as template. The self-organization of chromophores along the DNA template based on canonical base pairing would be advantageous because sequence selective base pairing could provide a structural basis for programmed complexity within the chromophore assembly. The self-assembly is governed by two interactions. The chromophore-nucleoside conjugates as guest molecules are recognized via hydrogen bonds to the corresponding counter bases in the single stranded DNA template. Moreover, the π-π interactions between the stacked chromophores stabilize these self-assembled constructs with increasing length. Longer DNA templates are more attractive for self-assembled antenna. The helicity in the stack of porphyrins as guest molecules assembled on the DNA template can be switched by environmental changes, such as pH variations. DNA-templated stacks of ethynyl ...

25 years and still going strong: 2′-O-(pyren-1-yl)methylribonucleotides – versatile building blocks for applications in molecular biology, diagnostics and materials science

“…34–37 Pyrene arrays utilizing 2′- O -(pyren-1-yl)methylribonucleotides as the key components are highlighted in this section.…”

Nanoarchitectonics with Porphyrin Functionalized DNA

“…The various approaches showing the diversity of available functionalities have been reviewed independently, 4−6 in particular using organic chromophores, 7−10 and shall not be covered here in detail, but a focus is given on porphyrins as modifiers. 11 The formation of porphyrin assemblies is fascinating from the point of view of creating new functional materials, and applications in the fields of energy or electron transfer, light harvesting, optics, catalysis, and many more have been reported numerously.…”

2‐Methoxypyridine as a Thymidine Mimic in Watson–Crick Base Pairs of DNA and PNA: Synthesis, Thermal Stability, and NMR Structural Studies

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