Energy Transfer in Single-Stranded DNA-Templated Stacks of Naphthalene Chromophores

Abstract

We have investigated energy transfer in a novel self-assembled DNA hybrid structure composed of diaminopurine-equipped naphthalene derivatives that are hydrogen-bonded along a single-stranded oligothymine template. By performing time-resolved measurements of the naphthalene donor luminescence decay in the absence and presence of a cyanine Cy3.5 acceptor bonded covalently to the 5′ end of the oligothymine, we have examined the role of temperature and DNA template length on energy transfer from donors to the acceptor. We find that energy transfer rates decline with increasing temperature over a fairly narrow (±5 °C) range over which changes in circular dichroism and donor luminescence lifetime indicate that the chiral assemblies are dissociating. In addition, the transfer rates exhibit a complex dependence on template length, increasing from initially low values for 10 bases toward an optimum for 30 bases and then declining again toward 60 bases. We find that for short (∼10 bases) templates, incomplete filling and disorder reduces the overall transfer efficiency, while longer assemblies are more ordered but suffer from larger donor–acceptor separations, resulting in the observed peak at intermediate template length. In order to replicate the observed transfer dynamics, we have constructed a model assuming Förster energy transfer occurs between donors and acceptors whose geometric arrangement had been determined through molecular dynamics simulations of the whole assembly structure. For short DNA templates, the model is found to overestimate the transfer rates because it does not include effects of incomplete complex assembly and stacking faults. In contrast, the model underestimates the transfer rates for long, ordered assemblies indicating that additional mechanisms, such as diffusion of excitations along the donor stacks, need to be included. These results suggest that efficient energy transfer, in excess of that expected from simple Förster calculations, is feasible even for long DNA-templated assemblies of π-stacked conjugated chromophores. Such structures may therefore act as molecular wires transporting energy from one end to another.

Long‐Distance Electronic Energy Transfer in Light‐Harvesting Supramolecular Polymers

“…Polymeric and dendritic materials appear particularly promising in this context, due to the covalent joining of large numbers of light absorbing molecules. [24][25][26][27][28][29][30][31][32][33][34][35][36] Alternatively, DNA has been used as a supramolecular scaffold [37][38][39][40][41][42][43][44][45][46][47][48][49] for the construction and the study of light-harvesting antenna systems. We have recently reported on the assembly of water soluble linear [50,51] and two-dimensional [52] supramolecular polymers [53][54][55][56][57] from short amphiphilic pyrene oligomers (oligopyrenotides).…”

From Interaction to Function in DNA‐Templated Supramolecular Self‐Assemblies

“…By varying the size of the template from 10 to 40 thymine units, the researchers observed an optimum in the acceptor emission for a stack of 30 donor chromophores (Figure , bottom). The combination between time‐resolved spectroscopy and molecular modelling simulations showed that, for longer templates, efficient energy transfer occurs in excess of that expected with simple Förster Resonance Energy Transfer calculations …”

“…Bottom: fluorescence spectra (excitation at 400 nm) for DNA templates of different lengths (from 10 to 40 thymine units). Adapted with permissions from references and . Copyrights 2011 American Chemical Society and 2011 The Royal Society of Chemistry.…”

Elektronischer Energietransfer über lange Distanzen in lichtsammelnden supramolekularen Polymeren

“…In natürlich vorkommenden lichtsammelnden Komplexen (LHCs) werden Photonen durch geometrisch definierte Anordnungen proteingebundener Farbstoffmoleküle absorbiert. [24][25][26][27][28][29][30][31][32][33][34][35][36] Eine andere Mçglichkeit besteht in der Verwendung der DNA als supramolekulares Gerüst [37][38][39][40][41][42][43][44][45][46][47][48][49] für die Konstruktion und Untersuchung lichtsammelnder Antennensysteme. Das Design und die Entwicklung künstlicher lichtsammelnder Systeme sind eine akademische und industrielle Herausforderung mit weitreichenden çkonomischen und çkologischen Auswirkungen.…”

“…Polymere und dendritische Materialien scheinen zu diesem Zweck besonders vielversprechend, da in diesen Anordnungen eine Vielzahl von absorbierenden und leitenden Molekülen kovalent miteinander verbunden ist. [24][25][26][27][28][29][30][31][32][33][34][35][36] Eine andere Mçglichkeit besteht in der Verwendung der DNA als supramolekulares Gerüst [37][38][39][40][41][42][43][44][45][46][47][48][49] für die Konstruktion und Untersuchung lichtsammelnder Antennensysteme. Wir berichteten kürzlich über die Herstellung wasserlçslicher linearer [50,51] und zweidimensionaler [52] supramolekularer Polymere [53][54][55][56][57] aus kurzen, amphiphilen Pyrenoligomeren (Oligopyrenotiden).…”