Influence of a GC Base Pair on Excitation Energy Transfer in DNA-Assembled Phenanthrene π-Stacks

Abstract

The effect of a GC base pair on the excitation energy transfer in a DNA-based, light harvesting assembly of phenanthrene and pyrene chromophores is described. After absorption of light at 320 nm by the stacked phenanthrene building blocks, the excitation energy is transferred to the pyrene and leads to the formation of a phenanthrene-pyrene exciplex. The fluorescence intensity depends on the number of light absorbing phenanthrenes, as well as on the type of DNA base pair flanking the phenanthrene stack. In comparison to an AT base pair, a GC base pair located next to the stacked aromatic residues results in a reduction of fluorescence. The degree of quenching is dependent on the length of the phenanthrene stack that separates the GC base pair from the exciplex. Overall, a large number of stacked phenanthrenes positively affects exciplex fluorescence by increasing the quantity of absorbed light and, at the same time, reducing the effect of quenching by GC base pairs.

Formation of Two‐Dimensional Supramolecular Polymers by Amphiphilic Pyrene Oligomers

“…[58] Despite abundant information about its behavior in the aggregated state, data on J-and/or H-type interactions between pyrenes is very limited. [59,60] We investigate pyrene-modified nucleic acids as biosensors, [61] DNAbased light-harvesting [62,63] and energy-transfer systems [64] or as nanoscale templates for chromophore assembly. [65] Recently, a phosphodiester-linked pyrene heptamer (or heptapyrenotide [66] ) was found to form rod-like structures by supramolecular polymerization.…”

DNA‐Organized Light‐Harvesting Antennae: Energy Transfer in Polyaromatic Stacks Proceeds through Interposed Nucleobase Pairs

“…Only AÀ T base pairs were used in the vicinity of the chromophores, as the quenching effect of G is well known. [27,28] However, GÀ C base pairs were used at the ends to increase the stability of the duplexes. In duplex 0, the phenanthrenes form an uninterrupted stack, whereas in duplexes 1 -5 the phenanthrenes are separated by one to five AÀ T base pairs.…”

Utilizing the Organizational Power of DNA Scaffolds for New Nanophotonic Applications

“…An initial example of such a light harvesting MPW was based on a 7‐helix origami bundle architecture that demonstrated picosecond time‐scale funneling from pyrene through Cy3 to a final AF647 acceptor, see Figure A for a schematic and some representative data which reported 85% AE at pyrene excitation as compared to direct AF647 excitation . Other investigations into the antennae capabilities of MPWs included aggregate systems similar to those discussed above 165b,172. For example, 8 π‐stacked phenanthrenes formed through dsDNA presented 230% AE over direct excitation of a pyrene, though this effect was limited to a ≈2 nm length construct 165a.…”

“…Porphyrins are some of the classical dyes used to study this phenomena in MPWs, the other common dyes being cyanines, as they will form H‐type aggregates in the MPWs 53b,164. The Häner group looked extensively at DNA templated MPWs with different dyes and an MPW of π‐stacked phenanthrenes (up to 8) that could transfer light to the end‐point pyrene dye . Continued investigations into these types of systems even demonstrated heteroaggregates systems using perylenediimide and pyrene templated by DNA .…”

“…Other investigations into the antennae capabilities of MPWs included aggregate systems similar to those discussed above 165b,172. For example, 8 π‐stacked phenanthrenes formed through dsDNA presented 230% AE over direct excitation of a pyrene, though this effect was limited to a ≈2 nm length construct 165a. Within the light‐capture paradigm, dye‐aggregates are of particular interest as their absorbance properties are greatly modified, shifting the absorbance peaks and allowing for greater coverage of broad white‐light spectra .…”