Efficient energy transfer from pyrene to perylene assembled inside DNA duplex

Abstract

Pyrene (donor) and perylene (acceptor) were assembled in a DNA duplex to increase the apparent Stokes' shift of perylene. Multiple donors were introduced in the vicinity of acceptors via D-threoninol and natural base pairs were inserted between donors and acceptors in order to suppress undesired interactions between them. When two pyrene moieties were located in proximity to one perylene with one base pair inserted between them, efficient FRET occurred within the duplex. Thus, strong emission at 495 nm was observed from perylene when excited at 345 nm where pyrene has its absorption. The apparent Stokes' shift became as large as 115 nm with a high FRET efficiency (Phi>1). However, the introduction of more than two pyrenes did not enhance the fluorescence intensity of perylene, due to the short Förster radius (R(0)) of the donor pyrene.

Deducing the conformational space for an octa-proline helix

“…Emission spectra recorded for PY-P 8 -PER in dilute methanol solution, with excitation at 350 nm, show contributions from both uorophores, although the relative yield for perylene emission far outweighs that for pyrene. This situation is fully consistent with EET along the molecular axis, as has been demonstrated [48][49][50] for other molecular dyads bearing the same terminals. Several methods can be used to determine the probability (P EET ) for intramolecular EET in this system, while working with dilute (<2 mM) solutions ensures the absence of complications from bimolecular EET.…”

“…48) and including the use of a polynucleotide scaffold to provide incremental separation distances. 49 The Förster critical distance 50 for this pair is ca. 23 Å while the spectral overlap integral 51 is reported to be ca.…”