DNA-Based Assemblies for Photochemical Upconversion

Abstract

In the present study DNA was used as a scaffold for the supramolecular assembly of organic chromophores for photochemical upconversion (PUC). Initially, a green-to-blue PUC was observed using free chromophores in solution: tris(2,2'-bipyridine)ruthenium(II), [Ru(bpy)3](2+), which acts as a long-wavelength absorber (λex = 500 nm), and an in situ energy donor to an acceptor (R)-1-O-[4-(1-pyrenylethynyl)phenylmethyl]glycerol (PEPy or TINA monomer), which acts as an annihilator and short-wavelength photoemitter (λem = 420 nm). Then, DNA duplexes possessing TINA monomers were synthesized, and complexes with [Ru(bpy)3](2+) were investigated. In contrast to the dynamic interactions of [Ru(bpy)3](2+) with TINA monomer free in solution, ground-state complex formation was the predominant mechanism of interaction between [Ru(bpy)3](2+) and DNA duplexes bearing two TINA monomers at the 5' ends as shown by fluorescence, circular dichroism (CD), and UV-vis spectroscopy studies. The use of TINA-modified DNAs led to PUC occurring at concentrations significantly lower than that for free chromophores in solution: 2.5 μM [Ru(bpy)3](2+) and 5.0 μM TINA-modified duplex in the DNA-based systems in aqueous buffer versus 46 μM [Ru(bpy)3](2+) and 4.6 mM TINA monomer for the free donor and acceptor in DCM, respectively. Providing vast capabilities of DNA in the development of novel photonic systems as a result of the controllable organization of various chromophores, this study opens a new perspective for the development of DNA-based light-harvesting systems using PUC.

G‐Quadruplex Supramolecular Assemblies in Photochemical Upconversion

“…The interactions of these constructs with [Ru(bpy) 3 ] 2 + and with the Zn 2 + derivative of 5,10,15,20-tetrakis-(1-methyl-4-pyridyl)-21 H,23H-porphine (ZnTMpyP4, Figure 1 C) were investigated. Even though we never observed PUC in solutions containing TINA monomer and ZnTMpyP4, [18,39] this porphyrin represents a class of photosensitizers based on porphyrin and phthalocyanine derivatives, which are commonly used in PUC in combination with polycyclic aromatic chromophores. [16] This prompted us to investigate the interaction of ZnTMpyP4 with TINA-modified G4-DNAs.…”

“…One should bear in mind that intensities give only a qualitative analysis of PUC. [40] In comparison with the duplex D1 that produced the highest upconverted fluorescence in the presence of [Ru(bpy) 3 ] 2 + (duplex D4 in reference [18] ), the intensity of the upconverted signal for TG4 TX/ [Ru(bpy) 3 ] 2 + was significantly lower at the same DNA strand concentration (10 mm, Figure 6). It should be mentioned that the effective TINA concentration in the duplex is four times higher (40 mm) than in G4-DNA (10 mm) at the same strand concentration because two TINA molecules are present on each strand in D1.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] Recently, we demonstrated that photochemical upconversion (PUC) [15][16][17] in which low-energy photons are absorbed and reemitted as high-energy light can be accomplished by arrangement of two chromophores on the DNA duplex: an acceptor, TINA monomer (Figure 1 A) was attached at the 5'-end of the duplex and a donor, tris(2,2'-bipyridine)ruthenium(II) ([Ru(bpy) 3 ] 2 + , Figure 1 B) was present in solution as a ligand forming a complex with TINA-modified DNA duplex. [18] The sequence of reactions resulting in PUC and Jablonski diagram are shown in Figure 2. The use of DNA as a scaffold was crucial to bringing two chromophores in a close proximity so that PUC occurred at low chromophore concentrations (mM) after de-gassing of aqueous solutions for 24 h with argon.…”

“…2 + , C) a cationic porphyrin ZnTMpyP4, and D) TINAmodified G-quadruplexes and reference duplex D1 (abbreviated as D4 in Ref. [18]). 2 + and TINA monomer resulting in PUC; ISC is an intersystem crossing, TTeT is triplet-triplet energy transfer, and TTA is triplettriplet annihilation.…”

“…This suggests that end-to-end intermolecular clustering of pyrene-containing DNAs plays an important role in DNA-based PUC. [18] The new de-gassing method enables quick evaluation of PUC in aqueous buffers. This study shows how tetramolecular G4-DNAs can be chemically modified with organic chromophores and used for the creation of reaction centres enabling chemical reactions such as photochemical upconversion to occur.…”