Control of the Photocatalytic Activity of Bimetallic Complexes of Pyropheophorbide-a by Nucleic Acids

Abstract

Photocatalytic activity of a photosensitizer (PS) in an oligodeoxyribonucleotide duplex 5'-PS~ODN1/ODN2~Q-3' is inhibited because of close proximity of a quencher Q. The ODN2 in this duplex is selected to be longer than the ODN1. Therefore, in the presence of a nucleic acid (analyte), which is fully complementary to the ODN2 strand, the duplex is decomposed with formation of an analyte/ODN2~Q duplex and a catalytically active, single stranded PS~ODN1. In this way the catalytic activity of the PS can be controlled by the specific nucleic acids. We applied this reaction earlier for the amplified detection of ribonucleic acids in live cells (Arian, D.; Cló, E.; Gothelf, K.; Mokhir, A. Chem.-Eur. J.2010, 16(1), 288). As a photosensitizer (PS) we used In(3+)(pyropheophorbide-a)chloride and as a quencher (Q)--Black-Hole-Quencher-3 (BHQ-3). The In(3+) complex is a highly active photocatalyst in aqueous solution. However, it can coordinate additional ligands containing thiols (e.g., proteins, peptides, and aminoacids), that modulate properties of the complex itself and of the corresponding bio- molecules. These possible interactions can lead to undesired side effects of nucleic acid controlled photocatalysts (PS~ODN1/ODN2∼Q) in live cells. In this work we explored the possibility to substitute the In(3+) complex for those ones of divalent metal ions, Zn(2+) and Pd(2+), which exhibit lower or no tendency to coordinate the fifth ligand. We found that one of the compounds tested (Pd(pyropheophorbide-a) is as potent and as stable photosensitizer as its In(3+) analogue, but does not coordinate additional ligands that makes it more suitable for cellular applications. When the Pd complex was introduced in the duplex PS~ODN1/ODN2~Q as a PS, its photocatalytic activity could be controlled by nucleic acids as efficiently as that of the corresponding In(3+) complex.

Modular Assembly of a Pd Catalyst within a DNA Scaffold for the Amplified Colorimetric and Fluorimetric Detection of Nucleic Acids

“…Photochemical reactions have been employed to trigger the photocatalytic formation of singlet oxygen for the generation of fluorescent reporters. [13] While such systems have resulted in the amplified detection of DNA, RNA, and peptide nucleic acids (PNAs), the approach remains limited by hurdles such as the covalent attachment of profluorescent molecules or photosensitizers to probe ODNs and the need for external stimuli to achieve multiple turnovers.A potential solution to these drawbacks is grounded in the use of DNA as a structural component, rather than an analyte, in catalytic systems. ODNs on their own are versatile components for catalysis, able to adopt complex threedimensional structures to catalyze DNA/RNA ligation, [14] DNA phosphorylation, [15] and the formation of nucleopeptide linkages.…”

“…Photochemical reactions have been employed to trigger the photocatalytic formation of singlet oxygen for the generation of fluorescent reporters. [13] While such systems have resulted in the amplified detection of DNA, RNA, and peptide nucleic acids (PNAs), the approach remains limited by hurdles such as the covalent attachment of profluorescent molecules or photosensitizers to probe ODNs and the need for external stimuli to achieve multiple turnovers.…”

Nano-Enabled SERS Reporting Photosensitizers

“…The organic layer was dried with Na 2 SO 4 , filtered and dried by rotary evaporation. The product was then resuspended in MeOH and was quantified spectrophotometrically using the molar absorption extinction coefficient of the Pd-pyropheophorbide a chromophore (ε 641nm = 39810 M -1 cm -1 ) 30 . These procedures gave 14.5 mg (13 μmoles) of Pd-pyrolipid for a 23% yield.…”

Selective Csp3–F Bond Functionalization with Lithium Iodide

“…Compound 8 was obtained after extraction of the crude reaction mixture with chloroform as a colorless oil in 99% yield (37 mg, 0.2 mmol) from 3-fluoropropan-1-ol (16 mg, 0.2 mmol) and LiI (80 mg, 0.6 mmol) after 18 hours by following method C. The spectroscopic data of 3-iodopropan-1-ol ( 8 ) are in accordance with the literature. 53…”