Metalloporphyrin/G-quadruplexes: From basic properties to practical applications

Abstract

Guanine-rich nucleic acids stimulate the formation of planar, Hoogsteen hydrogen bonds-stabilized G-quartet (1), Fig. 1(a). The following p-p stacking of G-quartets, leads to the self-assembly of G-quadruplexes. These G-quadruplexes reveal cation-induced stabilization by means of coordination, mainly in the presence of monovalent ions, generally in the order of stabilization of K + > NH 4 + > Rb + > Na + > Cs + > Li + [1]. The resulting G-quadruplexes may adopt various topologies, such as parallel, anti-parallel or mixed strand configurations [2]. For example, Fig. 1(b) outlines various forms of four-layer guanine-quartets exhibiting different configurations: (i) edge-loop dimeric hairpin structure, (ii) diagonal-loop dimeric hairpin, (iii) unimolecular single strand with diagonal central loop, and (iv) unimolecular edge-type ABSTRACT: Guanine-rich single-stranded nucleic acids self-assemble into G-quadruplex nanostructures (predominately in the presence of K + -ions). Metalloporphyrins bind to the G-quadruplex nanostructures to form supramolecular assemblies exhibiting unique catalytic, electrocatalytic and photophysical properties. This paper addresses the advances in the characterization and the implementation of the metalloporphyrin/G-quadruplexes complexes for various applications. Out of the different complexes, the most extensively studied complexes are the hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme and the Zn(II)-protoporphyrin IX-functionalized G-quadruplex. Specifically, the hemin/Gquadruplex was found to act as a catalyst for driving different chemical transformations that mimic the native horseradish peroxidase enzyme, and, also, to function as an electrocatalyst for the reduction of H 2 O 2 . Also, the hemin/G-quadruplex stimulates interesting photophysical and photocatalytic processes such as the electron-transfer quenching of semiconductor quantum dots or the chemiluminescence resonance energy transfer to semiconductor quantum dots. Alternatively, Zn(II)-protoporphyrin IX associated with G-quadruplexes exhibit intensified fluorescence properties. Beyond the straight forward application of the metalloporphyrin/G-quadruplexes as catalysts that stimulate different chemical transformations, the specific catalytic, electrocatalytic and photocatalytic functions of hemin/G-quadruplexes are heavily implemented to develop sophisticated colorimetric, electrochemical, and optical sensing platforms. Also, the unique fluorescence properties of Zn(II)-protoporphyrin IX-functionalized G-quadruplexes are applied to develop fluorescence sensing platforms. The article exemplifies different sensing assays for analyzing DNA, ligand-aptamer complexes and telomerase activity using the metalloporphyrins/Gquadruplexes as transducing labels. Also, the use of the hemin/G-quadruplex as a probe to follow the operations of DNA machines is discussed.

Interaction of hemin with quadruplex DNA

“…Figure 1a and b display an alteration in the absorption spectra of hemin after titration with the G 4 DNA in presence of K + and Na + ions, respectively. As observed, the intensity of the soret band increases with addition of the G 4 DNA and then a red shift appears with an increase in the concentration of G 4 . The values of red shift and hypochromicity (%) were also plotted against the concentration of hemin and are presented in Fig.…”

Rational design of supramolecular hemin/G-quadruplex–dopamine aptamer nucleoapzyme systems with superior catalytic performance

“… 7 One of the most studied DNAzymes is the hemin/G-quadruplex (hGQ) horseradish peroxidase mimicking DNAzyme. 8 Similar to the native enzyme, this DNAzyme catalyzes the H 2 O 2 -mediated oxidation of organic substrates to chromophoric 9 or fluorescent 10 products, or catalyzes the generation of chemiluminescence in the presence of luminol and H 2 O 2 . 11 Also, this DNAzyme catalyzes biologically relevant reactions such as the H 2 O 2 -mediated oxidation of phenols, 12 thiols, 13 NADH, 14 and aniline, 15 and the aerobic oxidation of thiols or NADH.…”

Light‐Induced Reversible Reconfiguration of DNA‐Based Constitutional Dynamic Networks: Application to Switchable Catalysis

“…[11] Thebase sequence encoded in nucleic acids provides ar ich arsenal to control the structures, functions and switchable reconfiguration properties of oligonucleotides. [12] Fore xample,s tructural information includes the dictated formation of duplex nucleic acids and their separation by the strand displacement process,o rt he formation of triplex DNAstructures.Base-dictated functions of nucleic acids include catalytic properties (for example, DNAzymes), [13,14] sequence-specific binding properties of oligonucleotides (for example,a ptamers), [15] and enzymemimicking functions of catalyst-aptamer conjugates (for example,n ucleoapzymes). [16] In addition, the switchable signal-triggered reconfiguration of nucleic acid structures is well established.…”