G-Quadruplexes as Sensing Probes

Abstract

Guanine-rich sequences of DNA are able to create tetrastranded structures known as G-quadruplexes; they are formed by the stacking of planar G-quartets composed of four guanines paired by Hoogsteen hydrogen bonding. G-quadruplexes act as ligands for metal ions and aptamers for various molecules. Interestingly, the G-quadruplexes form a complex with anionic porphyrin hemin and exhibit peroxidase-like activity. This review focuses on overview of sensing techniques based on G-quadruplex complexes with anionic porphyrins for detection of various analytes, including metal ions such as K , organic molecules, nucleic acids, and proteins. Principles of G-quadruplex-based detection methods involve DNA conformational change caused by the presence of analyte which leads to a decrease or an increase in peroxidase activity, fluorescence, or electrochemical signal of the used probe. The advantages of various detection techniques are also discussed.

Recent Developments in G-Quadruplex Probes

“…For the sake of brevity, only the application of recently developed G-quadruplex probes are highlighted, and those interested in earlier work in the field of G-quadruplex-based sensing assays, or those that employ previously reported G-quadruplex probes, can consult several excellent reviews on the topic Neo et al, 2012;Ma et al, 2012;Ruttkay-Nedecky et al, 2013).…”

“…Finally, we highlight recent examples of G-quadruplex small-molecule probes that have been used as G-quadruplex DNA imaging agents in living cells. Here, we focus mainly on examples that have been described in the last few years, as previous reviews on G-quadruplex probes describing earlier developments have been published by our group and others (Neo et al, 2012;Largy et al, 2013;Ren et al, 2015;Ruttkay-Nedecky et al, 2013;Vummidi et al, 2013). For ease of access, a summary of the photophysical properties of the G-quadruplex probes highlighted in this review can be found in Table 1.…”

Voltammetry and molecular assembly of G-quadruplex DNAzyme on single-crystal Au(111)-electrode surfaces – hemin as an electrochemical intercalator

“…Electronic conductivity of "non-canonical" DNA forms, quadruplexes in particular have also been addressed, but such reports have only begun to appear much more recently [27][28][29][30][31][32][33] , and with little if any direct approach to interfacial ; (c) surface immobilized G-quadruplexes finally offer perspectives for ultra-sensitive detection of metal ions [40][41][42] , complex biomolecules such as peptides [23][24][25][26][27][28][29][30] , and perhaps other analytes.…”

“…The G-qs's resemble the telomer ends in the chromosomes [23][24][25][26][27][28] . Their natural biological functions are largely unknown, but G-qs peptide binding and recognition has attracted interest in peptide sensing, therapy and other biotechnology [26][27][28] .…”

Porphyrins in complex with DNA: Modes of interaction and oxidation reactions

“…Consequently, as discussed in Section 2, the formation of activated compound I-type species is certainly not optimal and high concentration of H 2 O 2 is necessary. However, electron abstraction is relatively easy to achieve (with several possible oxidative species, compound I, compound II, free radicals) and the "peroxidase" mimicking capacity of hemin/quadruplex DNA complex, with H 2 O 2 in the presence of chromogenic and fluorogenic substrates, has led to a plethora of elegant applications [139,[182][183][184][185][186][187][188]. The peroxidase reactivity remains when hemin is covalently bound to a nucleic acid vector [185].…”