The interactions between a small molecule and G-quadruplexes are visualized by fluorescence lifetime imaging microscopy

Abstract

Guanine-rich oligonucleotides can fold into quadruple-stranded helical structures known as G-quadruplexes. Mounting experimental evidence has gathered suggesting that these non-canonical nucleic acid structures form in vivo and play essential biological roles. However, to date, there are no small-molecule optical probes to image G-quadruplexes in live cells. Herein, we report the design and development of a small fluorescent molecule, which can be used as an optical probe for G-quadruplexes. We demonstrate that the fluorescence lifetime of this new probe changes considerably upon interaction with different nucleic acid topologies. Specifically, longer fluorescence lifetimes are observed in vitro for G-quadruplexes than for double- and single-stranded nucleic acids. Cellular studies confirm that this molecule is cell permeable, has low cytotoxicity and localizes primarily in the cell nucleus. Furthermore, using fluorescence lifetime imaging microscopy, live-cell imaging suggests that the probe can be used to study the interaction of small molecules with G-quadruplexes in vivo.

NMR Structure of a Triangulenium‐Based Long‐Lived Fluorescence Probe Bound to a G‐Quadruplex

“…Relative conformation of morpholino groups with respect to the triangulenium core of the free and CMA-bound ligand could reduce the intramolecular quenching to differed extents and may explain the enhancement in fluorescence intensity when DAOTA-M2 is bound to G-quadruplex. [6] Our current study provides structural rationale for hypothesis [6,7] that DAOTA-M2 has two different excited state lifetimes. Favorable geometric feature of DAOTA-M2 offer extensive stacking in comparison to most reported G-quadruplex ligands that cover only one or two guanines in G-quartet.…”

In vivo biodistribution studies and ex vivo lymph node imaging using heavy metal-free quantum dots

“…For these measurements, a diode laser with a variable repetition rate was used to enable the adjustment of the time window to collect the entire decay before re-exciting the sample [67].…”

On the binding modes of metal NHC complexes with DNA secondary structures: implications for therapy and imaging

“…Therefore, significant efforts have been devoted to the discovery of specific probes for visualizing and distinguishing G4 structures from other nucleic acid molecules likely to be found in biological environments. 96 In this context, based on the representative examples described in this review, metal NHCs certainly hold great promise.…”