title: Homogeneous selecting of a quadruplex-binding ligand-based gold nanoparticle fluorescence resonance energy transfer assay.
abstract: G-quadruplexes are higher-order DNA and RNA structures formed from G-rich sequences that are built around tetrads of hydrogen-bonded guanine bases. There is considerable interest in the design of ligands that target G-quadruplex DNA because of their potential anticancer activity. We designed a fluorescence resonance energy transfer (FRET) system to identify molecules that stabilize G-quadruplexes in a homogeneous medium using unmodified gold nanoparticles (GNPs) as a fluorescence quencher. The assay exploits the different adsorption abilities of GNPs for single-stranded DNA and double-stranded DNA. Fluorescein-tagged probe DNA adsorbed onto the surface of GNPs can quench the fluorescence of a DNA probe. Intramolecular folding of an oligonucleotide of the human telomeric sequence into a G-quadruplex structure led to fluorescence enhancement in the presence of quadruplex-binding ligands. G-quadruplex formation, induced by specific binding of GDNA ligands, was investigated by CD measurements. Melting of the G-quadruplex was monitored in the presence of putative G-quadruplex-binding molecules by measuring the absorbance at 295 nm. Two series of natural drugs were studied, and flavonoids were shown to increase the melting temperature of the G-quadruplex. This increase in the Tm value was well-correlated with an increase in FRET efficiency. The combined data from fluorescence measurements and melting experiments indicate that the FRET approach offers a simple, sensitive, and effective method to identify ligands with potential anticancer activity.
authors.affiliation: Key Laboratory of Applied Surface and Colloid Chemistry, MOE, Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi'an 710062, China. jinyan@snnu.edu.cn
authors.forename: Yan
authors.initials: Y
authors.lastname: Jin
authors.forename: Hongyan
authors.initials: H
authors.lastname: Li
authors.forename: Jinyan
authors.initials: J
authors.lastname: Bai
mesh_terms: D000970:Antineoplastic Agents / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D001483:Base Sequence; D004353:Drug Evaluation, Preclinical; D004365:Drugs, Chinese Herbal / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D005419:Flavonoids / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D031541:Fluorescence Resonance Energy Transfer; D054856:G-Quadruplexes / Q000187:drug effects; D006046:Gold / Q000737:chemistry*; D006801:Humans; D008024:Ligands; D053768:Metal Nanoparticles / Q000737:chemistry*; D013379:Substrate Specificity; D016615:Telomere / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D004365:Drugs, Chinese Herbal; D005419:Flavonoids; D008024:Ligands; D006046:Gold