INTEGRATED MULTISENSOR RANGE FINDERS

Initially, the system presented was designed to increase the autonomy of robots working in difficult surroundings congested with obstacles. The system can have applications other than in robotics. The system combines: an ultrasonic telemeter for distance measurement, an optical device based on photovoltaic cells, allowing the classification of tints of plane obstacles in a group of colours previously defined by the user, and a range finding system composed of a monochromatic laser associated with a solid state detector used for the localisation of the vertical edges of polyhedral obstacles. Each of these base sensors delivers an elementary information (distance, tint, coordinates of vertical edges) which is determined by processing the echo from the obstacle of a previously transmitted signal (active detection)

Improved performances of catalytic G-quadruplexes (G4-DNAzymes) via the chemical modifications of the DNA backbone to provide Gquadruplexes with double 3′-external G-quartets

Here we report on the design of a new catalytic G-quadruplex-DNA system (G4-DNAzyme) based on the modification of the DNA scaffold to provide the DNA pre-catalyst with two identical 3′-ends, known to bemore catalytically proficient than the 5′-ends. To this end, we introduced a 5′-5′ inversion of polarity site in the middle of the G4-forming sequences AG4A andAG6A to obtain d(3′AGG5′-5′GGA3′) (orAG2-G2A) and d(3′AGGG5′-5′GGGA3′) (or AG3-G3A) that fold into stable G4 whose tetramolecular nature was confirmed via nuclear magnetic resonance (NMR) and circular dichroism(CD) investigations. Both AG2-G2AandAG3-G3A display two identical external G-quartets (3′-ends) known to interact with the cofactor hemin with a high efficiency, making the resulting complex competent to performhemoprotein-like catalysis (G4-DNAzyme). A systematic comparison of the performances of modified and unmodified G4s lends credence to the relevance of the modification exploited here (5′-5′ inversion of polarity site), which represents a new chemical opportunity to improve the overall activity of catalytic G4s

“One Ring to Bind Them All”—Part I: The Efficiency of the Macrocyclic Scaffold for G-Quadruplex DNA Recognition

Macrocyclic scaffolds are particularly attractive for designing selective G-quadruplex ligands essentially because, on one hand, they show a poor affinity for the “standard” B-DNA conformation and, on the other hand, they fit nicely with the external G-quartets of quadruplexes. Stimulated by the pioneering studies on the cationic porphyrin TMPyP4 and the natural product telomestatin, follow-up studies have developed, rapidly leading to a large diversity of macrocyclic structures with remarkable-quadruplex binding properties and biological activities. In this review we summarize the current state of the art in detailing the three main categories of quadruplex-binding macrocycles described so far (telomestatin-like polyheteroarenes, porphyrins and derivatives, polyammonium cyclophanes), and in addressing both synthetic issues and biological aspects

“One Ring to Bind Them All”—Part II: Identification of Promising G-Quadruplex Ligands by Screening of Cyclophane-Type Macrocycles

A collection of 26 polyammonium cyclophane-type macrocycles with a large structural diversity has been screened for G-quadruplex recognition. A two-step selection procedure based on the FRET-melting assay was carried out enabling identification of macrocycles of high affinity (ΔT1/2 up to 30°C) and high selectivity for the human telomeric G-quadruplex. The four selected hits possess sophisticated architectures, more particularly the presence of a pendant side-arm as well as the existence of a particular topological arrangement appear to be strong determinants of quadruplex binding. These compounds are thus likely to create multiple contacts with the target that may be at the origin of their high selectivity, thereby suggesting that this class of macrocycles offers unique advantages for targeting G-quadruplex-DNA

Mix and measure fluorescence screening for selective quadruplex binders

The human genome contains thousands of regions, including that of the telomere, that have the potential to form quadruplex structures. Many of these regions are potential targets for therapeutic intervention. There are many different folding patterns for quadruplex DNAs and the loops exhibit much more variation than do the quartets. The successful targeting of a particular quadruplex structure requires distinguishing that structure from all of the other quadruplex structures that may be present. A mix and measure fluorescent screening method has been developed, that utilizes multiple reporter molecules that bind to different features of quadruplex DNA. The reporter molecules are used in combination with DNAs that have a variety of quadruplex structures. The screening is based on observing the increase or decrease in the fluorescence of the reporter molecules. The selectivity of a set of test molecules has been determined by this approach

Identification of new DNA i-motif binding ligands through a fluorescent intercalator displacement assay

i-Motifs are quadruplex DNA structures formed from sequences rich in cytosine and held together by intercalated, hemi-protonated cytosine–cytosine base pairs. These sequences are prevalent in gene promoter regions and may play a role in gene transcription. Targeting these structures with ligands could provide a novel way to target genetic disease but there are very few ligands which have been shown to interact with i-motif DNA. Fluorescent intercalator displacement (FID) assays are a simple way to screen ligands against DNA secondary structures. Here we characterise how thiazole orange interacts with i-motif DNA and assess its ability for use in a FID assay. Additionally, we report FID-based ligand screening using thiazole orange against the i-motif forming sequence from the human telomere to reveal new i-motif binding compounds which have the potential for further development

Small-molecule G-quadruplex stabilizers reveal a novel pathway of autophagy regulation in neurons

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Genetic instability triggered by G-quadruplex interacting Phen-DC compounds in Saccharomyces cerevisiae

G-quadruplexes are nucleic acid secondary structures for which many biological roles have been proposed but whose existence in vivo has remained elusive. To assess their formation, highly specific G-quadruplex ligands are needed. Here, we tested Phen-DC3 and Phen-DC6, two recently released ligands of the bisquinolinium class. In vitro, both compounds exhibit high affinity for the G4 formed by the human minisatellite CEB1 and inhibit efficiently their unwinding by the yeast Pif1 helicase. In vivo, both compounds rapidly induced recombination-dependent rearrangements of CEB1 inserted in the Saccharomyces cerevisiae genome, but did not affect the stability of other tandem repeats lacking G-quadruplex forming sequences. The rearrangements yielded simple-deletion, double-deletion or complex reshuffling of the polymorphic motif units, mimicking the phenotype of the Pif1 inactivation. Treatment of Pif1-deficient cells with the Phen-DC compounds further increased CEB1 instability, revealing additional G4 formation per cell. In sharp contrast, the commonly used N-methyl-mesoporphyrin IX G-quadruplex ligand did not affect CEB1 stability. Altogether, these results demonstrate that the Phen-DC bisquinolinium compounds are potent molecular tools for probing the formation of G-quadruplexes in vivo, interfere with their processing and elucidate their biological roles

Synthesis, analysis and biological evaluation of novel indolquinonecryptolepine analogues as potential anti-tumour agents.

A small library of cryptolepine analogues were synthesised incorporating halogens and/or nitrogen containing side chains to optimise their interaction with the sugar-phosphate backbone of DNA to give improved binding, interfering with topoisomerase II hence enhancing cytotoxicity. Cell viability, DNA binding and Topoisomerase II inhibition is discussed for these compounds. Fluorescence microscopy was used to investigate the uptake of the synthesised cryptolepines into the nucleus. We report the synthesis and anti-cancer biological evaluation of nine novel cryptolepine analogues, which have greater cytotoxicity than the parent compound and are important lead compounds in the development of novel potent and selective indoloquinone anti-neoplastic agents

Rudimentary G-Quadruplex-Based Telomere Capping In Saccharomyces Cerevisiae

Telomere capping conceals chromosome ends from exonucleases and checkpoints, but the full range of capping mechanisms is not well defined. Telomeres have the potential to form G-quadruplex (G4) DNA, although evidence for telomere G4 DNA function in vivo is limited. In budding yeast, capping requires the Cdc13 protein and is lost at nonpermissive temperatures in cdc13-1 mutants. Here, we use several independent G4 DNA-stabilizing treatments to suppress cdc13-1 capping defects. These include overexpression of three different G4 DNA binding proteins, loss of the G4 DNA unwinding helicase Sgs1, or treatment with small molecule G4 DNA ligands. In vitro, we show that protein-bound G4 DNA at a 3\u27 overhang inhibits 5\u27-\u3e 3\u27 resection of a paired strand by exonuclease I. These findings demonstrate that, at least in the absence of full natural capping, G4 DNA can play a positive role at telomeres in vivo