Detection of competing DNA structures by thermal gradient gel electrophoresis: from self-association to triple helix formation by (G,A)-containing oligonucleotides

Sequence-specific recognition of DNA can be achieved by triple helix-forming oligonucleotides that bind to the major groove of double-helical DNA. These oligonucleotides have been used as sequence-specific DNA ligands for various purposes, including sequence-specific gene regulation in the so-called ‘antigene strategy’. In particular, (G,A)-containing oligonucleotides can form stable triple helices under physiological conditions. However, triplex formation may be in competition with self-association of these oligonucleotides. For biological applications it would be interesting to identify the conditions under which one structure is favoured as compared to the other(s). Here we have directly studied competition between formation of a parallel (G,A) homoduplex and that of a triple helix by a 13 nt (G,A)-containing oligonucleotide. Temperature gradient gel electrophoresis allows simultaneous detection of competition between the two structures, because of their different temperature dependencies and gel electrophoretic mobilities, and characterisation of this competition.

Telomerase inhibitors based on quadruplex ligands selected by a fluorescence assay

The reactivation of telomerase activity in most cancer cells supports the concept that telomerase is a relevant target in oncology, and telomerase inhibitors have been proposed as new potential anticancer agents. The telomeric G-rich single-stranded DNA can adopt in vitro an intramolecular quadruplex structure, which has been shown to inhibit telomerase activity. We used a fluorescence assay to identify molecules that stabilize G-quadruplexes. Intramolecular folding of an oligonucleotide with four repeats of the human telomeric sequence into a G-quadruplex structure led to fluorescence excitation energy transfer between a donor (fluorescein) and an acceptor (tetramethylrhodamine) covalently attached to the 5′ and 3′ ends of the oligonucleotide, respectively. The melting of the G-quadruplex was monitored in the presence of putative G-quadruplex-binding molecules by measuring the fluorescence emission of the donor. A series of compounds (pentacyclic crescent-shaped dibenzophenanthroline derivatives) was shown to increase the melting temperature of the G-quadruplex by 2–20°C at 1 μM dye concentration. This increase in Tm value was well correlated with an increase in the efficiency of telomerase inhibition in vitro. The best telomerase inhibitor showed an IC50 value of 28 nM in a standard telomerase repeat amplification protocol assay. Fluorescence energy transfer can thus be used to reveal the formation of four-stranded DNA structures, and its stabilization by quadruplex-binding agents, in an effort to discover new potent telomerase inhibitors.

A revision of the lepidopterous family Sphingidae. By the Hon. Walter Rothschild ... and Karl Jordan ... (With 67 plates). Issued at the Zoological Museum, Tring, March 1903.

Novitates zoologicae. Vol. IX. Supplement, v. 2

Bénéfices de la diversité culturelle en entreprises : Études de cas dans les entreprises québécoises

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Bénéfices de la diversité culturelle en entreprises : Études de cas dans les entreprises québécoises

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Composition of benthic taxa collected during POLARSTERN cruise ANT-XXI/5 (BENDEX) at Bouvet Island and Spiess Seamound

Bouvet (Bouvetøya) is a geologically young and very remote island just south of the Polar Front. Here we report samples taken during the RV "Polarstern" cruise ANTXXI/2 on 3 days in November 2003 and January 2004. This work was part of SCAR's EASIZ programme and intended, by providing data on the marine fauna of this "white gap" in the Atlantic sector of the Southern Ocean, to contribute to identifying the role of Bouvet in the faunal exchange between the Sub- and high Antarctic. While this goal demands extensive molecular analysis of the material sampled (future work), a checklist of the samples and data at hand widens the faunal and environmental inventory substantially. We suggest some preliminary conclusions on the relationship of Bouvet Island's fauna with that of other regions, such as Magellanic South America, the Antarctic Peninsula, and the high Antarctic Weddell Sea, which have been sampled previously. There seem to be different connections for individual higher taxa rather than a generally valid consistent picture.

The youth of the Duchess of Angoulême,

Mode of access: Internet.

The life and letters of Madame Élisabeth de France, followed by the Journal of the Temple,

Edition limited to 800 numbered sets.

La dernière dauphine, Madame duchesse d'Angoulême (1778-1851) /

Mode of access: Internet.

Europe's children, 1939 to 1943 /

"Limited autographed edition"--back flap.

Mémoires particuliers

Ed. by L. E. Audot. cf. Bibl. nat. cat.

Madame de Beaumarchais d'après sa correspondance inédite,

Mode of access: Internet.

Encyclopédie méthodique : Architecture /

Mode of access: Internet.