70 research outputs found
[Ru(Me_4phen)_2dppz]^(2+), a Light Switch for DNA Mismatches
[Ru(Me_4phen)_2dppz]^(2+) serves as a luminescent âlight switchâ for single base mismatches in DNA. The preferential luminescence enhancement observed with mismatches results from two factors: (i) the complex possesses a 26-fold higher binding affinity toward the mismatch compared to well-matched base pairs, and (ii) the excited state emission lifetime of the ruthenium bound to the DNA mismatch is 160 ns versus 35 ns when bound to a matched site. Results indicate that the complex binds to the mismatch through a metalloinsertion binding mode. Cu(phen)_2^(2+) quenching experiments show that the complex binds to the mismatch from the minor groove, characteristic of metalloinsertion. Additionally, the luminescence intensity of the complex with DNA containing single base mismatches correlates with the thermodynamic destabilization of the mismatch, also consistent with binding through metalloinsertion. This complex represents a potentially new early cancer diagnostic for detecting deficiencies in mismatch repair
A Ruthenium(II) Complex as a Luminescent Probe for DNA Mismatches and Abasic Sites
[Ru(bpy)_2(BNIQ)]^(2+) (BNIQ = Benzo[c][1,7]naphthyridine-1-isoquinoline), which incorporates the sterically expansive BNIQ ligand, is a highly selective luminescent probe for DNA mismatches and abasic sites, possessing a 500-fold higher binding affinity toward these destabilized regions relative to well-matched base pairs. As a result of this higher binding affinity, the complex exhibits an enhanced steady-state emission in the presence of DNA duplexes containing a single base mismatch or abasic site compared to fully well-matched DNA. Luminescence quenching experiments with Cu(phen)_2^(2+) and [Fe(CN)_6]^(3â) implicate binding of the complex to a mismatch from the minor groove via metalloinsertion. The emission response of the complex to different single base mismatches, binding preferentially to the more destabilized mismatches, is also consistent with binding by metalloinsertion. This work shows that high selectivity toward destabilized regions in duplex DNA can be achieved through the rational design of a complex with a sterically expansive aromatic ligand
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Photochemically active DNA-intercalating ruthenium and related complexes â insights by combining crystallography and transient spectroscopy
Recent research on the study of the interaction of ruthenium polypyridyl compounds and defined sequence nucleic acids is reviewed. Particular emphasis is paid to complexes [Ru(LL)2(Int)]2+ containing potentially intercalating ligands (Int) such as dipyridophenazine (dppz), which are known to display light-switching or photo-oxidising behaviour, depending on the nature of the ancillary ligands. X-ray crystallography has made a key contribution to our understanding, and the first complete survey of structural results is presented. These include sequence, enantiomeric, substituent and structural specificities. The use of ultrafast transient spectrocopic methods to probe the ultrafast processes for complexes such as [Ru(TAP)2(dppz)]2+ and [Ru(phen)2(dppz)]2+ when bound to mixed sequence oligonucleotides are reviewed with particular attention being paid to the complementary advantages of transient (visible) absorption and time-resolved (mid) infra-red techniques to probe spectral changes in the metal complex and in the nucleic acid. The observed photophysical properties are considered in light of the structural information obtained from X-ray crystallography. In solution, metal complexes can be expected to bind at more than one DNA step, so that a perfect correlation of the photophysical properties and factors such as the orientation or penetration of the ligand into the intercalation pocket should not be expected. This difficulty can be obviated by carrying out TRIR studies in the crystals. Dppz complexes also undergo insertion, especially with mismatched sequences. Future areas for study such as those involving non-canonical forms of DNA, such as G-quadruplexes or i-motifs are also briefly considered
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Monitoring one-electron photo-oxidation of guanine in DNA crystals using ultrafast infrared spectroscopy
To understand the molecular origins of diseases caused by ultraviolet and visible light, and also to develop photodynamic therapy, it is important to resolve the mechanism of photoinduced DNA damage. Damage to DNA bound to a photosensitizer molecule frequently proceeds by one-electron photo-oxidation of guanine, but the precise dynamics of this process are sensitive to the location and the orientation of the photosensitizer, which are very difficult to define in solution. To overcome this, ultrafast time-resolved infrared (TRIR) spectroscopy was performed on photoexcited ruthenium polypyridylâDNA crystals, the atomic structure of which was determined by X-ray crystallography. By combining the X-ray and TRIR data we are able to define both the geometry of the reaction site and the rates of individual steps in a reversible photoinduced electron-transfer process. This allows us to propose an individual guanine as the reaction site and, intriguingly, reveals that the dynamics in the crystal state are quite similar to those observed in the solvent medium
Chapitre IV. PÚres, MÚres et Filles Structures relationnelles et gouvernement chez les cloßtrées
Ă lâinstar des textes normatifs, les supĂ©rieurs masculins forment une « matrice » qui agit Ă de multiples niveaux dans la vie des moniales. Ils reprĂ©sentent la loi vivante, ce sont bien les « pĂšres » comme les appellent les religieuses. Une trappistine observait judicieusement que « les hommes en clĂŽture Ă©taient bien plus cĂ©libataires que les femmes », voulant signifier par lĂ que, si aucune femme ne pouvait rentrer dans les couvents dâhommes, ces derniers, en tant que prĂȘtres, mĂ©decins ou ou..
Chapitre VI. Bilans : Des moniales face Ă elles-mĂȘmes
« Que reste-t-il quand il ne reste rien ? », pour reprendre la belle question de Maurice Bellet, ou encore, que reste-t-il de ces candidates Ă la disparition dâelles-mĂȘmes ? De fait, la construction dâhistoires personnelles se heurte Ă lâune des utopies monastiques les plus tenaces qui veut que lâentrĂ©e au couvent sâapparente Ă une petite mort ou Ă une disparition de soi. Le vocabulaire de lâentrĂ©e est dâailleurs explicite : la postulante vient sâensevelir ou sâenterrer au monastĂšre. Jusquâau..
Introduction
Travailler sur les moniales contemplatives contemporaines, câest rejoindre une rĂ©alitĂ© millĂ©naire. Pour lâĂ©tudiante-historienne que jâĂ©tais en 1992 lors de mon premier contact avec la vie monastique, pĂ©nĂ©trer dans un cloĂźtre signifiait remonter le temps. La clĂŽture devenait lâenceinte mĂ©diĂ©vale ; les moniales, les dĂ©positaires dâune façon de vivre aussi ancienne quâimmuable. Le choc a Ă©tĂ© rude en dĂ©couvrant les lieux, les personnes, les archives. Ce nâĂ©tait pas une rĂ©alitĂ© sans Ăąge, mais ĂągĂ©e..
Chapitre I. Fondations
En dĂ©pit dâune analyse conceptuelle de la vie contemplative, montrant que celle-ci se vit de façons diverses et autorise plusieurs rapports au monde, la dĂ©limitation de notre objet, « les monastĂšres de contemplatives », a posĂ© de nombreux problĂšmes. Dans la mesure oĂč lâon prenait comme critĂšre lâabsence dâĆuvres externes, les changements dâorientation (de la vie mixte Ă la vie exclusivement cloĂźtrĂ©e par exemple) au sein dâun mĂȘme ordre et mĂȘme au sein dâune mĂȘme maison Ă©taient problĂ©matiques...
Femmes cloßtrées des temps contemporains
Recherche en histoire qui fait largement place aux vĂ©cus personnels, cet ouvrage explore la vie des moniales contemplatives Ă lâĂ©poque contemporaine Ă partir de quatre couvents de carmĂ©lites (Jambes et Floreffe) et de clarisses (Malonne et Saint-Servais) de la province de Namur. LâenquĂȘte monographique est prĂ©cĂ©dĂ©e dâun relevĂ© gĂ©nĂ©ral des fondations de contemplatives en Wallonie et Ă Bruxelles aux 19e et 20e siĂšcles qui tĂ©moigne de lâimportance du phĂ©nomĂšne : en 2000, malgrĂ© la fermeture dâune cinquantaine de maisons depuis les annĂ©es 1960, il restait encore cinquante couvents de contemplatives. Au total, quelque 300 femmes ont Ă©tĂ© professes dans les maisons Ă©tudiĂ©es, les deux tiers entrĂ©es entre 1880 et 1930. ComplĂ©tĂ©es par les tĂ©moignages oraux, les archives conventuelles constituent lâessentiel des sources exploitĂ©es, avec une attention particuliĂšre Ă la production poĂ©tique et littĂ©raire des moniales (chants, poĂšmes, piĂšces de thĂ©Ăątre, sketches, etc.), ce qui permet de toucher du doigt lâaspect « pulsionnel » du vĂ©cu religieux. Le thĂšme central qui Ă©merge de lâĂ©tude est celui de la « sĂ©paration du monde », utopie et fondement du monachisme
Chapitre III. La clĂŽture et le monde
Sâil est une chose spĂ©cifique Ă la rĂ©alitĂ© que nous Ă©tudions, câest la dimension de retrait. Non un retrait individuel â nous serions dans lâĂ©rĂ©mitisme â, mais un retrait vĂ©cu en groupe. La modalitĂ© du rapport au monde apparaĂźt comme un Ă©lĂ©ment clĂ© pour la dĂ©finition de la vie monastique. « La sĂ©paration du monde, dans un cĂ©libat dĂ©finitif, est lâaspect le plus gĂ©nĂ©ralement observable de la vie monastique » affirme Pierre Miquel dans son article consacrĂ© au monachisme. LâĂ©tymologie du terme «..
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