Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 115
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Opt Express ; 21(26): 31751-68, 2013 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-24514771

RESUMO

The estimation and compensation of quasi-static aberrations is mandatory to reach the ultimate performance of high-contrast imaging systems. COFFEE is a focal plane wave-front sensing method that consists in the extension of phase diversity to high-contrast imaging systems. Based on a Bayesian approach, it estimates the quasi-static aberrations from two focal plane images recorded from the scientific camera itself. In this paper, we present COFFEE's extension which allows an estimation of low and high order aberrations with nanometric precision for any coronagraphic device. The performance is evaluated by realistic simulations, performed in the SPHERE instrument framework. We develop a myopic estimation that allows us to take into account an imperfect knowledge on the used diversity phase. Lastly, we evaluate COFFEE's performance in a compensation process, to optimize the contrast on the detector, and show it allows one to reach the 10(-6) contrast required by SPHERE at a few resolution elements from the star. Notably, we present a non-linear energy minimization method which can be used to reach very high contrast levels (better than 10(7) in a SPHERE-like context).


Assuntos
Algoritmos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Astros Celestes , Telescópios , Aumento da Imagem/instrumentação , Interpretação de Imagem Assistida por Computador/instrumentação
2.
Opt Lett ; 37(23): 4808-10, 2012 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-23202053

RESUMO

Exoplanet direct imaging is a challenging goal of today's astronomical instrumentation. Several high-contrast imaging instruments dedicated to this task are currently being integrated; they are ultimately limited by the presence of quasi-static speckles in the imaging focal plane. These speckles originate in residual quasi-static optical aberrations, which must be measured and compensated for, typically at a nanometric level. We present a novel focal plane wavefront sensor (WFS) designed for this particular application. It is an extension of the phase diversity technique to coronagraphic imaging. This sensor requires no dedicated hardware and uses only two scientific images differing from a known aberration, which can be conveniently introduced by the adaptive optics subsystem. The aberrations are therefore calibrated all the way down to the scientific camera, without any differential aberrations between the sensor and the scientific camera. We show the potential of this WFS by means of simulations, and we perform a preliminary experimental validation.

3.
Nat Commun ; 13(1): 312, 2022 01 25.
Artigo em Inglês | MEDLINE | ID: mdl-35078973

RESUMO

A fourth of the global seabed sediment volume is buried at depths where temperatures exceed 80 °C, a previously proposed thermal barrier for life in the subsurface. Here, we demonstrate, utilizing an extensive suite of radiotracer experiments, the prevalence of active methanogenic and sulfate-reducing populations in deeply buried marine sediment from the Nankai Trough subduction zone, heated to extreme temperature (up to ~120 °C). The small microbial community subsisted with high potential cell-specific rates of energy metabolism, which approach the rates of active surface sediments and laboratory cultures. Our discovery is in stark contrast to the extremely low metabolic rates otherwise observed in the deep subseafloor. As cells appear to invest most of their energy to repair thermal cell damage in the hot sediment, they are forced to balance delicately between subsistence near the upper temperature limit for life and a rich supply of substrates and energy from thermally driven reactions of the sedimentary organic matter.


Assuntos
Bactérias/metabolismo , Radioisótopos de Carbono/metabolismo , Sedimentos Geológicos/microbiologia , Temperatura Alta , Microbiota , Sulfatos/metabolismo , Radioisótopos de Enxofre/metabolismo , Bactérias/crescimento & desenvolvimento , Sedimentos Geológicos/análise , Sedimentos Geológicos/química , Traçadores Radioativos
4.
J Opt Soc Am A Opt Image Sci Vis ; 27(11): A157-70, 2010 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-21045877

RESUMO

In this paper we derive an analytical model of a long-exposure star image for an adaptive-optics(AO)-corrected coronagraphic imaging system. This expression accounts for static aberrations upstream and downstream of the coronagraphic mask as well as turbulence residuals. It is based on the perfect coronagraph model. The analytical model is validated by means of simulations using the design and parameters of the SPHERE instrument. The analytical model is also compared to a simulated four-quadrant phase-mask coronagraph. Then, its sensitivity to a miscalibration of structure function and upstream static aberrations is studied, and the impact on exoplanet detectability is quantified. Last, a first inversion method is presented for a simulation case using a single monochromatic image with no reference. The obtained result shows a planet detectability increase by two orders of magnitude with respect to the raw image. This analytical model presents numerous potential applications in coronographic imaging, such as exoplanet direct detection, and circumstellar disk observation.

5.
Rev Laryngol Otol Rhinol (Bord) ; 130(4-5): 293-4, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-20597414

RESUMO

Mucoceles of the paranasal sinuses are well-described complication of chronic sinusitis in adults. They are extremely rare in children and the main predisposing factor is cystic fibrosis (CF). We report a case of bilateral ethmoid and maxillary sinus mucopyoceles, associated with CF occurring in a six months old boy. The main symptom was a complete nasal obstruction. The marsupialization of mucocele was performed by endoscopic surgery. One year follow-up showed no recurrence.


Assuntos
Fibrose Cística/complicações , Mucocele/cirurgia , Doenças dos Seios Paranasais/cirurgia , Endoscopia , Humanos , Lactente , Masculino , Mucocele/diagnóstico , Obstrução Nasal/etiologia , Obstrução Nasal/cirurgia , Doenças dos Seios Paranasais/diagnóstico
6.
Opt Express ; 16(22): 18406-16, 2008 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-18958119

RESUMO

The phase diversity technique is a useful tool to measure and pre-compensate for quasi-static aberrations, in particular non-common path aberrations, in an adaptive optics corrected imaging system. In this paper, we propose and validate by simulations an extension of the phase diversity technique that uses long exposure adaptive optics corrected images for sensing quasi-static aberrations during the scientific observation, in particular for high-contrast imaging. The principle of the method is that, for a sufficiently long exposure time, the residual turbulence is averaged into a convolutive component of the image and that phase diversity estimates the sole static aberrations of interest. The advantages of such a procedure, compared to the processing of shortexposure image pairs, are that the separation between static aberrations and turbulence-induced ones is performed by the long-exposure itself and not numerically, that only one image pair must be processed, that the estimation benefits from the high SNR of long-exposure images, and that only the static aberrations of interest are to be estimated. Long-exposure phase diversity can also be used as a phasing sensor for a segmented aperture telescope. Thus, it may be particularly useful for future planet finder projects such as EPICS on the European ELT.

7.
Phys Med Biol ; 63(21): 215012, 2018 10 24.
Artigo em Inglês | MEDLINE | ID: mdl-30353889

RESUMO

Four-dimensional (4D) Ultrafast ultrasound imaging was recently proposed to image and quantify blood flow with high sensitivity in 3D as well as anatomical, mechanical or functional information. In 4D Ultrafast imaging, coherent compounding of tilted planes waves emitted by a 2D matrix array were used to image the medium at high volume rate. 4D ultrafast imaging, however, requires a high channel count (>1000) to drive those probes. Alternative approaches have been proposed and investigated to efficiently reduce the density of elements, such as sparse or under-sampled arrays while maintaining a decent image quality and high volume rate. The row-columns configuration presents the advantage of keeping a large active surface with a low amount of elements and a simple geometry. In this study, we investigate the row and column addressed (RCA) approach with the orthogonal plane wave (OPW) compounding strategy using real hardware limitations. We designed and built a large 7 MHz 128 + 128 probe dedicated to vascular imaging and connected to a 256-channel scanner to implement the OPW imaging scheme. Using this strategy, we demonstrate that 4D ultrafast Power Doppler imaging of a large volume of [Formula: see text] up to [Formula: see text] depth, both in vitro on flow phantoms and in vivo on the carotid artery of a healthy volunteer at a volume rate of 834 Hz.


Assuntos
Imageamento Tridimensional/métodos , Artérias Carótidas/diagnóstico por imagem , Artérias Carótidas/fisiologia , Hemodinâmica , Humanos , Fatores de Tempo , Ultrassonografia Doppler/métodos
8.
Opt Express ; 14(17): 7515-34, 2006 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-19529118

RESUMO

The detection of extrasolar planets implies an extremely high-contrast, long-exposure imaging capability at near infrared and probably visible wavelengths. We present here the core of any Planet Finder instrument, that is, the extreme adaptive optics (XAO) subsystem. The level of AO correction directly impacts the exposure time required for planet detection. In addition, the capacity of the AO system to calibrate all the instrument static defects ultimately limits detectivity. Hence, the extreme AO system has to adjust for the perturbations induced by the atmospheric turbulence, as well as for the internal aberrations of the instrument itself. We propose a feasibility study for an extreme AO system in the frame of the SPHERE (Spectro-Polarimetry High-contrast Exoplanet Research) instrument, which is currently under design and should equip one of the four VLT 8-m telescopes in 2010.

9.
Rev Laryngol Otol Rhinol (Bord) ; 127(3): 145-9, 2006.
Artigo em Francês | MEDLINE | ID: mdl-17007186

RESUMO

UNLABELLED: Amphicrine adenoma is an extremely rare tumor of the middle ear. We report three cases obtained over a twenty year period. THE AIM OF THIS STUDY: is to discuss our clinical cases and review the literature. MATERIALS AND METHODS: Three cases of middle ear amphicrine tumour were reviewed. RESULTS: During a 10 year period (1986-2006) three cases of middle ear amphicrine tumour were treated at our unit (2 male, 1 female). The presenting complaint was hearing loss in all 3 cases. Amphicrine adenoma is diagnosed by an immuno-histological examination of pathological specimens. Differential diagnosis can be difficult and one individual was initially treated as an adenocarcinoma by radiotherapy. This patient succumbed to cerebral mycosis two years post-radiotherapy. The other two patients have no evidence of recurrence eight and nine years post treatment. CONCLUSION: Historically, differential diagnosis between amphicrine adenoma and adenocarcinoma of the middle ear has been very difficult. Carcinoid tumour is considered to be a more agressive form of amphicrine adenoma. Tumour progression is through loco regional invasion. Complete excision by surgical management with long term follow up is the treatment of choice.


Assuntos
Adenoma/patologia , Neoplasias da Orelha/patologia , Orelha Média/patologia , Adenoma/cirurgia , Adulto , Tumor Carcinoide/patologia , Tumor Carcinoide/cirurgia , Neoplasias da Orelha/cirurgia , Orelha Média/cirurgia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
10.
Rev Laryngol Otol Rhinol (Bord) ; 126(4): 257-62, 2005.
Artigo em Francês | MEDLINE | ID: mdl-16496554

RESUMO

The incidence of benign paroxysmal positional vertigo (BPPV) of the horizontal and superior semicircular canals is much less than that of BPPV due to affection of the posterior semicircular canal. Their diagnosis is however much more difficult and still prone to controversies. The provocative manoeuvre of the BPPV of the horizontal canal (BPPV-HSC) is the manoeuvre of rotation of the head in dorsal position. A horizontal positional nystagmus is obtained. There are two forms of BPPV-HSC: the geotropic form and the ageotropic form. In the geotropic form, the liberatory manoeuvre is a "barbecue" rotation of 180 with 360 degrees towards the healthy side. In the ageotropic form, there is no universal liberatory manoeuvre. Moreover as some cases of neurological aetiology have been recognized, it is not appropriate to apply ineffective manoeuvres. The BPPV of the superior canal (BPV-SSC) is very rare. The provocative manoeuvre is the Dix and Hallpike's manoeuvre. It causes positional torsional and vertical nystagmus with an opposite direction to that obtained for a BPPV of the contra-lateral posterior canal. The liberatory manoeuvre is a Semont manoeuvre, which is identical to that we would make for a contra-lateral BPPV of the posterior canal.


Assuntos
Nistagmo Fisiológico , Postura , Canais Semicirculares , Vertigem/fisiopatologia , Testes Calóricos , Movimentos da Cabeça , Humanos , Canais Semicirculares/fisiopatologia , Vertigem/diagnóstico , Vertigem/etiologia , Testes de Função Vestibular/métodos
11.
Science ; 349(6246): 420-4, 2015 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-26206933

RESUMO

Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10(4) cells cm(-3). Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed.


Assuntos
Organismos Aquáticos/classificação , Archaea/classificação , Bactérias/classificação , Carvão Mineral/microbiologia , Sedimentos Geológicos/microbiologia , Consórcios Microbianos , Água do Mar/microbiologia , Organismos Aquáticos/genética , Organismos Aquáticos/metabolismo , Archaea/genética , Archaea/metabolismo , Bactérias/genética , Bactérias/metabolismo , Biomarcadores/metabolismo , Dióxido de Carbono/metabolismo , Japão , Metano/metabolismo , Mathanococcus/classificação , Mathanococcus/genética , Mathanococcus/metabolismo , Methanosarcina barkeri/classificação , Methanosarcina barkeri/genética , Methanosarcina barkeri/metabolismo , Oceano Pacífico
12.
Obstet Gynecol ; 45(3): 287-91, 1975 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-1113946

RESUMO

Clinical experience with the latex and new estane balloons and a short and flexible guide is described. The extraovular balloon as an intrauterine pressure sensor is compared to the open-ended transcervical intraamniotic catheter, and the balloon is considered superior in many respects. The transcervical extraovular water-filled 0.8-ml estane balloon is recommended for use in place of the open-ended transcervical catheter in all clinical situations in obstetrics in which there is a need for monitoring intrauterine pressure.


Assuntos
Cateterismo/instrumentação , Trabalho de Parto , Monitorização Fisiológica , Pressão , Útero , Aborto Induzido , Cesárea , Feminino , Humanos , Injeções Intravenosas , Trabalho de Parto Induzido , Manometria , Ocitocina/administração & dosagem , Ocitocina/farmacologia , Poliuretanos , Gravidez , Primeiro Trimestre da Gravidez , Borracha
13.
Obstet Gynecol ; 50(2): 205-11, 1977 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-876560

RESUMO

Diagnostic ultrasound is a useful tool in the management of high-risk pregnancies and provides valuable information about abnormal fetal growth patterns including excessive fetal size and intrauterine growth retardation. Two patterns of growth retardation can be distinguished ultrasonically. Fetuses exhibiting "reduced growth potential" type patterns have little risk of fetal distress and are readily recognized as small for gestational age at birth. Fetuses suffering from uteroplacental insufficiency frequently exhibit a pattern of biparietal growth arrest in the third trimester. These fetuses have a high risk of fetal distress and should be closely monitored with other parameters of fetal-placental function including serial estriols and oxytocin challenge tests. Utilizing conventional pediatric growth criteria, the existence of intrauterine growth retardation is often unrecognized in this latter group.


Assuntos
Doenças Fetais/diagnóstico , Feto/fisiologia , Ultrassonografia , Traumatismos do Nascimento/prevenção & controle , Feminino , Sofrimento Fetal/epidemiologia , Sofrimento Fetal/etiologia , Sofrimento Fetal/prevenção & controle , Crescimento , Humanos , Recém-Nascido , Missouri , Doenças Placentárias/diagnóstico , Gravidez , Complicações na Gravidez , Estudos Prospectivos , Risco , Crânio/embriologia
14.
Science ; 291(5511): 2105-6, 2001 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-11256410
15.
Eur J Pharmacol ; 56(1-2): 61-7, 1979 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-223858

RESUMO

Cumulative log dose-response curves of soterenol, isoproterenol, phenylephrine and norepinephrine on isolated pregnant rat uterus at different days of gestation, were investigated. Soterenol produced a sustained inhibition of spontaneous motility during the whole pregnancy and this effect was blocked by butoxamine. The affinity of myometrium for the beta 2-adrenoceptor agonist was parallel to the concentration of progesterone in plasma during pregnancy. Isoproterenol, norepinephrine and phenylephrine caused dual, alpha- and beta-mediated responses, their relative dominance varied with the concentration and the days of pregnancy, alpha-Adrenoceptor effects of the amines coincided with increased plasma concentrations of estrogens, whereas beta ones were in parallel with the increment of plasma progesterone. It is concluded that: (a) there exist in the pregnant rat uterus beta 2-receptor-mediated responses influenced by the length of gestation; and (b) the concentration-pregnancy-dependent biphasic actions of isoproterenol, norepinephrine or phenylephrine suggest that their variable hormone-modulated ability interacts with both alpha- and beta-adrenoceptive uterine sites.


Assuntos
Prenhez , Receptores Adrenérgicos alfa/efeitos dos fármacos , Receptores Adrenérgicos beta/efeitos dos fármacos , Receptores Adrenérgicos/efeitos dos fármacos , Contração Uterina/efeitos dos fármacos , Animais , Butoxamina/farmacologia , Relação Dose-Resposta a Droga , Estrogênios/sangue , Etanolaminas/antagonistas & inibidores , Etanolaminas/farmacologia , Feminino , Técnicas In Vitro , Isoproterenol/farmacologia , Norepinefrina/farmacologia , Perfusão , Fenilefrina/farmacologia , Gravidez , Ratos
16.
Curr Med Res Opin ; 11(10): 631-7, 1990.
Artigo em Inglês | MEDLINE | ID: mdl-2107060

RESUMO

A double-blind, placebo-controlled study was carried out in 231 adult patients suffering from acute diffuse pharyngitis or acute tonsillitis with fever and dysphagia to assess the effectiveness of niflumic acid combined with standard antibiotic therapy in relieving pain and inflammation. Patients were allocated at random to receive either 4 capsules of 250 mg niflumic acid or placebo daily in addition to 1.5 million units phenoxymethyl penicillin for 4 to 5 days. Clinical assessments before and after 2 and 4 days of treatment showed that there was faster resolution of fever, pain, adenopathy, pharyngeal congestion and dysphagia, and improved patient comfort in the niflumic acid group. Few side-effects were recorded and there were only 4 drop-outs due to side-effects in patients receiving niflumic acid.


Assuntos
Ácidos Nicotínicos/uso terapêutico , Ácido Niflúmico/uso terapêutico , Penicilina V/uso terapêutico , Tonsilite/tratamento farmacológico , Adolescente , Adulto , Idoso , Transtornos de Deglutição/classificação , Transtornos de Deglutição/tratamento farmacológico , Transtornos de Deglutição/etiologia , Método Duplo-Cego , Quimioterapia Combinada , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Multicêntricos como Assunto , Ácido Niflúmico/efeitos adversos , Ácido Niflúmico/farmacologia , Placebos , Ensaios Clínicos Controlados Aleatórios como Assunto , Tonsilite/complicações
17.
J Am Diet Assoc ; 83(5): 538-45, 1983 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-6630815

RESUMO

Nutrient composition of diets of low-income pregnant women was determined by laboratory analysis and by calculation from food tables. Twenty-two diet composites, each representing a subject's 24-hour intake, were so evaluated. Findings from use of the two methods were compared. Mean analyzed and calculated values compared favorably for food energy, protein, fat, carbohydrate, potassium, magnesium, and zinc, although large differences in values as determined by the two methods were found in some single diet composites. Analyzed values compared less favorably with calculated values for calcium, phosphorus, iron, sodium, and the six vitamins studied.


Assuntos
Dieta , Análise de Alimentos , Pobreza , Gravidez , Adolescente , Adulto , Feminino , Humanos , Minerais/análise , Vitaminas/análise
18.
J Am Diet Assoc ; 83(5): 546-50, 1983 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-6630816

RESUMO

Nutrient intake of a group of 22 young, mainly black, low-income pregnant women was evaluated by use of data resulting from laboratory analysis of foods prepared and consumed in the home over a 24-hour period. Magnesium, zinc, and folacin were the nutrients least well supplied in the foods consumed. Analyzed values for daily intake of the three were below 50% of the RDAs. Mean energy intake was considerably lower than recommended allowances, even though mean gain in weight was somewhat greater than that recommended for normal pregnancy, a finding like that of other investigators. The wide range in daily intake of energy and various nutrients among subjects is comparable with that found in a number of other studies, which showed that many individuals have marked deviations in intake from day to day. Analyzed diets also were examined in terms of nutrient density. Mean nutrient density for protein, calcium, phosphorus, vitamin A, thiamin, riboflavin, niacin, and ascorbic acid compared favorably with that of the RDAs, in contrast with the poor nutrient density for zinc, magnesium, and folacin. Laboratory analysis of the diets had the advantage of providing information about nutrient content of foods as prepared and consumed in the home. The analysis had particular advantage in the evaluation of content of zinc, magnesium, and folacin, as data for the three nutrients in food composition tables are limited.


Assuntos
Dieta , Análise de Alimentos , Pobreza , Gravidez , Adolescente , Adulto , Comportamento Alimentar , Feminino , Humanos , Pessoa de Meia-Idade , Avaliação de Processos e Resultados em Cuidados de Saúde
19.
Carbohydr Res ; 328(3): 343-54, 2000 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-11072841

RESUMO

The distribution of carboxymethyl substituents in the alpha-(1 --> 6)-linked maltotriosyl repeating units of a carboxymethylpullulan (CMP) series was investigated by high resolution NMR spectroscopy on very short oligomers (DPn = 1.2-1.5) obtained by acid hydrolysis. A series of 2D NMR experiments on parent pullulan, hydrolysed pullulan and CMP was used to assign the proton and carbon chemical shifts of CMP acid hydrolysates. The degree of substitution (DS) and the relative distribution of -CH2COONa groups at OH-2, OH-3, OH-4 and OH-6 of glucose residues (DSi) were determined from 1H NMR measurements. From a set of CMP samples, widely different in degree of substitution, it was observed that the substitution at C-2 is predominant and decreases according to the order C-2 > C-3 > C-6 > C-4. Taking into account the availability of each OH group in the parent pullulan, an order of relative reactivity of hydroxyl groups is defined according to the relation: Ri = DSi/ni, where ni is the number of free OH groups in a maltotriose unit (MTU) for a given site C-i, the reactivity order was found to be OH-2 > OH-4 > OH-6 > OH-3.


Assuntos
Glucanos/química , Espectroscopia de Ressonância Magnética , Sequência de Carboidratos , Hidrólise , Dados de Sequência Molecular , Estrutura Molecular , Peso Molecular
20.
J Photochem Photobiol B ; 26(2): 165-74, 1994 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-7815190

RESUMO

The influence of the nature of ligands on the efficiency of ruthenium complexes for photosensitizing DNA cleavage was investigated. Ru(bipy)2dppz2+ and Ru(bpz)2dppz2+ were selected as DNA breakers on the basis of their high affinity for DNA due to the presence of a dppz ligand which can partially intercalate in the major groove of DNA. Their photosensitizing properties were compared to those of Ru(bipy)3(2+), a complex which binds to DNA with a far lower constant. Upon irradiation, these complexes promoted the formation of single strand breaks in supercoiled phi X 174 DNA. Unexpectedly, Ru(bipy)2dppz2+ was found to be less efficient than Ru(bipy)3(2+) whatever the dye concentration or the [base pair]/[Ru] molar ratio r. Scavenging experiments have shown that the oxidative DNA cleavage induced by Ru(bipy)2dppz2+ mainly results from a Type II mechanism. The behavior of Ru(bipy)2dppz2+ was different: this compound was clearly more efficient than Ru(bipy)3(2+) as DNA breaker and its efficiency was not modified by the presence of oxygen or by addition of scavengers of reactive oxygen species. In this case, a mechanism involving electron transfer between the excited state of the ruthenium complex and the guanine residue was proposed in agreement emission lifetime measurements. The change in mechanism observed between Ru(bipy)2dppz2+ and Ru (bipy)2dppz2+ results from an increase of the reduction potential of the ruthenium complexes in the excited state, which appears to be the main factor controlling the efficiency.


Assuntos
Dano ao DNA , DNA Super-Helicoidal/efeitos dos fármacos , DNA Viral/efeitos dos fármacos , Substâncias Intercalantes , Compostos Organometálicos/farmacologia , Fármacos Fotossensibilizantes/farmacologia , Bacteriófago phi X 174 , Ligantes , Luz , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Compostos Organometálicos/química , Fenazinas/química , Fenazinas/farmacologia , Fármacos Fotossensibilizantes/química , Piridinas/química , Piridinas/farmacologia , Rutênio , Relação Estrutura-Atividade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA