Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 187
Filtrar
1.
BMC Vet Res ; 16(1): 21, 2020 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-31969162

RESUMEN

BACKGROUND: Ovine footrot caused by Dichelobacter nodosus (D nodosus) is an infectious disease affecting sheep worldwide. Switzerland plans a nationwide footrot eradication program, based on PCR-testing of interdigital swab samples. The aim of this study was to test for the presence of D nodosus in clinically footrot-free sheep flocks which had been subjected to different treatment strategies, to assess whether they were feasible for the eradication process, especially focussing on antimicrobial flock treatments. Clinical scoring and PCR-results were compared. Ten farms had used hoof bathing and hoof trimming without causing bleeding, ten had used individual treatments and flock vaccines to gain the free status and ten had become free through whole-flock systemic macrolide treatment. For every farm, three risk-based collected pool samples were analysed for the occurrence of virulent and benign D nodosus by PCR detection of aprV2/aprB2. RESULTS: Six flocks from any treatment group tested positive for aprB2 in all pools. Clinical signs were absent at the time of sampling, but some flocks had experienced non-progressive interdigital inflammation previously. Two flocks tested aprV2-positive in the high-risk pool. One of them underwent a progressive footrot outbreak shortly after sampling. Individual retesting indicated, that virulent D nodosus most likely was reintroduced by a recently purchased ram. In the second flock, a ram was tested positive and treated before clinical signs occurred. CONCLUSIONS: All treatment strategies eliminated the causative agent and were found to be suitable for implementation in the PCR-based eradication process. PCR-testing proved to be more sensitive than visual scoring, as it also detected clinically healthy carriers. It will be of benefit as a diagnostic tool in elimination and surveillance programs.


Asunto(s)
Dichelobacter nodosus/aislamiento & purificación , Panadizo Interdigital/prevención & control , Infecciones por Bacterias Gramnegativas/veterinaria , Enfermedades de las Ovejas/prevención & control , Crianza de Animales Domésticos/métodos , Animales , Dichelobacter nodosus/efectos de los fármacos , Dichelobacter nodosus/patogenicidad , Desinfectantes/uso terapéutico , Femenino , Panadizo Interdigital/tratamiento farmacológico , Panadizo Interdigital/microbiología , Infecciones por Bacterias Gramnegativas/diagnóstico , Infecciones por Bacterias Gramnegativas/prevención & control , Pezuñas y Garras/microbiología , Macrólidos , Masculino , Prevalencia , Reacción en Cadena en Tiempo Real de la Polimerasa/veterinaria , Ovinos , Enfermedades de las Ovejas/diagnóstico , Suiza , Vacunación/veterinaria
2.
Phys Rev Lett ; 117(1): 013001, 2016 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-27419565

RESUMEN

We experimentally demonstrate a nonlinear detection scheme exploiting time-reversal dynamics that disentangles continuous variable entangled states for feasible readout. Spin-exchange dynamics of Bose-Einstein condensates is used as the nonlinear mechanism which not only generates entangled states but can also be time reversed by controlled phase imprinting. For demonstration of a quantum-enhanced measurement we construct an active atom SU(1,1) interferometer, where entangled state preparation and nonlinear readout both consist of parametric amplification. This scheme is capable of exhausting the quantum resource by detecting solely mean atom numbers. Controlled nonlinear transformations widen the spectrum of useful entangled states for applied quantum technologies.

3.
Phys Rev Lett ; 115(24): 245301, 2015 Dec 11.
Artículo en Inglés | MEDLINE | ID: mdl-26705638

RESUMEN

We report on the experimental observation of scaling in the time evolution following a sudden quench into the vicinity of a quantum critical point. The experimental system, a two-component Bose gas with coherent exchange between the constituents, allows for the necessary high level of control of parameters as well as the access to time-resolved spatial correlation functions. The theoretical analysis reveals that when quenching the system close to the critical point, the energy introduced by the quench leads to a short-time evolution exhibiting crossover reminiscent of the finite-temperature critical properties in the system's universality class. Observing the time evolution after a quench represents a paradigm shift in accessing and probing experimentally universal properties close to a quantum critical point and allows in a new way benchmarking of quantum many-body theory with experiments.


Asunto(s)
Modelos Teóricos , Teoría Cuántica , Gases/química , Rubidio/química
4.
Tierarztl Prax Ausg G Grosstiere Nutztiere ; 43(1): 49-59; quiz 60, 2015.
Artículo en Alemán | MEDLINE | ID: mdl-25634729

RESUMEN

Water is an essential source of life and is available to animals as free water, water content of feed, film water (e. g. dew) and metabolic water. The water requirements of small ruminants are influenced by the type of feed, climate, stage of production, type and length of the fleece or hair coat, husbandry factors and the general health of the animal. Differences in water metabolism, drinking behaviour and the efficiency of temperature regulation are further influenced by species, breed, production type, husbandry system, acclimatisation and adaptation. Small ruminants have been, and are still predominantly kept in extensive husbandry systems. They are therefore genetically and phenotypically well adapted to these conditions and possess a range of physiological and behavioural mechanisms to deal with adverse and suboptimal weather conditions. Regarding animal welfare, there is considerable debate in the discussion and assessment of what constitutes a sufficient water supply for small ruminants under different husbandry conditions, often involving differences between theoretical demands and practical experience. This publication reviews and summarises the current literature regarding water requirements, water metabolism and thermoregulatory mechanisms of small ruminants to provide the basis for an informed assessment of extensive husbandry systems in terms of compliance with animal-welfare requirements.


Asunto(s)
Crianza de Animales Domésticos/métodos , Bienestar del Animal/normas , Deshidratación/veterinaria , Enfermedades de las Cabras/prevención & control , Enfermedades de las Ovejas/prevención & control , Abastecimiento de Agua/normas , Crianza de Animales Domésticos/normas , Animales , Regulación de la Temperatura Corporal/fisiología , Deshidratación/prevención & control , Cabras , Ovinos , Temperatura
5.
Phys Rev Lett ; 113(10): 103004, 2014 Sep 05.
Artículo en Inglés | MEDLINE | ID: mdl-25238356

RESUMEN

A major challenge in quantum metrology is the generation of entangled states with a macroscopic atom number. Here, we demonstrate experimentally that atomic squeezing generated via nonlinear dynamics in Bose-Einstein condensates, combined with suitable trap geometries, allows scaling to large ensemble sizes. We achieve a suppression of fluctuations by 5.3(5) dB for 12,300 particles, from which we infer that similar squeezing can be obtained for more than 10(7) atoms. With this resource, we demonstrate quantum-enhanced magnetometry by swapping the squeezed state to magnetically sensitive hyperfine levels that have negligible nonlinearity. We find a quantum-enhanced single-shot sensitivity of 310(47) pT for static magnetic fields in a probe volume as small as 90 µm3.

6.
Tierarztl Prax Ausg G Grosstiere Nutztiere ; 42(1): 49-58; quiz 59, 2014.
Artículo en Alemán | MEDLINE | ID: mdl-24518884

RESUMEN

The publication of the "Recommendations of husbandry and welfare of sheep and goats" by the German Small Ruminant Veterinary Association provides guidelines that are also used for assessing animal welfare. The included statements concerning lameness are reviewed according to the available literature and commented on with the help of practical examples. Diagnostic tools, criteria, appropriate measures and target values are discussed to facilitate the application of the guidelines.


Asunto(s)
Crianza de Animales Domésticos/normas , Enfermedades del Pie/veterinaria , Enfermedades de las Cabras/fisiopatología , Cojera Animal/fisiopatología , Enfermedades de las Ovejas/fisiopatología , Animales , Enfermedades del Pie/diagnóstico , Enfermedades del Pie/fisiopatología , Enfermedades del Pie/terapia , Enfermedades de las Cabras/diagnóstico , Enfermedades de las Cabras/terapia , Cabras , Pezuñas y Garras/fisiopatología , Cojera Animal/diagnóstico , Cojera Animal/terapia , Guías de Práctica Clínica como Asunto , Ovinos , Enfermedades de las Ovejas/diagnóstico , Enfermedades de las Ovejas/terapia , Oveja Doméstica
8.
Vet Rec ; 174(2): 46, 2014 Jan 11.
Artículo en Inglés | MEDLINE | ID: mdl-24362004

RESUMEN

A study on parenteral antibiotic treatment in sheep footrot was conducted on 10 farms in southern Germany to obtain information on the efficacy of gamithromycin under practical use conditions compared with a positive control. On each farm, 20 (10 on one farm) lame sheep were clinically evaluated and divided into two groups. On day 1, sheep were treated once according to group with either long-acting oxytetracycline (OTC) at 20 mg/kg bodyweight or gamithromycin at 6 mg/kg; clinical responses were assessed 21 days later. When compared with day 1, both treatments reduced clinical lameness, as reflected in the reduction in the number of footrot-affected feet (OTC: 79.3 per cent; gamithromycin: 93.7 per cent) and in the severity of the lesions. The difference between the two treatments was significant (P<0.01) with an OR of 6.1 in favour of gamithromycin. Of the 33 sheep that were still lame on day 21, nine mildly affected animals were not re-treated and the remaining 24 sheep were re-treated with gamithromycin. On day 42, all but two (on the same farm) of the 33 sheep were cured, giving an overall response rate in this study to one or two parenteral antibiotic treatments of 99 per cent.


Asunto(s)
Antibacterianos/uso terapéutico , Panadizo Interdigital/tratamiento farmacológico , Cojera Animal/tratamiento farmacológico , Macrólidos/uso terapéutico , Oxitetraciclina/uso terapéutico , Enfermedades de las Ovejas/tratamiento farmacológico , Animales , Ovinos , Resultado del Tratamiento
9.
Phys Rev Lett ; 111(25): 253001, 2013 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-24483741

RESUMEN

Many cold atom experiments rely on precise atom number detection, especially in the context of quantum-enhanced metrology where effects at the single particle level are important. Here, we investigate the limits of atom number counting via resonant fluorescence detection for mesoscopic samples of trapped atoms. We characterize the precision of these fluorescence measurements beginning from the single-atom level up to more than one thousand. By investigating the primary noise sources, we obtain single-atom resolution for atom numbers as high as 1200. This capability is an essential prerequisite for future experiments with highly entangled states of mesoscopic atomic ensembles.

10.
Artículo en Alemán | MEDLINE | ID: mdl-23242149

RESUMEN

The second part of the recommendations deals with the healthcare and the regulatory framework for the husbandry of sheep and goats. The suggested concept for healthcare aims to develop an individual health plan for every flock. This health plan focuses not only on the prevention of notifiable diseases, but also on chronic and slow infections as well as on parasite monitoring. The emphasis is on early detection of diseases and prophylaxis. In conjunction with this, the handling of lameness, shearing, animal trade and quarantine as well as cleaning and disinfection in sheep and goat flocks are intensively discussed. There are detailed federal and European legal regulations concerning the transport and the physical well-being of animals. These laws are clearly presented and advice for their practical implementation is provided.


Asunto(s)
Crianza de Animales Domésticos/métodos , Crianza de Animales Domésticos/normas , Bienestar del Animal/normas , Cabras , Oveja Doméstica , Crianza de Animales Domésticos/legislación & jurisprudencia , Bienestar del Animal/legislación & jurisprudencia , Animales , Alemania , Enfermedades de las Cabras/diagnóstico , Enfermedades de las Cabras/prevención & control , Ovinos , Enfermedades de las Ovejas/diagnóstico , Enfermedades de las Ovejas/prevención & control
11.
Tierarztl Prax Ausg G Grosstiere Nutztiere ; 40(6): 403-12; quiz 413, 2012.
Artículo en Alemán | MEDLINE | ID: mdl-23242151

RESUMEN

Lameness in sheep induced by infectious agents can cause problems regarding animal welfare, diagnosis and treatment. Individual lame animals and lameness caused by systemic disease, but especially flock problems due to infectious causes of lameness, such as foot rot, can for various reasons pose a problem for veterinary treatment. The causes of lameness in sheep are described with a special focus on infectious flock problems, and the different treatment options such as foot trimming, foot baths and local and systemic antibiotic therapy as well as vaccination are discussed based on a review of recent international research. The limited choice of drugs licensed for use in sheep in Germany is highlighted. Treatment, therefore, often requires off-label use or the import of footbathing agents licensed in other European countries. The legal consequences of this lack of nationally licensed veterinary products in dealing with a "minor species" are discussed, with a final call for political solutions that will help improve this unsatisfactory situation.


Asunto(s)
Panadizo Interdigital/microbiología , Panadizo Interdigital/terapia , Cojera Animal/microbiología , Cojera Animal/terapia , Enfermedades de las Ovejas/microbiología , Enfermedades de las Ovejas/terapia , Crianza de Animales Domésticos , Animales , Antibacterianos/uso terapéutico , Alemania , Hidroterapia , Ovinos
12.
Tierarztl Prax Ausg G Grosstiere Nutztiere ; 40(5): 314-25, 2012 Oct 17.
Artículo en Alemán | MEDLINE | ID: mdl-23076761

RESUMEN

Recommendations for the different forms of sheep and goat husbandry based on the legal regulations are summarized. These are given in particular respect to transhumance, tending, alpine farming, and indoor housing. The requirements for pasture, housing, supply of water and food, lambing, rearing of lambs, and health management are intensively discussed. The general requirements of the extensive as well as of the intensive husbandry of sheep and goats are defined. Examples of species-specific capabilities for adaption, the limits of adaption, and signs of decompensation are provided. Compliance with these recommendations should accord the animals entrusted to our care the "five freedoms (13)": 1. Freedom from hunger and thirst, 2. freedom from discomfort, 3. freedom from pain, injury, or disease, 4. freedom to express normal behaviour, and 5. freedom from fear and distress.


Asunto(s)
Crianza de Animales Domésticos/normas , Bienestar del Animal/normas , Cabras , Oveja Doméstica , Animales , Guías como Asunto , Ovinos , Medicina Veterinaria
13.
Phys Rev Lett ; 107(19): 193001, 2011 Nov 04.
Artículo en Inglés | MEDLINE | ID: mdl-22181600

RESUMEN

We experimentally investigate the mixing and demixing dynamics of Bose-Einstein condensates in the presence of a linear coupling between two internal states. The observed amplitude reduction of the Rabi oscillations can be understood as a result of demixing dynamics of dressed states as experimentally confirmed by reconstructing the spatial profile of dressed state amplitudes. The observations are in quantitative agreement with numerical integration of coupled Gross-Pitaevskii equations without free parameters, which also reveals the criticality of the dynamics on the symmetry of the system. Our observations demonstrate new possibilities for changing effective atomic interactions and studying critical phenomena.

14.
Nature ; 480(7376): 219-23, 2011 Nov 30.
Artículo en Inglés | MEDLINE | ID: mdl-22139418

RESUMEN

Historically, the completeness of quantum theory has been questioned using the concept of bipartite continuous-variable entanglement. The non-classical correlations (entanglement) between the two subsystems imply that the observables of one subsystem are determined by the measurement choice on the other, regardless of the distance between the subsystems. Nowadays, continuous-variable entanglement is regarded as an essential resource, allowing for quantum enhanced measurement resolution, the realization of quantum teleportation and quantum memories, or the demonstration of the Einstein-Podolsky-Rosen paradox. These applications rely on techniques to manipulate and detect coherences of quantum fields, the quadratures. Whereas in optics coherent homodyne detection of quadratures is a standard technique, for massive particles a corresponding method was missing. Here we report the realization of an atomic analogue to homodyne detection for the measurement of matter-wave quadratures. The application of this technique to a quantum state produced by spin-changing collisions in a Bose-Einstein condensate reveals continuous-variable entanglement, as well as the twin-atom character of the state. Our results provide a rare example of continuous-variable entanglement of massive particles. The direct detection of atomic quadratures has applications not only in experimental quantum atom optics, but also for the measurement of fields in many-body systems of massive particles.

15.
Ophthalmologe ; 102(11): 1043-6, 1048-50, 2005 Nov.
Artículo en Alemán | MEDLINE | ID: mdl-16283191

RESUMEN

BACKGROUND: To reduce the risk of endophthalmitis PVP-iodine is typically used preoperatively. Since iodine is contraindicated in patients with a specific allergic history or severe thyroid disorder we studied the effect of Lavasept, which contains Polyhexanid as an antiseptic alternative. PATIENTS AND METHODS: In a randomized controlled double-blind trial 3 drops of 0.2% Lavasept, 1.25% PVP-iodine or Ringer's solution were applied preoperatively to 67 patients, which have had a minimum of 5 colony forming units (cfu's) in the conjunctival swap. The effectiveness and tolerability were measured. RESULTS: After application of Lavasept or PVP-iodine, the number of cfu was statistically significantly reduced. Lavasept reduced the number of bacterial colonies significantly better than PVP-iodine (p=0.05). All test solutions were equally well tolerated. CONCLUSION: The use af Lavasept is safe, well tolerated and reduces the microbiological contamination of the conjunctival fornix effectively. lt provides a more effective reduction of the cfu's than PVP-iodine 1.25% and this effect tends to be prolonged. Lavasept is a good alternative option in ophthalmology for preoperative antisepsis.


Asunto(s)
Infecciones Bacterianas del Ojo/etiología , Infecciones Bacterianas del Ojo/prevención & control , Procedimientos Quirúrgicos Oftalmológicos/efectos adversos , Povidona Yodada/administración & dosificación , Cuidados Preoperatorios/métodos , Antiinfecciosos Locales/administración & dosificación , Biguanidas/administración & dosificación , Método Doble Ciego , Infecciones Bacterianas del Ojo/microbiología , Humanos , Estudios Prospectivos , Resultado del Tratamiento
16.
Ophthalmologe ; 101(4): 377-83, 2004 Apr.
Artículo en Alemán | MEDLINE | ID: mdl-15067419

RESUMEN

BACKGROUND: We examined the efficacy and tolerability of Lavasept (polyhexamethylenbiguanid or PHMB)-an iodine-free antiseptic-in comparison to polyvinylpyrolidon iodine and Ringer's solution, as an alternative preoperative antiseptic. PATIENTS AND METHODS: In a randomized controlled double-blind trial 3 drops of Lavasept, 1.25%, PVP-iodine or Ringer's solution were applied preoperatively in 29 patients. The number of colony forming units (cfu) grown from conjunctival smears and conjunctival hyperaemia, corneal epitheliopathy and ocular surface pain were assessed preoperatively, intraoperatively and 1 day postoperatively. RESULTS: Despite intraoperative application of PVP-iodine, 40% of patients receiving Ringers solution still presented with more than 5 colony forming units (cfu) at the end of the procedure, while all patients that had additional preoperative Lavasept or PVP-iodine achieved relative sterility with less than 5 cfu (p < 0.05). While the effect of Lavasept lasted until the next day, conjunctival microbial colonisation recurred in eyes treated with PVP-iodine. As expected conjunctival hyperaemia and corneal epitheliopathy increased significantly postoperatively but no differences were observed between the 3 solutions tested. CONCLUSION: The preoperative application of Lavasept reduces the conjunctival flora safely and effectively. The microbicidal efficacy is equal to PVP-iodine, but potentially longer lasting. No signs of local or systemic intolerability were observed. Lavasept may be used as a potential alternative preoperative antiseptic and is suitable for iodine-intolerant patients.


Asunto(s)
Biguanidas/uso terapéutico , Extracción de Catarata , Desinfectantes/uso terapéutico , Cuidados Preoperatorios/métodos , Adulto , Biguanidas/efectos adversos , Ensayo de Unidades Formadoras de Colonias , Conjuntiva/microbiología , Método Doble Ciego , Femenino , Humanos , Soluciones Isotónicas/administración & dosificación , Soluciones Isotónicas/efectos adversos , Masculino , Povidona Yodada/efectos adversos , Povidona Yodada/uso terapéutico , Lactato de Ringer , Resultado del Tratamiento
17.
Pharmacogenomics J ; 4(2): 91-101, 2004.
Artículo en Inglés | MEDLINE | ID: mdl-14770174

RESUMEN

This study reports that Cyp3a41 gene contains 13 exons and is localized on the chromosome 5. CYP3A41 is a female-specific isoform that is predominantly expressed in the liver. Estrogen signaling is not responsible for its female specificity. CYP3A41 expression in kidney and brain is observed only in 50% of mice examined. PXR mediates dexamethasone-dependent suppression of CYP3A41. In contrast to CYP3A11, CYP3A41 expression is not induced by pregnenolone-16alpha-carbonitrile (PCN) in wild-type mice, but is significantly suppressed by PCN in PXR(-/-) mice. Phenobarbital and TCPOBOP induce CYP3A11 expression only in the presence of CAR, but have no effect on CYP3A41 expression. Immunoblot and erythromycin demethylase activity analysis reveal robust CYP3A induction after PCN treatment, which is poorly correlated to CYP3A41. These findings suggest a differential role for CAR/PXR in regulating individual CYP3A isoforms by previously characterized CYP3A inducers.


Asunto(s)
Hidrocarburo de Aril Hidroxilasas/genética , Sistema Enzimático del Citocromo P-450/genética , Oxidorreductasas N-Desmetilantes/genética , Oxidorreductasas/genética , Receptores Citoplasmáticos y Nucleares/fisiología , Receptores de Esteroides/fisiología , Factores de Transcripción/fisiología , Animales , Hidrocarburo de Aril Hidroxilasas/biosíntesis , Receptor de Androstano Constitutivo , Citocromo P-450 CYP3A , Sistema Enzimático del Citocromo P-450/biosíntesis , Dexametasona/farmacología , Relación Dosis-Respuesta a Droga , Femenino , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Regulación Enzimológica de la Expresión Génica/fisiología , Isoenzimas/biosíntesis , Isoenzimas/genética , Isoenzimas/fisiología , Masculino , Proteínas de la Membrana , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/enzimología , Oxidorreductasas/biosíntesis , Oxidorreductasas N-Desmetilantes/biosíntesis , Receptor X de Pregnano , Receptores Citoplasmáticos y Nucleares/biosíntesis , Receptores Citoplasmáticos y Nucleares/deficiencia , Receptores Citoplasmáticos y Nucleares/genética , Receptores de Esteroides/biosíntesis , Receptores de Esteroides/deficiencia , Receptores de Esteroides/genética , Factores de Transcripción/deficiencia , Factores de Transcripción/genética
18.
Appl Microbiol Biotechnol ; 65(2): 149-57, 2004 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-14752579

RESUMEN

The continuous culture of Clostridium thermocellum, a thermophilic bacterium capable of producing ethanol from cellulosic material, is demonstrated at elevated hydrostatic pressure (7.0 MPa, 17.3 MPa) and compared with cultures at atmospheric pressure. A commercial limitation of ethanol production by C. thermocellum is low ethanol yield due to the formation of organic acids (acetate, lactate). At elevated hydrostatic pressure, ethanol:acetate (E/A) ratios increased >10(2) relative to atmospheric pressure. Cell growth was inhibited by approximately 40% and 60% for incubations at 7.0 MPa and 17.3 MPa, respectively, relative to continuous culture at atmospheric pressure. A decrease in the theoretical maximum growth yield and an increase in the maintenance coefficient indicated that more cellobiose and ATP are channeled towards maintaining cellular function in pressurized cultures. Shifts in product selectivity toward ethanol are consistent with previous observations of hydrostatic pressure effects in batch cultures. The results are partially attributed to the increasing concentration of dissolved product gases (H2, CO2) with increasing pressure; and they highlight the utility of continuous culture experiments for the quantification of the complex role of dissolved gas and pressure effects on metabolic activity.


Asunto(s)
Reactores Biológicos/microbiología , Celobiosa/metabolismo , Clostridium/crecimiento & desarrollo , Hidrógeno/metabolismo , Ácido Acético/metabolismo , Monóxido de Carbono/farmacología , Clostridium/metabolismo , Medios de Cultivo , Etanol/metabolismo , Hidrógeno/farmacología , Presión Hidrostática
19.
Gen Physiol Biophys ; 23(4): 467-88, 2004 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-15815081

RESUMEN

A homology model of rabbit CYP 2B4 was constructed on the basis of the crystallographic structure of truncated mammalian CYP 2C5/3 and bacterial soluble CYPs. To validate the CYP 2B4 homology model photoaffinity labeling was employed. Three probes (I-III) containing a photo-labile azido-group and an amino-group on opposite ends of the molecule were designed for photoaffinity labeling of the CYP 2B4 in increasing distance from the heme iron. Spectroscopic data proved probes I (the shortest) and II (a middle sized) to be coordinated with the heme iron via their amino-groups in the enzyme active center while the probe III (the longest) was not bound in this way. This binding orientation of probes I and II is in accordance with the model predicting ion-pairing of the negatively charged side chain of CYP 2B4 Asp 105 and a positively charged nitrogen located in an appropriate position in structures of probes I and II, only. The lack of heme binding of the probe III is clear from its docking into the CYP 2B4 model since no Asp 105 ion-pairing is possible. The target of photoactivated probe II, Arg 197, in a distance of about 16.5 A from the heme iron, exactly matches the position of that amino acid residue, predicted from the CYP 2B4 homology model. Moreover, using this technique, a substrate access channel has been identified. To assess the predicted substrate-binding pocket, an interaction of a specific CYP 2B4 substrate, diamantane, was examined. In "silico" docking revealed strong binding of diamantane in an orientation allowing experimentally observed C4-hydroxylation. Our homology model of CYP 2B4 is thus consistent with experimental metabolic and photoaffinity labeling data.


Asunto(s)
Hidrocarburo de Aril Hidroxilasas/análisis , Hidrocarburo de Aril Hidroxilasas/química , Modelos Químicos , Modelos Moleculares , Técnicas de Sonda Molecular , Análisis Espectral/métodos , Secuencia de Aminoácidos , Hidrocarburo de Aril Hidroxilasas/clasificación , Sitios de Unión , Simulación por Computador , Familia 2 del Citocromo P450 , Isoenzimas/análisis , Isoenzimas/química , Datos de Secuencia Molecular , Etiquetas de Fotoafinidad/análisis , Etiquetas de Fotoafinidad/química , Unión Proteica , Conformación Proteica , Homología de Secuencia de Aminoácido
20.
Artículo en Inglés | MEDLINE | ID: mdl-14565490

RESUMEN

The synthesis of 1-(2-deoxy-beta-D-erythro-pentofuranosyl)imidazole-4-hydrazide having the features of an ambigous base is reported. The recognition of the analogue by DNA polymerases as an incoming triphosphate as well as a template base was investigated. The mutagenic properties was evaluated by PCR. The potential of this new monomer for DNA diversification is illustrated by the reactivity of the nucleobase towards various aldehydes.


Asunto(s)
ADN Polimerasa Dirigida por ADN/metabolismo , Nucleósidos/metabolismo , ADN/genética , Nucleótidos de Desoxiadenina/metabolismo , Nucleótidos de Desoxiguanina/metabolismo , Variación Genética , Imidazoles , Cinética , Mutagénesis , Reacción en Cadena de la Polimerasa , Especificidad por Sustrato
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA
...