972 resultados para time-resolved photoluminescence, energy transfer, quenching, photon up-conversion
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Purpose:NR2E3 (PNR) is an orphan nuclear receptor essential for proper photoreceptor determination and differentiation. In humans, mutations in NR2E3 have been associated with the recessively inherited enhanced short wavelength sensitive (S-) cone syndrome (ESCS) and, more recently, with autosomal dominant retinitis pigmentosa (adRP). NR2E3 acts in concert with the transcription factors Crx and Nrl to repress cone-specific genes and activate rod-specific genes. NR2E3 and Crx have been shown to physically interact by their DNA-binding domain (DBD), which may also be implicated in the dimerization process of the nuclear receptor. However, neither NR2E3 homodimerization nor NR2E3/Crx complex formation has been investigated in detail. Methods:In this present work, we analyzed the dimerization of the NR2E3 protein and its interaction with Crx by bioluminescence resonance energy transfer (BRET2) which utilizes Renilla luciferase (hRluc) protein and its substrate DeepBlueC as an energy donor and a mutant green fluorescent protein (GFP2) as the acceptor. We investigated, on whole intact cells, the role of NR2E3 DBD-mutations in dimerization and association with Crx. Results:We clearly showed that NR2E3 formed homodimers in HEK-293T cells. Moreover, all causative NR2E3 mutations present in the DBD of the protein showed an alteration in dimerization, except for the R76Q and the R104W mutants. Interestingly, the adRP-linked G56R mutant was the only DBD-NR2E3 mutant that showed a correct interaction with Crx. Finally, we observed a decrease in rhodospin gene transactivation for all DBD-NR2E3 mutants tested and no potentiation for the adRP-linked G56R mutant. In addition, the p.G56R mutant enhanced the transrepression of M-opsin promoter, while all other DBD-NR2E3 mutants did not repress M-opsin transactivation. Conclusions:A defect, either in the dimer formation or in the interaction of NR2E3 with Crx, leads to abnormal transcriptional activity on rhodopsin and M-opsin promoter and to an atypical retinal development; while the titration of Crx by p.G56R-NR2E3 leads to low levels of rhodopsin and M-opsin expression and may be responsible for the strong adRP phenotype.
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We previously demonstrated the synergistic therapeutic effect of the cetuximab (anti-epidermal growth factor receptor [EGFR] monoclonal antibody, mAb)-trastuzumab (anti-HER2 mAb) combination (2mAbs therapy) in HER2(low) human pancreatic carcinoma xenografts. Here, we compared the 2mAbs therapy, the erlotinib (EGFR tyrosine kinase inhibitor [TKI])-trastuzumab combination and lapatinib alone (dual HER2/EGFR TKI) and explored their possible mechanisms of action. The effects on tumor growth and animal survival of the three therapies were assessed in nude mice xenografted with the human pancreatic carcinoma cell lines Capan-1 and BxPC-3. After therapy, EGFR and HER2 expression and AKT phosphorylation in tumor cells were analyzed by Western blot analysis. EGFR/HER2 heterodimerization was quantified in BxPC-3 cells by time-resolved FRET. In K-ras-mutated Capan-1 xenografts, the 2mAbs therapy gave significantly higher inhibition of tumor growth than the erlotinib/trastuzumab combination, whereas in BxPC-3 (wild-type K-ras) xenografts, the erlotinib/trastuzumab combination showed similar growth inhibition but fewer tumor-free mice. Lapatinib showed no antitumor effect in both types of xenografts. The efficacy of the 2mAbs therapy was partly Fc-independent because F(ab')(2) fragments of the two mAbs significantly inhibited BxPC-3 growth, although with a time-limited therapeutic effect. The 2mAbs therapy was associated with a reduction of EGFR and HER2 expression and AKT phosphorylation. BxPC-3 cells preincubated with the two mAbs showed 50% less EGFR/HER2 heterodimers than controls. In pancreatic carcinoma xenografts, the 2mAbs therapy is more effective than treatments involving dual EGFR/HER2 TKIs. The mechanism of action may involve decreased AKT phosphorylation and/or disruption of EGFR/HER2 heterodimerization.
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A fluctuation relation for aging systems is introduced and verified by extensive numerical simulations. It is based on the hypothesis of partial equilibration over phase-space regions in a scenario of entropy-driven relaxation. The relation provides a simple alternative method, amenable of experimental implementation, to measure replica symmetry breaking parameters in aging systems. The connection with the effective temperatures obtained from the fluctuation-dissipation theorem is discussed
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CD8+ cytotoxic T lymphocyte (CTL) can recognize and kill target cells that express only a few cognate major histocompatibility complex class I-peptide (pMHC) complexes. To better understand the molecular basis of this sensitive recognition process, we studied dimeric pMHC complexes containing linkers of different lengths. Although dimers containing short (10-30-A) linkers efficiently bound to and triggered intracellular calcium mobilization and phosphorylation in cloned CTL, dimers containing long linkers (> or = 80 A) did not. Based on this and on fluorescence resonance energy transfer experiments, we describe a dimeric binding mode in which two T cell receptors engage in an anti-parallel fashion two pMHC complexes facing each other with their constant domains. This binding mode allows integration of diverse low affinity interactions, which increases the overall binding and, hence, the sensitivity of antigen recognition. In proof of this, we demonstrated that pMHC dimers containing one agonist and one null ligand efficiently activate CTL, corroborating the importance of endogenous pMHC complexes in antigen recognition.
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Yritykset tarvitsevat nopealla toimitusajalla uudenlaista osaamista omaavia työntekijöitä. Tämän vuoksi kouluttajien täytyy pystyä reagoimaan nopeasti työelämän esittämiin haasteisiin Kehittämällä uusi toimintamalli muuttuvien ammattitaitovaatimusten mukaisen koulutuksen käynnistämiseksi voidaan saavuttaa mittavia taloudellisia ja ajallisia säästöjä uusien osaajien koulutuksessa. Mallin avulla tapauskohtaisesti oikeat henkilöt tekevät oikea aikaisesti juuri oikeita toimenpiteitä ja näin toimien päästään mahdollisimman lyhyeen koulutusaikaan koulutustarvesignaalien vastaanottamisesta hetkeen, jolloin opiskelijat ovat valmiita siirtymään työelämään. Mikäli koulutuksen käynnistämiseen liittyvien tehtävien kanssa työskentelevät henkilöt, joilla ei ole kokonaisnäkemystä tai heiltä puuttuu päätösvalta päätösten tekemiseksi, niin tärkeää aikaa ja energiaa kuluu hukkaan. Samoin jos signaalien oikeita kulkuväyliä työelämästä oppilaitokselle ei tunnisteta tai ei osata hyödyntää, koulutusten aloittaminen viivästyy tai koulutusjää kokonaan toteutumatta.Tiiviissä yhteistyössä metallialan yritystoiminnan jakoulutuksen järjestäjän kanssa kehitetty robotisoitu laserhitsauskoulutus mahdollistaa juuri oikeanlaista osaamista omaavien työtekijöiden tuottamisen mahdollisimman tehokkaasti. Tehokkuus on todettavissa koulutuksen käynnistämiseen ja kouluttamiseen tarvittavan ajan lyhenemisenä sekä koulutuksesta syntyvien kustannusten vähenemisenä.
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We have studied the current transport and electroluminescence properties of metal oxide semiconductor MOS devices in which the oxide layer, which is codoped with silicon nanoclusters and erbium ions, is made by magnetron sputtering. Electrical measurements have allowed us to identify a Poole-Frenkel conduction mechanism. We observe an important contribution of the Si nanoclusters to the conduction in silicon oxide films, and no evidence of Fowler-Nordheim tunneling. The results suggest that the electroluminescence of the erbium ions in these layers is generated by energy transfer from the Si nanoparticles. Finally, we report an electroluminescence power efficiency above 10−3%. © 2009 American Institute of Physics. doi:10.1063/1.3213386
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Electrically driven Er3+ doped Si slot waveguides emitting at 1530 nm are demonstrated. Two different Er3+ doped active layers were fabricated in the slot region: a pure SiO2 and a Si-rich oxide. Pulsed polarization driving of the waveguides was used to characterize the time response of the electroluminescence (EL) and of the signal probe transmission in 1 mm long waveguides. Injected carrier absorption losses modulate the EL signal and, since the carrier lifetime is much smaller than that of Er3+ ions, a sharp EL peak was observed when the polarization was switched off. A time-resolved electrical pump & probe measurement in combination with lock-in amplifier techniques allowed to quantify the injected carrier absorption losses. We found an extinction ratio of 6 dB, passive propagation losses of about 4 dB/mm, and a spectral bandwidth > 25 nm at an effective d.c. power consumption of 120 μW. All these performances suggest the usage of these devices as electro-optical modulators.
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Modulation of signalling pathways can trigger different cellular responses, including differences in cell fate. This modulation can be achieved by controlling the pathway activity with great precision to ensure robustness and reproducibility of the specification of cell fate. The development of the photoreceptor R7 in the Drosophila melanogasterretina has become a model in which to investigate the control of cell signalling. During R7 specification, a burst of Ras small GTPase (Ras) and mitogen-activated protein kinase (MAPK) controlled by Sevenless receptor tyrosine kinase (Sev) is required. Several cells in each ommatidium express sev. However, the spatiotemporal expression of the boss ligand and the action of negative regulators of the Sev pathway will restrict the R7 fate to a single cell. The Drosophila suppressor of cytokine signalling 36E (SOCS36E) protein contains an SH2 domain and acts as a Sev signalling attenuator. By contrast, downstream of receptor kinase (Drk), the fly homolog of the mammalian Grb2 adaptor protein, which also contains an SH2 domain, acts as a positive activator of the pathway. Here, we apply the Förster resonance energy transfer (FRET) assay to transfected Drosophila S2 cells and demonstrate that Sev binds directly to either the suppressor protein SOCS36E or the adaptor protein Drk. We propose a mechanistic model in which the competition between these two proteins for binding to the same docking site results in either attenuation of the Sev transduction in cells that should not develop R7 photoreceptors or amplification of the Ras-MAPK signal only in the R7 precursor.
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NR2E3 encodes the photoreceptor-specific nuclear hormone receptor that acts as a repressor of cone-specific gene expression in rod photoreceptors, and as an activator of several rod-specific genes. Recessive variants located in the ligand-binding domain (LBD) of NR2E3 cause enhanced short wavelength sensitive- (S-) cone syndrome (ESCS), a retinal degeneration characterized by an excess of S-cones and non-functional rods. We analyzed the dimerization properties of NR2E3 and the effect of disease-causing LBD missense variants by bioluminescence resonance energy transfer (BRET(2) ) protein interaction assays. Homodimerization was not affected in presence of p.A256V, p.R039G, p.R311Q, and p.R334G variants, but abolished in presence of p.L263P, p.L336P, p.L353V, p.R385P, and p.M407K variants. Homology modeling predicted structural changes induced by NR2E3 LBD variants. NR2E3 LBD variants did not affect interaction with CRX, but with NRL and rev-erbα/NR1D1. CRX and NRL heterodimerized more efficiently together, than did either with NR2E3. NR2E3 did not heterodimerize with TLX/NR2E1 and RXRα/NR2C1. The identification of a new compound heterozygous patient with detectable rod function, who expressed solely the p.A256V variant protein, suggests a correlation between LBD variants able to form functional NR2E3 dimers and atypical mild forms of ESCS with residual rod function.
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La question de savoir si la relation est différente réellement de son fondement se rencontre fréquemment dans les textes médiévaux à partir du milieu du treizième siècle. Elle se pose avant tout dans un cadre aristotélicien de discussion des catégories et revient à se demander si la catégorie de relation ajoute véritablement une chose supplémentaire, la relation, dans la réalité. Cette question s'inscrit dans une représentation réaliste des relations : pour la plupart des auteurs du treizième et du quatorzième siècle, le fait que des choses soient réellement reliées entre elles ne fait pas de doute. Deux hommes de même taille sont bel et bien égaux, c'est-à-dire réellement reliés entre eux par une relation d'égalité. La difficulté est alors de comprendre comment ces choses sont reliées entre elles, ou encore, ce qu'est exactement cette relation dont il est alors question. Faut-il dire que l'égalité dans chacun des hommes de même taille est une nouvelle chose qui s'ajoute à la substance de chacun d'eux et aux accidents de taille, appartenant à la catégorie de quantité, sur lesquels ces relations d'égalité sont fondées ? Ou faut-il dire que l'égalité est réelle d'une autre manière, c'est-à-dire sans pour autant ajouter une nouvelle chose à ce à quoi elle advient ? Ce problème, qui se rencontre déjà dans les tensions existant entre les différents exposés qu'Aristote a consacrés à cette catégorie, a reçu de multiples réponses. Celles-ci nous éclairent sur la manière dont le réel est appréhendé au Moyen-Âge et sur les débats ontologiques de l'époque. Le travail ici résumé entreprend de délimiter précisément ces réponses et propose une manière de les classer. -- Realism about relations: study of the answers given to the problem of the difference between a relation and its foundation (1250-1350) Summary Whether relation is really distinct from its foundation or not is a question that can easily be found in medieval texts from the mid-thirteenth century onwards. It comes from an aristotelian background, the discussion about the categories, and asks if the category of relation really posits another thing, i.e. a relation, in reality. It results from a realist perspective on relations. In fact, most thirteenth and fourteenth century thinkers held without doubt that things outside the mind are really connected between them. Two men sharing the same height are really equal, that is, really linked to each other by a relation of equality. What is then left to understand is how these things are linked between them, or the exact nature of the aforementioned relation. Should we say that the equality in each of the equally sized men is a new thing that adds to the substance of each of them and to the accidents of height, belonging tho the category of quantity, on which these relations are founded? Or should we say that equality is real in another way, that is, without adding a new thing to the subject acquiring it? We can already find this issue in Aristotle himself, emerging from disagreeing texts devoted to this category. It received various answers that enable us to understand better how reality was defined in the Middle Age and some of the ontological debates of the time. The work that is here summed up attempts to precisely delineate these various answers and to provide a way of classifying them.
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Tämän tutkielman tarkoituksena on ollut kartoittaa pankkien yrityksille tarjoamien elektronisten pankkipalveluiden nykytilaa suhteessa aiheesta kirjoitettuun teoriaan. Yrityspuolella pankkipalvelun käyttäjä ei välttämättä ole samalla omistaja, kuten yksityishenkilöille tarkoitetuissa palveluissa. Tästä johtuen tämä kenttä tarjoaa aivan uutta tutkittavaa vanhempien, lähinnä yksityishenkilöiden suhteen tehtyjen tutkimusten rinnalle. Yrityksille tarkoitetut elektroniset pankkipalvelut ovat pohjautuneet pitkälti vuosikymmeniä vanhoihin eräsiirtojärjestelmiin, joita aletaan vasta nyt muuttaa internetpohjaisiksi. Yritysten tarpeet sekä vaatimukset pankkien verkkopalveluiden suhteen tulevat olemaan moninaisia ja poikkeamaan paljonkin aiemmin rakennetuista yksityisten verkkopalveluista. Avainsanoja tällä saralla tulevat olemaan personointi, kustomointi, tehokkuus, turvallisuus, reaaliaikainen tieto sekä kommunikointi.Tutkielmaan on tuotu lisäsyvyyttä arvioimalla elektronisen kaupankäynnin tulevaisuutta, jossa myös pankkien rooli tulee olemaan todennäköisesti merkittävä. Tätä tukee yritysten siirtyminen mm. elektroniseen laskutukseen, sekä –kaupankäyntiin. Pankkien tulisikin löytää jokin luonteva (välittäjän) rooli kehittyvillä business to business sekä business to consumer markkinoilla. Tämä alue voi pitää ratkaisun avaimet käsissä siihen, kuinka katetaan esimerkiksi netotuspalveluiden aiheuttamat tulonmenetykset. Nämä ovat strategisia kysymyksiä, jolloin tulee päättää minne asti tarjottavia palveluita voidaan venyttää pankkipalveluiden nimissä ja mitkä taas selkeästi toteuttaa vaikkapa partneripalveluina. Tulevaisuudessa verkossa surffaaminen tulee kuitenkin keskittymään suuriin portaaleihin, ja näin ollen onkin syytä varmistaa jo ajoissa että on itse luomassa riittävän houkuttavaa kokonaisuutta omien ja partnerien tarjoamien palveluiden osalta, sekä varmistaa myös näkyvyys muissa kriittisissä keskittymissä verkossa.
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Streptavidin, a tetrameric protein secreted by Streptomyces avidinii, binds tightly to a small growth factor biotin. One of the numerous applications of this high-affinity system comprises the streptavidin-coated surfaces of bioanalytical assays which serve as universal binders for straightforward immobilization of any biotinylated molecule. Proteins can be immobilized with a lower risk of denaturation using streptavidin-biotin technology in contrast to direct passive adsorption. The purpose of this study was to characterize the properties and effects of streptavidin-coated binding surfaces on the performance of solid-phase immunoassays and to investigate the contributions of surface modifications. Various characterization tools and methods established in the study enabled the convenient monitoring and binding capacity determination of streptavidin-coated surfaces. The schematic modeling of the monolayer surface and the quantification of adsorbed streptavidin disclosed the possibilities and the limits of passive adsorption. The defined yield of 250 ng/cm2 represented approximately 65 % coverage compared with a modelled complete monolayer, which is consistent with theoretical surface models. Modifications such as polymerization and chemical activation of streptavidin resulted in a close to 10-fold increase in the biotin-binding densities of the surface compared with the regular streptavidin coating. In addition, the stability of the surface against leaching was improved by chemical modification. The increased binding densities and capacities enabled wider high-end dynamic ranges in the solid-phase immunoassays, especially when using the fragments of the capture antibodies instead of intact antibodies for the binding of the antigen. The binding capacity of the streptavidin surface was not, by definition, predictive of the low-end performance of the immunoassays nor the assay sensitivity. Other features such as non-specific binding, variation and leaching turned out to be more relevant. The immunoassays that use a direct surface readout measurement of time-resolved fluorescence from a washed surface are dependent on the density of the labeled antibodies in a defined area on the surface. The binding surface was condensed into a spot by coating streptavidin in liquid droplets into special microtiter wells holding a small circular indentation at the bottom. The condensed binding area enabled a denser packing of the labeled antibodies on the surface. This resulted in a 5 - 6-fold increase in the signal-to-background ratios and an equivalent improvement in the detection limits of the solid-phase immunoassays. This work proved that the properties of the streptavidin-coated surfaces can be modified and that the defined properties of the streptavidin-based immunocapture surfaces contribute to the performance of heterogeneous immunoassays.
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Tämä diplomityö käsittelee erään rullakuljettia valmistavan yrityksen suunniteluprosessin tehostamista suunnitteluautomaatilla. Diplomityön tavoitteena oli parametrisoida asiakkaan 3D-tuotemalli ja luoda erillinen käyttöliittymä, jolla mallia voidaan määrätyissä rajoissa varioida. Diplomityön tuloksena syntyi toimiva Microsoft Excelilla toteutettu suunnitteluautomaatti, jolla voitiin varioida SolidWorksilla luotua tuotemallia. Suunnitteluautomaatti päivitti mallin lisäksi myös tuotteen valmistuspiirustukset ja komponenttien valmistukseen käytettävät työstökoneiden ohjaustiedostot. Automaatin käyttö lyhensi tuotteen variointiin kuluvaa aikaa alkuperäisestä yhdestä työviikosta kahteen tuntiin, poisti suunnitteluvirheet lähes kokonaan ja vähensi yrityksen rutiinisuunnitteluun käyttämää työaikaa.
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Nanoparticles offer adjustable and expandable reactive surface area compared to the more traditional solid phase forms utilized in bioaffinity assays due to the high surface to-volume ratio. The versatility of nanoparticles is further improved by the ability to incorporate various molecular complexes such as luminophores into the core. Nanoparticle labels composed of polystyrene, silica, inorganic crystals doped with high number of luminophores, preferably lanthanide(III) complexes, are employed in bioaffinity assays. Other label species such as semiconductor crystals (quantum dots) or colloidal gold clusters are also utilized. The surface derivatization of such particles with biomolecules is crucial for the applicability to bioaffinity assays. The effectiveness of a coating is reliant on the biomolecule and particle surface characteristics and the selected coupling technique. The most critical aspects of the particle labels in bioaffinity assays are their size-dependent features. For polystyrene, silica and inorganic phosphor particles, these include the kinetics, specific activity and colloidal stability. For quantum dots and gold colloids, the spectral properties are also dependent on particle size. This study reports the utilization of europium(III)-chelate-embedded nanoparticle labels in the development of bioaffinity assays. The experimental covers both the heterogeneous and homogeneous assay formats elucidating the wide applicability of the nanoparticles. It was revealed that the employment of europium(III) nanoparticles in heterogeneous assays for viral antigens, adenovirus hexon and hepatitis B surface antigen (HBsAg), resulted in sensitivity improvement of 10-1000 fold compared to the reference methods. This improvement was attributed to the extreme specific activity and enhanced monovalent affinity of the nanoparticles conjugates. The applicability of europium(III)-chelate-doped nanoparticles to homogeneous assay formats were proved in two completely different experimental settings; assays based on immunological recognition or proteolytic activity. It was shown that in addition to small molecule acceptors, particulate acceptors may also be employed due to the high specific activity of the particles promoting proximity-induced reabsorptive energy transfer in addition to non-radiative energy transfer. The principle of proteolytic activity assay relied on a novel dual-step FRET concept, wherein the streptavidin-derivatized europium(III)-chelate-doped nanoparticles were used as donors for peptide substrates modified with biotin and terminal europium emission compliant primary acceptor and a secondary quencher acceptor. The recorded sensitized emission was proportional to the enzyme activity, and the assay response to various inhibitor doses was in agreement with those found in literature showing the feasibility of the technique. Experiments regarding the impact of donor particle size on the extent of direct donor fluorescence and reabsorptive excitation interference in a FRET-based application was conducted with differently sized europium(III)-chelate-doped nanoparticles. It was shown that the size effect was minimal
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The central goal of food safety policy in the European Union (EU) is to protect consumer health by guaranteeing a high level of food safety throughout the food chain. This goal can in part be achieved by testing foodstuffs for the presence of various chemical and biological hazards. The aim of this study was to facilitate food safety testing by providing rapid and user-friendly methods for the detection of particular food-related hazards. Heterogeneous competitive time-resolved fluoroimmunoassays were developed for the detection of selected veterinary residues, that is coccidiostat residues, in eggs and chicken liver. After a simplified sample preparation procedure, the immunoassays were performed either in manual format with dissociation-enhanced measurement or in automated format with pre-dried assay reagents and surface measurement. Although the assays were primarily designed for screening purposes providing only qualitative results, they could also be used in a quantitative mode. All the developed assays had good performance characteristics enabling reliable screening of samples at concentration levels required by the authorities. A novel polymerase chain reaction (PCR)-based assay system was developed for the detection of Salmonella spp. in food. The sample preparation included a short non-selective pre-enrichment step, after which the target cells were collected with immunomagnetic beads and applied to PCR reaction vessels containing all the reagents required for the assay in dry form. The homogeneous PCR assay was performed with a novel instrument platform, GenomEra™, and the qualitative assay results were automatically interpreted based on end-point time-resolved fluorescence measurements and cut-off values. The assay was validated using various food matrices spiked with sub-lethally injured Salmonella cells at levels of 1-10 colony forming units (CFU)/25 g of food. The main advantage of the system was the exceptionally short time to result; the entire process starting from the pre-enrichment and ending with the PCR result could be completed in eight hours. In conclusion, molecular methods using state-of-the-art assay techniques were developed for food safety testing. The combination of time-resolved fluorescence detection and ready-to-use reagents enabled sensitive assays easily amenable to automation. Consequently, together with the simplified sample preparation, these methods could prove to be applicable in routine testing.