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101.
Kristian Fog Nielsen Jesper Mølgaard Mogensen Maria Johansen Thomas O. Larsen Jens Christian Frisvad 《Analytical and bioanalytical chemistry》2009,395(5):1225-1242
Filamentous fungi in the Aspergillus section Nigri (the black aspergilli) represent some of the most widespread food and feed contaminants known but they are also some of the
most important workhorses used by the biotechnological industry. The Nigri section consists of six commonly found species (excluding A. aculeatus and its close relatives) from which currently 145 different secondary metabolites have been isolated and/or detected. From
a human and animal safety point of view, the mycotoxins ochratoxin A (from A. carbonarius and less frequently A. niger) and fumonisin B2 (from A. niger) are currently the most problematic compounds. Especially in foods and feeds such as coffee, nuts, dried fruits, and grape-based
products where fumonisin-producing fusaria are not a problem, fumonisins pose a risk. Moreover, compounds such as malformins,
naptho-γ-pyrones, and bicoumarins (kotanins) call for monitoring in food, feed, and biotechnology products as well as for
a better toxicological evaluation, since they are often produced in large amounts by the black aspergilli. For chemical differentiation/identification
of the less toxic species the diketopiperazine asperazine can be used as a positive marker since it is consistently produced
by A. tubingensis (177 of 177 strains tested) and A. acidus (47 of 47 strains tested) but never by A. niger (140 strains tested). Naptho-γ-pyrones are the compounds produced in the highest quantities and are produced by all six common
species in the group (A. niger 134 of 140; A. tubingensis 169 of 177; A. acidus 44 of 47; A. carbonarius 40 of 40, A. brasiliensis 18 of 18; and A. ibericus three of three).
相似文献
102.
Jesper Kallestrup 《Acta Analytica》2009,24(3):155-171
Process reliabilists hold that in order for a belief to be justified, it must result from a reliable cognitive process. They
also hold that a belief can be basically justified: justified in this manner without having any justification to believe that
belief is reliably produced. Fumerton (1995), Vogel (2000), and Cohen (2002) have objected that such basic justification leads
to implausible easy justification by means of either epistemic closure principles or so-called track record arguments. I argue
that once we carefully distinguish closure principles from transmission principles, and epistemic consequences from epistemic
preconditions, neither version of this objection succeeds.
相似文献
Jesper KallestrupEmail: |
103.
The duplication of a cube and the trisection of an angle are two of the most famous geometric construction problems formulated in ancient Greece. In 1837 Pierre Wantzel (1814–1848) proved that the problems cannot be constructed by ruler and compass. Today he is credited for this contribution in all general treatises of the history of mathematics. However, his proof was hardly noticed by his contemporaries and during the following century his name was almost completely forgotten. In this paper I shall analyze the reasons for this neglect and argue that it was primarily due to the lack of importance attributed to such impossibility results at the time. 相似文献
104.
The versatility of CE is beneficial for the study of many types of molecular interactions, because different experimental designs can be made to suit the characteristics of a particular interaction. A very versatile starting point is the preequilibration type of affinity CE that has been used extensively for characterizing biomolecular interactions in the last 15 years. We review this field here and include a comprehensive overview of the existing preincubation ACE modes including their advantages and limitations as well as the methodological developments and applications within the bioanalytical field. 相似文献
105.
Towards biochips using microstructured optical fiber sensors 总被引:2,自引:0,他引:2
Rindorf L Høiby PE Jensen JB Pedersen LH Bang O Geschke O 《Analytical and bioanalytical chemistry》2006,385(8):1370-1375
In this paper we present the first incorporation of a microstructured optical fiber (MOF) into biochip applications. A 16-mm-long
piece of MOF is incorporated into an optic-fluidic coupler chip, which is fabricated in PMMA polymer using a CO2 laser. The developed chip configuration allows the continuous control of liquid flow through the MOF and simultaneous optical
characterization. While integrated in the chip, the MOF is functionalized towards the capture of a specific single-stranded
DNA string by immobilizing a sensing layer on the microstructured internal surfaces of the fiber. The sensing layer contains
the DNA string complementary to the target DNA sequence and thus operates through the highly selective DNA hybridization process.
Optical detection of the captured DNA was carried out using the evanescent-wave-sensing principle. Owing to the small size
of the chip, the presented technique allows for analysis of sample volumes down to 300 nL and the fabrication of miniaturized
portable devices.
相似文献
106.
In a seminal work, Bertil Matérn introduced several types of processes for modeling repulsive point processes. In this paper an algorithm is presented for the perfect simulation of the Matérn III process within a bounded window in Rd, fully accounting for edge effects. A simple upper bound on the mean time needed to generate each point is computed when interaction between points is characterized by balls of fixed radius R. This method is then generalized to handle interactions resulting from use of random grains about each point. This includes the case of random radii as a special case. In each case, the perfect simulation method is shown to be provably fast, making it a useful tool for analysis of such processes. 相似文献
107.
Johan Vibenholt Magnus Magnussen Christian Anthon Jesper Bendix 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(7):m177-m179
Five‐coordinate Cr(N)(salen) {salen is 2,2′‐[ethane‐1,2‐diylbis(nitrilomethylidyne)]diphenolate} reacts with [RhCl(COD)]2 (COD is 1,5‐cyclooctadiene) to yield the heterobimetallic nitride‐bridged title compound, namely chlorido‐2κCl‐[2(η4)‐1,5‐cyclooctadiene]{2,2′‐[ethane‐1,2‐diylbis(nitrilomethylidyne)]diphenolato‐1κ4O,N,N′,O′}‐μ‐nitrido‐1:2κ2N:N‐chromium(V)rhodium(I), [CrRh(C16H14N2O2)ClN(C8H12)]. The Cr—N bond of 1.5936 (14) Å is elongated by only 0.035 Å compared to the terminal Cr—N bond in the precursor. The nitride bridge is close to being linear [173.03 (9)°] and the Rh—N bond of 1.9594 (14) Å is very short for a monodentate nitrogen‐donor ligand, indicating significant π‐acceptor character of the Cr[triple‐bond]N group. 相似文献
108.
An analytical method for the quantification of thyroid hormones (3,5,3′,5′-tetraiodo-l-thyronine, 3,3′,5-triiodo-l-thyronine, 3,3′,5′-triiodothyronine, 3,5-diiodothyronine, 3,3′-diiodothyronine) in different water matrices has been developed. The method, consisting of solid phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS), was validated for tap and surface water as well as raw and treated waste water. The limits of quantifications (LOQs) were lowest in tap water, where they ranged from 1.1 to 13.3 ng L−1, and highest in raw wastewater (10.5–84.9 ng L−1). Of the target analytes 3,5,3′,5′-tetraiodo-l-thyronine (T4) could be quantified in the influent and effluent of a waste water treatment plant (WWTP) in Finland. The study showed that despite a relatively high removal rate during treatment (66%), part of the incoming T4 will reach the aquatic environment and, due to the high endocrine activity of this compound, further studies are needed in order to assess its environmental fate and impact on natural ecosystems. 相似文献
109.
Louise Marie Sørensen Jesper Mogensen Kristian Fog Nielsen 《Analytical and bioanalytical chemistry》2010,398(3):1535-1542
Here we present a method for simultaneous determination of the fungal metabolites mycophenolic acid, ochratoxin A (OTA) and
fumonisin B2 (FB2) in meat products. Extraction was performed with water–acetonitrile, followed by acetone-induced precipitation of salts and
proteins. Purification and identification of analytes was performed by mixed-mode reversed-phase anion-exchange chromatography
in direct ion-exchange mode, followed by liquid chromatography–tandem mass spectrometry (LC-MS/MS) detection. Quantification
was based on isotope dilution with fully 13C-labelled FB2 and OTA, and matrix-spiked calibration curves. Fermented sausages inoculated with an OTA- and FB2-producing strain of Aspergillus niger were analysed, but no analytes were detected. Analysis of 22 retail products showed one Parma meat with a very high level
of OTA contamination (56–158 μg/kg) that clearly exceeded the Italian regulatory limit of 1 μg/kg. This sample and uninfected
control samples were subsequently reanalysed, and the high OTA content was verified by two other techniques: (i) LC–time-of-flight
MS confirmed the accurate mass as well as chlorine isotope pattern; and (ii) sample methylation in methanol–BF3 and subsequent LC-MS/MS provided indirect confirmation by detection of the OTA methyl ester. In the contaminated Parma ham,
the high OTA level most likely originated from growth of Penicillium nordicum on the meat. 相似文献
110.
Brask J Wackerbarth H Jensen KJ Zhang J Nielsen JU Andersen JE Ulstrup J 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,56(1-2):27-32
Mapping of structure and function of proteins adsorbed on solid surfaces is important in many contexts. Electrochemical techniques based on single-crystal metal surfaces and in situ scanning probe microscopies (SPM) have recently opened new perspectives for mapping at the single-molecule level. De novo design of model proteins has evolved in parallel and holds promise for test and control of protein folding and for new tailored protein structural motifs. These two strategies are combined in the present report.We present a synthetic scheme for a new 4-alpha-helix bundle carboprotein built on a galactopyranoside derivative with a thiol anchor aglycon suitable for surface immobilization on gold. The galactopyranoside with thiol anchor and the thiol anchor alone were prepared for comparison. Voltammetry of the three molecules on Au(111) showed reductive desorption peaks caused by monolayer adsorption via thiolate-Au bonding. In situ STM of the thiol anchor disclosed an ordered adlayer with clear domains and molecular features. This holds promise, broadly for single-molecule voltammetry and the SPM and scanning tunnelling microscopy (STM) of natural and synthetic proteins. 相似文献