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111.
A. terreus isolates isolated from some bakery products, corn and rice were found to be able to produce territrems. 90% of theA. terreus isolated from bakery products were able to produce territrem A, with a mean of 0.09 ppm, while 80% ofA. terreus isolates produce territrem B with a mean of 0.24 ppm. On the other hand 31.8% of the isolates ofA. terreus from corn were able to produce territrem A with a mean of 0.44 ppm. ConcerningA. terreus isolates from rice, 66.7% were found to produce territrem A, with a mean of 5.28 ppm, and 77.8% of the isolates produced
territrem B with a mean of 1.79 ppm. 相似文献
112.
113.
Adaptive evolution of G-protein coupled receptor genes 总被引:2,自引:0,他引:2
The phylogeny and patterns of nucleotide substitutions in the visual
pigment genes, adrenergic receptor genes, muscarinic receptor genes, and in
the human mas oncogene were studied by comparing their DNA sequences. The
evolutionary tree obtained shows that the visual pigment genes and mas
oncogene form one cluster and that the receptor genes form another. In the
evolution of rhodopsin genes, synonymous substitutions outnumber
nonsynonymous substitutions. This is consistent with the neutral theory of
molecular evolution. However, the early evolutionary stages of alpha- and
beta-adrenergic and muscarinic receptors are notable for significantly more
nonsynonymous substitutions than synonymous substitutions, suggesting the
acquisition of novel functional adaptations. Variable rates of
nonsynonymous changes in different domains of these proteins reveal DNA
segments that might have been important in their functional adaptations.
相似文献
114.
Nielsen M Lundegaard C Blicher T Peters B Sette A Justesen S Buus S Lund O 《PLoS computational biology》2008,4(7):e1000107
CD4 positive T helper cells control many aspects of specific immunity. These cells are specific for peptides derived from protein antigens and presented by molecules of the extremely polymorphic major histocompatibility complex (MHC) class II system. The identification of peptides that bind to MHC class II molecules is therefore of pivotal importance for rational discovery of immune epitopes. HLA-DR is a prominent example of a human MHC class II. Here, we present a method, NetMHCIIpan, that allows for pan-specific predictions of peptide binding to any HLA-DR molecule of known sequence. The method is derived from a large compilation of quantitative HLA-DR binding events covering 14 of the more than 500 known HLA-DR alleles. Taking both peptide and HLA sequence information into account, the method can generalize and predict peptide binding also for HLA-DR molecules where experimental data is absent. Validation of the method includes identification of endogenously derived HLA class II ligands, cross-validation, leave-one-molecule-out, and binding motif identification for hitherto uncharacterized HLA-DR molecules. The validation shows that the method can successfully predict binding for HLA-DR molecules-even in the absence of specific data for the particular molecule in question. Moreover, when compared to TEPITOPE, currently the only other publicly available prediction method aiming at providing broad HLA-DR allelic coverage, NetMHCIIpan performs equivalently for alleles included in the training of TEPITOPE while outperforming TEPITOPE on novel alleles. We propose that the method can be used to identify those hitherto uncharacterized alleles, which should be addressed experimentally in future updates of the method to cover the polymorphism of HLA-DR most efficiently. We thus conclude that the presented method meets the challenge of keeping up with the MHC polymorphism discovery rate and that it can be used to sample the MHC "space," enabling a highly efficient iterative process for improving MHC class II binding predictions. 相似文献
115.
Jakobsen C. G. Søgaard T. M. M. Jean-Jean O. Frolova L. Yu. Justesen J. 《Molecular Biology》2001,35(4):575-583
Termination of translation in eukaryotes is governed by the ribosome, a termination codon in the mRNA, and two polypeptide chain release factors (eRF1 and eRF3). We have identified a human protein of 628 amino acids, named eRF3b, which is highly homologous to the known human eRF3 henceforth named eRF3a. At the nucleotide and at the amino acid levels the human eRF3a and eRF3b are about 87% identical. The differences in amino acid sequence are concentrated near the amino terminus. The most important difference in the nucleotide sequence is that eRF3b lacks a GGC repeat close to the initiation codon in eRF3a. We have cloned the cDNA encoding the human eRF3b, purified the eRF3b expressed in Escherichia coli, and found that the protein is active in vitroas a potent stimulator of the release factor activity of human eRFl. Like eRF3a, eRF3b exhibits GTPase activity, which is ribosome- and eRFl-dependent. In vivoassays (based on suppression of readthrough induced by three species of suppressor tRNAs: amber, ochre, and opal) show that the human eRF3b is able to enhance the release factor activity of endogenous and overexpressed eRF1 with all three stop codons. 相似文献
116.
Nicolaisen M Justesen AF Thrane U Skouboe P Holmstrøm K 《Journal of microbiological methods》2005,62(1):57-69
Cereal grain may be infected with a number of Fusarium species some of which are producers of highly toxic compounds such as the trichothecenes. Correct identification of these species is essential for risk assessment of cereal grain for human or animal consumption. Most of the available methods for identification are either time consuming or aimed at only one or a few target species. Microarray technology offers parallel analysis of a high number of DNA targets. In this study 57 capture oligonucleotides (CO) were designed based upon Fusarium ITS2 rDNA sequences, and used for microarray production. From this array COs could be selected that were able to hybridise specifically to labelled PCR products from the ITS region of Fusarium graminearum/Fusarium culmorum, Fusarium pseudograminearum, Fusarium poae, Fusarium sporotrichioides, Fusarium equiseti, Fusarium langsethiae and Fusarium tricinctum/Fusarium avenaceum. A few COs showed some cross hybridisation to non-target species. In a preliminary experiment it was shown that this cross hybridisation could be eliminated by increasing hybridisation stringency. The array could be used to detect individual Fusarium species in mixed samples and in environmental samples. This study demonstrates the feasibility of oligonucleotide microarrays for parallel detection of a number of Fusarium species. 相似文献
117.
In this study we describe the design, preparation and testing of superparamagnetic anion-exchangers, and their use together with cation-exchangers in the fractionation of bovine whey proteins as a model study for high-gradient magnetic fishing. Adsorbents prepared by attachment of trimethyl amine to particles activated in sequential reactions with allyl bromide and N-bromosuccinimide yielded a maximum bovine serum albumin binding capacity of 156 mg g(-1) combined with a dissociation constant of 0.60 microM, whereas ion-exchangers created by linking polyethylene imine through superficial aldehydes bound up to 337 mg g(-1) with a dissociation constant of 0.042 microM. The latter anion-exchanger was selected for studies of whey protein fractionation. In these, crude bovine whey was treated with a superparamagnetic cation-exchanger to adsorb basic protein species, and the supernatant arising from this treatment was then contacted with the anion-exchanger. For both adsorbent classes of ion-exchanger, desorption selectivity was subsequently studied by sequentially increasing the concentration of NaCl in the elution buffer. In the initial cation-exchange step quantitative removal of lactoferrin (LF) and lactoperoxidase (LPO) was achieved with some simultaneous binding of immunoglobulins (Ig). The immunoglobulins were separated from the other two proteins by desorbing with a low concentration of NaCl (< or = 0.4 M), whereas lactoferrin and lactoperoxidase were co-eluted in significantly purer form, e.g. lactoperoxidase was purified 28-fold over the starting material, when the NaCl concentration was increased to 0.4-1 M. The anion-exchanger adsorbed beta-lactoglobulin (beta-LG) selectively allowing separation from the remaining protein. 相似文献
118.
119.
Jakobsen CG Segaard TM Jean-Jean O Frolova L Justesen J 《Molekuliarnaia biologiia》2001,35(4):672-681
Termination of translation in eukaryotes is governed by the ribosome, a termination codon in the mRNA, and two polypeptide chain release factors (eRF1 and eRF3). We have identified a human protein of 628 amino acids, named eRF3b, which is highly homologous to the known human eRF3 henceforth named eRF3a. At the nucleotide and at the amino acid levels the human eRF3a and eRF3b are about 87% identical. The differences in amino acid sequence are concentrated near the amino terminus. The most important difference in the nucleotide sequence is that eRF3b lacks a GGC repeat close to the initiation codon in eRF3a. We have cloned the cDNA encoding the human eRF3b, purified the eRF3b expressed in Escherichia coli, and found that the protein is active in vitro as a potent stimulator of the release factor activity of human eRFl. Like eRF3a, eRF3b exhibits GTPase activity, which is ribosome- and eRFl-dependent. In vivo assays (based on suppression of readthrough induced by three species of suppressor tRNAs: amber, ochre, and opal) show that the human eRF3b is able to enhance the release factor activity of endogenous and overexpressed eRFl with all three stop codons. 相似文献
120.
Guranowski A Galbas M Hartmann R Justesen J 《Archives of biochemistry and biophysics》2000,373(1):218-224
It is known that the interferon-inducible 2',5'-oligoadenylate synthetase can catalyze the 2'-adenylation of various diadenosine polyphosphates. However, catabolism of those 2'-adenylated compounds has not been investigated so far. This study shows that the mono- and bis-adenylated (or mono- and bis-deoxyadenylated) diadenosine triphosphates are not substrates of the human Fhit (fragile histidine triad) protein, which acts as a typical dinucleoside triphosphate hydrolase (EC 3.6.1.29). In contrast, the diadenosine tetraphosphate counterparts are substrates for the human (asymmetrical) Ap(4)A hydrolase (EC 3.6.1.17). The relative rates of the hydrolysis of 0.15 mM AppppA, (2'-pdA)AppppA, and (2'-pdA)AppppA(2"'-pdA) catalyzed by the latter enzyme were determined as 100:232:38, respectively. The asymmetrical substrate was hydrolyzed to ATP + (2'-pdA)AMP (80%) and to (2'-pdA)ATP + AMP (20%). The human Fhit protein, for which Ap(4)A is a poor substrate, did not degrade the 2'-adenylated diadenosine tetraphosphates either. The preference of the interferon-inducible 2'-5' oligoadenylate synthetase to use Ap(3)A over Ap(4)A as a primer for 2'-adenylation and the difference in the recognition of the 2'-adenylated diadenosine triphosphates versus the 2'-adenylated diadenosine tetraphosphates by the dinucleoside polyphosphate hydrolases described here provide a mechanism by which the ratio of the 2'-adenylated forms of the signalling molecules, Ap(3)A and Ap(4)A, could be regulated in vivo. 相似文献