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排序方式: 共有321条查询结果,搜索用时 875 毫秒
61.
Senerovic L Stankovic N Spizzo P Basso A Gardossi L Vasiljevic B Ljubijankic G Tisminetzky S Degrassi G 《Biotechnology and bioengineering》2006,93(2):344-354
A complete, integrated process for the production of an innovative formulation of penicillin G acylase from Providencia rettgeri(rPAC(P.rett))of industrial applicability is reported. In order to improve the yield of rPAC, the clone LN5.5, carrying four copies of pac gene integrated into the genome of Pichia pastoris, was constructed. The proteinase activity of the recombinant strain was reduced by knockout of the PEP4 gene encoding for proteinase A, resulting in an increased rPAC(P.rett) activity of approximately 40% (3.8 U/mL vs. 2.7 U/mL produced by LN5.5 in flask). A high cell density fermentation process was established with a 5-day methanol induction phase and a final PAC activity of up to 27 U/mL. A single step rPAC(P.rett) purification was also developed with an enzyme activity yield of approximately 95%. The novel features of the rPAC(P.rett) expressed in P.pastoris were fully exploited and emphasized through the covalent immobilization of rPAC(P.rett). The enzyme was immobilized on a series of structurally correlated methacrylic polymers, specifically designed and produced for optimizing rPAC(P.rett) performances in both hydrolytic and synthetic processes. Polymers presenting aminic functionalities were the most efficient, leading to formulations with higher activity and stability (half time stability >3 years and specific activity ranging from 237 to 477 U/g (dry) based on benzylpenicillin hydrolysis). The efficiency of the immobilized rPAC(P.rett) was finally evaluated by studying the kinetically controlled synthesis of beta-lactam antibiotics (cephalexin) and estimating the synthesis/hydrolysis ratio (S/H), which is a crucial parameter for the feasibility of the process. 相似文献
62.
63.
Biljana Balen Mirta Tkalec Dubravko Pavoković Branka Pevalek-Kozlina Marijana Krsnik-Rasol 《Journal of Plant Growth Regulation》2009,28(1):36-45
In vitro propagated plants of Mammillaria
gracilis Pfeiff. (Cactaceae) develop calli without any exogenous growth regulators. This habituated tissue spontaneously regenerates morphologically
normal as well as hyperhydric shoots. In this study, a possible involvement of activated oxygen metabolism in habituation
and hyperhydricity in in vitro propagated plants of Mammillaria
gracilis Pfeiff. (Cactaceae) was investigated. Significantly higher malondialdehyde (MDA) and carbonyl contents as well as hydrogen peroxide (H2O2) production were observed in habituated callus (HC), hyperhydric regenerated shoots (HS), and tumors (TT) in comparison to
normal regenerated shoots (NS). Lipoxygenase (LOX) activity showed a similar trend, with a clear increase in activity in HC
and HS. The activities of antioxidative enzymes, namely, peroxidase (POX), ascorbate peroxidase (APX), and catalase (CAT),
were also higher in HC, HS, and TT, whereas an increase in superoxide dismutase (SOD) activity was observed in HC and HS.
The majority of antioxidative isoenzymes were common to all cactus tissues, although a few tissue-specific bands were noticed.
Significant decreases in phenylalanine ammonia lyase (PAL) activity, total phenolic content, and lignification were found
in HS, HC, and TT in comparison to NS. Our results showed the appearance of a prominent oxidative stress in HC, HS, and TT
as well as a strong induction of the antioxidant system indicating that activated oxygen metabolism could be involved in habituation
and hyperhydricity and linked to the loss of tissue organization in M. gracilis.
B. Balen and M. Tkalec contributed equally to this work. 相似文献
64.
Katarina Nikolic Branka Ivković Željka Bešović Slavko Marković Danica Agbaba 《Chirality》2009,21(10):878-885
A new and accurate HPLC method using β‐cyclodextrin chemically bonded to spherical silica particles as chiral stationary phase (CSP) was developed and validated for determination of S‐clopidogrel and its impurities R‐enantiomer and S‐acid as a hydrolytic product. The effects of acetonitrile and methanol content in the mobile phase and temperature on the resolution and retention of enantiomers were investigated. A satisfactory resolution of S‐clopidogrel active form and its impurities was achieved on ChiraDex® column (5 μm, 4 × 250 mm) at a flow rate of 1.0 ml/min and 17°C using acetonitrile, methanol and 0.01 M potassium dihydrogen phosphate solution (15:5:80 v/v/v) as mobile phase. The detection wavelength was set at 220 nm. The method was validated in terms of accuracy, precision, linearity, and robustness. The limit of detection for R‐enantiomer and S‐acid were 0.75 and 0.09 μg/ml, respectively, injection volume being 20 μl. Finally, the molecular modeling of the inclusion complexes between the analytes and β‐cyclodextrin was performed to investigate the mechanism of the enantiorecognition and to study the quantitative structure–retention relationships. Chirality, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
65.
Branka Dabovic Yan Chen Jiwon Choi Melinda Vassallo Harry C. Dietz Francesco Ramirez Harald von Melchner Elaine C. Davis Daniel B. Rifkin 《Journal of cellular physiology》2009,219(1):14-22
The latent TGF‐β binding proteins (LTBP) ‐1, ‐3, and ‐4 are extracellular proteins that assist in the secretion and localization of latent TGF‐β. The null mutation of LTBP‐4S in mice causes defects in the differentiation of terminal air‐sacs, fragmented elastin, and colon carcinomas. We investigated lung development from embryonic day 14.5 (E14.5) to day 7 after birth (P7) in order to determine when the defects in elastin organization initiate and to further examine the relation of TGF‐β signaling levels and air‐sac septation in Ltbp4S?/? lungs. We found that defects in elastogenesis are visible as early as E14.5 and are maintained in the alveolar walls, in blood vessel media, and subjacent airway epithelium. The air‐sac septation defect was associated with excessive TGF‐β signaling and was reversed by lowering TGF‐β2 levels. Thus, the phenotype is not directly reflective of a change in TGF‐β1, the only TGF‐β isoform known to complex with LTBP‐4. Reversal of the air‐sac septation defect was not associated with normalization of the elastogenesis indicating two separate functions of LTBP‐4 as a regulator of elastic fiber assembly and TGF‐β levels in lungs. J. Cell. Physiol. 219: 14–22, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
66.
Face mask ventilation is a life saving technique. This article will review aetiology and patophysiological consequences of inadequate mask ventilation. The main focus will be on circulatory changes during induction of anesthesia, before and in a short period after intubation that could be attributed to inadequate mask ventilation in humans. 相似文献
67.
68.
Goran Kovačević Sandra Radić Biserka Jelenčić Mirjana Kalafatić Hrvoje Posilović Branka Pevalek-Kozlina 《Plant Systematics and Evolution》2010,284(1-2):33-39
Symbiotic associations are of a wide significance in evolution and biodiversity. Green hydra is a typical example of endosymbiosis. In its gastrodermal myoepithelial cells, it harbors individuals of unicellular green algae. Morphological characteristics of isolated algae determined by light and electron microscopy are presented. Cytological morphometric parameters (cell area, cell radius, chloroplast area) of isolated algae from green hydra (Cx), as well as from reference species Chlorella kessleri (Ck) and Chlorella vulgaris (Cv), revealed similarity between the isolated endosymbiont and C. kessleri. Isoenzyme patterns of esterase (EST), peroxidase (POX), and catalase (CAT) were used for the investigation of genetic variability in endosymbiotic algae isolated from green hydra. Out of 14 EST isoenzymes observed in Cx species, 9 were expressed in the Cx sample. Results of the EST isoenzyme analysis indicated a higher degree of similarity between Cx and Cv than between Cx and Ck. Due to much higher heterogeneity, EST isoenzymes seem to be more suitable genetic markers for identification of different Chlorella species than CAT and POX isoenzymes. Results obtained suggest that symbiogenesis in green hydra has probably not been terminated yet. 相似文献
69.
Molecular Ecology Resources Primer Development Consortium An J Bechet A Berggren A Brown SK Bruford MW Cai Q Cassel-Lundhagen A Cezilly F Chen SL Cheng W Choi SK Ding XY Fan Y Feldheim KA Feng ZY Friesen VL Gaillard M Galaraza JA Gallo L Ganeshaiah KN Geraci J Gibbons JG Grant WS Grauvogel Z Gustafsson S Guyon JR Han L Heath DD Hemmilä S Hogan JD Hou BW Jakse J Javornik B Kaňuch P Kim KK Kim KS Kim SG Kim SI Kim WJ Kim YK Klich MA Kreiser BR Kwan YS Lam AW Lasater K Lascoux M Lee H Lee YS Li DL 《Molecular ecology resources》2010,10(2):404-408
This article documents the addition of 411 microsatellite marker loci and 15 pairs of Single Nucleotide Polymorphism (SNP) sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Acanthopagrus schlegeli, Anopheles lesteri, Aspergillus clavatus, Aspergillus flavus, Aspergillus fumigatus, Aspergillus oryzae, Aspergillus terreus, Branchiostoma japonicum, Branchiostoma belcheri, Colias behrii, Coryphopterus personatus, Cynogolssus semilaevis, Cynoglossus semilaevis, Dendrobium officinale, Dendrobium officinale, Dysoxylum malabaricum, Metrioptera roeselii, Myrmeciza exsul, Ochotona thibetana, Neosartorya fischeri, Nothofagus pumilio, Onychodactylus fischeri, Phoenicopterus roseus, Salvia officinalis L., Scylla paramamosain, Silene latifo, Sula sula, and Vulpes vulpes. These loci were cross-tested on the following species: Aspergillus giganteus, Colias pelidne, Colias interior, Colias meadii, Colias eurytheme, Coryphopterus lipernes, Coryphopterus glaucofrenum, Coryphopterus eidolon, Gnatholepis thompsoni, Elacatinus evelynae, Dendrobium loddigesii Dendrobium devonianum, Dysoxylum binectariferum, Nothofagus antarctica, Nothofagus dombeyii, Nothofagus nervosa, Nothofagus obliqua, Sula nebouxii, and Sula variegata. This article also documents the addition of 39 sequencing primer pairs and 15 allele specific primers or probes for Paralithodes camtschaticus. 相似文献
70.
Jean-Philip Truman Mónica García-Barros Matthew Kaag Dolores Hambardzumyan Branka Stancevic Michael Chan Zvi Fuks Richard Kolesnick Adriana Haimovitz-Friedman 《PloS one》2010,5(8)