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41.
The coding region of the copper/zinc superoxide dismutase (Cu/Zn SOD) cDNA from papaya fruit, Carica papaya L. cv. Tainong 2, was cloned into an expression vector, pET-20b(+). The Cu/Zn SOD was expressed in Escherichia coli and purified by His-tag technique. Two active forms of the enzyme (30% dimer and 70% monomer) in equilibrium were observed. The activity of the dimeric enzyme was higher than that of the monomeric form. The thermal inactivation rate constant K(d) values calculated for the dimer and monomer at 90 degrees C were -0.0203 and -0.0216 min(-1), and the half-lives for inactivation were 41.9 and 31.8 min, respectively. This indicated that the dimeric enzyme was more stable than its monomeric form. The dimerization of the enzyme was inhibited under acidic pH (below 3.0) or imidazole buffer (above 0.5 M), whereas it was not affected under alkaline pH (above 9.0). Both activity and forms of the enzyme were not affected by 1-4% SDS. Furthermore, the dimeric enzyme was much more resistant to proteolytic attack after 3 h of incubation at 37 degrees C with trypsin or chymotrypsin. In addition, mutation of the papaya Cu/Zn SOD at position 48 from Leu to Phe (L48F) affected the association of monomer, whereas a mutant with Lys substitution (L48K) at the same position tended to dissociate into monomeric form. 相似文献
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43.
TD ST GEORGE 《Australian veterinary journal》1989,66(12):393-395
44.
N. Motoyama L.R. Kao P.T. Lin W.C. Dauterman 《Pesticide biochemistry and physiology》1984,21(2):139-147
The role of esterases as related to insecticide resistance was studied in an organophosphorus (OP)-resistant strain of the green rice leafhopper. As judged by p-nitrophenyl acetate hydrolysis, 21, 5, and 74% of the esterase activity was located in nuclei/mitochondria, microsomes, and the soluble fraction, respectively. All the fractions were active in hydrolyzing malathion, paraoxon, and fenvalerate. Hydrolysis of malathion and fenvalerate increased with time while that of paraoxon reached a plateau within 15 min. Since a considerable amount of p-nitrophenol was detected in the paraoxon reaction at 0°C and at zero time, the formation of p-nitrophenol may be due to phosphorylation of the esterases rather than phosphorotriesterase action. The results suggest a dual role for esterases in resistance mechanisms; a catalyst for hydrolysis of malathion and fenvalerate, and a binding protein for the oxygen analogs of other OP insecticides, both of which would protect the intrinsic target, acetylcholinesterase, from inhibition. Chromatofocusing of the soluble fraction resolved five esterase peaks, I–V. These esterases were active toward the three general substrates as well as for the three insecticides tested, except for Peak I in which the overall activity was too low. Thin-layer agar gel electrophoresis showed that the chromatofocusing peaks I–V corresponded to the electrophoretic bands E1–E5, some of which were previously shown to be associated with OP resistance. The dual role of these esterases may explain the cross-resistance between malathion and other OP insecticides as well as synergism between OP and carbamate insecticides. 相似文献
45.
46.
T. D. ST. GEORGE M.V.Sc. H. A. STANDFAST BSc. A. L. DYCE B.Sc.Agr. 《Australian veterinary journal》1976,52(5):242-242
47.
Biological control of Sclerotinia minor using a chitinolytic bacterium and actinomycetes 总被引:4,自引:0,他引:4
K. A. El-Tarabily † M. H. Soliman ‡ A. H. Nassar † H. A. Al-Hassani K. Sivasithamparam F. McKenna G. E. ST. J. Hardy 《Plant pathology》2000,49(5):573-583
Isolates of 85 bacteria and 94 streptomycete and 35 nonstreptomycete actinomycetes were obtained from a lettuce-growing field in Al-Ain, United Arab Emirates, on colloidal chitin agar, and screened for their ability to produce chitinase. Twenty-three bacteria and 38 streptomycete and 15 nonstreptomycete actinomycete isolates produced high levels of chitinase and were examined in vitro for their ability to suppress the growth of Sclerotinia minor , a pathogen causing basal drop disease of lettuce. The three most suppressive isolates were examined further for their production of β-1,3-glucanase and antifungal activity as well as their ability to colonize the roots and rhizosphere of lettuce in vitro and in planta . The three isolates, Serratia marcescens, Streptomyces viridodiasticus and Micromonospora carbonacea , significantly reduced the growth of S. minor in vitro , and produced high levels of chitinase and β-1,3-glucanase. Streptomyces viridodiasticus also produced antifungal metabolite(s) that significantly reduced the growth of the pathogen in vitro . When the pathogen was presented as the sole carbon source, all three isolates caused extensive hyphal plasmolysis and cell wall lysis. Serratia marcescens and St. viridodiasticus were competent to varying degrees in colonizing the roots of lettuce seedlings after 8 days on agar plates and the rhizosphere within 14 days in pots, with their competency being superior to that of M. carbonacea . All three isolates, individually or in combination, were antagonistic to S. minor and significantly reduced incidence of disease under controlled glasshouse conditions. 相似文献
48.
感染E.tenella对肉仔鸡生长、营养物质表观存留率及血液生理指标的影响 总被引:1,自引:0,他引:1
为了研究玉米 -豆粕型基础饲养下感染球虫对肉仔鸡生长、营养物质表观存留率、血液生理指标的影响 ,用 48只 1周龄 ( AA)肉仔鸡进行试验 ,按体重随机分为 2组 ,代谢期 1周。试验组鸡 1 4日龄时分别感染柔嫩艾美耳球虫卵囊 9万个 /只。结果表明 :试验组除饲料转化比 ,在代谢期后 4天间有显著差异外 ,其余多数生长性能指标在两组间无显著差异 ( P>0 .1 )。但感染球虫降低了试验组鸡的营养物质的表观存留率 相似文献
49.
Lindenberg AM Larsson J Sokolowski-Tinten K Gaffney KJ Blome C Synnergren O Sheppard J Caleman C Macphee AG Weinstein D Lowney DP Allison TK Matthews T Falcone RW Cavalieri AL Fritz DM Lee SH Bucksbaum PH Reis DA Rudati J Fuoss PH Kao CC Siddons DP Pahl R Als-Nielsen J Duesterer S Ischebeck R Schlarb H Schulte-Schrepping H Tschentscher T Schneider J von der Linde D Hignette O Sette F Chapman HN Lee RW Hansen TN Techert S Wark JS Bergh M Huldt G van der Spoel D Timneanu N Hajdu J Akre RA Bong E 《Science (New York, N.Y.)》2005,308(5720):392-395
The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids. 相似文献
50.
By employing cells mutating at a very high spontaneous rate and a grid plate containing a medium totally selective against mutant cells, direct microscopic observation was made of mutant cells of recent origin passing through a limited number of phenomic lag divisions. 相似文献