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71.
应用两种免疫印迹法对二代ELISA测试的69份血清进行了追加试验。结果表明:8份ELISA阴性血清免疫印迹均阴性,61份ELISA阳性血清有1份免疫印迹阴性。ELISA假阳性率为1.67%。在60份免疫印迹阳性血清中,抗结构区(capsid),非结构区NS_3和NS_4抗体的阳性率分别为83%、93.3%和70%。其中丙型肝炎相关性抗体的分布,以抗capsid、NS_3、NS_4抗体都阳性为主(58.7%)。在输血后急性肝炎和肝细胞癌患者中。丙型肝炎相关性抗体的分布没有统计学上的差异。 相似文献
72.
为降焦减害提高卷烟吸味,利用现代生物技术,在卷烟制丝过程中加入一定量的MJQ酶制剂,通过正交试验选择最优条件,即温度为100 ℃、贮存时间为24 h、浓度为1 %.经后续对比试验及焦油测试与评吸,可以验证在卷烟制丝过程中喷洒MJQ酶制剂,对卷烟的焦油量有明显的降低,卷烟吸味得到了明显的改善. 相似文献
73.
Morris Aaron J.; Davenport Robert C.; Tolan Dean R. 《Protein engineering, design & selection : PEDS》1996,9(1):61-67
Lys146 of rabbit aldolase A [D-fructose-1,6-bis(phosphate):D-glyceraldehyde-3-phosphate lyase, EC 4.1.2.13
[EC]
] was changedto arginine by site-directed mutagenesis. The kcat of the resultingmutant protein, K146R, was 500 times slower than wild-type insteady-state kinetic assays for both cleavage and condensationof fructose-1,6-bis(phosphate), while the Km for this substratewas unchanged. Analysis of the rate of formation of catalyticintermediates showed K146R was significantly different fromthe wild-type enzyme and other enzymes mutated at this site.Single-turnover experiments using acid precipitation to trapthe Schiff base intermediate on the wild-type enzyme failedto show a build-up of this intermediate on K146R. However, K146Rretained the ability to form the Schiff base intermediate asshown by the significant amounts of Schiff base intermediatetrapped with NaBH4. In the single-turnover experiments it appearedthat the Schiff base intermediate was converted to productsmore rapidly than it was produced. This suggested a maximalrate of Schiff base formation of 0.022 s1, which wasclose to the value of kcat for this enzyme. This observationis strikingly different from the wild-type enzyme in which Schiffbase formation is >100 times faster than kcat. For K146Rit appears that steps up to and including Schiff base formationare rate limiting for the catalytic reaction. The carbanionintermediate derived from either substrate or product, and theequilibrium concentrations of covalent enzyme-substrate intermediates,were much lower on K146R than on the wild-type enzyme. The greaterbulk of the guanidino moiety may destabilize the covalent enzyme-substrateintermediates, thereby slowing the rate of Schiff base formationsuch that it becomes rate limiting. The K146R mutant enzymeis significantly more active than other enzymes mutated at thissite, perhaps because it maintains a positively charged groupat an essential position in the active site or perhaps the Argfunctionally substitutes as a general acid/base catalyst inboth Schiff base formation and in subsequent abstraction ofthe C4-hydroxyl proton. 相似文献
74.
75.
用微乳液聚合方法以N-异丙基丙烯酰胺为单体合成了温敏性微凝胶聚N-异丙基丙烯酰胺(PNIPAM),研究了其对两种蛋白质和两种酶的吸附性能,测定了吸附等温线和温度对吸附量的影响。结果表明,微凝胶在低临界溶解温度(LCST)附近吸附蛋白质和酶的量有一突跃,例如在LCST前后,1 g纳米颗粒吸附的酪蛋白的质量分别为225 mg和415 mg;吸附的枯草杆菌蛋白酶的质量分别为12 000U/mg和27 500 U/mg。蛋白质和酶是通过物理吸附作用结合到PNIPAM微凝胶上,可以用调节温度的方法,来控制温敏微凝胶对蛋白质和酶的吸附与脱附。 相似文献
76.
Zheng Ya-Jun; Merz Kenneth M. Jr; Farber Gregory K. 《Protein engineering, design & selection : PEDS》1993,6(5):479-484
Two mechanisms for an aldoseketose isomerization havebeen examined using high level ab initio and semiempirical molecularorbital methods. The proton transfer pathway via an enediolintermediate is shown to be favored in the absence of a metalion, while the hydride transfer pathway becomes favored in thepresence of a metal ion. Our calculations explain why the protontransfer pathway is operative in most aldoseketose isomerizationreactions. These calculations also provide further support forthe previously proposed metal ion-mediated hydride transfermechanism for xylose isomerase. 相似文献
77.
78.
Flaking and extrusion as mechanical treatments for enzyme-assisted aqueous extraction of oil from soybeans 总被引:6,自引:7,他引:6
B. P. Lamsal P. A. Murphy L. A. Johnson 《Journal of the American Oil Chemists' Society》2006,83(11):973-979
Flaking and extruding dehulled soybeans were evaluated as a means of enhancing oil extraction efficiency during enzyme-assisted
aqueous processing of soybeans. Cellulase, protease, and their combination were evaluated for effectiveness in achieving high
oil extraction recovery from extruded flakes. Aqueous extraction of extruded full-fat soy flakes gave 68% recovery of the
total available oil without using enzymes. A 0.5% wt/wt protease treatment after flaking and extruding dehulled soybeans increased
oil extraction recovery to 88% of the total available oil. Flaking and extruding enhanced protease hydrolysis of proteins
freeing more oil. Treating extruded flakes with cellulase, however, did not enhance oil extraction either alone or in combination
with protease. Discrepancies in oil extraction recoveries were encountered when merely considering crude free fat because
some oil became bound to denatured protein during extrusion and/or sample drying. Bound fat was unavailable for determination
by using the hexane extraction method, but was accounted for by using the acid hydrolysis method for total oil determination.
Oil extraction recovery from extruded soybean flakes was affected by oil determination methods, which was not the case for
unextruded full-fat soy flour. 相似文献
79.
介绍了加酶洗涤剂的发展以及酶在洗涤剂中的应用。探讨了加酶洗涤剂中表面活性剂及其浓度、洗涤温度和洗涤时间对洗涤效果的影响,pH值对酶活性的影响。对影响酶洗涤效果的各种因素进行了阐述。并论述了酶在洗涤剂中的其他应用。 相似文献
80.
Biosynthesis of the aldehydic sex pheromone components released by females ofHeliothis zea was found to be catalyzed by primary alcohol oxidases residing in the cuticle that covers the glands. Activity, as indicated by conversion of primary alcohol to aldehyde, was as high in cell-free cuticle as it was in intact pheromone glands. Studies indicated that some activity was associated with the surface of the epicuticle and could be removed, into buffer, by sonication. However, the majority of activity lies within the inner epicuticle and exo- and endocuticular layers. The oxidase was not functional in pharate pupae that did not have mature adult cuticle but became functional just prior to adult emergence. The enzyme in individual glands was saturated at alcohol concentrations above 100 n. moles. Nonionic detergents did not affect the activity of the oxidase in the cuticle but treatment with either 7 M urea or 1% SDS resulted in total loss of activity. Studies on the effect of pH indicated an optimum at 6.4; however, activity was high throughout the range of 5–9. The oxidase was functional in both dichloromethane and hexane, suggesting that this enzyme system may have applications for organic synthesis of aldehydes. 相似文献