共查询到19条相似文献,搜索用时 62 毫秒
1.
以生产头孢菌素C(CPC)过程中的副产物去乙酰头孢菌素C(DCPC)为原料,用固定化D-氨基酸氧化酶(DAAO)和固定化戊二酰基酰化酶(GA),连续两步进行酶裂解,制备了去乙酰基7-氨基头孢烯酸(D-7-ACA),总收率72%。滴加浓度为1 mol/L的过氧化氢可使去乙酰基戊二酰基7-ACA(D-G l-7-ACA)的收率提高6%。提高氧气流速和改善搅拌形式可以加快DAAO酶反应速度,使中间产物残留减少3%。高纯度的去乙酰头孢菌素C钠盐(DCPCNa)可以提高该两步酶法反应的收率和产品质量,延长酶的使用寿命。 相似文献
2.
3.
4.
5.
6.
7.
7-氨基-3-乙烯基头孢烷酸的合成 总被引:1,自引:0,他引:1
以7-苯乙酰氨基-3-氯甲基-4-头孢烷酸对甲氧基苄酯(GCLE)为起始原料,通过Wittig反应、酚解和酶解三步反应制备7-氨基-3-乙烯-4-头孢烷酸(7-AVCA),探讨了Wittig反应的溶剂,酚解反应的催化剂以及酶解反应的温度、pH值对完全反应所需时间的影响。结果表明,当Wittig反应中加入溶剂丙酮,酚解反应中加入适量强酸催化,酶解反应的温度控制在30℃,pH值8.2±0.1时,制得目标产物所需时间最短(<20 h)。该工艺极大的缩短了整体反应的时间,总摩尔收率达60.2%,非常适于规模化生产。 相似文献
8.
报道了在多聚磷酸(PPA)中将冠醚酰化的方法,合成了4′-乙酰基苯并-15-冠-5,以此为原料,在酸性条件下与氨基酸脲作用,合成了4′-乙酰基缩氨硫脲基苯并-15-冠-5。经由IR、MS和元素分析对合成的两种物质的结构进行了表征。 相似文献
9.
10.
以青霉素亚砜硅酯为原料经催化扩环制备头孢G酸。对 11种扩环催化剂进行了筛选 ,研制出了新型高效扩环催化剂MAB -Ⅱ ,使头孢G酸收率可达 93% (以质量计 ) ,w(C1 6 H1 6 N2 O4S) =( 93~ 96 ) %。其最佳工艺条件为 :n(C1 9H2 6 N2 O5 SSi)∶n(C8H1 0 NO) =1.0 0∶( 0 40~ 0 43) ;扩环温度 :10 5~ 10 8℃ ;扩环时间 :2 0~ 2 5h ;水解温度 :6 0℃ ;水解时间 :30~ 35min。以IR、MS谱图验证了头孢G酸的结构 相似文献
11.
产GL-7ACA酰化酶基因工程菌的高活性表达 总被引:1,自引:0,他引:1
实现了戊二酰基-7-氨基头孢烷酸(GL-7ACA)酰化酶的组成型表达,并通过替换重组质粒启动子的RBS序列,在摇瓶培养条件下,使新构建的重组质粒pGEMKT-HPRfACY在大肠杆菌JM105中表达GL-7ACA酰化酶酶活达到0.44 U/mL,是替换前的2倍. 使用廉价的玉米浆作为培养基中氮源主要来源,使JM105/pGEMKT-HPRfACY菌株酶活提高到2.98 U/mL. 采用补料批式培养,利用流加营养物控制发酵中后期的pH值,在pH为7.5的条件下,酶活峰值达到6.37 U/mL. 该体系无需诱导,工艺操作过程简单,成本低廉. 相似文献
12.
13.
《Ceramics International》2022,48(7):9371-9377
Cubic Li7-3xGaxLa3Zr2O12 is a cubic phase with a space group of I-43d instead of Ia-3d. This structure is more conducive to the migration of lithium ions. However, the effect of Ga on the size and environment of lithium ion transport channels has not been researched. In this work, Li7-3xGaxLa3Zr2O12 (x = 0–0.25) was formulated, and the crystal structure was obtained by neutron diffraction. The results indicated that the minimum channel size to control Li+ migration in LLZO was the bottleneck size between the Li2 and Li3 sites (bottleneck size 2), and compared with lanthanum ions, the zirconium ions were closer to lithium ions. As the Ga content increased, bottleneck size 2 levelled off, while the lithium concentration and the distance between skeleton ions and lithium ions decreased. As a result, the lithium ionic conductivity primarily increased and then decreased. When doping 0.2 pfu of Ga, LLZO exhibited the highest lithium ionic conductivity of 1.45 mS/cm at 25 °C due to the coordinated regulation of Li+ concentration, bottleneck size, and the distance between skeleton ions and lithium ions. 相似文献
14.
Estimation using pooled sampling has long been an area of interest in the group testing literature. Such research has focused primarily on the assumed use of fixed sampling plans (i), although some recent papers have suggested alternative sequential designs that sample until a predetermined number of positive tests (ii). One major consideration, including in the new work on sequential plans, is the construction of debiased estimators that either reduce or keep the mean square error from inflating. However, whether under the above or other sampling designs unbiased estimation is in fact possible has yet to be established in the literature. In this article, we introduce a design that samples until a fixed number of negatives (iii), and show that an unbiased estimator exists under this model, whereas unbiased estimation is not possible for either of the preceding designs (i) and (ii). We present new estimators under the different sampling plans that are either unbiased or that have reduced bias relative to those already in use as well as generally improve on the mean square error. Numerical studies are done in order to compare designs in terms of bias and mean square error under practical situations with small and medium sample sizes. 相似文献
15.
16.
17.
18.
Systemized organic functional group controls in polydiacetylenes and their effects on color changes 下载免费PDF全文
A variety of organic functional groups have been successfully installed into polydiacetylenes (PDAs) and applied to the color change‐controlled system of PDA sensors. Ten diacetylene compounds possessing different functionalities and lengths were systemically synthesized and fully characterized using spectroscopic methods. The polymerized vesicle solution with these compounds showed different temperatures required to induce a color change (from blue to red) depending on the functionalities installed on 10,12‐pentacosadiynoic acid (PCDA) molecules. In addition, the results reported here reveal that the intermolecular interactions of PCDA molecules and the intermolecular distance play a key role to the color of PDA system. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45011. 相似文献