全文获取类型
收费全文 | 87篇 |
免费 | 0篇 |
专业分类
化学 | 83篇 |
晶体学 | 1篇 |
物理学 | 3篇 |
出版年
2021年 | 2篇 |
2018年 | 1篇 |
2016年 | 1篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 5篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2006年 | 2篇 |
2005年 | 10篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1966年 | 3篇 |
1965年 | 1篇 |
排序方式: 共有87条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
Two novel metabolites, containing four bromotyrosine units, have been isolated from the sponge . 相似文献
55.
Petrukhin OM Avdeeva EN Shavnya YV Yankauskas VP Kazlauskas RM Bychkov AS Zolotov YA 《Talanta》1987,34(1):111-121
Some new ion-selective electrodes for silver and gold are described. They are based on the ion-associate species formed by the cyanide, chloride or thiourea complexes of the metals, with hydrophobic anions or cations, as appropriate. The electrodes have been applied to the determination of gold and silver in various technological process solutions in industry. 相似文献
56.
57.
Kazlauskas R 《Chemistry & biology》2012,19(4):435-437
A human enzyme variant, PON1-G3C9, accidentally catalyzes the hydrolysis of organophosphorus chemical weapons. In this issue of Chemistry & Biology, Goldsmith and coworkers describe a new PON1 variant with improved hydrolysis by several hundred fold; enough that it may protect animals from a toxic dose. 相似文献
58.
Shona Duncan Qing Jing Adrian Katona Romas J. Kazlauskas Jonathan Schilling Ulrike Tschirner Waleed Wafa AlDajani 《Applied biochemistry and biotechnology》2010,160(6):1637-1652
The recalcitrance of lignocellulosic biomass to enzymatic release of sugars (saccharification) currently limits its use as
feedstock for biofuels. Enzymatic hydrolysis of untreated aspen wood releases only 21.8% of the available sugars due primarily
to the lignin barrier. Nature uses oxidative enzymes to selectively degrade lignin in lignocellulosic biomass, but thus far,
natural enzymes have been too slow for industrial use. In this study, oxidative pretreatment with commercial peracetic acid
(470 mM) removed 40% of the lignin (from 19.9 to 12.0 wt.% lignin) from aspen and enhanced the sugar yields in subsequent
enzymatic hydrolysis to about 90%. Increasing the amount of lignin removed correlated with increasing yields of sugar release.
Unfortunately, peracetic acid is expensive, and concentrated forms can be hazardous. To reduce costs and hazards associated
with using commercial peracetic acid, we used a hydrolase to catalyze the perhydrolysis of ethyl acetate generating 60–70 mM
peracetic acid in situ as a pretreatment to remove lignin from aspen wood. A single pretreatment was insufficient, but multiple
cycles (up to eight) removed up to 61.7% of the lignin enabling release of >90% of the sugars during saccharification. This
value corresponds to a predicted 581 g of fermentable sugars from 1 kg of aspen wood. Improvements in the enzyme stability
are needed before the enzymatically generated peracetic acid is a commercially viable alternative. 相似文献
59.
Rational design of enzymes with improved properties, such as enantioselectivity, usually focuses mutations within the substrate binding site. On the other hand, directed evolution of enzymes usually targets the entire protein and discovers beneficial mutations far from the substrate binding site. In this paper, we propose an explanation for this discrepancy and show that a combined approach--random mutagenesis within the substrate binding site--is better. To increase the enantioselectivity (E) of a Pseudomonas fluorescens esterase (PFE) toward methyl 3-bromo-2-methylpropionate, we focused mutagenesis into the substrate binding site at Trp28, Val121, Phe198, and Val225. Five of the catalytically active mutants (13%) showed better enantioselectivity than wild-type PFE. The increases in enantioselectivity were higher (up to 5-fold, reaching E = 61) than with mutants identified by random mutagenesis of the entire enzyme. 相似文献
60.
DeLu Yin Vince M. Purpero Ryota Fujii Qing Jing Romas J. Kazlauskas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(9):3037-3046
Some serine hydrolases also catalyze a promiscuous reaction— reversible perhydrolysis of carboxylic acids to make peroxycarboxylic acids. Five X‐ray crystal structures of these carboxylic acid perhydrolases show a proline in the oxyanion loop. Here, we test whether this proline is essential for high perhydrolysis activity using Pseudomonas fluorescens esterase (PFE). The L29P variant of this esterase catalyzes perhydrolysis 43‐fold faster (kcat comparison) than the wild type. Surprisingly, saturation mutagenesis at the 29 position of PFE identified six other amino acid substitutions that increase perhydrolysis of acetic acid at least fourfold over the wild type. The best variant, L29I PFE, catalyzed perhydrolysis 83‐times faster (kcat comparison) than wild‐type PFE and twice as fast as L29P PFE. Despite the different amino acid in the oxyanion loop, L29I PFE shows a similar selectivity for hydrogen peroxide over water as L29P PFE (β0=170 vs. 160 M ?1), and a similar fast formation of acetyl‐enzyme (140 vs. 62 U mg?1). X‐ray crystal structures of L29I PFE with and without bound acetate show an unusual mixture of two different oxyanion loop conformations. The type II β‐turn conformation resembles the wild‐type structure and is unlikely to increase perhydrolysis, but the type I β‐turn conformation creates a binding site for a second acetate. Modeling suggests that a previously proposed mechanism for L29P PFE can be extended to include L29I PFE, so that an acetate accepts a hydrogen bond to promote faster formation of the acetyl‐enzyme. 相似文献