首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15篇
  免费   0篇
化学   11篇
物理学   4篇
  2001年   1篇
  1999年   1篇
  1996年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1972年   3篇
  1970年   1篇
  1969年   1篇
  1967年   1篇
排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
    
The enzymatic hydrolysis of a 4-0-methylglucuronoxylan of white sweetclover (Melilotus albus) by a highly purified homogeneous endo-1, 4--xylanase fromAspergillus niger 14 has shown that the enzyme hydrolyzes 97% of the polysaccharide in 72 h. Acidic and neutral oligosaccharides were found in the hydrolysate after the action of the enzyme. An investigation of the hexauronic acid isolated has shown that the glucuronic acid is attached to the nonreducing end of the xylooligosaccharide, which demonstrates the specific action of the enzyme on the polysaccharide.M. V. Lomonosov Odessa Technological Institute of the Food Industry. A. N. Bakh Institute of Biochemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 477–483, July–August, 1980.  相似文献   
2.
The coupling of photosensitive reagents has been carried out with the goal of obtaining the predetermined distribution of binding sites either for “surface” or “spacial” immobilization of biomacromolecules. The correlation holds between light intensity and the number of readant groups emerged in a matrix.  相似文献   
3.
The influence of the pH, temperature, and dimethyl sulfoxide concentration on the hydration degree of the poly-N-isopropylacrylamide gel and the activity of -chymotrypsin immobilized into the polymer was studied. The behavior of more hydrophilic preparations based on polyacrylamide and copolymer of acrylamide and acrylic acid was studied for comparison. An increase in both the temperature and dimethyl sulfoxide content decreases the hydration of the poly-N-isopropylacrylamide, which correlates with a decrease in the activity of the immobilized enzyme. The use of substrates with different structures and an irreversible inhibitor proves that the change in the properties of -chymotrypsin immobilized into the poly-N-isopropylacrylamide gel is related to the change in the rate constants of enzymatic reactions. Comparison of all experimental data obtained suggested an opportunity of local interactions between the protein globule and polymeric chains with a change in the hydration degree of poly-N-isopropylacrylamide during its phase transition.  相似文献   
4.
Summary 1. The stems of the fodder grassPhleum pratense contain a considerable amount of polysaccharides, lignin, and ash substances. They are characterized by a comparatively small amount of nitrogenous substances.2. The hemicelluloses of the material consist mainly of an arabinoglucuronoxylan the main chain of which consists of residues of -D-xylose connected in the 1 4 position. Side chains contain residues of L-arabofuranose, D-xylopyranose, and D-glucuronic and 4-O-methylglucuronic acids.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 686–689, November–December, 1975.  相似文献   
5.
Temperature dependencies of kinetic and equilibrium parameters of urea hydrolysis catalyzed by native urease and the urease immobilized in a thermosensitive poly-N-isopropylacrylamide gel have been studied. The swelling ratio of the collapsed urease-containing gel is shown to increase in the presence of urea. Below a lower critical solution temperature (LCST) of the polymer, the immobilized u reaseactually has thesame catalytic properties as the native enzyme. At temperatures above LCST, the observed catalytic activity of the immobilized enzyme depends chiefly not only on the thermoreversible matrix state, but also on gel water content.  相似文献   
6.
The basic experimental characteristics of incoherent interactions of 400 GeV protons on emulsion nuclei, such as the multiplicity of charged secondaries, one-particle distributions and two-particle correlations, are reported and discussed in details. They are compared with the results of other experiments on hadron-nucleus interactions at lower energies. We have shown from both the quantitative and qualitative comparison of the data presented with predictions of various model approaches to nuclear production, that most of them cannot explain the complete set of experimental observations.An analysis of the experimental data presented gives strong support to the idea that the production mechanism in high-energy hadron-nucleus interactions has two or multi-component character.  相似文献   
7.
Absorption and emission (5D47F5) spectra are reported for these complexes in methanol at room temperature. The effects of substitutents on the bands are discussed.We are indebted to A. A. Petrov for direction and for valuable comments.  相似文献   
8.
The effect of added nucleophiles (methanol and 1,4-butanediol) on the steady-state kinetics of α-chymotryptic hydrolysis of a series of N-acetyl-L-amino acid methyl esters, R-CH(NHCOCH3)C(O)OCH3, has been studied. As a result, the rate and equilibrium constants of the ‘elementary’ steps of the enzyme process have been determined. It has also been demonstrated how the free energy–reaction coordinate profile changes if the structure (the size of the hydrocarbon chain) of the ‘chemically inert’ substrate fragment R is varied. The effects observed can be described by the following equation: where ΔGs and ΔGa are the free energies of formation of metastable intermediates, i.e., the enzyme–substrate complex and the acylenzyme, respectively, ΔG2≠ and ΔG3≠ are the free energies of activation for the chemical steps, i.e., enzyme acylation and acylenzyme hydrolysis, respectively; and ΔGtrans(R) is the free energy of transfer of substrate group R from water into a nonaqueous solvent. To explain the results obtained, a mechanism for enzyme–substrate interaction is suggested according to which the potential free energy of sorption of substrate group R on the enzyme is 2 ΔGtrans(R). Such a high gain in the free energy of hydrophobic interaction may only be realized if (a) in the free enzyme the sorption region has a thermodynamically unfavorable contact with the aqueous medium, and (b) water is forced out of the active center as a result of the hydrophobic interaction of substrate group R with the enzyme. Such a model is in agreement with the published x-ray data on the structure of the crystalline enzyme. The kinetic experiment has proved that not all the potential free energy of sorption is realized as binding force. Thus the true free energy of the binding of substrate group R with the protein does not exceed half the maximum value, both in the enzyme–substrate complex and acylenzyme.  相似文献   
9.
10.
Conclusions 1. The action of an aqueous solution of caustic soda on xylan leads to the formation of both a molecular and an alkoxide form of this polysaccharide. The composition and amount of the alkoxide formed depend on the conditions of treating the xylan with alkali.2. In the reaction of an aqueous solution of caustic soda with xylan, the hydrogen of the alcohol grouping on the second carbon atom exhibits the greatest reactivity.3. The result of IR spectroscopy confirm the existence of a chemical interaction of the xylan with caustic soda.4. According to X-ray analysis, the action of a solution of caustic soda on xylan leads to a decrease in intermolecular interaction, to a more ordered supermolecular structure, and to the appearance of crystallinity.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 4, pp. 206–210, 1969  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号