共查询到20条相似文献,搜索用时 31 毫秒
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W. W. W. DE JONG 《Nature: New biology》1971,234(49):176-177
STUDIES of adult1 and foetal2 haemoglobin from the chimpanzee (Pan troglodytes) have shown that the amino-acid compositions of tryptic and chymotryptic peptides of the α, β and γ-chains are indistinguishable from those of man. The primary structures of chimpanzee α, β and γ-chains are therefore almost certainly identical to the homologous human chains. The two types of γ-chains found in man3, Gγ and Aγ, with glycine and alanine in position γ136, respectively, are likewise present in the chimpanzee2. 相似文献
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《Journal of Genetic Engineering and Biotechnology》2014,12(2):103-110
In the present investigation were evaluated the antifungal and antibacterial activities of Nano-silver (NS). Two separate experiments were done to evaluate the potential of silver nanoparticles in controlling the contamination of G × N15 micro-propagation. In the first experiment, a factorial experiment based on a completely randomized design with 15 treatments including five different NS concentrations (0, 50, 100, 150 and 200 ppm) and three soaking time of explants (3, 5 and 7 min) with five replications was conducted. In the other experiment, NS was added to Murashige and Skoog (MS) medium with concentrations of 0, 50, 100, 150 and 200 ppm in a completely randomized design. Results showed that the application of 100 and 150 ppm NS both as an immersion and as added directly to the culture medium significantly reduces internal and external contaminations compared with the control group. Using NS in culture medium was more efficient to reduce fungal and bacterial contamination than immersion. High concentrations of NS had an adverse effect on the viability of G × N15 single nodes and this effect was more serious in immersed explants in NS than directly added NS ones regarding the viability of buds and plantlet regeneration. In conclusion, due to high contamination of woody plants especially fruit trees and also adverse environmental effects of mercury chloride, the NS solution can be used as a low risk bactericide in micro-propagation of G × N15 and can be an appropriate alternative to mercury chloride in the future. 相似文献
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Agns Anne Christian Bourdillon Sandra Daninos Jacques Moiroux 《Biotechnology and bioengineering》1999,64(1):101-107
The inversion of configuration of L‐alanine can be carried out by combining its selective oxidation in the presence of NAD+ and L‐alanine dehydrogenase, electrochemical regeneration of the NAD+ at a carbon felt anode, and reductive amination of pyruvate, i.e., reduction of its imino derivative at a mercury cathode, the reaction mixture being buffered with concentrated ammonium/ammonia (1.28M / 1.28M). The dehydrogenase exhibits astonishing activity and stability under such extreme conditions of pH and ionic strength. The main drawback of the process is its slowness. At best, the complete inversion of a 10 mM solution of L‐alanine requires 140 h. A careful and detailed quantitative analysis of each of the key steps involved shows that the enzyme catalyzed oxidation is so thermodynamically uphill that it can be driven efficiently to completion only when both the coenzyme regeneration and the pyruvate reduction are very effective. The first condition is easily fulfilled. Under the best conditions, it is the rate of the chemical reaction producing the imine which controls the whole process kinetically. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 64: 101–107, 1999. 相似文献
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Yu. N. Vorobjev 《Molecular Biology》2005,39(5):777-784
Three-dimensional atomic models of complexes between yeast tRNAPhe and 10- or 15-mer oligonucleotides complementary to the 3′-terminal tRNA sequence have been constructed using computer modeling. It has been found that rapidly formed primary complexes appear when an oligonucleotide binds to the coaxial acceptor and T stems of the tRNAPhe along the major groove, which results in the formation of a triplex. Long stems allow the formation of a sufficiently strong complex with the oligonucleotide, which delivers its 3′-terminal nucleotides to the vicinity of the T loop adjoining the stem. These nucleotides destabilize the loop structure and initiate conformational rearrangements involving local tRNAPhe destruction and formation of the final tRNAPhe-oligonucleotide complementary complex. The primary complex formation and the following tRNAPhe destruction constitute the “molecular wedge” mechanism. An effective antisence oligonucleotide should consist of three segments—(1) complex initiator, (2) primary complex stabilizer, and (3) loop destructor—and be complementary to the (free end)/loop-stem-loop tRNA structural element. 相似文献
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Aimed at achieving a good understanding of the 3-dimensional structures of human α1A-adrenoceptor (α1A-AR), we have successfully developed its homology model based on the crystal structure of β2-AR. Subsequent structural refinements were performed to mimic the receptor’s natural membrane environment by using molecular
mechanics (MM) and molecular dynamics (MD) simulations in the GBSW implicit membrane model. Through molecular docking and
further simulations, possible binding modes of subtype-selective α1A-AR antagonists, Silodosin, RWJ-69736 and (+)SNAP-7915, were examined. Results of the modeling and docking studies are qualitatively
consistent with available experimental data from mutagenesis studies. The homology model built should be very useful for designing
more potent subtype-selective α1A-AR antagonists and for guiding further mutagenesis studies.
Figure The superposition of β2-AR crystal structure (gold ribbons) and α1A-AR homology model (blue ribbons) 相似文献
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V. A. Belyaev D. A. Kozlov A. A. Terent’ev A. E. Trenin 《Plasma Physics Reports》2017,43(10):1039-1041
A method for determining the lifetime of unstable ions is described. The method is based on measuring the decrease in the ion beam current onto a fixed detector with increasing path length of the ion beam from the ion source to the detector. The measurements performed for D? 2 and HD? molecular ions have shown that their lifetimes are 3.5 ± 0.1 and 4.4 ± 0.1 μs, respectively. 相似文献
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Jiří Vondrásek Jaroslav Šponar Pavel Hobza 《Journal of biomolecular structure & dynamics》2013,31(4):869-880
Abstract The empirical potential including the intra- and intermolecular energy terms was used to study the interaction of L-Lysine-L-Alanine-L-Alanine Tripeptide with four models of B-DNA with different compositions. On the basis of a detailed search of the respective potential energy surface, it was found that the peptide is preferentially bounded to the AT-rich sequences. Analysis of the different energy contributions indicated that the electrostatic term is responsible for this preference. The results agree with the experimental data on the selectivity of some DNA—binding proteins and polypeptides to AT—;rich DNA. 相似文献
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Moldogazieva NT Shaitan KV Antonov MY Vinogradova IK Terentiev AA 《Biochemistry. Biokhimii?a》2011,76(12):1321-1336
Conformational and dynamic properties of proteins and peptides play an important role in their functioning. However, mechanisms
that underlie this influence have not been fully elucidated. In the present work we computationally constructed analogs of
heptapeptide AFP14–20 (LDSYQCT) — one of the biologically active sites of human α-fetoprotein (AFP) — to study their conformational and dynamic
properties using molecular dynamics simulation. Analogs were obtained by point substitutions of amino acid residues taking
into account differences in their physicochemical properties and also on the basis of analysis of amino acid substitutions
in the AFP14–20-like motifs revealed in different physiologically active proteins. It is shown that changes in conformational mobility of
amino acid residues of analogs are due to disruption or arising of intramolecular interactions that, in turn, determine existence
of steric restrictions during rotation around covalent bonds of the peptide backbone. Substitution of an amino acid by another
one with significant difference in physicochemical properties may not lead to remarkable changes in conformational and dynamic
properties of the peptide if intramolecular interactions remain unchanged. 相似文献
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Further Characterization of <Emphasis Type="Italic">o</Emphasis><Superscript>s</Superscript> Mutation of Mouse β-Glucuronidase Locus 总被引:3,自引:0,他引:3
The operator noninducible mutation of the mouse β-glucuronidase locus is associated with a reduced electro-phoretic mobility for the enzyme. This suggests that the translational repressor, specified by the Tfm locus, recognizes a translatable segment of the messenger RNA it controls. 相似文献
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Site-directed mutagenesis of the calcium-binding site of α-amylase of <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> 总被引:1,自引:1,他引:0
Amylases that are active under acidic conditions (pH <6), at higher temperatures (>70 degrees C) and have less reliance on Ca(2+) are required for starch hydrolysis. The alpha-amylase gene of Bacillus licheniformis MTCC 6598 was cloned and expressed in Escherichia coli BL21. The calcium-binding site spanning amino acid residues from 104 to 200 in the loop regions of domain B and D430 in domain C of amylase were changed by site-directed mutagenesis and the resultant mutant amylases were analyzed. Calcium-binding residues, N104, D161, D183, D200 and D430, were replaced with D104 and N161, N183, N200 and N430, respectively. Mutant amylase with N104D had a slightly decreased activity at 30 degrees C but a significantly improved specific activity at pH 5 and 70 degrees C, which is desirable character for a food enzyme. The amylase mutants with D183N or D200N lost all activity while the mutant amylase with D161N retained its activity at 30 degrees C but had significantly less activity at 70 degrees C. On the other hand, the activity of the mutant amylase with D430N was not changed at 30 degrees C but had an improved activity at 70 degrees C. 相似文献