排序方式: 共有86条查询结果,搜索用时 46 毫秒
41.
Malviya N Srivastava M Diwakar SK Mishra SK 《Applied biochemistry and biotechnology》2011,165(2):397-405
Polyphenol oxidases (PPOs) are widely distributed enzymes among animals, plants, bacteria, and fungi. PPOs often have significant
role in many biologically essential functions including pigmentation, sclerotization, primary immune response, and host defense
mechanisms. In the present study, forty-seven full-length amino acid sequences of PPO from bacteria, fungi, and plants were
collected and subjected to multiple sequence alignment (MSA), domain identification, and phylogenetic tree construction. MSA
revealed that six histidine, two phenylalanine, two arginine, and two aspartic acid residues were highly conserved in all
the analyzed species, while a single cysteine residue was conserved in all the plant and fungal PPOs. Two major sequence clusters
were constructed by phylogenetic analysis. One cluster was of the plant origin, whereas the other one was of the fungal and
bacterial origin. Motif GGGMMGDVPTANDPIFWLHHCNVDRLWAVWQ was found in all the species of bacterial and fungus sources. In addition,
seven new motifs which were unique for their group were also identified. 相似文献
42.
An atom economical, selective, and convenient one-pot protocol for the synthesis of the medicinally privileged novel chromeno [2,3-d] pyrimidine scaffold, viz, multicomponent reaction of barbituric acid derivatives, 1,3 cyclic diketone, and various aldehydes in the presence of tetra n-butyl ammonium iodide (TBAI) as an electrolyte in water media under room temperature, is reported. This ecologically sound novel concept offers environmentally benign synthetic route, short reaction times, and easy workup procedure with excellent yield (88% to 90%) and is also beneficial for diversity-oriented large-scale processes. The synthesized products were characterized by IR, MS, NMR, and CHN analysis. 相似文献
43.
Arti A. Singh Siti N.A. Zulkifli Michaela Meyns Patricia Y. Hayes James J. De Voss 《Tetrahedron: Asymmetry》2011,22(18-19):1709-1719
A series of highly enantioenriched hydroxy- and dihydroxy-fatty esters were required as part of our ongoing investigation into cytochrome P450BioI. This mediates the biosynthesis of pimelic acid via C–C bond cleavage of long chain fatty acids within Bacillus subtilis. Herein we report the synthesis of various stereoisomers of methyl 7-hydroxytetradecanoate, methyl 8-hydroxytetradecanoate, and methyl 7,8-dihydroxytetradecanoate in highly enantioenriched form, using a combination of asymmetric synthesis and a preparative enantioselective HPLC is reported. 相似文献
44.
Let R be a commutative ring with identity. Let Γ(R) denote the maximal graph corresponding to the non-unit elements of R, i.e., Γ(R) is a graph with vertices the non-unit elements of R, where two distinct vertices a and b are adjacent if and only if there is a maximal ideal of R containing both. In this paper, we have shown that, for any finite ring R which is not a field, Γ(R) is a Euler graph if and only if R has odd cardinality. Moreover, for any finite ring R ? R 1×R 2× · · · ×R n, where the R i is a local ring of cardinality p i αi for all i, and the p i’s are distinct primes, it is shown that Aut(Γ(R)) is isomorphic to a finite direct product of symmetric groups. We have also proved that clique(G(R)’) = χ(G(R)’) for any semi-local ring R, where G(R)’ denote the comaximal graph associated to R. 相似文献
45.
Arti Singh 《Optimization》2017,66(11):1931-1951
AbstractIn this paper, an optimal portfolio execution problem under price model which exhibits cointegration behaviour is proposed. The proposed problem is formulated as a quadratic programming problem. With different statistical procedures and parameter estimation methods, employed on real market financial data, the four portfolios are constructed with which, computational study is performed. It is shown that the trading strategies constructed out of portfolios with cointegrated price dynamics show significant reduction in execution cost. 相似文献
46.
Mashhood Ali S Maheshwari A Inder Fozdar B 《Magnetic resonance in chemistry : MRC》2007,45(3):253-256
(1)H NMR spectroscopic study of citalopram (CT) in the absence as well as in the presence of beta-cyclodextrin (beta-CD) in aqueous solution revealed the formation of four 1:1 beta-CD-CT inclusion complexes. The stoichiometry of the complexes was determined by the continuous variation (Job) method, which was further confirmed by Scott's method. The binding constants (K(R) and K(R, S)) were calculated using Scott's method. The structures of all the complexes have been proposed as shown in the diagrams. All the CT proton resonances showed splitting in the presence of beta-CD, owing to chiral discrimination by the beta-CD, between the two enantiomers. The chiral discrimination appears to be due to different modes of binding of the R- and S-CT in the complexes involving a CN-containing aromatic ring. 相似文献
47.
Sunil Kumar Khurshid Ahmad Santosh Kumar Behera Dipak T. Nagrale Anurag Chaurasia Manoj Kumar Yadav Sneha Murmu Yachana Jha Mahendra Vikram Singh Rajawat Deepti Malviya Udai B. Singh Raja Shankar Minaketan Tripathy Harsh Vardhan Singh 《Molecules (Basel, Switzerland)》2022,27(9)
Ralstonia solanacearum is among the most damaging bacterial phytopathogens with a wide number of hosts and a broad geographic distribution worldwide. The pathway of phenotype conversion (Phc) is operated by quorum-sensing signals and modulated through the (R)-methyl 3-hydroxypalmitate (3-OH PAME) in R. solanacearum. However, the molecular structures of the Phc pathway components are not yet established, and the structural consequences of 3-OH PAME on quorum sensing are not well studied. In this study, 3D structures of quorum-sensing proteins of the Phc pathway (PhcA and PhcR) were computationally modeled, followed by the virtual screening of the natural compounds library against the predicted active site residues of PhcA and PhcR proteins that could be employed in limiting signaling through 3-OH PAME. Two of the best scoring common ligands ZINC000014762512 and ZINC000011865192 for PhcA and PhcR were further analyzed utilizing orbital energies such as HOMO and LUMO, followed by molecular dynamics simulations of the complexes for 100 ns to determine the ligands binding stability. The findings indicate that ZINC000014762512 and ZINC000011865192 may be capable of inhibiting both PhcA and PhcR. We believe that, after further validation, these compounds may have the potential to disrupt bacterial quorum sensing and thus control this devastating phytopathogenic bacterial pathogen. 相似文献
48.
Malviya J. Kala S. Sharma L. K. Singh R. K. P. 《Russian Journal of Organic Chemistry》2019,55(5):686-693
Russian Journal of Organic Chemistry - Clean, practical, and efficient electrochemical synthesis of pharmaceutically relevant 4H-pyran derivatives by one-pot three-component combination of an aryl... 相似文献
49.
Recent studies in single-molecule enzyme kinetics reveal that the turnover statistics of a single enzyme is governed by the waiting time distribution that decays as mono-exponential at low substrate concentration and multi-exponential at high substrate concentration. The multi-exponentiality arises due to protein conformational fluctuations, which act on the time scale longer than or comparable to the catalytic reaction step, thereby inducing temporal fluctuations in the catalytic rate resulting in dynamic disorder. In this work, we study the turnover statistics of a single enzyme in the presence of inhibitors to show that the multi-exponentiality in the waiting time distribution can arise even when protein conformational fluctuations do not influence the catalytic rate. From the Michaelis-Menten mechanism of inhibited enzymes, we derive exact expressions for the waiting time distribution for competitive, uncompetitive, and mixed inhibitions to quantitatively show that the presence of inhibitors can induce dynamic disorder in all three modes of inhibitions resulting in temporal fluctuations in the reaction rate. In the presence of inhibitors, dynamic disorder arises due to transitions between active and inhibited states of enzymes, which occur on time scale longer than or comparable to the catalytic step. In this limit, the randomness parameter (dimensionless variance) is greater than unity indicating the presence of dynamic disorder in all three modes of inhibitions. In the opposite limit, when the time scale of the catalytic step is longer than the time scale of transitions between active and inhibited enzymatic states, the randomness parameter is unity, implying no dynamic disorder in the reaction pathway. 相似文献
50.
Arti Maheshwari Deepak Sharma 《Journal of inclusion phenomena and macrocyclic chemistry》2010,68(3-4):453-459
A detailed NMR (1H, COSY, and ROESY) spectroscopic study of complexation of Flunarazine (FL) with α- and β-CD was carried out. 1H NMR titration studies confirmed the formation of FL/α-CD and FL/β-CD complexes as evidenced by chemical shift variations of the proton resonances of both the CDs and FL. The stoichiometry of the complexes was determined to be 1:2 (FL/α-CD) and 1:1 (FL/β-CD) and overall binding constants were also calculated. It was confirmed with the help of ROESY spectral data that only one of the F-substituted aromatic ring and phenyl ring penetrate the α-CD cavity while both F-substituted aromatic rings as well as phenyl ring penetrates the β-CD cavity during complexation. The binding modes of FL/CD cavity interactions derived from ROESY experimental data show that the resulting complex of FL with β-CD possesses better induced fit interaction as compared to α-CD, which is responsible for the enhanced molecular stability with β-CD in comparison to α-CD. The mode of penetration of guest into the CD cavity and structures of the complexes has been established. 相似文献