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排序方式: 共有110条查询结果,搜索用时 31 毫秒
91.
Dr. Rajeev Ramanan Sodiq O. Waheed Prof. Christopher J. Schofield Dr. Christo Z. Christov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(46):11827-11836
Arginine methylation is an important mechanism of epigenetic regulation. Some Fe(II) and 2-oxoglutarate dependent Jumonji-C (JmjC) Nϵ-methyl lysine histone demethylases also have N-methyl arginine demethylase activity. We report combined molecular dynamic (MD) and Quantum Mechanical/Molecular Mechanical (QM/MM) studies on the mechanism of N-methyl arginine demethylation by human KDM4E and compare the results with those reported for N-methyl lysine demethylation by KDM4A. At the KDM4E active site, Glu191, Asn291, and Ser197 form a conserved scaffold that restricts substrate dynamics; substrate binding is also mediated by an out of active site hydrogen-bond between the substrate Ser1 and Tyr178. The calculations imply that in either C−H or N−H potential bond cleaving pathways for hydrogen atom transfer (HAT) during N-methyl arginine demethylation, electron transfer occurs via a σ-channel; the transition state for the N−H pathway is ∼10 kcal/mol higher than for the C−H pathway due to the higher bond dissociation energy of the N−H bond. The results of applying external electric fields (EEFs) reveal EEFs with positive field strengths parallel to the Fe=O bond have a significant barrier-lowering effect on the C−H pathway, by contrast, such EEFs inhibit the N−H activation rate. The overall results imply that KDM4 catalyzed N-methyl arginine demethylation and N-methyl lysine demethylation occur via similar C−H abstraction and rebound mechanisms leading to methyl group hydroxylation, though there are differences in the interactions leading to productive binding of intermediates. 相似文献
92.
Sinenhlanhla X. H. Mthembu Phiwayinkosi V. Dludla Khanyisani Ziqubu Tawanda M. Nyambuya Abidemi P. Kappo Evelyn Madoroba Thembeka A. Nyawo Bongani B. Nkambule Sonia Silvestri Christo J. F. Muller Sithandiwe E. Mazibuko-Mbeje 《Molecules (Basel, Switzerland)》2021,26(9)
Polyphenols are naturally derived compounds that are increasingly being explored for their various health benefits. In fact, foods that are rich in polyphenols have become an attractive source of nutrition and a potential therapeutic strategy to alleviate the untoward effects of metabolic disorders. The last decade has seen a rapid increase in studies reporting on the bioactive properties of polyphenols against metabolic complications, especially in preclinical models. Various experimental models involving cell cultures exposed to lipid overload and rodents on high fat diet have been used to investigate the ameliorative effects of various polyphenols against metabolic anomalies. Here, we systematically searched and included literature reporting on the impact of polyphenols against metabolic function, particularly through the modulation of mitochondrial bioenergetics within the skeletal muscle. This is of interest since the skeletal muscle is rich in mitochondria and remains one of the main sites of energy homeostasis. Notably, increased substrate availability is consistent with impaired mitochondrial function and enhanced oxidative stress in preclinical models of metabolic disease. This explains the general interest in exploring the antioxidant properties of polyphenols and their ability to improve mitochondrial function. The current review aimed at understanding how these compounds modulate mitochondrial bioenergetics to improve metabolic function in preclinical models on metabolic disease. 相似文献
93.
Christo Christov Alexander Kantardjiev Tatyana Karabencheva Frederik Tielens 《Chemical physics letters》2004,400(4-6):524-530
The influences of the electrostatic environment on the mechanisms of generation of rotational strengths in near-UV of β-lactamase TEM-1 are studied in two aspects: the first is the effects of ionized tyrosine chromophores and the second – the effects of the changes of the excitation energies of the chromophores under the local electrostatic interactions. The mechanisms of generation of rotational strengths by tyrosinate chromophores are described. It is shown that both effects (tyrosine ionizations and Coulomb interactions) influence the mechanisms of rotational strengths and the relative contributions of the chromophores in the near-UV. 相似文献
94.
Nina G. Sultanova Ivan D. Nikolov Christo D. Ivanov 《Optical and Quantum Electronics》2003,35(1):21-34
Ten types of American, Japanese, and German optical plastic (OP) materials are examined. The principal OPs are analysed: polymethyl methacrylate, polystyrene, polycarbonate, and styrene acrylonitrile. Refractive indices are measured and calculated for the principal and some new applicable OPs, namely NAS-21 Novacor, CTE-Richardson, Zeonex E48R, Optorez 1330 and Bayer for wavelengths from 435.8 to 1052 nm. A theoretical examination was made for computer modelling of OPs indices using Cauchy's dispersion formula. The dispersion coefficients and Abbe constants are calculated. The OPs indices computed for numerous laser wavelengths 442–1060 nm are presented. A more effective device and technology for the measurement of refractive index of OPs is realized with an accuracy of ±0.001. 相似文献
95.
Grabchev I Chovelon JM Petkov C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,71(1):100-104
A new 4-bromo-1,8-naphthalimide-labelled polyamidoamine (PAMAM) dendrimer from zero generation has been synthesised and characterised. Its functional characteristics, determined in acetonitrile solvent are discussed. The ability of the dendrimer to detect metal cations has been evaluated in acetonitrile by monitoring the quenching of the fluorescence intensity. Different metal cations have been tested Co(2+), Ni(2+), Cu(2+) and Fe(3+) for the purpose. The results have shown clearly that only Fe(3+) could be efficiently detected using the dendrimer. 相似文献
96.
Petrov P Yuan J Yoncheva K Müller AH Tsvetanov CB 《The journal of physical chemistry. B》2008,112(30):8879-8883
A transition from spherical to wormlike micelles of a poly(ethylene oxide) 20- block-poly(propylene oxide) 70- block-poly(ethylene oxide) 20 triblock copolymer Pluronic P123 induced by solubilization of a tetrafuctional monomer, Pentaerythritol tetraacrylate (PETA), in aqueous media has been studied. The wormlike micelles shape was locked by UV cross-linking of PETA within the micelles resulting in stabilized polymeric micelles (SPMs). The stability of SPMs in a good solvent for both polyether blocks like THF, and upon dilution below the critical micelle concentration (CMC) of P123 in water was confirmed by dynamic light scattering (DLS) and scanning force microscopy (SFM). Formation of cadmium sulfide (CdS) nanoparticles within the wormlike SPMs was carried out via the reduction of Cd (2+) with NaS and analyzed by transmission electron microscopy (TEM) and UV-vis absorption measurements. A stable water-dispersible hybrid system consisting of CdS quantum dots embedded into the wormlike SPMs was obtained. 相似文献
97.
Barbara Trzebicka Paweł Weda Alicja Utrata‐Wesołek Andrzej Dworak Christo Tsvetanov 《Journal of polymer science. Part A, Polymer chemistry》2010,48(18):4074-4083
An approach to nanoparticles based upon the thermosensitivity of a copolyether is described. Two thermosensitive copolymers of glycidol with molar masses of 800,000 g/mol randomly substituted with ethyl isocyanate (28 and 35% substitution) were used to obtain mesoglobules. The effects of copolymer concentration and of the presence of surfactants (sodium dodecyl sulfate and hexadecyltrimethylammonium bromide) on the size of the mesoglobules formed were investigated. The obtained mesoglobules were monomodal and of narrowly distributed diameters, as shown by dynamic light scattering and atomic force microscopy measurements. The radical nucleated copolymerization of N‐isopropylacrylamide with N,N′‐methylenebisacrylamide as a crosslinker was performed in the presence of the mesoglobules. Nanoparticles of monomodal size distribution and low dispersity were obtained. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4074–4083, 2010 相似文献
98.
The reaction of dichlorides of 3,3-disubstituted allenylphosphonic acids with chlorosulphonylisocyanate involves (2+2)-cycloaddition of the reagent at the C2-C3 double bond and results in the formation of 1-chlorosulphonyl-3-dichlorophosphonylmethyliden-2-azetidinones, until now inknown in the literature. 相似文献
99.
Christo Daiev Stoyan Alexandrov Lilan Daieva 《Analytical and bioanalytical chemistry》1968,239(6):369-377
Two non-destructive neutron activation methods has been described for the determination of indium in thallium metal and thallium compounds. The sensitivity of the first method based on114mIn corresponds to 1×10?6g (standard deviation 4,5–8%). The second method (by means of116mIn) permits the determination of ultramicro amounts of indium up to 5×10?11g with a standard deviation of 15%. The influence of many elements (such as Ga, Cu, Al, Cd, Zn, Pb, Ca, Mg, Bi, Fe) has been examined. The methods have been applied to the determination of indium in thallium metal, oxide, nitrate, sulphate and chloride. The data obtained agreed whith those of the spectrochemical determination. 相似文献
100.
Ana N. Nedelcheva Nikolay G. Vladimirov Christo P. Novakov Iliyana V. Berlinova 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5736-5744
A series of block copolymers comprising poly(N‐isopropylacrylamide) (PNIPAM) and poly(ethylene oxide) (PEO) end‐functionalized with a quaternary ammonium group (RQ) was synthesized by free‐radical polymerization of N‐isopropylacrylamide with well‐defined RQPEO macroazoinitiators. The radical termination occurred mainly by disproportionation, as confirmed by combining the data from size exclusion chromatography (SEC) and rheology measurements. The copolymers denoted RQExNy differ in type of the terminal group [FQ = C8F17(CH3)2N+ or MQ = (CH3)3N+] and in the length of the PEO (Ex; x = 4, 6, or 10 K) and PNIPAM (Ny; y = 7 or 17–19 K) blocks. The type of the terminal group determined the behavior of the block copolymers in the dilute and semidilute regime. Self‐assembled species formed by both FQ and MQ modified block copolymers were detected by static light scattering measurements at 25 °C and above the lower critical solution temperature (LCST). The LCST of the block copolymers depended on the type of the RQ group and the length of the blocks. FQ‐modified copolymers form elastic gels below and above the LCST. It was inferred that the FQ groups and the PNIPAM blocks form segregated microdomains that serve as junctions to maintain a viscoelastic network. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5736–5744, 2004 相似文献