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11.
Tobias M. Hedison Muralidharan Shanmugam Derren J. Heyes Ruth Edge Nigel S. Scrutton 《Angewandte Chemie (International ed. in English)》2020,59(33):13936-13940
Redox active metalloenzymes catalyse a range of biochemical processes essential for life. However, due to their complex reaction mechanisms, and often, their poor optical signals, detailed mechanistic understandings of them are limited. Here, we develop a cryoreduction approach coupled to electron paramagnetic resonance measurements to study electron transfer between the copper centers in the copper nitrite reductase (CuNiR) family of enzymes. Unlike alternative methods used to study electron transfer reactions, the cryoreduction approach presented here allows observation of the redox state of both metal centers, a direct read‐out of electron transfer, determines the presence of the substrate/product in the active site and shows the importance of protein motion in inter‐copper electron transfer catalyzed by CuNiRs. Cryoreduction‐EPR is broadly applicable for the study of electron transfer in other redox enzymes and paves the way to explore transient states in multiple redox‐center containing proteins (homo and hetero metal ions). 相似文献
12.
An efficient and modest protocol has been utilized for the synthesis of bicyclic dilactam derivatives through one-pot multicomponent domino reaction starting from various cyclic ketones under mild condition. The synthesized motif shows four stereogenic centers with two quaternary amine functionalities and such molecular arrangements are very fascinating and rare to obtain. We propose a mechanism for the formation of bicyclic dilactams through aldol condensation/condensation of cyanoacetamides/cyclization of condensed intermediate. 相似文献
13.
14.
Sivakumar T Manavalan R Muralidharan C Valliappan K 《Journal of separation science》2007,30(18):3143-3153
Statistical experimental design and Derringer's desirability function were applied to develop an improved RP-HPLC method for the simultaneous analysis of amlodipine and atorvastatin in pharmaceutical formulations. Four independent factors were considered: acetonitrile content in the mobile phase; buffer pH; buffer concentration; and flow rate. The preliminary screening step was carried out, according to a 2(4-1) fractional factorial design, to identify the significant factors affecting the analysis time response. Then central composite design was applied for a response surface study, in order to examine in depth the effects of the most important factors. Subsequently, Derringer's desirability function was employed to simultaneously optimize the six responses: retention factor of first peak; two resolutions; and three retention times, each having a different target. This procedure allowed deduction of two separate optimum conditions, intended for the analysis of quality control and plasma samples, within the experimental domain. The predicted optimum for the quality control samples was: methanol-acetonitrile-15 mM K(2)HPO(4) buffer (pH 5.33) (10:42.08:47.92, v/v/v) as the mobile phase and 1.12 mL/min as the flow rate. The method using this optimized condition showed higher sensitivity and shorter analysis time than the previously published reports. The optimized assay condition was validated according to International Conference on Harmonization guidelines. 相似文献
15.
E. Mothi Mohamed Samraj Muralidharan Krishnaswamy Panchanatheswaran Rengan Ramesh John N. Low Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):o367-o369
Molecules of the title compound, alternatively called (R,R)‐N,N′‐bis(3‐methoxysalicylidene)‐trans‐cyclohexane‐1,2‐diamine, C22H26N2O4, contain two intramolecular O—H⃛N hydrogen bonds and adopt a conformation with approximate twofold rotational symmetry. The molecules are linked by three C—H⃛O hydrogen bonds [H⃛O = 2.45–2.55 Å, C⃛O = 3.329 (2)–3.398 (2) Å and C—H⃛O = 142–172°] into a continuous framework. 相似文献
16.
S. Ramalingam V. S. Muralidharan A. Subramania 《Journal of Solid State Electrochemistry》2009,13(11):1777-1783
Cu-TiO2 nanocomposites were prepared by electrodeposition method onto copper substrate using an acid copper plating bath containing
dispersed nanosized TiO2. The composition of codeposited TiO2 nanoparticles in the composite coatings was controlled by the addition of different concentrations of TiO2 nanoparticles in the bath solution. The average crystallite size was calculated by using X-ray diffraction analysis and it
was ~32 nm for electrodeposited copper and ~33 nm for Cu-TiO2 composite coatings. The crystallite structure was fcc for electrodeposited copper and Cu-TiO2 nanocomposite coatings. The surface morphology and composition of the nanocomposites were examined by scanning electron microscopy
and energy dispersive X-ray spectroscopy analysis. The effect of TiO2 content on the corrosion and wear resistance properties of the nanocomposite coatings was also presented. The codeposited
TiO2 nanoparticles in the deposit increased the corrosion and wear resistance, which were closely related with TiO2 content in the nanocomposites. The wear resistance and microhardness of the Cu-TiO2 nanocomposite coatings were higher than electrodeposited copper. The corrosion resistance property of the electrodeposited
copper and Cu-TiO2 nanocomposite coatings was evaluated by electrochemical impedance and Tafel polarization studies. Cu-TiO2 composite coatings were more corrosion resistant than electrodeposited copper. 相似文献
17.
P. Mohan K. Arunsunai Kumar G. Paruthimal Kalaignan V. S. Muralidharan 《Journal of Solid State Electrochemistry》2012,16(12):3695-3702
Pristine- and chromium-substituted LiNiO2 nanoparticles were synthesized by sol-gel method using nitrate precursor at 800?°C for 12?h. Physical properties of the synthesized product were analyzed using Fourier transform infrared, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive analysis X-ray. XRD studies revealed a well-defined layer structure and a linear variation of lattice parameters with the addition of chromium and no impurities. Surface morphology and particle size of synthesized materials were changed with chromium addition using SEM and TEM analyses. Assembled lithium-ion cells were evaluated for charge/discharge studies at different rates, cyclic voltammetry, and electrochemical impedance spectra. The initial discharge capacity of LiNiO2 cathode material was found to be 168?mA hg?1; however, discharge capacity increased in chromium substitution. Electrochemical impedance spectroscopy revealed that LiCr0.10Ni0.90O2 could enhance charge transfer resistance upon cycling. The substitution of Ni with chromium, LiCr0.10Ni0.90O2, had better cycle life, low irreversible capacity, and excellent electrochemical performance. 相似文献
18.
R. Kalirajan V. Muralidharan S. Jubie B. Gowramma S. Gomathy S. Sankar K. Elango 《Journal of heterocyclic chemistry》2012,49(4):748-754
This article focuses on the synthesis of new series of pyrazole‐substituted 9‐anilinoacridine derivatives 5a – m and 6a – l . The compounds were confirmed by physical and analytical data. The synthesized compounds when screened for in vitro antioxidant activity showed promising activity for many compounds. The selected compounds were screened for cytotoxic activity showed promising inhibition of HEp‐2 cell line for the compounds 6c , 6e , and 6f . 相似文献
19.
K. Muralidharan 《商业与工业应用随机模型》2001,17(4):331-343
The modulated power law process (MPLP) is often used to model failure data from repairable system, when both renewal type behaviour and time trends are present. The MPLP allows for the failure rate of a system to be affected by the failure and repair. Since the MLEs of the estimates do not have closed form expressions, they have to be approximated, and hence deriving a test procedure will be difficult. Black and Rigdon (1996) have proposed asymptotic MLEs and asymptotic likelihood ratio tests for the parameters which also do not have closed form expressions and hence are not easy for application. In this paper, we derive a closed form expression for the test statistics which is simple and easy to apply for testing (i) H0: β=1 versus H1: β≠1 when κ is known and (ii) H0: (β=1 and κ=1) versus H1: (β≠1 or κ≠1). The simulation study for percentiles and powers are given. We also compare the performance of the test with that of Black and Rigdon's (1996) test. Some numerical examples are also provided to illustrate the testing procedures. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
20.
Arun K. Prasad P. Giridhar Visalakshi Ravindran V. Muralidharan 《Journal of Solid State Electrochemistry》2001,6(1):63-68
Zinc-cobalt alloy electrodeposits offer enhanced corrosion protection to steel, compared to zinc deposits. A near neutral
zinc-cobalt alloy sulfate bath was developed. In the absence of β-naphthol and sodium lauryl sulfate (SLS), only a light grey
and non-uniform deposit was obtained. Addition of boric acid yielded a grey and uniform deposit. To obtain the grey uniform
alloy deposit, the optimum bath composition was: 0.5 M ZnSO4, 0.5 M CoSO4, 40 g/L H3BO3, 0.865 g/L SLS and 0.345 g/L β-naphthol. The current efficiency for alloy deposition was 50% in the current density range
0.5–2.5 A/dm2. X-ray fluorescence studies on the alloy deposit formed on steel revealed 58–75% zinc on the surface. Anodic stripping voltammetric
studies were carried out on zinc-cobalt alloy films formed on glassy carbon to identify the phases formed in the alloy. Zn-Co
alloy film dissolution peaks suggested the existence of β, β1 and γ phases of the alloy.
Electronic Publication 相似文献