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排序方式: 共有343条查询结果,搜索用时 15 毫秒
1.
2.
An electrolytic device for decomposition of water has been developed which readily gives hydrogen and oxygen for isotopic measurement with a mass spectrometer. A 20-mul sample can be decomposed quantitatively in 10 min with good reproducibility. The results produced are comparable with those obtained by reduction with uranium. 相似文献
3.
Boruah A Rao IN Nandy JP Kumar SK Kunwar AC Iqbal J 《The Journal of organic chemistry》2003,68(12):5006-5008
A cis-proline derived cyclic mimic of a type VI beta-turn is synthesized via a ring-closing metathesis reaction. The solution NMR conformational study indicates that the major conformer of the cyclic peptide adopts a type VIa beta-turn in CDCl(3) and a type VIb beta-turn in DMSO-d(6). 相似文献
4.
Acetates derived from the adducts of the Baylis-Hillman reaction can be reacted in a regioselective manner with amines in the presence of palladium(0) catalyst to afford alpha-dehydro-beta-amino esters (2 and 3) in good yields. The regioselectivity of the reaction can be controlled by temperature and reaction medium leading to the synthesis of regioisomers 2 or 3. The alpha-dehydro-beta-amino acid 3 is a turn inducer, and the dipeptides 6 derived from it show the presence of an eight-membered intramolecular hydrogen bond. Also, cobalt(II) chloride catalyzes the cleavage of epoxy peptides with alpha-dehydro-beta-amino acid derivative 3b to afford the corresponding dipeptide derivatives 8, which exhibit an intramolecular hydrogen bond and thus mimic a beta-turn. This intramolecular hydrogen bonding preorganizes the corresponding diallylated peptide 8c for cyclization via ring-closing metathesis to afford the cyclic peptide 9 as a constrained mimic of a beta-turn. 相似文献
5.
Nandy JP Prabhakaran EN Kumar SK Kunwar AC Iqbal J 《The Journal of organic chemistry》2003,68(5):1679-1692
A novel chemo- and diastereoselective aerobic epoxidation of the N-cinnamoyl peptides catalyzed by polyaniline-supported cobalt(II) salen (PASCOS) is described. The N-cinnamoyl proline derived peptides 1 show a high pi-facial selectivity during these epoxidations. The origin of this diastereoselectivity in 1 has been attributed to (i) the propensity of the N-cinnamoyl proline amide to exist predominantly as trans rotamer in CDCl3, DMSO-d6, and CH3CN medium and (ii) existence of these peptides as organized structures (gamma- and beta-turns) due to the presence of intramolecular hydrogen bonds. An extensive solution NMR and MD simulation study on 1d and 1f indicates that the origin of the high pi-facial selectivity is due to the well-defined gamma- and beta-turns which result in the hindrance of one face of the cinnamoyl double bond in the transition state of the epoxidation reaction. 相似文献
6.
Mechanically attached, solid-state films of [Os(4,4'-diphenyl-2,2'-dipyridyl)2Cl2] have been formed on gold macro- and microelectrodes and their voltammetric properties investigated. The voltammetric response of these films associated with the Os(2+/3+) redox reaction is reminiscent of that observed for an ideal reversible, solution phase redox couple only when the contacting electrolyte contains of the order of 40% v/v of acetonitrile (ACN). The origin of this effect appears to involve preferential solvation of the redox centres by acetonitrile which facilitates the incorporation of charge compensating counterions. Scanning electron microscopy reveals that voltammetric cycling in 40:60 ACN-H2O containing 1.0 M LiClO4 as the electrolyte induces the formation of microcrystals. Voltammetry conducted under semi-infinite linear diffusion conditions has been used to determine the apparent diffusion coefficient, Dapp, for homogeneous charge transport through the deposit. The dynamics of charge transport decrease with increasing film thickness but appear to increase with increasing electrolyte concentration. These observations suggest that ion transport rather than the rate of electron self-exchange limit the overall rate of charge transport through these solids. When in contact with 40:60 ACN-H2O containing 1.0 M LiClO4 as electrolyte, Dapp values for oxidation and reduction are identical at 1.7 +/- 0.4 x 10(-12) cm2 s(-1). In the same electrolyte, the standard heterogeneous electron transfer rate constant, k(o), determined by fitting the full voltammogram using the Butler-Volmer formalism, is 8.3 +/- 0.5 x 10(-7) cm s(-1). The importance of these results for the rational design of solid state redox active materials for battery, display and sensor applications is considered. 相似文献
7.
A kinetic assay for total calcium in serum was developed which is based on the activation of Ca(++)-ATPase by free Ca(++) [Ca(++)](f) maintained by EGTA in the reaction mixture. The concentration of Ca(++)(f) was dependent on total reference calcium added or serum calcium. Ca(++)-ATPase activity was coupled to the reduction of NADH by pyruvate kinase (PK) and lactate dehydrogenase (LDH) and monitored by change in absorbance at 340 nm. The calcium in normal serum was 10.08 +/- 0.24 mg/dl (n = 35) by our method while with o-cresolphthalein complexone (CPC) method, the total calcium in the same 35 serum samples was 10.14 +/- 0.54 mg/dl. The range of within-run coefficient of variations (CVs) by this method was 0.9-2.87% at 8-12 mg/dl and day-to-day CVs were 0.72-3.17%. The presence of other ions and standard clinical interfering agents did not affect this assay system. The correlation between values obtained with our method (y) and CPC method (x) for normal serum was: y = 1.064x-0.580 mg/dl (r = 0.912, n = 59). 相似文献
8.
Riaz Qadeer Javed Hanif M. Saleem M. Afzal 《Journal of Radioanalytical and Nuclear Chemistry》1992,157(2):321-334
The adsorption of thorium on activated charcoal has been studied as a function of shaking time, amount of adsorbent, pH, concentration of adsorbate and temperature. Adsorption of thorium obeys the Langmuir isotherm. H0 and S0 were calculated from the slope and intercept of ln KD vs. 1/T plots. The influence of different anions and cations on thorium adsorption has been examined. The adsorption of other metal ions on activated charcoal has been studied under specified conditions to check its selectivity. Consequently, thorium was removed from Cs, Co, Ba, Cr, Sr, Cd, Cu, Mn and Zn. More than 98% adsorbed thorium on activated charcoal can be recovered with 55 ml 3M HNO3 solution. Wavelength dispersive X-rays fluorescence spectrometer was used for measuring thorium concentration. 相似文献
9.
Mujahid Farid Muhammad Abubakar Zaki Ul Zaman Asam Wajiha Sarfraz Mohsin Abbas Muhammad Bilal Shakoor Shafaqat Ali Sajid Rashid Ahmad Asim Jilani Javed Iqbal Abdullah G. Al-Sehemi Omar A. Al-Hartomy 《Molecules (Basel, Switzerland)》2022,27(13)
We investigated how different doses of microwave irradiation (MR) affect seed germination in Sorghum, including the level of remediation against textile and surgical wastewater (WW) by modulating biochemical and morpho-physiological mechanisms under glutamic acid (GA) application. The experiment was conducted to determine the impact of foliar-applied GA on Sorghum under wastewater conditions. Plants were treated with or without microwave irradiation (30 s, 2.45 GHz), GA (5 and 10 mM), and wastewater (0, 25, 50, and 100). Growth and photosynthetic pigments were significantly decreased in plants only treated with various concentrations of WW. GA significantly improved the plant growth characteristics both in MR-treated and -untreated plants compared with respective controls. HMs stress increased electrolyte leakage (EL), hydrogen peroxide (H2O2), and malondialdehyde (MDA) content; however, the GA chelation significantly improved the antioxidant enzymes activities such as ascorbate oxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) both in MR-treated and -untreated plants under WW stress compared with respective controls. The results suggested that the MR-treated plants accumulate higher levels of HMs under GA addition in comparison to the WW-only-treated and MR-untreated plants. The maximum increase in Cd accumulation was observed in the range of 14–629% in the roots, 15–2964% in the stems, and 26–4020% in the leaves; the accumulation of Cu was 18–2757% in the roots, 15–4506% in the stems, and 23–4605% in the leaves; and the accumulation of Pb was 13–4122% in the roots, 21–3588% in the stems, and 21–4990% in the leaves under 10 mM GA and MR-treated plants. These findings confirmed that MR-treated sorghum plants had a higher capacity for HMs uptake under GA and could be used as a potential candidate for wastewater treatment. 相似文献
10.
Javed Iqbal Banzeer Ahsan Abbasi Tariq Mahmood Safia Hameed Akhtar Munir Sobia Kanwal 《应用有机金属化学》2019,33(8)
In the present report, Nickel oxide nanoparticles (NiONPs) were synthesized using Rhamnus virgata (Roxb.) (Family: Rhamnaceae) as a potential stabilizing, reducing and chelating agent. The formation, morphology, structure and other physicochemical properties of resulting NiONPs were characterized by Ultra violet spectroscopy, X‐ray diffraction (XRD), Fourier Transform Infrared analysis (FTIR), Scanning electron microscopy (SEM), Energy‐dispersive‐spectroscopy (EDS), Transmission electron microscopy (TEM), Raman spectroscopy and dynamic light scattering (DLS). Detailed in vitro biological activities revealed significant therapeutic potential for NiONPs. The antimicrobial efficacy of biogenic NiONPs was demonstrated against five different gram positive and gram negative bacterial strains. Klebsiella pneumoniae and Pseudomonas aeruginosa (MIC: 125 μg/mL) were found to be the least susceptible and Bacillus subtilis (MIC: 31.25 μg/mL) was found to be the most susceptible strain to NiONPs. Biogenic NiONPs were reported to be highly potent against HepG2 cells (IC50: 29.68 μg/ml). Moderate antileishmanial activity against Leishmania tropica (KMH23) promastigotes (IC50: 10.62 μg/ml) and amastigotes (IC50: 27.58 μg/ml) cultures are reported. The cytotoxic activity was studied using brine shrimps and their IC50 value was recorded as 43.73 μg/ml. For toxicological assessment, NiONPs were found compatible towards human RBCs (IC50: > 200 μg/ml) and macrophages (IC50: > 200 μg/ml), deeming particles safe for various applications in nanomedicines. Moderate antioxidant activities: total antioxidant capacity (TAC) (51.43%), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) activity (70.36%) and total reducing power (TRP) (45%) are reported for NiONPs. In addition, protein kinase and alpha amylase inhibition assays were also performed. Our results concluded that Rhamnus virgata synthesized NiONPs could find important biomedical applications with low cytotoxicity to normal cells. 相似文献