scispace - formally typeset
Topic

Selenourea

About: Selenourea is a(n) research topic. Over the lifetime, 353 publication(s) have been published within this topic receiving 4054 citation(s).

...read more

Papers
  More

Journal ArticleDOI: 10.1016/0003-9861(91)90456-S
Abstract: Various inorganic selenocompounds dose-dependently inhibited the rat brain prostaglandin (PG) D synthase, both in the purified enzyme preparation and in the crude brain supernatant. All of the quadrivalent selenium compounds tested had a very limited range of IC 50 values in the purified enzyme (11–12 μ m ) and in the brain supernatant (9–15 μ m ). A divalent selenium compound was also inhibitory, but a hexavalent selenium compound was ineffective. In contrast, organic selenocompounds such as selenomethionine and selenourea had no effect on the PGD synthase activity. Furthermore, sodium sulfate and sodium sulfite up to 10 m m did not inhibit the activity. The inhibition by selenium required the preincubation of the metal with sulfhydryl compounds such as dithiothreitol (DTT), indicating that the formation of selenotrisulfide or some other adduct(s) is essential for the inhibition. Furthermore, the inhibition was reversed by an excess amount of dithiothreitol, suggesting that the selenotrisulfide derivative of DTT binds to the SH group of the PGD synthase. The kinetic analysis revealed the inhibition by selenite to be noncompetitive with a K i value of 10.1 μ m . On the other hand, glutathione-dependent PGD synthase from rat spleen was much less inhibited, and PGF synthase and PGD 2 11-ketoreductase activities were not inhibited by the selenium compound.

...read more

Topics: Selenium Compound (58%), Prostaglandin-D synthase (57%), Selenourea (54%) ...read more

73 Citations


Journal ArticleDOI: 10.1039/A707101I
Abstract: A vesicle mediated high performance liquid chromatographic (HPLC)–microwave digestion (MW)–hydride generation (HG) system coupled on-line with atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS) has been assessed for selenium species separation and detection. Selenocystine, selenomethionine, selenoethionine, selenourea, SeIV and SeVI are separated by vesicle mediated chromatography prior to on-line selenocompounds microwave digestion with a KBrO3–HBr mixture to generate SeIV continuously, which is finally transformed into SeH2, in a continuous manner with a merging flow of sodium tetrahydroborate(III). Analytical characteristics of this coupling are compared with those obtained coupling HPLC–ICP-MS via conventional nebulisation. Detection limits (DLs) obtained for selenocystine, selenomethionine, selenoethionine, selenite and selenate in spiked human urine, when ICP-MS was used as detector, ranged between 1.0 and 5.3 µg l–1 (51–267 pg), while precision ranged between±3.4 and±8.4%. This continuous system, vesicle mediated HPLC–MW–HG–atomic detection, allows the separation and detection of selenocystine, selenourea, selenomethionine, selenoethionine, selenite and selenate in human urine. The analytical versatility of such coupling (with ICP-MS as the atomic detector) allows basal selenium speciation in urine. Three different normally occurring selenium species in human urine, simply diluted (1+1), have been found. The relative sophistication of the vesicle mediated–HPLC–MW–HG–ICP-MS interface, versus HPLC–ICP-MS via conventional nebulisation, can be justified because of its considerably higher sensitivity for most of the selenocompounds assayed, lower matrix interferences and the possibility of simultaneous interference free 77Se and 78Se monitoring.

...read more

Topics: Inductively coupled plasma mass spectrometry (56%), Microwave digestion (55%), Selenium (54%) ...read more

68 Citations


Journal ArticleDOI: 10.1016/0584-8539(76)80136-5
Abstract: The i.r. spectra of solid and in CH3CN dissolved normal urea and thiourea, their 15N and 2H isotopic species, and solid selenourea-D4 were recorded. The normal coordinate analysis of 13 in-plane vibrations of these molecules, including the in-plane vibrations of urea-18O assigned by Laulicht [1] has been made using Wilson's GF matrix method and the Urey Bradley force field. The Urey—Bradley force field reproduces well the heavy istope frequency shifts. Several sets of force constants have been calculated and their validity is discussed in terms of other bond characteristics. The values of KCN force constants increase in this order of urea, thiourea and selenourea. The frequency shifts and the differences in the force constants of ureas and thioureas in the solid phase and in solution show that hydrogen bonding strongly affects the potential energy distribution, specially for the CO stretching mode.

...read more

Topics: Thiourea (55%), Selenourea (54%), Potential energy (50%)

67 Citations


Open accessJournal ArticleDOI: 10.1021/JACS.6B11021
Abstract: We report a tunable library of N,N,N′-trisubstituted selenourea precursors and their reaction with lead oleate at 60–150 °C to form carboxylate-terminated PbSe nanocrystals in quantitative yields. Single exponential conversion kinetics can be tailored over 4 orders of magnitude by adjusting the selenourea structure. The wide range of conversion reactivity allows the extent of nucleation ([nanocrystal] = 4.6–56.7 μM) and the size following complete precursor conversion (d = 1.7–6.6 nm) to be controlled. Narrow size distributions (σ = 0.5–2%) are obtained whose spectral line widths are dominated (73–83%) by the intrinsic single particle spectral broadening, as observed using spectral hole burning measurements. The intrinsic broadening decreases with increasing size (fwhm = 320–65 meV, d = 1.6–4.4 nm) that derives from exciton fine structure and exciton–phonon coupling rather than broadening caused by the size distribution.

...read more

Topics: Selenourea (56%), Doppler broadening (54%), Spectral hole burning (52%) ...read more

66 Citations


Journal ArticleDOI: 10.1021/JP0678047
Daocheng Pan1, Qiang Wang1, Shichun Jiang1, Xiangling Ji1  +1 moreInstitutions (1)
Abstract: Colloidal CdSe and CdS quantum dots were synthesized at low temperatures (60-90 degrees C) by a two-phase approach at a toluene-water interface. Oil-soluble cadmium myristate (Cd-MA) was used as cadmium source, and water-soluble Na2S, thiourea, NaHSe, Na2SeSO3, and selenourea were used as sulfur and selenium sources, respectively. When a cadmium precursor in toluene and a selenium precursor in water were mixed, CdSe nanocrystals were achieved at a toluene-water interface in the range of 1.2-3.2 nm in diameter. Moreover, we also synthesized highly luminescent CdSe/CdS core-shell quantum dots by a two-phase approach using poorly reactive thiourea as sulfur source in an autoclave at 140 degrees C or under normal pressure at 90 degrees C. Colloidal solutions of CdSe/CdS core-shell nanocrystals exhibit a photoluminescence quantum yield (PL QY) up to 42% relative to coumarin 6 at room temperature.

...read more

Topics: Selenourea (52%), Quantum dot (52%), Thiourea (50%)

63 Citations


Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202114
202011
201912
201816
201716
201611

Top Attributes

Show by:

Topic's top 5 most impactful authors

Mamoru Koketsu

19 papers, 256 citations

Hideharu Ishihara

11 papers, 129 citations

Heinz Heimgartner

8 papers, 163 citations

Anvarhusein A. Isab

7 papers, 90 citations

B. Mishra

7 papers, 123 citations

Network Information
Related Topics (5)
Steric effects

16.1K papers, 319.6K citations

83% related
Trifluoromethanesulfonate

7.7K papers, 163.7K citations

82% related
Pyridine

39.7K papers, 561.9K citations

82% related
Furan

9K papers, 111.2K citations

82% related
Cis–trans isomerism

7.8K papers, 122.5K citations

82% related