Vanadate

About: Vanadate is a research topic. Over the lifetime, 4497 publications have been published within this topic receiving 120109 citations. The topic is also known as: vanadate.

Morphological control and luminescence properties of lanthanide orthovanadate LnVO4 (Ln = La to Lu) nano-/microcrystals viahydrothermal process

Abstract: Lanthanide orthovanadate LnVO4 (Ln = La to Lu) nano-/microcrystals with multiform crystal structures (monoclinic and tetragonal) and morphologies (separated nanoparticles, micropancake, microdoughnut and spherical aggregates) were successfully synthesized by a facile, effective, and environmentally friendly hydrothermal method. X-Ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, photoluminescence spectra, low-voltage cathodoluminescence, and kinetic decays were used to characterize the samples. The experimental results indicated that the use of the organic additive trisodium citrate (Cit3−) has an obvious impact on the morphologies of the products. The possible formation mechanisms for LnVO4 nano-/microcrystals with diverse well-defined morphologies have been presented in detail. Additionally, we systematically investigate the luminescent properties of the LuVO4:Ln3+ (Ln = Eu, Sm and Dy). Due to an efficient energy transfer from vanadate groups to the dopants, LuVO4:Ln3+ (Ln = Eu, Sm and Dy) phosphors showed the strong characteristic emission of Ln3+ under ultraviolet excitation and low-voltage electron beam excitation. Furthermore, the PL emission color of LuVO4:Ln3+ (Ln = Eu, Sm and Dy) phosphors can be tuned from blue to red, orange-red, and green easily by partial replacement VO43− with PO43− and changing the doping concentrations (x) of Ln3+.

The search for a hypothalamic Na+,K+-ATPase inhibitor.

Abstract: Accumulating experimental evidence suggests that natriuresis in response to intravascular volume expansion is promoted by an endogenous regulator of Na+,K+-adenosine triphosphatase (ATPase). Efforts to purify this substance by a number of laboratories have as yet been unsuccessful. The properties of partially purified inhibitors from plasma, urine, and tissue often fail to possess the characteristics thought to be consistent with those of a physiological regulator. These include potency (Ki of approximately 1 nM), reversibility of inhibition, specificity for Na+,K+-ATPase, and responsiveness to relevant physiological stimuli. Two rather different candidate substances, extracted from urine and hypothalamus, have been purified to a high degree. Neither is a peptide, and both are of low molecular weight and resistant to acid hydrolysis. The substance from urine is rather nonpolar and interacts with digoxin-specific antibodies, while that from hypothalamus is polar and does not appear to share epitopes with the cardiac glycosides. On the serosal surface of the toad urinary bladder, the hypothalamic substance causes a reversible inhibition of Na+ transport, inhibits rubidium uptake in red blood cells by acting on the membrane's exterior surface, inhibits binding of ouabain to purified Na+,K+-ATPase, and reversibly inhibits hydrolysis of adenosine 5'-triphosphate by the enzyme with a Ki of 1.4 nM. The hypothalamic inhibitor may be differentiated from ouabain by their respective ionic requirements for optimal inhibition of enzymatic activity, and although both ouabain and the hypothalamic inhibitor fix Na+,K+-ATPase in its E2 conformation, the hypothalamic inhibitor does not promote phosphorylation of the enzyme by inorganic phosphate in the presence of Mg2+. Ionic requirements for inhibition also differentiate the hypothalamic inhibitor from vanadate ion, as does the inhibitor's activity in the presence of norepinephrine. Further enzymological and physiological studies will be facilitated by structural characterizations of the inhibitory substances and by the availability of a method to measure their concentrations in physiological fluids.

Reaction of Vanadate with Aquatic Humic Substances: An ESR and 51V NMR Study

Abstract: Electron spin resonance (ESR) spectroscopy and 51V nuclear magnetic resonance (NMR) spectroscopy have been used to study the interaction of vanadate with aqueous solutions of humic substances (HS) at different pH values and at different concentrations. Under acidic pH conditions, ESR spectra show that humic substances reduce vanadium(V) to vanadium(IV) without further reduction to vanadium(III). The reduced vanadium(IV) ion is bound to oxygen donor atoms, probably at carboxylic acid sites in the humic substances. 51V NMR spectra show that the VO2+ cation is immediately reduced and that the decavanadate cation decomposes to the VO2+ cation prior to reduction. The overall rate of reduction depends on both concentration and pH. There is no reduction above pH 6, which suggests that the standard reduction potential of humic substances is about +0.65 V. Near pH 7, vanadate is stabilized by binding to humic substances. As the concentration of humic substances increases, the total vanadium NMR signal intensity de...

Acridine orange as a fluorescent probe for lysosomal proton pump.

Abstract: Acridine orange was found to accumulate in pure lysosomal particles (tritosomes) in vitro, and the quenching of its fluorescence correlated well with the delta pH (inside acid) across the lysosomal membrane. Use of this dye showed that Mg-ATP caused lysosomal acidification. This acidification was sensitive to N,N'-dicyclohexylcarbodiimide, N-ethylmaleimide, and azide, but not to oligomycin, ouabain or vanadate. These results supported the idea of the existence of a lysosomal H+-pump, suggested in a previous paper (Ohkuma et al. (1982) Proc. Natl. Acad. Sci. U.S. 79, 2758-2762).