Speciation of Metal Ions by Spectroscopic Methods
Imran Ali, Hassan Y. Aboul-Enein in Instrumental Methods in Metal Ion Speciation, 2006
Metal ion speciation involves the use of various spectroscopic techniques, such as ultraviolet-visible, flame atomic absorption, atomic emission, hydride generation, graphite furnace, inductively coupled plasma (ICP), and x-ray. In spite of the development of advanced chromatographic and electrophoresis methods for metal ion speciation, spectroscopic methods continue to be utilized for metal ion speciation due to certain advantages. The spectroscopic method of arsenic determination is based on the reaction of ammonium molybdate with arsenate in acidic medium to form an arsenatecontaining molybdenum heteropolyacid that can be reduced to molybdenum blue with stannous chloride, hydrazine, or ascorbic acid. Mass spectrometry has been coupled to ICP, resulting in a delicate research tool intended for the well-trained scientist only, in a more robust and well-established analytical technique for trace and ultra-trace determination, with a few thousand instruments in use worldwide. Hollow cathode lamps for different elements are used as the radiation sources.
Conjugation Pathways
Jack P. Uetrecht, William Trager in Drug Metabolism, 2007
Conjugation pathways involve the addition of a hydrophilic group such as glucuronic acid to a drug, and the mechanism involves an enzyme and a cofactor that is the source of this hydrophilic group. Glucuronidation is the most common conjugation pathway, both because of the range of substrates that can undergo glucuronidation and because it is often a quantitatively important pathway. Glucuronidation is usually a low-affinity, high-capacity system. Acetylation decreases the polarity of a drug rather than increasing it, but the substrates, e.g., aromatic amines, hydroxylamines, and hydrazines, are often toxic, and acetylation usually decreases this toxicity. Glutathione conjugates are often converted to mercapturic acids before excretion in urine. The number of drugs susceptible to S-methylation is limited but greater than the number turned over by catechol-O-methyltransferase (COMT). N-methyltransferase, active toward histamine and the catechol neurotransmitters, e.g., norepinephrine, is even more restrictive than COMT in terms of the metabolism of exogenous compounds.
Reduction-Oxidation Processes
Jiaping Paul Chen in Decontamination of Heavy Metals, 2012
Reduction-oxidation processes can be used for treatment of metallic waste streams or understanding of natural/engineered processes that can change the nature of heavy metals. The chemical-induced reduction uses chemical agents to reduce/convert metal ion to its elemental form. As solution pH can change the solution chemistry of metal wastewater, it may significantly affect the treatment results of reduction. The reduction agent can be organic compounds from living or dead biomass natural organic matter, and industrial organic waste. The commonly used reducing agents are sodium borohydride, hydrazine, and formaldehyde. The biological reduction and the precipitation of the metal species can be carried out in a moving sand bed reactor. The most expensive operational cost in the biological reduction of sulfate is the electron donor. The treatment of hexavalent chromium (Cr(VI)) involves first the reduction of Cr(VI) to the trivalent form by a reducing reagent with a high dosage.
Comparing hydrazine-derived reactive groups as inhibitors of quinone-dependent amine oxidases
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2017
Ashley A. Burke, Elizabeth S. Severson, Shreya Mool, Maria J. Solares Bucaro, Frederick T. Greenaway, Charles E. Jakobsche
Lysyl oxidase has emerged as an important enzyme in cancer metastasis. Its activity has been reported to become upregulated in several types of cancer, and blocking its activity has been shown to limit the metastatic potential of various cancers. The small-molecules phenylhydrazine and β-aminopropionitrile are known to inhibit lysyl oxidase; however, issues of stability, toxicity, and poorly defined mechanisms limit their potential use in medical applications. The experiments presented herein evaluate three other families of hydrazine-derived compounds – hydrazides, alkyl hydrazines, and semicarbazides – as irreversible inhibitors of lysyl oxidase including determining the kinetic parameters and comparing the inhibition selectivities for lysyl oxidase against the topaquinone-containing diamine oxidase from lentil seedlings. The results suggest that the hydrazide group may be a useful core functionality that can be developed into potent and selective inhibitors of lysyl oxidase and eventually find application in cancer metastasis research.
Anabolic profiles in late‐stage cancer patients responsive to hydrazine sulfate
Published in Nutrition and Cancer, 1981
The anabolic profiles of 59 late‐stage cancer patients responsive to hydrazine sulfate were examined; the drug had been given either as a sole agent or added to preexisting therapy to which the patients had become refractory. Most of the patients (79.7%) responded with Indicated Appetite Improvement (IAI), expressed by protocol‐code, clinical evaluation and/or direct quantitation. In those patients receiving hydrazine sulfate alone the IAI was 86.1%; in those in whom hydrazine sulfate was added to pre‐existing therapy the IAI was 69.6%. Of those cases expressed in direct quantitation the average weight gain for patients receiving hydrazine sulfate alone was 8.2 lbs, whereas the average weight gain for those with pre‐existing therapy was 0.6 lbs (p = 0.01). The results suggest the use of hydrazine sulfate as a specific chemotherapy for cancer cachexia, and implicate ineffective concurrent or prior therapy as an apparent negative factor in the generation of anabolic response.
Characterisation of hydrazides and hydrazine derivatives as novel aspartic protease inhibitors
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2010
Waseem Ahmed, Mubeen Rani, Ishtiaq A. Khan, Asif Iqbal, Khalid M. Khan, M. A. Haleem, M. Kamran Azim
Virtual screening of an in-house virtual library of synthetic compounds using FlexX, followed by enzyme inhibition, identified hydrazide and hydrazine derivatives as novel aspartic protease inhibitors. These compounds inhibited human cathepsin D and Plasmodium falciparum plasmepsin-II with low micromolar concentrations (IC50 = 1-2.5 μM). Modelling studies with plasmepsin-II predicted binding of ligands at the centre of the extended substrate-binding cleft, where hydrazide/hydrazine parts of the inhibitors acted as the transition state mimic by forming electrostatic interactions with catalytic aspartates.
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