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Topic: Dioxygen

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	Oxygen - Wikipedia, the free encyclopedia
		Epoxides are ethers in which the oxygen atom is part of a ring of three atoms.
		One unexpected oxygen compound is dioxygen hexafluoroplatinate O
		Oxygen derivatives are prone to form free radicals, especially in metabolic processes.
	en.wikipedia.org /wiki/Oxygen (1905 words)

	ITQB Metalloproteins & Bioenergetics Laboratory -Dioxygen Toxicity
		Therefore dioxygen is usually constrained to one electron transfer at a time.
		The one-electron reduction of dioxygen to superoxide is thermodinamically unfavourable.
		Therefore, a collision of dioxygen with a reduced flavin may lead to the formation of superoxide.
	www.itqb.unl.pt /~Metalloproteins_Bioenergetics/oxygen_tox.htm (620 words)

	Haemoglobin - a molecular lung: 2 (Site not responding. Last check: 2007-11-01)
		This is useful in studying the uptake of dioxygen by deoxyhaemoglobin or deoxymyoglobin and for studying the role of dioxygen species in the body.
		Dioxygen bonds reversibly to the iron(II) ion in the centre of the haem groups in haemoglobin and myoglobin - it is taken up at high oxygen pressures in the lungs and released at low oxygen pressures in the muscles (see Figure 4 in Part 1).
		As dioxygen is released to myoglobin converting it to oxymyoglobin, carbon dioxide enters the cell and is converted into hydrogen and hydrogencarbonate ions by the enzyme carbonic anhydrase.
	www.ul.ie /~childsp/CinA/Issue65/TOC28_Haemoglobin.htm (2435 words)

	BC Online: 8A - Chemistry of Oxygen
		This study guide will show that dioxygen is a ground state diradical that has low solubity in aqueuous solution, reacts in a kinetically sluggish fashion in oxidation reaction, and forms toxic byproducts as it gets reduced.
		Dioxygen toxicity: Since toxicity arises from the reduction products of oxygen, enzymes that use oxygen have evolved to bind oxygen and its reduction products tightly (through metal-oxygen bonds) so they are not released into the cells where they can cause damage.
		However, it can also be metabolized to form reactive nitrogen intermediates (much as with dioxygen) which can be deleterious to the body, if they damage native biomolecules, or advantageous, when they are used by immune cells like macrophages in the destruction of engulfed bacteria.
	employees.csbsju.edu /hjakubowski/classes/ch331/oxphos/oldioxygenchem.html (4957 words)

	MRI ABSTRACT (Site not responding. Last check: 2007-11-01)
		The optimized geometry of the ferrous dioxygen form is in good agreement with the structure of a model compound of this species and the calculated diamagnetic singlet ground state is consistent with the reported lack of ESR spectrum of this species.
		The dioxygen ligand in the reduced form is shown to preferentially bind to the heme iron in an asymmetric "end-on" geometry.
		The diamagnetic singlet ground state of the ferrous dioxygen and the doublet ground state of the reduced ferrous dioxygen species found with inclusion of configuration interaction are in agreement with the DFT results.
	www.molres.org /abs/1998d_dlh.html (366 words)

	BC Online: 5C - A Model Binding System: Mb, Hb, and O2 (Site not responding. Last check: 2007-11-01)
		Dioxygen is transported from lungs, gills, or skin of an animal to capillaries, where it can be delivered to respiring tissue.
		Dioxygen is one of those ligands, leading to the absorbance of high energy photons, causing the solution to appear bright red (since blue light is absorbed).
		For the binding of dioxygen to hemoglobin, thermodynamic cycles could be drawn showing either binding of ligand and subsequent conformational changes in protein structure or conformational changes in protein structure proceeding binding.
	employees.csbsju.edu /hjakubowski/classes/ch331/bind/olbindhemoglobin.html (6713 words)

	Tyrosinase - Wikipedia, the free encyclopedia
		When a person has a mutated tyrosinase gene they have albinism, a hereditary disease that one in every 17,000 person has in the United States.
		The active site in the tyrosinase enzyme contains two closely located copper atoms that interact with dioxygen to form a highly reactive chemical intermediate that then oxidizes the substrate.
		The activity of tyrosinase is similar to catechol oxidase, a related class of copper oxidases.
	en.wikipedia.org /wiki/Tyrosinase (221 words)

	Structure
		A stereo view of a fragment of the water channel by which the dioxygen molecule approaches the trinuclear copper center is shown, together with the side chain residues of Glu-498, Asp-499, and Asp-501 involved in hydrogen bonds with the solvent molecules in the channel.
		To the left is the trinuclear copper center and dioxygen molecule.
		The Glu-498 side chain, which binds to one of the oxygen atoms of the refined dioxygen molecule, is also represented.
	www.udel.edu /chem/bahnson/chem645/websites/laccase/index_files/Page337.htm (357 words)

	The Dioxygen Complex of Ferro-peroxidase (Site not responding. Last check: 2007-11-01)
		All ferro-peroxidases form complexes with dioxygen, typically by photolysis of the CO adduct in the presence of dioxygen.
		This gave us a dioxygen adduct that is stable enough for structure determination by a multiwire area detector.
		Water 595 of the native structure (its location in the native structure is shown as an orange sphere) is displaced by the unbound oxygen atom (OB).
	chem-faculty.ucsd.edu /kraut/oxy.html (324 words)

	MOLECULE DESCRIPTION (Site not responding. Last check: 2007-11-01)
		Hemoglobin is an oxygen binding protein whose function is to transport dioxygen from outside the body to the capillaries.
		The binding of dioxygen by hemoglobin is cooperative.
		The conformational changes that occur when one molecule of dioxygen binds may increase the affinity of the other remain three sites for dioxygen, because they bind to hemoglobin at a faster rate after the first is bound.
	www.users.csbsju.edu /~hjakubow/classes/rasmolchime/99ch331proj/Hb-Zac/page1.html (761 words)

	A New Approach for Studying Fast Biological Reactions Involving Dioxygen: The Reaction of Fully Reduced Cytochrome c ...
		This approach is based on the photolysis of a synthetic caged dioxygen carrier, which produces dioxygen on a fast time scale.
		The fact that dioxygen is generated in situ on a nanosecond or faster time scale avoids potential complications related to the fate of photodissociated CO in a conventional CO flow-flash experiment.
		The cobalt complex is stable at room temperature under anaerobic conditions and releases dioxygen upon irradiation at 355 nm with a quantum yield of 0.04.
	pubs.acs.org /cgi-bin/abstract.cgi/bichaw/2000/39/i47/abs/bi000955u.html (315 words)

	Dioxygen uptake by Co(salen)
		The importance of solid-state packing effects in determining oxygenation ability is further indicated by kinetic studies of dioxygen uptake at the crystal surfaces of the different forms of Co(salen).
		Measurements involving different temperatures and pressure conditions have shown that, following an induction period and after attainment of equilibrium, the kinetics of dioxygen absorption at the surface were no longer important and the uptake was controlled only by the rate of diffusion of dioxygen into the crystal.
		The uptake of dioxygen is then investigated for the complex in DMSO solution to establish whether a 1:1 or a 2:1 complex is formed under these conditions.
	wwwchem.uwimona.edu.jm:1104 /lab_manuals/c31lex2.html (1657 words)

	Ólöf Einarsdóttir, UCSC Chemistry Department (Site not responding. Last check: 2007-11-01)
		The mechanism by which dioxygen is reduced to water by cytochrome oxidase remains elusive.
		This represents a new approach to study the fast dioxygen reactions of cytochrome oxidase and it avoids mechanistic ambiguities associated with the fate of photodissociated CO in traditional flow-flash experiments.
		The kinetics are being probed by time-resolved optical absorption spectroscopy on time scales from nanoseconds to milliseconds in conjunction with pH indicators located in the extra-vesicular space or covalently bound to the lipids or the protein's extracellular surface.
	www.chemistry.ucsc.edu /einarsdottir_o.html (696 words)

	Science magazine-Matthias Selke
		The reaction of the dioxygen molecule with a class of organic phosphorous compounds called phosphines is one of the better known reactions in all of chemistry.
		The singlet dioxygen molecule is reactive enough to accomplish this type of chemistry at extremely low temperatures.
		Selke’s team was able to observe the primary adduct between the phosphine and singlet oxygen by nuclear magnetic resonance spectroscopy, and establish its structure.
	www.calstatela.edu /univ/ppa/newsrel/sciencemag-selke.htm (547 words)

	Preparation of polyoxymethylene dimethyl ethers by acid-activated catalytic conversion of methanol with formaldehyde ... (Site not responding. Last check: 2007-11-01)
		The process according to claim 11 wherein the source of dioxygen is a dioxygen enriched gas stream obtained by physically separating a gaseous mixture, containing at least about 10 volume percent dioxygen, into a dioxygen depleted stream and a dioxygen-enriched gas stream.
		Suitable sources of dioxygen are air or a dioxygen-enriched gas stream obtained by physically separating a gaseous mixture containing at least about 10 volume percent dioxygen into a dioxygen-depleted stream and a dioxygen-enriched gas stream.
		The dioxygen can be added to the reaction mixture as pure molecular oxygen, or diluted with an inert gas such as nitrogen or argon.
	www.freepatentsonline.com /6265528.html (7362 words)

	COLL 577 - Dioxygen activation on transition-metal surfaces from first-principles calculations (Site not responding. Last check: 2007-11-01)
		Dioxygen activation on transition-metal surfaces from first-principles calculations
		Self-consistent periodic DFT-GGA calculations are used to investigate various fundamental aspects of the adsorption process, such as the binding of oxygen molecules and atoms on transition metal surfaces.
		Trends in the dissociation barrier of dioxygen on flat and stepped surfaces are examined.
	membership.acs.org /c/coll/neworleans/P615051.HTM (184 words)

	Donald T Sawyer/Oxygen Chemistry (Site not responding. Last check: 2007-11-01)
		Sobkowiak, A.; Naro‘g, N.; Sawyer, D.T., "Iron(III, II)-Induced Activation of Dioxygen for the Oxygenation of Cyclohexene and Related Unsaturated Hydrocarbons," J. Molecular Catalysis A: Chemical, 2000, 159, 247—256.
		Professor Sawyer is the author of 311 research publications in the areas of oxygen chemistry, bioinorganic chemistry, redox chemistry and activation of dioxygen, transition-metal coordination chemistry, electrochemistry, and gas chromatography.
		He was Chairman of the 1971 Gordon Research Conference on Analytical Chemistry, has served on advisory panels for NSF, NIH, and the Research Corporation, and was Science Advisor to the Los Angeles District of the U.S. Food and Drug Administration from 1975 to 1982.
	mywebpage.netscape.com /sawyerdt/instant/aboutme.html (1039 words)

	Cytochrome bd Oxidase, Oxidative Stress, and Dioxygen Tolerance of the Strictly Anaerobic Bacterium Moorella ...
		tolerate traces of dioxygen (7, 8, 39, 48).
		At the times indicated, 1-ml aliquots of the cultures were withdrawn via syringe and centrifuged, and the cell pellets were suspended in equal volumes of 50 mM Tris-HCl, pH 8.0, prior to measurement of the OD The results are average of three replicate experiments with standard deviations between 0 and 8%.
		was shown to support dioxygen uptake in several acetogens (7).
	jb.asm.org /cgi/content/full/187/6/2020 (6154 words)

	[No title]
		Copper is a biologically essential trace element, which functions at the active sites of enzymes involved in electron transfer, processing of dioxygen, and in manipulation of certain nitrogen oxides.
		Reversible copper(I)/dioxygen interactions occur in hemocyanin proteins, which are blood dioxygen carriers in molluscs and arthropods.
		To understand the nature of these reactions, and for the possible development of reagents for oxidation of organics, ligands which bind three copper ions in close proximity are being synthesized and their copper chemistry developed.
	www.jhu.edu /~chem/karlin/new/023.html (708 words)

	Tolman Research Group : Summary of Research Projects in the Tolman Group
		A goal of our research is to understand on a fundamental chemical level how these processes occur through the detailed study of small molecule analogs of the metalloprotein active sites using a combination of experimental and theoretical methods.
		A diiron(II) complex that forms a dioxygen adduct that reacts with phosphines via a mechanism that involves substrate coordination.
		In a project jointly directed with Professor Larry Que, we have focused on using sterically hindered carboxylates (Figure 6) in which interligand steric interactions are relied upon to induce low coordination numbers and nuclearities in derived complexes, with hydrophobic shielding effects of the large organic substituents acting to stabilize reactive species and influence redox properties.
	www.chem.umn.edu /groups/tolman/research.html (944 words)

	Stahl Group - University of Wisconsin Madison (Site not responding. Last check: 2007-11-01)
		There is a dramatic need for environmentally benign oxidation chemistry in the pharmaceutical and chemical industries.
		We are currently investigating a series of new transition-metal-catalyzed reactions for the selective oxidation of organic substrates by dioxygen.
		Formally, these reactions proceed by a two stage catalytic cycle: (1) oxidation of the substrate by an oxidized transition metal catalyst and (2) regeneration of the oxidized catalyst by dioxygen (Scheme 1).
	www.chem.wisc.edu /~stahl/oxidation.html (186 words)

	When Metal Meets Air: New Catalysts For Oxidizing Molecules May Result, UD Chemists Say
		To better understand the catalysts used in industrial oxidation processes, Theopold's research team is studying the reactions of dioxygen.
		Though it is "a strong oxidizer," Theopold notes, "dioxygen is not very reactive by itself--which explains why all these organic materials sitting around don't spontaneously burst into flames." Once dioxygen gets going, however, it will quickly incinerate every molecule in its path.
		Dioxygen undergoes some surprising reactions with chromium, he notes.
	www.eurekalert.org /pub_releases/1997-04/UoD-WMMA-150497.php (420 words)

	abstract53 (Site not responding. Last check: 2007-11-01)
		The electrochemical properties of an unusual diquinone containing four carbonyl groups in the molecule (a carboxylic derivatized 1,4,5,8-naphthalenetetrone) were studied in aqueous solution and in monolayer form on a gold electrode surface.
		Monolayer covalent immobilization of the diquinone was achieved owing to the carbodiimide coupling of its carboxylic group with amino groups of cystamine chemisorbed previously onto the gold electrode surface.
		Cyclic voltammetry, constant potential electrolysis and rotating ring-disk electrode measurements were used to reveal the four-electron transfer process for dioxygen reduction mediated by the monolayer of immobilized diquinone.
	chem.ch.huji.ac.il /~eugeniik/abstract53.htm (210 words)

	American Scientist Online - How Plants Produce Dioxygen (Site not responding. Last check: 2007-11-01)
		Over the past 200 years, scientists have come to appreciate that plants harness solar energy to manufacture carbohydrates and sugars from carbon dioxide and water.
		Less well appreciated is that a byproduct of photosynthesis is molecular oxygen, or dioxygen.
		The authors describe their efforts to model this complex and infer a mechanism for the production of dioxygen.
	www.americanscientist.org /amsci/articles/98articles/Szalai.html (148 words)

	Valentine Reseach
		They are (1) investigations of the modes of activation of dioxygen and species derived from dioxygen, i.e.
		The object of the first project is an increased understanding of the nature of reactive intermediates produced in reactions of metalloenzymes and other metal-containing catalysts that bind dioxygen, catalyze dioxygen reduction, or catalyze reactions of dioxygen with organic substrates.
		Reactions of metal ions and complexes with dioxygen, superoxide, peroxides, and single oxygen donors are being studied.
	www.chem.ucla.edu /dept/InterDis/JSV_Brochure.html (625 words)

	Sample problem solution (Site not responding. Last check: 2007-11-01)
		Defects in the glycolytic pathway are associated with hemoglobin function.
		Dioxygen affinity of hemoglobin is lowered by 2,3-bisphosphoglycerate.
		The rate of synthesis of 2,3-bisphosphoglycerate is controlled by the level of 1,3-bisphosphoglycerate, a glycolytic intermediate.
	www.siu.edu /departments/biochem/bmb_courses/mbmb451b/sample_problems/mbmb451b_spsol_10.html (70 words)

	Mass spectrometric determination of dioxygen bond splitting in the "peroxy" intermediate of cytochrome c oxidase -- ...
		Mass spectrometric determination of dioxygen bond splitting in the "peroxy" intermediate of cytochrome c oxidase
		Bovine cytochrome c oxidase (CcO) catalyzes the oxidation of ferrocytochrome c and the reduction of dioxygen to water in a
		Because the P form is produced in the reaction of two-electron reduced enzyme with dioxygen, the original expectation was
	www.pnas.org /cgi/content/full/96/23/13114 (3250 words)

	TolmanResearch2004.htm
		A key discovery was a novel and quite thermodynamically stable superoxo complex, which we postulated to have the structure shown in the Figure (bottom).
		Multimetallic arrays in proteins that feature substantial carboxylate ligation are of special interest due to the significance of the reactions they perform and the complexity of their structures and mechanisms of action.
		In a project jointly directed with Professor Larry Que, we have focused on using sterically hindered carboxylates (Figure) in which interligand steric interactions are relied upon to induce low coordination numbers and nuclearities in derived complexes, with hydrophobic shielding effects of the large organic substituents acting to stabilize reactive species and influence redox properties.
	www.chem.umn.edu /groups/tolman/res.html (2342 words)

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