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Topic: Isoprene

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	Isoprene - Wikipedia, the free encyclopedia
		Isoprene is formed naturally in plants and animals and is generally the most common hydrocarbon found in the human body.
		Isoprene is produced in the chloroplasts of leaves of certain tree species through the DMAPP pathway; the enzyme isoprene synthase is responsible for its biosynthesis.
		Isoprene affects the oxidative state of large air masses, is an important precursor for ozone, a pollutant in the lower atmosphere.
	en.wikipedia.org /wiki/Isoprene (858 words)

	Home page of Dr. Mark Potosnak, Assistant Research Professor, DEES/DRI
		Isoprene affects oxidation cycles in the atmosphere, and in turn the rate of emission depends on both the genetic potential of the plant and environmental factors.
		Isoprene is produced enzymatically in the chloroplast of many plant species and may provide a protective benefit to the photosynthetic apparatus during transient episodes of heat stress.
		Isoprene in the atmosphere is reduced by the hydroxyl radical (and by ozone to a lesser extent) on a timescale of 2 hours, which couples isoprene emissions and atmospheric chemistry.
	www.dri.edu /People/Mark.Potosnak (894 words)

	Isoprene Emission (Site not responding. Last check: 2007-11-06)
		An important plant emitted hydrocarbon is isoprene and a simple model of leaf isoprene emission as proposed by Guenther, in the paper detailed in the acknowledgment below, is formulated in Wimovac.
		The leaf isoprene model produces simple empiracle responses of isoprene emission in response to key leaf microclimate properties such as light intensity, temperature and relative humidity.
		Isoprene emission rates were constant between CO concentrations of 50 and 600 and decreased at lower concentrations and at higher concentrations.
	www.face.bnl.gov /Modelling/isoprene.htm (809 words)

	Isoprene -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-06)
		It is most readily available industrially as a by-product of the thermal (The process whereby heavy molecules of naphtha or petroleum are broken down into hydrocarbons of lower molecular weight (especially in the oil-refining process)) cracking of (Any of various volatile flammable liquid hydrocarbon mixtures; used chiefly as solvents) naphtha or oil.
		Isoprene is formed naturally in plants and animals and is generally the most common (An organic compound containing only carbon and hydrogen) hydrocarbon found in the human body.
		The estimated production rate of isoprene in the human body is 15 (Click link for more info and facts about µmol) µmol/kg/h, equivalent to approximately 17 mg/day for a 70 kg person.
	www.absoluteastronomy.com /encyclopedia/i/is/isoprene.htm (688 words)

	Isoprene and Monoterpenes. (Site not responding. Last check: 2007-11-06)
		Isoprene is the predominant VOC emitted by forest species such as poplar, oak, willow, sycamore and eucalyptus making up as much as 80 %.
		Several studies in recent years have shown isoprene to be a key VOC in tropospheric chemistry on both regional and global scales.
		Isoprene is almost exclusively emitted during daylight hours, hence reaction with hydroxyl radicals will be the major degradation path for isoprene in the troposphere.
	www.chem.leeds.ac.uk /Atmospheric/Field/biogenic.html (263 words)

	isoprene on Encyclopedia.com
		It is readily polymerized by the use of special catalysts; large numbers of isoprene molecules join together to form a single large, threadlike polyisoprene molecule.
		ON THE SEASONALITY OF ISOPRENE EMISSIONS FROM A MIXED TEMPERATE FOREST.
		Compositions of isoprene and halogenated EPDM rubbers.(ethylene-propylene diene monomer)
	www.encyclopedia.com /html/i1/isoprene.asp (337 words)

	Comparison of Modeled versus Observed Isoprene Concentrations (Site not responding. Last check: 2007-11-06)
		Analyses of isoprene reactivity, in the context of ozone formation, suggests that isoprene is the dominant hydrocarbon in the rural atmosphere and an important hydrocarbon in the urban atmosphere (Chameides et al., 1992; Cardelino and Chameides, 1990).
		Isoprene concentrations from the model were then converted from units of parts per billion-volume (ppb-V) to part per billion-carbon (ppb-C), in conformance with the reporting conventions of the analytical laboratories.
		The vertical concentration gradient of isoprene is relatively weak between 10 meters and 50 meters and of the wrong sign to mitigate model bias.
	capita.wustl.edu /OTAG/Reports/Isoprene/ISOPRENE.html (3074 words)

	Evolutionary significance of isopreneemission from mosses -- Hanson et al. 86 (5): 634 -- American Journal of Botany
		of isoprene emission from Sphagnum capillifolium (Ehrh.) Hedw.
		as isoprene emission from ferns, gymnosperms, and angiosperms
		from isoprene emission and the absence of isoprene emission
	www.amjbot.org /cgi/content/full/86/5/634 (3276 words)

	Encyclopedia: Isoprene
		In chemistry, isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently.
		Atmospheric chemistry is a multidisciplinary field of research in which the chemistry of the atmosphere is studied.
		The terpenoids, sometimes referred to as isoprenoids, are a class of naturally occurring chemicals similar to terpenes, derived from five-carbon isoprene units assembled and modified in thousands of ways.
	www.nationmaster.com /encyclopedia/Isoprene (1882 words)

	NTP: Abstract for TR-486 - Isoprene
		Isoprene, the monomeric unit of natural rubber and naturally occurring terpenes and steroids, is primarily obtained as a by-product of naphtha cracking for ethylene production.
		Isoprene was selected for toxicologic evaluation because of its structural similarity to 1,3-butadiene, a potent, multi-organ, rodent carcinogen, and the potential for human exposure due to its large annual production volume.
		Under the conditions of this 2-year inhalation study, there was clear evidence of carcinogenic activity of isoprene in male F344/N rats based on increased incidences of mammary gland fibroadenoma and carcinoma, renal tubule adenoma, and testicular interstitial cell adenoma.
	ntp.niehs.nih.gov /index.cfm?objectid=070AD25B-FB3F-FDB8-D11F713DEF059A89 (1044 words)

	EPA/OPPT/High Production Volume Challenge Program (HPV): Robust Summaries & Test Plans: C5 Noncyclics (Site not responding. Last check: 2007-11-06)
		Isoprene, the 2-methyl analogue of 1,3-butadiene, is estimated to be the most abundant hydrocarbon (anthropogenic or biogenic) across much of the eastern U.S. Isoprene naturally occurs in the environment as emissions from vegetation.
		Isoprene may be released to the environment as emissions during wood pulping, biomass combustion, and rubber abrasion, tobacco smoke, gasoline, wood smoke, turbine, and automobile exhaust.
		Because of the widespread levels of isoprene in the atmosphere and the fact that its concentrations are largely affected by local climate and flora, isoprene is ideally suited to a hazard evaluation that uses exiting human epidemiological data rather than solely relying on inaccurate animal testing.
	www.epa.gov /chemrtk/c5ncyl/c5pcrcmt.htm (2525 words)

	Isoprene (Site not responding. Last check: 2007-11-06)
		The recently-cloned isoprene synthases of aspen and kudzu are members of the terpene synthase family of enzymes and there are no homologous genes in bacterial or the human genome.
		Isoprene is the root member of the isoprenoid family of compounds.
		Photosynthesis is required for isoprene emission thus isoprene is not emitted from plants at night.
	www.wisc.edu /biotron/Sharkey/ResearchIsoprene.htm (128 words)

	Isoprene
		The important role of isoprene in atmospheric chemistry was already introduced in Section 1.2.
		The most important sink of isoprene is reaction with OH (85%), but reactions with ozone (11%) and NO are also non-negligible.
		The monthly (24h-averaged) surface distribution of isoprene is shown in Figure 3.15 for January and July.
	www.mpch-mainz.mpg.de /~kuhlmann/rvkdisshtml/node48.html (1020 words)

	Fall.94 (Site not responding. Last check: 2007-11-06)
		Typically, 1-2% of CO2 fixed in photosynthesis is emitted as isoprene, and globally it is estimated that 300-400 million tons of isoprene is emitted by forests each year.
		The laboratory is probing the metabolic regulation of isoprene synthesis in leaves and the linkage of isoprene synthesis to light-dependent reactions in the chloroplast.
		The researchers have recently discovered the enzyme isoprene synthase and are working to characterize it and the developmental regulation of the isoprene synthase gene.
	www.colorado.edu /Chemistry/directory.dir/faculty.dir/biochem.dir/fall.dir/fallres.html (552 words)

	Ozone Quenching Properties of Isoprene and Its Antioxidant Role in Leaves -- Loreto et al. 126 (3): 993 -- PLANT ...
		Isoprene is formed in and emitted by plants and the reason for this apparent carbon waste is still unclear.
		of ozone (1) or with 300 ppm ozone and 3 ppm isoprene (2).
		We measured the ozone uptake by the leaf in absence and in presence of isoprene.
	www.plantphysiol.org /cgi/content/full/126/3/993 (4254 words)

	Isoprene Emissions
		From the large group of compounds that have been identified as being of biogenic origin, it is isoprene for which we probably have the best knowledge on formation mechanism within the plant, and thus the dependence of the emission on ambient conditions, for various plant species.
		The strong emission of isoprene into a layer of just 80 meters height causes OH to be depleted to very small values, which in turn correspond to a very long lifetime (>5 h) of this otherwise shortlived compound.
		The effect of the assumption to emitting isoprene in the whole PBL was only a 20% reduction in peak isoprene concentrations near the surface and the vertical gradient was still very steep.
	www.mpch-mainz.mpg.de /~kuhlmann/rvkdisshtml/node34.html (748 words)

	EXECUTIVE SUMMARY (Site not responding. Last check: 2007-11-06)
		Previous evaluations of BEIS2 based on direct comparisons of isoprene fluxes from vegetation are based on a limited range of vegetation types and ambient conditions and therefore may not be representative of the full range of conditions represented by the OTAG model application.
		Because the OTAG UAM-V isoprene predictions are 12 km x 12 km grid cells averaged over a 50 m lowest layer, the focus of the model/measured comparison was during the afternoon when the atmosphere is "well-mixed" so that the predicted 50 m layer-average isoprene concentrations are more representative of the surface measured isoprene concentrations.
		It is speculated that this early morning modeled isoprene spike may be due to inconsistencies between the RAMS generated atmospheric mixing profiles and the BEIS2 derived isoprene emissions.
	capita.wustl.edu /OTAG/Reports/morris/EXECSUM.html (7835 words)

	Elective haemodialysis increases exhaled isoprene -- Lirk et al. 18 (5): 937 -- Nephrology Dialysis Transplantation
		to endogenous accumulation of isoprene, whereas the increase
		Volatile alkanes and increased concentrations of isoprene in exhaled air during hemodialysis.
		Breath isoprene during acute respiratory exacerbation in cystic fibrosis.
	ndt.oxfordjournals.org /cgi/content/full/18/5/937 (2303 words)

	Identification of Urinary Metabolites of Isoprene in Rats and Comparison with Mouse Urinary Metabolites -- Buckley et ...
		Identification of Urinary Metabolites of Isoprene in Rats and Comparison with Mouse Urinary Metabolites -- Buckley et al.
		Isoprene, a major commodity chemical used in production of polyisoprene elastomers, has been shown to be carcinogenic in rodents.
		C]isoprene/kg to rats and mice, isoprene was excreted unchanged
	dmd.aspetjournals.org /cgi/content/abstract/27/7/848 (315 words)

	Alkoxy radicals from isoprene: Reaction Pathways (Site not responding. Last check: 2007-11-06)
		It constitutes about 40% by mass of non-methane organic compound emissions to the atmosphere, and it is emitted almost exclusively by natural sources.
		The yields of these species are determined by the site of OH addition to isoprene and the fate of the alkoxy radicals; the latter topic is our focus.
		The OH-initiated degradation of isoprene in the atmosphere is expected to produce four
	www.esf.edu /chemistry/dibble/presentations/isoprene.htm (284 words)

	Shell Chemicals - Isoprene (Site not responding. Last check: 2007-11-06)
		Shell chemicals companies are the only isoprene producers with production locations in multiple regions, an important factor in meeting the needs of global customers.
		Unlike many other isoprene producers, Shell chemicals companies are also ethylene producers, affording us better and more consistent access to crude C5s, the feedstock for isoprene production.
		Isoprene is an important base material for the production of synthetic rubbers.
	www.shellchemicals.com /isoprene/1,1098,1116,00.html (269 words)

	Environmental Health Perspectives: Formation of strong airway irritants in mixture... @ HighBeam Research (Site not responding. Last check: 2007-11-06)
		Dose-response curves were established for isoprene, methacrolein (28), [O.sub.3] and formaldehyde (29); we used data for methylvinyl ketone, allylglycidyl ether, N[O.sub.2], formic acid, acetic acid, acetone, saturated aldehydes, and 3-methylfuran to calculate/estimate the response for these substances in the reaction mixtures.
		We chose the initial concentrations of isoprene, [O.sub.3], and N[O.sub.2] on the basis of the reaction rates and their concentration-response relationships, so the residual concentrations in the reaction mixture were close to but below their NOELs in the bioassay.
		The concentration of isoprene in the lung is low (25-200 ppb) and somewhat lower in an occupied room (~ 20 ppb) (42).
	highbeam.com /library/doc0.asp?DOCID=1G1:80486958&... (4151 words)

	Effects of transient changes in PAR and leaf temperature on isoprene emission (Site not responding. Last check: 2007-11-06)
		Isoprene is the major non-methane hydrocarbon entering the atmosphere in the Eastern US and the genus Quercus is a major source of isoprene in this area.
		Models of isoprene emission based on the responses of leaves to environmental factors are important for predicting ozone pollution in high ozone areas.
		Isoprene emission increased more slowly than leaf temperature resulting in a time lag between temperature change and isoprene emission change.
	abstracts.aspb.org /pb1997/45/0789.shtml (317 words)

	isoprene (Site not responding. Last check: 2007-11-06)
		regulation of isoprene formation in leaves of green plants.
		of isoprene formation during the growth and sporulation of Bacillus subtilis.
		W.P. Wagner, D. Helmig, and R. Fall (2000) Isoprene biosynthesis in Bacillus subtilisvia the methylerythritol phosphate pathway.
	www.colorado.edu /chemistry/falllab/isoprene.htm (193 words)

	Information Bridge: DOE Scientific and Technical Information
		In this 3-year project we (a) characterized the physiological regulation of isoprene formation in B. subtilis and its relationship to isoprene formation in plant chloroplasts; (b) analyzed genetic controls on isoprene formation in B. subtilis; and (c) developed models to explain the biochemical rationale for isoprene formation.
		We are also pursued (d) new methods for continuous measurement of isoprene release in bioreactors, and (e) determined the presence of isoprene-forming Bacillus on plant roots and used B. subtilis as a biocontrol agent for protection of plant roots from plant pathogenic bacteria.
		These include: (1) establishing the enzymatic basis of isoprene formation in B. subtilis, and demonstrating throughout growth in a bioreactor that isoprene synthase activity rises and falls with each of three peaks of isoprene release (i.e.
	www.osti.gov /bridge/product.biblio.jsp?osti_id=814920 (597 words)

	Natural Abundance Carbon Isotope Composition of Isoprene Reflects Incomplete Coupling between Isoprene Synthesis and ...
		Isoprene emission from leaves is dynamically coupled to photosynthesis through the use of primary and recent photosynthate
		isoprene was obtained by extractions from leaves of myrtle-1.
		Wildermuth MC, Fall R (1996) Light-dependent isoprene emission: characterization of a thylakoid-bound isoprene synthase in Salix discolor chloroplasts.
	www.plantphysiol.org /cgi/content/full/131/4/1727 (5105 words)

	AUFBAU1 [ORGANIC CHEMISTRY: ISOPRENE]
		Suggest the reason why 'diene' is present in the systematic name of isoprene (2-methylbuta-1,3-diene).
		Manufacturers require far greater amounts of isoprene than can be obtained from natural sources.
		Partial hydrogenation of isoprene gives two liquid alkenes, "V" and "W": whereas complete hydrogenation gives liquid alkane "X".
	www.wissensdrang.com /auf1isop.htm (437 words)

	Edinburgh Research Archive : Item 1842/767 (Site not responding. Last check: 2007-11-06)
		Isoprene is the most abundant volatile organic compound (VOC) emitted from vegetation, mainly trees.
		Because it plays an important role in tropospheric chemistry leading to formation of pollutants and enhancing the lifetime of the greenhouse gas methane, concern about the response of isoprene emissions to the rise in atmospheric CO2 concentration and global climate change has been increasing over the last few years.
		Predicted warmer climate, extended drought periods, the possible shift in plant species in favour of isoprene emitters and the increase in length of growing season, may caus...
	hdl.handle.net /1842/767 (214 words)

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