(n.) A tenacious, elastic, gummy substance obtained from the milky sap of several plants of tropical South America (esp. the euphorbiaceous tree Siphonia elastica or Hevea caoutchouc), Asia, and Africa. Being impermeable to liquids and gases, and not readly affected by exposure to air, acids, and alkalies, it is used, especially when vulcanized, for many purposes in the arts and in manufactures. Also called India rubber (because it was first brought from India, and was formerly used chiefly for erasing pencil marks) and gum elastic. See Vulcanization.
Example Sentences:
(1) The addition of amine fluorides to a copal recin (Copalite) and a chlorine caoutchouc varnish (Pergut S-40) has been studied.
(2) Isolation of pentachlorophenol is carried out from water extracts obtained from the dry caoutchouc films, so the same method can be used for examination of the rubber articles designed for the medicinetoo.
(3) The tonoplast-bound ATPase of Hevea brasiliensis (caoutchouc tree) was solubilized with dichloromethan and purified 100-fold with two ammonium sulfate precipitation steps and a G-200 gel filtration step.
(4) Preparation of shoulder-specimens after injection of silicone-caoutchouc are done to examine the vascular system.
(5) Investigating possible application of the DCT-30 thermoelastoplastic shows advantages of some physico-technical properties of this product based on natural caoutchouc and latex by comparison with base-rubber onene.
(6) Silicon-caoutchouc and Vestolit-PVC were the substances used.
(7) Working environments have been tested in plants producing asbestos products, asbestos-cement products, textile asbestos products, asbestos-caoutchouc plates, asbestos boards and asbestos frictional materials for automotive industry, Measurements of total dust concentrations and concentrations of asbestos fibres 5 micron long supported workers' exposure investigations.
Isoprene
Definition:
(n.) An oily, volatile hydrocarbon, obtained by the distillation of caoutchouc or guttaipercha.
Example Sentences:
(1) The location of the internal trans and cis isoprene units in ficaprenol-11 isolated from Ficus elastica was determined by 13C nuclear magnetic resonance.
(2) An enzymatic comparison with a variety of polyprenol substrates indicates that the solubilized kinase prefers long-chain (C90-95) polyprenols with saturated alpha-isoprene units.
(3) Analysis by mass spectrometry and by nuclear magnetic resonance showed that the molecule is formed by condensation of 10 unsaturated isoprene units and 1 saturated isoprene unit.
(4) The chemical structure of synthetic dolichol-19, which was prepared by the addition of a saturated isoprene unit to the polyprenol-18 isolated from Ginkgo biloba, was confirmed to be identical with that of pig liver dolichol-19.
(5) The number of internal trans isoprene residues in this compound was three in comparison with two such residues in long-chain C95-dolichol.
(6) It was demonstrated that C30-C80-polyprenyl phosphates with unsaturated alpha-isoprene unit were as active as natural acceptor (undecaprenyl phosphate) in this enzymic system.
(7) Hb adducts also accumulated linearly after repeated daily administration of 100 mumol [14C]butadiene or 500 mumol [14C]isoprene per kilogram body wt to mice and rats, respectively, for 3 days.
(8) The relative amount of the metabolites present in blood was highest for low concentrations of inhaled isoprene and for shorter exposure durations.
(9) Three side-chains monocarboxylic acids hydroxylated in allylic positions in the isoprene moiety were also characterized.
(10) Catalytic hydrogenolysis has been used as a means of distinguishing between classes of polyprenyl phosphate sugars which contain saturated alpha-isoprene units from those in which this grouping is allylic.
(11) Two isoprenoids with 9 to 10 isoprene chains (polyprenoids), N-(p-methylbenzyl)decaprenylamine and N-solanesyl-N,N'-bis(3,4-dimethoxybenzyl)ethylenediamine overcame the multidrug resistance almost completely in cultured Chr-24, whereas they only slightly sensitized the parental KB cells to anticancer agents.
(12) This was independent of inhaled isoprene concentration.
(13) The incorporation of radioactive farnesyl pyrophosphate and radioactive geranylnerol and the lack of incorporation of radioactive geranylgeraniol into betulaprenols-6 to -9 demonstrated that they are formed by the cis-additions of isoprene residues to all-trans-farnesyl pyrophosphate.
(14) In brain, spleen, and intestine one-third and in other tissues 10-20% of the total ubiquinone contained 10 isoprene units.
(15) The compound is thus designated MK-8(2H), indicating a menaquinone with eight isoprene units but only seven double bonds in the side chain.
(16) The isoprenoid pattern for dolichol and dolichyl-P, respectively, is modified to longer polyprenols in the two fractions as seen in the percent distribution of the individual isoprenes.
(17) Six differential observations were made: (1) Plastoquinone and ubiquinones, with a side chain of more than two isoprene units, are by far better mediators than their short-chain homologues.
(18) 14CO2 exhalation after the end of the 6-hr exposure was minimal (2%) at the 20 ppm exposure and increased up to 18% at the higher isoprene exposure concentrations.
(19) A biosynthesis of hexahydroprenols by addition of cis-isoprene units to all-trans-geranylgeranyl pyrophosphate, or a dihydro or tetrahydro derivative thereof, is suggested.
(20) A method for the determination of neophytadiene in the total particulate matter of cigarette smoke was developed and applied to test its relationship to isoprene deliveries.