(n.) A non-metallic, gaseous element, strongly acid or negative, or associated with chlorine, bromine, and iodine, in the halogen group of which it is the first member. It always occurs combined, is very active chemically, and possesses such an avidity for most elements, and silicon especially, that it can neither be prepared nor kept in glass vessels. If set free it immediately attacks the containing material, so that it was not isolated until 1886. It is a pungent, corrosive, colorless gas. Symbol F. Atomic weight 19.
Example Sentences:
(1) Fluorination with [18F]acetylhypofluorite yields 6-[18F]fluoro-L-dopa with 95% radiochemical purity; fluorination of the same substrate with [18F]F2 yields a mixture of all three structural isomers in a ratio of 70:16:14 for 6-, 5-, and 2-fluoro compounds.
(2) Recent studies with fluorine-18 (F-18) fluorodeoxyglucose suggest inhomogeneity of myocardial glucose metabolism in the normal human heart, which may relate to substrate availability.
(3) In vitro sensitizing activities were correlated to the promotion efficiency of radiolytic hydroxylation of thymine to thymine glycol and to the one-electron reduction potential of a variety of fluorinated and non-fluorinated nitroazole derivatives.
(4) The new fluorinated adenine analog, fludarabine, has been tested for efficacy in many tumor types over the past ten years.
(5) The campaign’s focus was the damage to the ozone layer caused by fluorinated gases, such as HFCs.
(6) After administration of niflumic acid, flufenamic and antrafenine, the urinary elimination of ionized fluorine increase in all the subjects.
(7) The introduction of fluorines at C-24 and extension of the sterol side chain at C-26 and C-27 by methylene groups results in vitamin D analogues that have biological activity in vivo similar to those of the respective nonfluorinated natural sterols.
(8) Early prenatal suppression of the fetal adrenal cortex with fluorinated corticosteroids can prevent virilization of female fetuses with 21-hydroxylase deficiency.
(9) The fluorine modification of nitroazole sensitizers could enhance both the absolute activity and the tumor affinity.
(10) Haemophilus influenzae strains with varied ampicillin resistance and beta-lactamase production patterns were tested against three investigational fluorinated quinolones (CI-960, fleroxacin, temafloxacin) using Haemophilus Test Medium (HTM) and National Committee for Clinical Laboratory Standards (NCCLS) methods.
(11) It has been found that workers in factories who have not been considered as subjected to fluorine hazard and therefore have not been controlled had significantly elevated urinary fluoride levels.
(12) (19)F-Nuclear magnetic resonance studies of specifically fluorinated hemoglobin derivatives have been used to determine the apparent pK(a) of the histidine beta146 imidazole in deoxyhemoglobin.
(13) To measure [Ca2+]i, fluorine NMR spectra were acquired in a separate group of hearts loaded with the Ca2+ indicator 5F-BAPTA [5,5'-difluoro derivative of 1,2-bis-(o-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid].
(14) This is due to the influence of the fluorine substituent(s) on the basicity of the amine function proximal to the fluoromethylene group, this effect being amplified by geminal disubstitution.
(15) In intact cells of all 5-FC-susceptible strains the metabolism of 5-FU progressed to the formation of other fluorinated derivatives which were visualized as a single, broad resonance band at a lower field with respect to 5-FC and 5-FU.
(16) A major advance in antimicrobial chemotherapy was the synthesis of newer quinolones containing at least 1 fluorine atom and a piperazinyl group.
(17) We studied the relationship between antitumor efficacy of UFT, which is a most widely used drug among fluorinated pyrimidines recently, and its effect on the content and the inhibition rate of thymidylate synthase (TS) in 15 human tumor xenografts derived from stomach, colon, breast and pancreatic cancer patients.
(18) Fluorine-19 nuclear magnetic resonance images of rabbit hearts have been obtained with the administration of a fluorinated contrast compound.
(19) 31P NMR measurements of the magnesium-dependent shift between alpha- and beta-phosphates of ATP demonstrate that there is no measurable lowering of Mgi during loading with fluorinated o-aminophenol-N,N,O-triacetate.
(20) Thus, for fluoroanilines with a fluorine substituent at the para position bioactivation to the reactive benzoquinoneimine can be a direct result of the cytochrome P-450 dependent conversion.
Halogen
Definition:
(n.) An electro-negative element or radical, which, by combination with a metal, forms a haloid salt; especially, chlorine, bromine, and iodine; sometimes, also, fluorine and cyanogen. See Chlorine family, under Chlorine.
Example Sentences:
(1) 5-Bromo-5'-amino-2',5'-dideoxyuridine (11, ABrU) and 5-iodo-5'-amino-2',5'-dideoxyuridine (12, AIU) were prepared by halogenation of the 5-mercuriacetate of 5'-amino-2',5'-dideoxyuridine.
(2) Such disturbances may be induced by opiates, benzodiazepines, phenothiazines, butyrophenones, ketamine, etomidate, propofol, nitrous oxide, and halogenated inhalation anesthetics as well as by H2-blocking agents such as cimetidine.
(3) It is concluded that both halogenated and natural purine ribonucleotides interact in a similar manner with the enzyme molecule.
(4) The flumazenil analogue, Ro 16-0154, a benzodiazepine partial inverse agonist, has been labeled by halogen exchange to enable SPECT investigations of central benzodiazepine receptors in the human brain.
(5) The estrogen receptor seems to have a moderate tolerance for bulky substituents: All of the halogen and halomethyl substituents bind with an affinity at least 50% that of estradiol; in the three atom alkyl series, the affinity declined markedly from propargyl (44%) and allyl (38%) to propyl (5%), suggestive of detailed steric constraints or a preference for unsaturation.
(6) Annual savings in tonnes of CO 2 Install 2 kilowatt solar PV panels 0.4 Buy a new A++ refrigerator if yours is more than 4 years old, and only use a small-screen TV 0.1 Use LED or fluorescent lights where you currently have halogen lights installed 0.1 Buy an automated system to turn off appliances when not in use; get a meter that shows actual energy use and use it to monitor your household 0.1 Only use your washing machine and dishwasher when full to capacity and at lowest temperature 0.1 Never use the tumble dryer 0.1 Get rid of the freezer if you can, and replace your small appliances with "eco" varieties 0.1 Car (1.5 tonnes of CO 2 ) There is one car for every two people in the UK, and each one travels an average of about 9,000 miles a year.
(7) We have studied the time-resolved and the steady-state fluorescence of the DNA groove binders 4',6-diamidino-2-phenylindole (DAPI) and Hoechst 33258 with the double stranded DNAs poly(dA-dU) and poly(dI-dC) and their halogenated analogs, poly(dA-I5dU) and poly(dI-Br5dC).
(8) Halogenated anthelmintics were not metabolized to GSH conjugates in the helminths studied and did not inhibit GSH-S-aryltransferase activity towards chlorodinitrobenzene.
(9) Replacement of the 6-Cl group of amiloride by other halogen atoms had only modest effects on drug efficacy.
(10) This cannot be explained by metabolic activation of the halogenated hydrocarbons but could be due to a noxious effect on the mitotoc spindle.
(11) These observations indicate that Compound X is the halogenating intermediate in the chlorite reaction and that the rate of enzymatic chlorination is directly related to the stability of Compound X.
(12) As radiation sources, the following ones have proved useful: high-pressure mercury-vapour lamps, compound radiation systems consisting of high-pressure mercury-vapour burner, series coiled filament and reflector bulbs made of special glass as well as halogen metal-vapour lamps.
(13) This result suggests that a benefit may be expected in the clinic from the combined application of halogenated pyrimidines with repair inhibitors, if administered at a carefully screened range of concentrations.
(14) GC detection was carried out with a Coulson conductivity detector in the halogen (reductive) mode.
(15) Glutaraldehyde might inhibit Cl- transport in the TAL by cross-linking amino acid residues of the proteins essential for halogen transport across this segment.
(16) Treatment was administered with white light produced by a commercially available halogen-tungsten lamp.
(17) Various organic substances, which were measured by different indices such as total trihalomethanes (THM), total organic halogen (TOX) and the absorbence at 260 nm, could be recovered by this method much more efficiently and conveniently than by conventional methods.
(18) These results indicate that B cell mitogens act to release virus by a mechanism that differs from that of halogenated pyrimidines.
(19) Stability of halogenated volatile anesthetic is important because of the potential toxicity associated with the breakdown products.
(20) 111 chemicals of known rodent carcinogenicity (49 carcinogens, 62 noncarcinogens), including many promoters of carcinogenesis, nongenotoxic carcinogens, hepatocarcinogens, and halogenated hydrocarbons, were selected for study.