Results 291 to 300 of about 506,032 (344)

Chemical ionization of amino acids

Journal of the American Chemical Society, 1976
The H/sub 2/ chemical ionization (CI) mass spectra of 14 ..cap alpha..-amino acids have been determined and compared with the CH/sub 4/CI mass spectra. The H/sub 2/ CI spectra show a much lower MH/sup +/ abundance and increased abundances of fragment ions formed by sequential fragmentation of MH/sup +/.
C W, Tsang, A G, Harrison
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Chemical Measurement of Ionizing Radiations

Nature, 1949
RADIATION ‘dose’ is usually defined and measured in terms of the ionization produced in air. However, for biological dosage purposes it would be theoretically preferable to measure effects produced in media similar in composition to living tissue, and there are considerable experimental advantages in a direct measurement of the radiation energy ...
M J, DAY, G, STEIN
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Ionization of tocopherols and tocotrienols in atmospheric pressure chemical ionization

Rapid Communications in Mass Spectrometry, 2018
Rationale Tocopherols and tocotrienols are chemical compounds insusceptible to the ionization process under atmospheric pressure conditions. Therefore, the selection of the optimal ion source settings for their quantification requires special attention.
Ewa Bartosińska, Agnieszka Borsuk‐De Moor, Danuta Siluk, Michał J. Markuszewski, Paweł Wiczling   +4 more
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Dimethyl ether chemical ionization of arylalkylamines

Rapid Communications in Mass Spectrometry, 2000
The gas-phase reactions of dimethyl ether (DME) ions with a number of biologically active arylalkylamines of the general formula R(1)R(2)C(6)H(3)CHR(3)(CH(2))(n)NR(4)R(5), where R(1) = H or OH, R(2) = H, F, NO(2), OH or OCH(3), R(3) = H or OH, R(4) and R(5) = H or CH(3), have been studied by means of chemical ionization mass spectrometry.
Ramos, L.E., Cardoso, A.M., Ferrer Correia, A.J., Nibbering, N.M.M.   +3 more
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A Sensitive Chemical Dosimeter for Ionizing Radiation

Nature, 1959
A NUMBER of chemical systems have been employed for the measurement of the quantity of ionizing radiation. Among the most sensitive dosimeters are those employing dyes1. One system utilizes the destruction of a dye2,3 and another the production of a coloured dye by transformation of the leuco form4. These systems are not particularly sensitive and, for
G, OSTER, B, BROYDE
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Chemical Effect of Ionizing Radiation on Cytosine

Science, 1962
The formation of uracil and the breakdown of the pyrimidine ring were observed when an aqueous solution of cytosine was irradiated. These two effects were investigated with the aid of radioactive tracer techniques and ultraviolet absorption studies.
C A, PONNAMPERUMA, R M, LEMMON, M, CALVIN   +2 more
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Chemical ionization mass spectrometry

Accounts of Chemical Research, 1968
Chemical ionization mass spectrometry is a technique of mass spectrometry wherein the ionization of the substance of interest is effected by ion-molecule reactions rather than by electron impact, photon impact, or field ionization. The spectrum of a substance produced by chemical ionization is different from the spectra produced by the other ionization
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Chemical ionization mass spectrometry of nucleosides

Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis, 1971
Abstract Basic reactions of nucleosides under conditions of chemical ionization have been investigated, using CH 4 or NH 3 as reagent gases at a pressure of 0.4 mm Hg. C 2 H 4 was found to be useful for the elucidation of some mechanistic and structural details, and was augmented by high resolution techniques.
M S, Wilson, I, Dzidic, J A, McCloskey
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Chemical ionization mass spectrometry of nitrosamines

Talanta, 1984
The mass spectra of eight nitrosamines have been recorded, with excitation by chemical ionization (CI) and electron impact (EI). Comparison of the intensities of the base peaks under CI and El conditions gives intensity ratios in the range 1.4-1.9 for low resolution measurements and up to 10 for high resolution measurements, confirming the enhanced ...
Y, Fang, D, Jiahua, L, Shili
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Chemical ionization pyrolytical spectra of DNA

Journal of Pharmaceutical and Biomedical Analysis, 1990
The chemical ionization-pyrolytical (CI-Py) spectra of DNA and deuterated DNA (Herring Sperm) are recorded. The 200-800 a.m.u. region is examined for CH4, NH3, ND3, electron-capture and OH- CI spectra. The origin of major ion species is discussed.
H, Virelizier, D, Gaudin, R, Hagemann, K, Jankowski   +3 more
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