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Biomedical subjects

C J Brooks

Publications and source records attributed to C J Brooks.

At least 55 records · Page 3Linked to original sources
PubMed1978

Application of ion-exchange and lipophilic-gel chromatography to the purification and group fractionation of steroidal spirolactones, isolated from biological fluids.

Chromatography of steroidal spirolactones on DEAE-Sephadex A-25 under selected pH conditions allowed efficient separation of these compounds from other steroids and many of the endogenous components of human urine. The spirolactones were recovered in high yield, mostly over 90%. Lipophilic-gel chromatography provided a useful method for group fractionation of mixtures of these spirolactones with high recoveries (generally over 90%), unaffected by the presence of endogenous material from normal human urine.

Canrenoic Acid↗
PubMed1978

Oxidation of 3beta-hydroxyandrostenes by the 3beta-hydroxy-steroid oxidase (cholesterol oxidase) from Brevibacterium sterolicum prior to their analysis by gas-liquid chromatography-mass spectrometry.

The 3beta-hydroxysteroid oxidase from Brevibacterium sterolicum has been applied to the oxidation of a number of 3beta-hydroxyandrostenes, including polar steroids containing up to three other hydroxylic groups. The substrates, products, and derivatives thereof have been examined by gas-liquid chromatography. Retention index increments for these conversions, and for parallel transformations of other steroids, show considerable regularities, and together with mass spectrometric data afford characteristic structural information.

3-Hydroxysteroid Dehydrogenases↗
PubMed1978

Development of a procedure for the assay of an experimental steroid drug in dog plasma.

Studies of the estimation of 16alpha-cyano-3beta-cyclopentyloxypregn-5-en-20-one (an experimental drug) in dog plasma are described. Extraction using a salt/solvent pair (ammonium carbonate/ethyl acetate) is followed by a rapid chromatographic procedure employing Lipidex 5000, which affords a substantially purified fraction. After preparation of the t-butyldimethylsilyloxime, quantification of the drug is performed by selected ion monitoring. The [2H9]cyclopentyloxyl analogue is used as an internal standard. In a preliminary experiment, the advantages (in terms of both sensitivity and selectivity) of the use of an open tubular GLC column are demonstrated.

Animals↗
PubMed1977

Gas-liquid chromatography-mass spectrometry of phospholipid mixtures after enzymic hydrolysis.

Gas-liquid chromatography-mass spectrometry (GLC-MS), employing an open-tubular Silanox-type glass column, has been applied to the products of phospholipase C hydrolysis of natural and synthetic phospholipid mixtures. The materials studied were egg lysolecithin, synthetic L-alpha-l-stearoyl-2-oleoyl lecithin, bovine brain sphingomyelin, and phospholipids derived from human arterial tissue. l-Monoglycerides and ceramides were analysed as methaneboronates, and 1,2-diglycerides as trimethylsilyl ethers. The results indicate the potential value of open-tubular GLC-MS in a rapid procedure for the concurrent analysis of the major classes or polar lipids after enzymic dephosphorylation.

Chromatography, Gas↗
PubMed1977

Gas-liquid chromatography-mass spectrometry of thromboxane B2 and its detection in semen and human aorta by selected ion monitoring.

The gas-liquid chromatographic and mass spectrometric properties of some derivatives of thromboxane B2 methyl ester have been examined. Mass spectra were usually more informative at lower electron energies. The O-methyl- and O-n-propyloxime tri-trimethylsilyl ethers, and the tri-tert.-butyldimethylsilyl ether were used for selected ion monitoring (SIM). Thromboxane B2 was detected by SIM in bovine semen and in human aorta.

Animals↗
PubMed1977

The substrate specificity and stereochemistry, reversibility and inhibition of the 3-oxo steroid delta 4-delta 5-isomerase component of cholesterol oxidase.

1. 5-Cholesten-3-one was shown to be an intermediate in the conversion of cholesterol into 4-cholesten-3-one by Nocardia cholesterol oxidase. 2. The absence of a C-17 side chain from 5-androstene-3,17-dione slightly increased the Vmax. of the isomerase activity relative to 5-cholesten-3-one (1.7-fold), but greatly increased the Km. 3. Incubations of [4alpha-2H]-and [4beta-2H]-cholesterol with cholesterol oxidase showed that the 4beta-hydrogen atom can be transferred to the 6beta-position. However, incubations of cholesterol, 5-cholesten-3-one and 4-cholesten-3-one with the enzyme in 2H2O led to some incorporation of 2H into the 4-cholesten-3-one products, mostly at position 6beta. 4. Both the isomerase and the oxidase activities of cholesterol oxidase were inhibited by 5,10-seco-19-nor-5-cholestyne-3,10-dione.

3-Hydroxysteroid Dehydrogenases↗
PubMed1977

Characterization of diastereomeric and enantiomeric ephedrines by gas chromatography combined with electron impact mass spectrometry and isobutane chemical ionization mass spectrometry.

The diastereomeric hydroxyamines, ephedrine and psi-ephedrine, were well differentiated by gas chromatography of their N-acetyl O-trimethylsilyl derivatives. For the analytical separation of enantiomers, conversion into N-(R)-alpha-phenylbutyryl O-trimethylsilyl derivatives was effective in the cases of ephedrine, psi-ephedrine and nor-psi-ephedrine (but not that of nor-ephedrine, on the two stationary phases used). Electron impact mass spectra showed structurally diagnostic fragmentations, but the two diastereomeric amides from each pair of enantiomers yielded generally similar spectra. Molecular ions were of low abundance, but under chemical ionization conditions (isobutane) abundant protonated molecular ions were produced.

Chemical Phenomena↗
PubMed1977

Gas chromatography chemical ionization mass spectrometry of prostaglandin Falpha cyclic boronate derivatives.

The electron impact mass spectra of prostaglandins F 1alpha, F 2alpha and F 3alpha methyl ester cyclic 9,11-methane-, n-butane-, cyclohexane- and benzeneboronate 15-trimethylsilyl ethers show base peaks corresponding to [M-(C-16-C-20)]+, i.e. [M-71]+ for prostaglandins F 1alpha and F 2alpha but [M-69]+ for prostaglandin F 3alpha yielding identical ions in the latter two cases. Derivatives of prostaglandin F 2alpha and F 3alpha are difficult to separate by gas chromatography, so that the use of this ion type for single ion monitoring of either prostaglandin (as has been reported) is ambiguous. The chemical ionization mass spectra of these cyclic boronates, however, show distinctive base peaks for prostaglandins F 1alpha, F 2alpha and F 3alpha at m/e 317,315 and 313 respectively, corresponding to [M-RBO2H2-TMSO]+. Fragmentation patterns have been investigated by the use of [3,3,4,4-2H4]prostaglandin F 2alpha and by the formation of [2H9]trimethylsilyl ethers and a [2H3]methyl ester. Cleavage of the C-15-C-16 bond is of minor importance under chemical ionization conditions. The possible value of the [M-RBO2H2-TMSO]+ ions for single ion monitoring is explored: specificity is aided by the formation of the same ions from a series of boronates of characteristic retention indices.

Boron Compounds↗
PubMed1976

Applications of boronate derivatives in the study of ceramides by gas-liquid chromatography-mass spectrometry.

Methaneboronate derivatives of ceramides possess excellent gas-liquid chromatographic properties and give informative mass spectra. Molecular ions, present at high abundance where an unsaturated acyl substituent is present, are accompanied in the electron impact mass spectra by fragment ions which denote the acyl group and long-chain base. In the gas-liquid chromatographic-mass spectrometric analyses of natural ceramides, as methaneboronate derivatives, the properties of open-tubular columns are exploited to give good separations in moderate analysis times. An application is made to the analysis of ceramides derived from sphingomyelin of human arterial tissue.

Arteries↗
PubMed1976

New derivatives for the analysis of sphingosine long-chain bases by gas-liquid chromatography-mass spectrometry.

Cyclic derivatives formed by reaction of sphingosines with methane-, n-butane- and benzeneboronic acid have been examined by gas-liquid chromatography (GLC) and by combined GLC-mass spectrometry (MS). Analogous compounds have also been studied, in which the amino group has been protected, for example as an acetone Schiff base or N,N-dimethylaminomethylene derivative. Phytosphingosine (4D-hydroxysphinganine) yielded bis-alkaneboronates. Most of the derivatives were satisfactory for GLC. Molecular ions were apparent (1-100% relative abundance) in all electron impact mass spectra, and and (as [M+1](+)ions) were the base peaks in isobutane chemical ionisation mass spectra.

Arteries↗
PubMed1976

Mass spectra of delta 4- and 5 alpha-3-ketosteroids formed during the oxidation of some 3 beta-hydroxysteroids by cholesterol oxidase.

Thirty-six delta5- and 5'alpha-3beta-hydroxysteroids have been oxidized with cholesterol oxidase to give the corresponding delta4- and 5alpha-3-ketosteroids, respectively. The mass spectral characteristics of the products (or their trimethylsilyl ether derivatives, in the case of 3-keto-hydroxysteroids) varied considerably, depending especially on the nature of the C-17 sidechain. The ion of m/e 124 (or its equivalent) from cleavage of ring B was frequently a major fragment from delta4-3-ketosteroids, but in some instances was of insignificant abundance. Trimethylsilylation of the product of the oxidation of neoergosterol gave neoergosterone enol-trimethylsilyl ether. Fragmentations of the sidechain predominated in the mass spectra of the 5alpha-3-ketosteroids.

Cholesterol↗
PubMed1976

Trimethylsilyl group migration during electron impact and chemical ionization mass spectrometry of the trimethylsilyl ethers of 20-hydroxy-5alpha-pregnan-3-ones and 20-hydroxy-4-pregnen-3-ones.

The electron impact and chemical ionization (isobutane) mass spectra of the TMS derivatives of 20-hydroxy-5alpha-pregnan-3-ones and 20-hydroxy-4-pregnen-3-ones include ions [M--44]+-attributable to loss of a CH3CHO fragment from C-17 with migration of the TMS group to the charge-retaining fragment. Mass spectra of isotopically labelled ([3-18O], [20-18O] and [2H9-TMS]) analogues are consistent with this mechanism; [2H9-TMS] labelling further indicates that subsequent loss of a methyl group from [M--44]+-ions does not involve the TMS group. Corresponding ions are not observed at significant abundance in the spectra of 20beta-trimethylsilyloxy-5alpha-pregnane and 20beta-trimethylsilyloxy-4-pregnen-3-one 3-O-methyloxime. In the electron impact mass spectrum of the t-butyldimethylsilyl ether of 20beta-hydroxy-4-pregnen-3-one, an ion is observed corresponding to loss of 44 atomic mass units from the intense [M--C4H9]+ ion.

Electrochemistry↗