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At least 19 recordsLinked to original sources
PubMed1976

Metalloporphyrin contaminations in purified porphyrin preparations as demonstrated by mass spectrometry.

Mass spectrometric studies were performed on selected specimens from my collection of over 700 crystalline porphyrin esters prepared over 20 years as well as on similar preparations from other laboratories. Mass spectrometry was performed by J Moller (Department of Chemistry, Odense University) and Elfinn Larsen (Department of Chemistry, The Experimental Division, Risoe, of the Danish Atomic Energy Commission). Nearly all typical crystalline porphyrins contained Cu- and Ni- and minor amounts of Zn- and Fe2-porphyrins, most often above one molar per cent, sometimes 5--10% and occasionally more, up to 35%. There was no close correlation between the metal content and the melting point. A method is proposed for preparation of metal-free ester preparations: Dissolution of either free or esterified porphyrin in conc. H2SO4; mixing of the solution with 19 volumes of methanol; after at least 12 hours adding of 2 vol. CHCl3 and 2 vol. H2O, and washing the CHCl3, phase with 1/2 vol. distilled water until washwater becomes neutral (8--10 times). Preparations made in this way showed below 0.5% metalloporphyrin contamination. The method does not work with protoporphyrin, which is oxidized by conc. H2SO4. The acid extraction leaves some porphyrin partially esterified, which can be removed by preparative TLC. A TLC-method for detection of metalloporphyrin in porphyrin esters is described.

Coproporphyrins↗
PubMed1978

Some considerations on quantitative methodology and detection limits in organic mass spectrometry.

Mass spectrometric sensitivity data for the compounds cholesterol, cholestane, DDT, decafluorotriphenylphosphine, morphine, LSD and methyl stearate have been developed over a period of time and under a variety of conditions. This information is presented on both a relative and an absolute basis. With the exception of morphine, relative sensitivies were reproducible to within a factor of three over a six month period. This reproducibility facilitates quantitation and a single standard can be used for calibration of organic compounds from various classes. Detection limits of 50 femtograms for LSD are realized for samples introduced via the direct inlet probe.

Cholestanes↗
PubMed2026

Exploring the potential mechanism of Huang'e capsule against spontaneous benign prostatic hyperplasia in beagle dogs using high-performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry, gas chromatography-mass spectrometry, and network pharmacology.

OBJECTIVE: To investigate the therapeutic efficacy and potential mechanisms of Huang'e capsule (, HEC) against benign prostatic hyperplasia (BPH). METHODS: The chemical profile of HEC was characterized using high-performance liquid chromatographyquadrupole-time-of-flight tandem mass spectrometry (HPLC-Q-TOF-MS/MS) and gas chromatography-mass spectrometry (GC-MS) techniques. Network pharmacology was employed to analyze potential active compounds, core targets, and key signaling pathways. A spontaneous canine BPH model was used to evaluate the efficacy of HEC and to validate the predictions from network pharmacology. RESULTS: A total of 51 chemical components of HEC were identified, comprising 19 from HPLC-Q-TOF-MS/MS and 32 from GC-MS analyses. The "components-targets-pathways-disease" network analysis predicted active compounds including (s)-coriolic acid, ethyl linoleate, peroxysimulenoline, physcion, and kaempferol. Core targets identified included cytochrome P450 family 19 subfamily A member 1, estrogen receptor 2 (ESR2), ESR1, and androgen receptor (AR). Kyoto Encyclopedia of Genes and Genomes enrichment analysis suggested that HEC's effects on BPH involve pathways related to cancer, phosphatidylinositol 3-kinase (PI3K) -protein kinase B (Akt)-signaling, proteoglycans in cancer, and prostate cancer signaling. Animal experiments showed that HEC significantly improved maximum urinary flow rates, reduced prostate weight, volume, and prostate index, and ameliorated histopathological changes. HEC regulated the balance between apoptosis and proliferation by downregulating AR and estrogen receptor alpha expression, while upregulating estrogen receptor beta expression. CONCLUSION: These findings indicate that HEC effectively ameliorates spontaneous BPH in beagle dogs, likely by regulating the balance between cell apoptosis and proliferation through multiple signaling pathways.

Animals↗
PubMed1977

Source identification of urban airborne polycyclic aromatic hydrocarbons by gas chromatographic mass spectrometry and high resolution mass spectrometry.

Polycyclic aromatic hydrocarbons formed during the combustion of three common fuels (coal, wood and kerosene) were separated and identified by capillary-column gas chromatographic mass spectrometry and were compared to airborne polycyclic aromatic hydrocarbons from Indianapolis, a high coal consuming area, and Boston, a low coal consuming area. High resolution mass spectral data were utilized in the construction of alkyl homolog plots for the comparison of alkyl distribution within each sample.

Air Pollution↗
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↗
PubMedDate not supplied

The measurement of myocardial tissue gas tensions by mass spectrometry.

The mass spectrometer is a well established tool for the measurement of the partial pressures of gases in respiratory gas mixtures and in flowing blood. Only recently has mass spectrometry been applied to the measurement of gas tensions in tissue. Both blood and tissue gas tension measurements by mass spectrometry were made possible by the development of a special sampling catheter surrounded at its tip by a gas--but not liquid--permeable membrane. The partial pressure of each gas at the external surface of the membrane determines the flow of that gas across the membrane which, in turn, is measured by the mass spectrometer. The use of a Teflon membrane permits tissue measurements because its low permeability to gases reduces the sampling rate of gas molecules with the result that the depletion of gas molecules in the tissue surrounding the membrane is minimal. Mass spectrometry is the only technique whereby it is possible to measure regional tissue pO2 and pCO2 and other gas tensions simultaneously and continuously. One application of mass spectrometric tissue gas tension measurements is the monitoring of myocardial ischemia through measurements of myocardial tissue pO2 and pCO2. We have reviewed the work of others and ourselves in this field.

Adenosine Triphosphate↗
PubMed1978

Determination of imipramine in plasma by high pressure liquid chromatography and field ionization mass spectrometry: increased sensitivity in comparison with gas chromatography mass spectrometry.

A quantitative method is reported for the determination of imipramine in plasma samples in the low nanogram and subnanogram range. The sensitivity and precision of the technique, which involves high pressure liquid chromatography and direct probe field ionization mass spectrometry, are approximately an order of magnitude greater than are offered by gas chromatography mass spectrometry with selected ion monitoring using deuterated or other types of internal standards. [2H6]Imipramine, labeled in the ethylene bridge and in the aromatic rings, serves as the isotopic diluent. The method has been used for the determination of the comparative bioavailabilities of two different commercial preparations of imipramine. In these tests, subjects ingested a 25 mg tablet of one or the other drug preparation together with a solution containing an equivalent amount of imipramine deuterated in the ethylene bridge ([2H2]imipramine). The latter served as an internal check for intrasubject variability in absorption of the imipramine tablets. Typical results from one of the subjects are presented.

Adolescent↗
PubMed1978

Mass spectrometry of uronic acid derivatives. XI--Structure elucidation by mass spectrometry of aldobiouronic and pseudoaldobiouronic acids and their beta-elimination products as per-o-methyl derivatives.

Electron impact mass spectra of a series of aldobiouronic and pseudoaldobiouronic acid per-O-methyl derivatives and of the corresponding 4,5-unsaturated analogues, found normally among the products of methylation of uronic acid containing disaccharides as a result of methylation accompanying beta-elimination, have been studied. Using labelling experiments, metastable transition measurements and high resolution mass spectrometry, the fragmentation mechanisms of substances of this class have been deduced. Application of the information to the structure elucidation of this type of compound is discussed. It is concluded that from the mass spectra alone it is possible to determine the molecular weight, the cycle masses as well as the mode of linkage between the monomeric units. The appearance potentials of ions formed by cleavage of the glycosidic linkages have also been determined and the energetic differences encountered in the fission of the glycosidic linkages of various types of uronic acid containing oligosaccharides are discussed.

Hexuronic Acids↗
PubMed1976

Analysis of estrogen glucuronides. I--Characterization of estrogen glucuronides by gas chromatography mass spectrometry.

The mass spectral characterization of nine kinds of estrogen glucuronides was investigated. The glucuronides were analysed after conversion to n-propyl ester-O-TMS ether derivatives by gas chromatography mass spectrometry. The fragmentation of these derivatives is discussed using deuterium labels and TMS-d9 imidazole. A clear-cut difference was found between aliphatic and aromatic glucuronic acid conjugates. In particular the [M - 362]+- fragment ion was characteristic in the mass spectra of estrogen 3-glucuronides. On the other hand, four isomers of estriol and 16-epiestriol glucuronides containing an aliphatic acetal linkage were also characterized by the fragment ions of m/e value 204, 345, 415, and 431 and their relative intensities. Thus, all nine estrogen glucuronides were discriminated mass spectrometrically.

Chemical Phenomena↗
PubMed1977

Identification of hydroxyhalobiphenyls as their methyl ethers by gas chromatography mass spectrometry.

The mass spectra and gas chromatographic properties of 17 synthetic fluoro-, chloro- and bromomethoxy-biphenyls and 12 dichlorodimethoxybiphenyls have been examined. From this representative series it appears that the position of the methoxy group (ortho, meta and para to the biphenyl bond) in all monomethoxy compounds examined, and the positions of the two methoxy groups in most of the dimethoxy compounds, can be assigned unambiguously by their difference in fragmentation pattern. The value of this method was shown by metabolism experiments in which 4,4'-difluoro- and 4,4'-dibromobiphenyl were fed to rats and 4,4'-dichlorobiphenyl was administered to plants. All hydroxylated metabolites found were identified by gas chromatography mass spectrometry. Relationships between structure and gas chromatographic retention time of these compounds are discussed.

Animals↗
PubMed1977

Peptide sequencing: the utility of chemical ionization mass spectrometry.

Chemical ionization mass spectrometry is used at low resolution to determine the sequences of permethylated acetyl peptides. The method has been tested with 45 peptides, between 2 and 5 residues long, including examples of all of the common amino acids except cysteine and N-terminal asparagine. The isobutane chemical ionization spectra contain three principal types of N-terminal sequence ion and one type of C-terminal sequence ion. The redundant information available from these four types of sequence ion increase the reliability of the sequence determination. In prospect, isobutane chemical ionization mass spectrometry seems to be a useful technique for peptide sequence determination, and may have advantages in some cases.

Amino Acid Sequence↗
PubMed1978

Use of a time averaging computer for high resolution field desorption mass spectrometry.

Field desorption mass spectra often contain few peaks, the largest of which are [M]+. and [M+H]+ ions. Because of this lack of fragmentation accurate mass measurement is of primary concern in field desorption mass spectrometry. Although total ion yield per quantity of sample may rival electron impact or chemical ionization methods, ion yield per unit time is low. For this reason and because of varying [M]+./[M+H]+ ratios, elemental compositions as determined from stable isotope peaks are difficult to obtain. Low ion yield per unit time demands an integrating method for best high resolution results. The use of photoplates to obtain high resolution field desorption data is the only method reported thus far which takes advantage of integrating capability. This paper describes the use of a time averaging computer as an integrator for peak matching high resolution field desorption mass spectrometry using electrical detection. Accuracies better than 20 ppm are consistently obtained. Due to the sensitivity of the technique a wider range of reference compounds can be employed. This method incorporates the advantages of integrating capability with electrical detection, overcoming detection sensitivity problems associated with photoplates.

Adenosine↗
PubMed1977

Location of functional groups in antipyrine metabolites by mass spectrometry.

The mass spectra of antipyrine metabolites show characteristic fragmentation patterns which depend on the presence and position of functional groups. A substituent at position 4 is indicated by an intense key fragment at m/e 56 and a substituent at the methyl group in position 3 causes a significant increase in the intensity of the peak at m/e 82. The fragment at m/e 96, which is characteristic for antipyrine itself, is suppressed if there is a substituent in either position 3 or 4. Mass spectra of the glucuronides of 4-hydroxyantipyrine and 3-hydroxymethylantipyrine are also discussed.

Antipyrine↗
PubMed1978

Metabolic N-oxidation of 3-substituted pyridines: identification of products by mass spectrometry.

The mass spectral characteristics of the N-oxides of a range of 3-substituted pyridines, and of quinoline and isoquinoline, are described. The molecular ion is the base peak in the majority of cases, provided that thermolysis is minimized when using the direct probe or gas chromatography inlets. Chromatographic and mass spectral evidence is presented which indicates that biological oxidation of the heteroaromatic nitrogen of 3-substituted pyridines is a route of metabolism in vivo and in vitro.

Animals↗
PubMed1979

Determination of the configuration of epimeric diols of vitamin D3 series by mass spectrometry.

The mass spectral elimination of water in epimeric 1,3-diols of vitamin D3 (colecalciferol) series has been investigated. It was found that the mass spectra of these steroisomers differ sharply in the relative intensities of the ions M-H2O (m/e 382) and a-H2O (m/e +/- 34), where ion a (formed via formal cleavage of the 7, 8-double bond) is characteristic of vitamin D3 and its derivatives. So while epimeric 1, 3-diols of vitamin D3 series have very close UV and NMR characteristics, the comparison of the ratios of the peaks M-H2O and M.+, a-H2O and a, respectively, makes it possible to distinguish between stereoisomeric 1 alpha, 3 beta-, 1 beta, 3 beta-, 1 alpha, 3 alpha- and 1 beta, 3 alpha-diols using their mass spectra.

Dihydroxycholecalciferols↗