Mass Spectral Identification Research Articles

Mass spectral identification of a metabolite of chlorpropham in potatoes

Mass spectral identification of a metabolite of chlorpropham in potatoes

Mass spectral identification of benzothiazole derivatives leached into injections by disposable syringes.

Five benzothiazole derivatives leached into injections by the rubber plunger-seals of disposable syringes were identified by electron impact (EI) and chemical ionization (CI) mass spectrometry. These are 2-hydroxybenzothiazole, 2-mercaptobenzothiazole, 2-(methylmercapto)benzothiazole, 2-(2-hydroxyethoxy)benzothiazole and 2-(2-hydroxyethylmercapto)benzothiazole. 2-Mercaptobenzothiazole is used as a vulcanization accelerator. The other four compounds are formed from the zinc derivative of 2-mercaptobenzothiazole during sterilization with ethylene oxide. Toxicological, technological and legal consequences of the leaching are discussed briefly.

Mass spectral identification of the blocked N-terminal tryptic peptide of the ATPase inhibitor from beef heart mitochondria

The presence of a formyl blocking group at the N-terminus of the ATPase inhibitor has been identified and the partial sequence of the N-terminal peptide has been determined by fast atom bombardment and field desorption coupled to mass spectrometry. Minor discrepancies in amino acid sequence of the inhibitor between the present and published data [(1981) Proc. Natl. Acad. Sci. USA 78, 7403-7407] are reported and its relationships with other inhbitors are briefly discussed.

E.I. and C.I. mass-spectral identification of some derivatives of 7- O-(2-amino-2-deoxy-α- d-glucopyranosyl)- l- glycero- d- manno-heptose, obtained from lipopolysaccharides representative of the Vibrionaceae family

The electron-impact (e.i.) and chemical-ionization (c.i.) mass spectra of the 2-di- N-methyl ( 2), 2- N-acetyl ( 3), and 2-( N-acetyl)- N-methyl ( 4) derivatives of 1,5-di- O-acetyl-7- O-(2-amino-2-deoxy-3,4,6-tri- O-methyl-α- d-glucopyranosyl)-2,3,4,6-tetra- O-methyl- l- glycero- d- ma nno-heptitol, obtained from the methylation analysis of the core oligosaccharides of Aeromonas hydrophila Chemotypes I and II, are described and their fragmentation patterns proposed. The e.i.-mass spectrum of the 2-dimethylamino derivative 2 showed the primary fragment ion A 1, characteristic of the glycosyl group of this glycosylalditol, whereas the mass spectra of the 2-acetamido ( 3) and 2-( N-methylacetamido) derivatives ( 4) gave the respective primary ions, A 1-fragments, and ald +-fragments diagnostic of the glycosyl group and the alditol residue of the respective glycosylalditol. The c.i.-mass spectra of the glycosylalditol derivatives 2, 3, and 4 gave, as major peaks, the protonated molecular ion [MH] +, together with the primary fragment ion A 1 characteristic of the glycosyl group of the respective derivatives. The e.i.- and c.i.-mass spectra and fragmentation pattern of methyl 7- O-(2-acetamido-3,4,6-tri- O-acetyl-2-deoxy-α- d-glucopyranosyl)-2,3,4,6-tetra- O-acetyl- l- glycero-α- d- manno-heptopy ranoside ( 6) are also reported.

Myo-inositol esters of indole-3-acetic acid are endogenous components of Zea mays L. shoot tissue.

Indole-3-acetyl-myo-inositol esters have been demonstrated to be endogenous components of etiolated Zea mays shoots tissue. This was accomplished by comparison of the putative compounds with authentic, synthetic esters. The properties compared were liquid and gas-liquid chromatographic retention times and the 70-ev mass spectral fragmentation pattern of the pentaacetyl derivative. The amount of indole-3-acetyl-myo-inositol esters in the shoots was determined to be 74 nanomoles per kilogram fresh weight as measured by isotope dilution, accounting for 19% of the ester indole-3-acetic acid of the shoot. This work is the first characterization of an ester conjugate of indole-3-acetate acid from vegetative shoot tissue using multiple chromatographic properties and mass spectral identification. The kernel and the seedling shoot both contain indole-3-acetyl-myo-inositol esters, and these esters comprise approximately the same percentage of the total ester content of the kernel and of the shoot.

An improved procedure, involving mass spectrometry, for N-terminal amino acid sequence determination of proteins which are Nα-blocked

A modification to a previously described procedure [Gray & del Valle (1970) Biochemistry 9, 2134-2137; Rose, Simona & Offord (1983) Biochem. J. 215, 261-272] for mass-spectral identification of the N-terminal regions of proteins is shown to be useful in cases where the N-terminus is blocked. Three proteins were studied: vesicular-stomatitis-virus N protein, Sendai-virus NP protein, and a rabbit immunoglobulin lambda-light chain. These proteins, found to be blocked at the N-terminus with either the acetyl group or a pyroglutamic acid residue, had all failed to yield to attempted Edman degradation, in one case even after attempted enzymic removal of the pyroglutamic acid residue. The N-terminal regions of all three proteins were sequenced by using the new procedure.

The spontaneous polymerization of methyl methacrylate: 6. Polymerization in solution: participation of transfer agents in the initiation reaction

The rate of the spontaneous polymerization of methyl methacrylate is strongly affected by the addition of transfer agents. The kinetics are interpreted in terms of a participation of transfer agents in the initiation step. In this, the original biradical, .M 2., which is produced from two monomer molecules and which has a high self-termination probability, is converted into polymerizable monoradicals. Increase in the concentration of a strong transfer agent leads to double-transferred compound HH1, the mass spectral identification of which is to be regarded as first direct evidence for the existence of biradical .M 2..

Quaternary ammonium salts for butylation and mass spectral identification of volatile organic acids

Quaternary ammonium salts for butylation and mass spectral identification of volatile organic acids

Endogenous biosynthesis of prostacyclin and thromboxane and platelet function during chronic administration of aspirin in man.

To assess the pharmacologic effects of aspirin on endogenous prostacyclin and thromboxane biosynthesis, 2,3-dinor-6-keto PGF1 alpha (PGI-M) and 2,3-dinor-thromboxane B2 (Tx-M) were measured in urine by mass spectrometry during continuing administration of aspirin. To define the relationship of aspirin intake to endogenous prostacyclin biosynthesis, sequential urines were initially collected in individuals prior to, during, and subsequent to administration of aspirin. Despite inter- and intra-individual variations, PGI-M excretion was significantly reduced by aspirin. However, full mass spectral identification confirmed continuing prostacyclin biosynthesis during aspirin therapy. Recovery of prostacyclin biosynthesis was incomplete 5 d after drug administration was discontinued. To relate aspirin intake to indices of thromboxane biosynthesis and platelet function, volunteers received 20 mg aspirin daily followed by 2,600 mg aspirin daily, each dose for 7 d in sequential weeks. Increasing aspirin dosage inhibited Tx-M excretion from 70 to 98% of pretreatment control values; platelet TxB2 formation from 4.9 to 0.5% and further inhibited platelet function. An extended study was performed to relate aspirin intake to both thromboxane and prostacyclin generation over a wide range of doses. Aspirin, in the range of 20 to 325 mg/d, resulted in a dose-dependent decline in both Tx-M and PGI-M excretion. At doses of 325-2,600 mg/d Tx-M excretion ranged from 5 to 3% of control values while PGI-M remained at 37-23% of control. 3 d after the last dose of aspirin (2,600 mg/d) mean Tx-M excretion had returned to 85% of control, whereas mean PGI-M remained at 40% of predosing values. Although the platelet aggregation response (Tmax) to ADP ex vivo was inhibited during administration of the lower doses of aspirin the aggregation response returned to control values during the final two weeks of aspirin administration (1,300 and 2,600 mg aspirin/d) despite continued inhibition of thromboxane biosynthesis. These results suggest that although chronic administration of aspirin results in inhibition of endogenous thromboxane and prostacyclin biosynthesis over a wide dose range, inhibition of thromboxane biosynthesis is more selective at 20 than at 2,600 mg aspirin/d. However, despite this, inhibition of platelet function is not maximal at the lower aspirin dosage. Doses of aspirin in excess of 80 mg/d resulted in substantial inhibition of endogenous prostacyclin biosynthesis. Thus, it is unlikely that any dose of aspirin can maximally inhibit thromboxane generation without also reducing endogenous prostacyclin biosynthesis. These results also indicate that recovery of endogenous prostacyclin biosynthesis is delayed following aspirin administration and that the usual effects of aspirin on platelet function ex vivo may be obscured during chronic aspirin administration in man.

Gas chromatographic—mass spectrometric analysis of polychlorinated dibenzo- p-dioxins and organic compounds in high-temperature fly ash from municipal waste incineration

Fly ash from a high-temperature rotary kiln municipal waste incinerator is generally considered to be free of organic compounds. Samples were analyzed for residual organic compounds by gas chromatography—mass spectrometry. Mass spectral identification revealed the presence of polychlorinated dibenzo- p-dioxins (PCDDs), but no detectable tetra-isomers or penta-isomers. Polychlorinated dibenzofurans (PCDDs) as well as chlorinated benzenes, chlorinated cyclohexanes, and chlorinated biphenyls were found. A qualitative correlation was found between the levels of PCDDs and PCDFs with these other chlorinated species, which may indicate them to be precursors in the formation of PCDDs and PCDFs even at high-temperature conditions. A discussion of physical parameters which may affect the formation of PCDDs and PCDFs during incineration is also presented.

Identification of sulphur heterocycles in coal tar and pitch

The direct application of gas chromatography with a flame photometric sulphur detector and mass spectrometry to the identification of sulphur heterocycles in coal tar and pitch without the need for prior separation of a sulphur-rich fraction is described. Accurate mass measurement has allowed the assignment of atomic compositions to the sulphur heterocycles with little ambiguity, despite their presence as minor components in a complex aromatic mixture. Single ion chromatograms and retention indices calculated relative to aromatic hydrocarbons have been used to correlate the mass spectral identifications with the sulphur-selective gas chromatograms.

Reductive metabolism of carbon tetrachloride by human cytochromes P-450 reconstituted in phospholipid vesicles: mass spectral identification of trichloromethyl radical bound to dioleoyl phosphatidylcholine.

It has been proposed that covalent binding of reactive metabolites to liver membrane constituents may be responsible for the hepatoxicity of carbon tetrachloride. This study demonstrates that trichloromethyl free radical is the major reductive metabolite of carbon tetrachloride by cytochrome P-450 and that this free radical is capable of binding to double bonds of fatty acyl chains of the phospholipids in the membrane surrounding cytochrome P-450. The structural identification of the reactive free radical metabolite and the product of its addition to phospholipids was accomplished by use of a reconstituted system of human cytochromes P-450, NADPH-cytochrome P-450 reductase, and cytochrome b5 in phospholipid vesicles. The reconstituted vesicles contained a mixture of dioleoyl phosphatidylcholine and egg phosphatidylethanolamine that served as both structural components and targets for trichloromethyl free radical binding. After incubation of these vesicles under a N2 atmosphere in the presence of NADPH with 14CCl4, the phospholipids were extracted and then separated by high-pressure liquid chromatography. The dioleoyl phosphatidylcholine fraction was transesterified and the resulting single 14C-labeled fatty acid methyl ester was purified by reverse-phase chromatography. Desorption chemical ionization mass spectrometry with ammonia as reagent gas as well as desorption electron-impact mass spectrometry permitted identification of the molecular structure as a mixture of 9- and 10-(trichloromethyl)stearate methyl esters.

Mass Spectral Identification and Gas-Liquid Chromatographic Determination of Methyl 4-Chloroindolyl-3-Acetate in Canned and Frozen Peas

Methyl 4-chloroindolyl-3-acetate (MCIA), a naturally occurring auxin, has been identified in canned and frozen peas by gas-liquid chromatography (GLC)/mass spectrometry. Eight samples were analyzed for MCIA using slightly modified official AOAC multiple pesticide residue procedures employing GLC with microcoulometric detection. Levels of MCIA averaged 0.20 ppm for canned peas and 0.16 ppm for frozen peas. Recovery of MCIA from a fortified sample was 40%.

Characterization of Aniline-Acetone Condensation Products by Liquid Chromatography and Mass Spectroscopy

Abstract Liquid chromatography has proven to be an extremely valuable tool for many separations involving polymers and polymer chemicals, especially when used in conjunction with mass spectroscopy for chemical identification. The complex products of the condensation reaction of aniline with acetone have been characterized by liquid chromatography and mass spectroscopy. The LC separation procedure utilized a C18 Micro Bondapak (reverse phase) column with a water/tetrahydrofuran gradient system. Eluted peaks were trapped individually for field desorption mass spectral identification. Syringe deposition was used to transfer the isolated components to the field emitter. The major components found in the reaction mixture were oligomers of 2,2,4-trimethyl-l,2-dihydroquinoline (TMDQ), although several other monomeric and oligomeric side-products were observed and characterized. Forty-two components were identified in the product resin. These can be classified into eight major series of oligomers; all series have oligomers separated by the TMDQ monomer unit (173 amu).

Mass-spectral identification and purification of phycoerythrobilin and phycocyanobilin.

The bile-pigment chromophores of C-phycoerythrin (phycoerythrobilin) and C-phycocyanin (phycocyanobilin) were cleaved from their respective proteins with boiling methanol or butan-1-ol. They were purified as dicarboxylic acids by preparative reverse-phase liquid chromatography. Each pigment existed in two principal forms, which were characterized by using 20 pmol samples by proton-transfer chemical-ionization mass spectroscopy. These two principal forms were isomeric species, and all had protonated parent molecular ions with m/e 587, corresponding to a molecular weight of 586.

Environmental occurrence and mass spectral identification of ethylene glycol derivatives

Ethylene glycol derivatives are commonly used, commercial products. Surprisingly, there have been very few reported incidences of environmental contamination caused by these compounds even though their commercial production is quite high. Since few mass spectra of these chemicals are in reference collections, their proper identification could have been simply overlooked. Mass spectral characteristics of these compounds are outlined, along with methods for their exact structural determination.

Catalytic dechlorination of organochlorine compounds VI. Mass spectral identification of aldrin and dieldrin products

Catalytic dechlorination of organochlorine compounds VI. Mass spectral identification of aldrin and dieldrin products

Computer Techniques for Mass Spectral Identification

Computer Techniques for Mass Spectral Identification

Application of a text search system based on boolean strategy to mass spectral data identification

A general algorithm for text searching, operated on a tape-based minicomputer, has already been reported. This paper presents the application of the general text-searching algorithms to the Registry of Mass Spectral Data of 18,806 different entries. The text format allows multi-information input to be used to search the spectral library on the basis of data not necessarily extracted from mass spectra. Two library files have been generated; one is approximately half the size of the other, less important information having been deleted. The shorter library contains all 18,806 entries but enjoys much faster search times. Batch processing of searches is also possible. The text search is shown to be versatile in its operation, as the user can construct searches to be either broad or very selective, depending on the application. The search also has the capability to examine the data base internally and to check certain data for their validity.

Catalytic dechlorination of organochlorine compounds IV. Mass spectral identification of DDT and heptachlor products

Catalytic dechlorination of organochlorine compounds IV. Mass spectral identification of DDT and heptachlor products