Showing papers in "Journal of Mass Spectrometry in 1975"
TL;DR: Phosphoramide mustard is implicates as a leading condidate for the biologically active form of cyclophosphamide for which blood levels, cytotoxicity and alkylating activity are considered.
Abstract: Thin-layer chromatography and mass spectrometry were used to isolate and identify cyclophosphamide metabolites present in blood of mice. Blood was removed 5, 15, 30 and 45 minutes after intraperitoneal administration and extracted with chloroform followed by methanol. Thin-layer chromatography of the two extracts and the residual solid with or without prior methylation, collection of resulting alkylating components, determination of radioactivity and mass spectral analysis, served to identify cyclophosphamide, 4-ketocyclophosphamide, alcophosphamide, N-dechloroethylcyclophosphamide, carboxyphosphamide, phosphoramide mustard and nor-HN2. The absence of detectable levels of 4-hydroxycyclophosphamide or aldophosphamide in the blood of cyclophosphamide-treated mice suggests that cyclophosphamide is converted rapidly in the liver to carboxyphosphamide, 4-ketocyclophosphamide, phosphoramide mustard and nor-HN2. Direct administration of synthetic 4-hydroxycyclophosphamide to mice and extraction of blood with chloroform demonstrated the recovery of this metabolite in vivo. Analysis of extracts of blood from mice treated with phosphoramide mustard indicated the presence of nor-HN2, 3-(2-chloroethyl)-1,3-oxazolidin-2-one and unchanged drug. Consideration of blood levels, cytotoxicity and alkylating activity of metabolites identified in, or inferred from, this study, implicates phosphoramide mustard as a leading candidate for the biologically active form of cyclophosphamide.
132 citations
TL;DR: In this article, three different methods for achiving a cationisation are described and discussed: (1) field-indiced cationization at low anode temperatures using a heterogenous reaction of the molecules in the gas phase with molecules of a salt in the adsorption layer on the field anode; (2) largely thermally induced catisation at high emitter temperatures and low electric fields, causing less thermal excitation to the molecules, using the field desorption technique.
Abstract: In General cationised molecules are more stable than redical molecular ions or protonated molecules. The fragmentation of the polar molecules resulting from a cationsation by for instance alkali ions, has a higher activation energy than splitting off fuctional groups after a protonation. Cationisation is therefore an intersting tool for the determination of molecular weights. Three different methods for achiving a cationisation are described and discussed: (1) field-indiced cationisation at low anode temperatures using a heterogenous reaction of the molecules in the gas phase with molecules of a salt in the adsorption layer on the field anode; (2) a largely thermally induced catisation at high emitter temperatures and low electric fields; (3) a cationisation, causing less thermal excitation to the molecules, using the field desorption technique.
108 citations
TL;DR: A mass fragmentographic method is described for the simultaneous assay of both the acidic and alcoholic metabolites of tyramine, octopamine, dopamine and norepinephrine, successfully applied for the measurement of nanogram quantities of these metabolites in human ventricular and lumbar cerebrospinal fluids and in the rat brain.
Abstract: A mass fragmentographic method is described for the simultaneous assay of both the acidic and alcoholic metabolites of tyramine, octopamine, dopamine and norepinephrine The method was successfully applied for the measurement of nanogram quantities of these metabolites in human ventricular and lumbar cerebrospinal fluids and in the rat brain Mass fragmentography was carried out on the methyl ester/pentafluoroproprionyl derivatives of the acidic and the pentafluoropropionyl derivatives of the alcoholic metabolites, employing an 8 ft 3% SE-54 column Chemical methods for the synthesis of a number of deuterated isomers (isotopomers) of the above metabolites are also described These isotopomers were utilized as internal reference standards for the assay of the metabolites in biological materials They were also used to study the fragmentation reactions of these metabolite derivatives
104 citations
TL;DR: A method for quantification of phencyclidine in body fluids using gas chromatography chemical ionization mass spectrometry with selected ion recording was developed by as mentioned in this paper, which was used to identify 4-phenyl-4-piperidinocyclohexanol and 1-(1phenylcyclohexyl)-4-hydroxypiperidine.
Abstract: A method has been developed for quantification of phencyclidine [1-(1-phenylcyclohexyl)piperidine] in body fluids using gas chromatography chemical ionization mass spectrometry with selected ion recording Pentadeuterated phencyclidine was synthesized and used as the internal standard In developing the method it was discovered that phencyclidine thermally fragments to 1-phenylcyclohexene at elevated temperatures The sensitivity and specificity of the method permits determination of 1 ng of phencyclidine in 1 ml of body fluid The concentrations of the drug in blood samples from five individuals, who ingested unknown quantities of phencyclidine, were found to range from 50 ng/ml to 27 μg/ml Following intravenous administration of 1 mg of phencyclidine hydrochloride to a 125 kg dog, the blood concentration of the drug peaked at 176 ng/ml and exhibited a half-life of approximately one hour Two metabolities of phencyclidine were detected in human and dog urine after enzymatic hydrolysis The metabolities were tentatively identified as 4-phenyl-4-piperidinocyclohexanol and 1-(1-phenylcyclohexyl)-4-hydroxy-piperidine by electron impact and chemical ionization mass spectral analysis of the metabolites and their trimethylsilyl derivatives Structural confirmation was achieved by synthesis of the metabolities A third metabolite was found in urine from rhesus monkeys and was tentatively identified as 1-(1-phenyl-4-hydroxycyclohexyl)-4-hydroxypiperidine
96 citations
TL;DR: The types of ion occurring in the field desorption mass spectra of inorganic and organic salts are discussed in this article, where specific aspects for the analyses of salts by FRSMS are outlined.
Abstract: The types of ion occurring in the field desorption mass spectra of inorganic and organic salts are discussed. In contrast to general experience with field desorption mass spectrometry molecular ions are either absent or of low intensity. The energetically and kindetically favoured process of cluster formation, however, generates ions from which the molecular structure can be easily derved. Some specific aspects for the analyses of salts by field desrption mass spectrometry are outlined.
81 citations
TL;DR: In this paper, it is shown that charge stripping provides information on ion structure which is complementary to that given by collision-induced dissociation, which preferentially samples higher energy ions.
Abstract: Through studies on [C6H6]+ and [C6H5]+ it is shown that charge stripping provides information on ion structure which is complementary to that given by collision-induced dissociation. Stripping involves a more uniform sampling over the range of ion internal energies than does collision-induced dissociation which preferentially samples higher energy ions.
80 citations
TL;DR: Limited acid hydrolysis combined with a second experimen utilizing either an enzyme with broad specificity, a set of enzymes, or dipeptidyl aminopeptidase I on the original and/or Edman-degraded molecule was found to be the best choice.
Abstract: A generally applicable strategy for polypeptide sequencing has been developed which involves cleavage of a large peptide (for example, primary degradation peptides obtained by tryptic or cyanogen bromide cleavage of a protein) to a mixture of small peptides whose individual amino acid sequences are then determined without their prior isolation. This is accomplished by conversion of the peptide mixture into the corresponding mixture of O-trimethylsilylated polyamino alcohols through reduction of the N-acetylated peptide esters with lithium aluminum deuteride, followed by treatment with trimethylsilyldiethylamine. The conditions for the enzymatic or chemical cleavage were optimized to yield mixtures of peptides best suited for this technique and which represented complete overlap. Limited acid hydrolysis combined with a second experimen utilizing either an enzyme with broad specificity, a set of enzymes, or dipeptidyl aminopeptidase I on the original and/or Edman-degraded molecule was found to be the best choice. This sequencing strategy was evaluated using 0.4 to 1.4 μmol of peptides with known structures (ribonuclease S-peptide, glucagon) and then applied to primary degradation peptides of rabbit skeletal muscle actin up to twenty amino acids long (0.4 to 1 μmol per experiment).
48 citations
TL;DR: In this article, the authors show that the composite peak observed in the unimolecular fragmentation (i) [C3H4]-· [C 3H3]+ + H· is present only if the decomposing molecular ion is large enough to also produce [C6H8]2+ ions.
Abstract: Composite metastable peaks are generated in the unimolecular fragmentations (i) [C3H5]+ [C3H3]+ + H2 (flat-top upon flat-top) and (ii) [C4H9]+ [C3H5]+ + CH4 (flat-top and gaussian). The measurement of appearance potentials and kinetic energy releases lead us to conclude, in agreement with earlier proposals, that in (i) the components can arise from the generation of the isomeric cyclopropenium and propargyl daughter cations. In (ii) the components are proposed to arise from the fragmentation of tert- and sec-butyl cations yielding allyl as the common daughter ion.
The composite peak observed in the fragmentation (iii) [C3H4]+· [C3H3]+ + H· is shown to be present only if the decomposing molecular ion is large enough to also produce [C6H8]2+ ions. The second component in (iii) then arises from the reaction [C6H8]2+ [C6H6]2+ + H2.
44 citations
TL;DR: The results of the translational energy loss measurements compare well with excitation energies predicted for each reaction form breakdown curves showing the relative abundances of the ionsas a fuction of internal energy as discussed by the authors.
Abstract: Collision-induced dissociation of the molecular ions and of some of the fragment ions foremed on ionization of methanol, ethanol and n-propnol have been studied at high energy resolution in a mass spectrometer. The translational energy lost upon collision and the kinetic energy releasedupon fragmentation of the collisionally excited species have been measured by the methods of ion kinetic energy spectromety. The results of the translational energy loss measurements compare well with excitation energies predicted for each reaction form breakdown curves showing the relative abundances of the ionsas a fuction of internal energy. This correspondence is evidebce that the ionic reactions following electron-impact excitation and those following collisional excitation with neutral molecules at relative traslational energies in the range of several kilovolts are at least qualitatively independent of the method of excitation. The occurrence of the corresponding spontaneous fragmentations in the alcohols has also been studied and the kinetic energy releases accompanying these reactions have been determined. In a few cases, metastable peaks were observed which did not increase in intensity when collision gas added and this phenomenon is associated with particular features of the reaction thermochemistry. Reactions which generally occur to very small extents in mass spectromety, such as methylene elimination, have been observed in highly excited ions. The methods developed in this study allow the decription of the thermochemistry of the reaction of highly excited ions, indlcuding the experimental determination of the partitioning of the nonfixed energy of the activated complex. This procedure complemets and extends energy partitioning studies made on metastable ions in which the partitioning of the reverse activation energy is the more readily accessible.
41 citations
Abstract: The molecular ions of isomeric octanes retain their structural identity, while their alkyl fragments [CnH2n+1]+ (n = 3 to 7) isomerise to common structures prior to decomposition. Structures for [C6H13]+ and [C7H15]+ ions are proposed.
40 citations
TL;DR: In this article, complex mixtures of O-trimethylsilylated polyamino alcohols, which have been generated by either acid or enzymatic hydrolysis of polypeptides and subsequent derivatization, are completely characterized by a gas chromatograph mass spectrometer computer system.
Abstract: Complex mixtures of O-trimethylsilylated polyamino alcohols, which have been generated by either acid or enzymatic hydrolysis of polypeptides and subsequent derivatization, are completely characterized by a gas chromatograph mass spectrometer computer system. These peptide derivatives possess excellent gas chromatographic properties; a wide range of derivatives from di- to hexapeptides may be separated in a single chromatographic experiment. The identification of these compounds, either manually or with the assistance of the computer, is based on three sets of data which are automatically generated after the g.c.m.s. computer experiment: (1) mass spectra, which exhibit sequence-determining ions of high abundance; (2) selected ion records, which allow efficient location of peptide derivatives in the gas chromatogram as well as resolution of incompletely separated fractions; (3) retention indices, which can be calculated from values which have been assigned to each amino acid residue.
TL;DR: In this article, collisional activation spectra of [C8H8]+·, [C 8H8]2+, [C6H6]+· and [C 6H5]+ ions from fifteen different sources are reported.
Abstract: Collisional activation spectra of [C8H8]+·, [C8H8]2+, [C6H6]+· and [C6H5]+ ions from fifteen different sources are reported. Decomposing [C8H8]+· ions of ten of these precursors isomerise to a mixture of mainly the cyclooctatetraene and, to a smaller extent, the styrene structure. Three additional structures are observed with [C8H8]+· ions from the remaining precursors. [C8H8]2+., [C8H8]+·, [C6H6]+· and [C6H5]+· ions mostly decompose from common structures although some exceptions are reported.
TL;DR: The electron impact mass spectra of twenty acetates and methylates of spirostanol and related furostanol glycosides of high molecular weight (above 650) have been investigated, and the most probable fragmentation patterns of the glycoside derivatives are presented as mentioned in this paper.
Abstract: The electron impact mass spectra of twenty acetates and methylates of spirostanol and related furostanol glycosides of high molecular weight (above 650) have been investigated, and the most probable fragmentation patterns of the glycoside derivatives are presented. High resolution mass spectrometry provides useful information concerning the structures of both aglycone and sugar moieties as well as the molecular size of the oligoglycosides.
TL;DR: In this article, the authors measured the metastable ion peak shapes, dimensions and relative abundances for the three fragmentations [C3H6]+· [c3H4]+· + H2, [CH6]-[CH4]-[cH5]- [cH3]-[H2]-] + H· and [H3H−[C3]−[H·+H·]−H· +H· and concluded that the differences in their internal energy differences can be attributed to internal energy difference.
Abstract: Metastable ion peak shapes, dimensions and relative abundances have been measured for the three fragmentations [C3H6]+· [C3H4]+· + H2, [C3H6]+· [C3H5]+ + H· and [C3H6]+· [C3H3]+ + H2 + H·. [C3H6]+· ions were derived from propene, cyclopropane, tetrahydrofuran, cyclohexanone, 2-methyl but-1-ene and cis-pent-2-ene. Activation energies for these fragmentations have been evaluated. Three daughter ion dissociations ([C3H5]+ [C3H3]+ + H2, [C3H5]+ [C3H4]+· + H· and [C3H4]+· [C3H3]+ + H·) have been similarly examined.
Ion structures have been determined and the metastable energy releases have been correlated with the thermochemical data. It is concluded that the molecular ions of propene and cyclopropane become structurally indistinguishable prior to fragmentation and that differences in their metastable ion characteristics can be ascribed wholly to internal energy differences; the latter can be correlated with the photoelectron spectra of the isomers. The pathway for the consecutive fragmentation which generates the metastable ion peak (m/e 42 m/e.39) has been shown to be
It is likewise concluded that fragmentating [C3H6]+· ions generated from the various precursor molecules are also structurally indistinguishable and cannot be classified with either molecular ion of the isomeric C3H6 hydrocarbons.
TL;DR: A rapid, sensitive method of analysis for methylphenidate and ritalinic acid in blood and urine has been developed using gas chromatography mass spectrometry and selected ion monitoring for separation and detection.
Abstract: A rapid, sensitive method of analysis for methylphenidate and ritalinic acid in blood and urine has been developed using gas chromatography mass spectrometry and selected ion monitoring for separation and detection. The methylphenidate is isolated by solvent extraction into chloroform and the ritalinic acid is isolated by salting out into isopropyl alcohol, followed by methylation and subsequent solvent extraction. The method has been applied to the study of methylphenidate metabolism and excretion in adults and hyperactive children undergoing treatment with methylphenidate.
TL;DR: It is shown that the coefficient of variation of the single ions monitoring method is substantially lower than that of the multiple ion monitoring method, and small quantities of a compound are most accurately determined by adding a labelled version of the compound solely to act as a carrier, plus an internal standard giving an ion in common with the compound being measured.
Abstract: Single and multiple ion monitoring is employed to evaluate whether deuteriomethylated allobarbitone or methylated quinalbarbitone is the better internal standard for quantifying methylated allobarbitone through a g.c.m.s. system based on a quadrupole mass spectrometer. It is shown that the coefficient of variation of the single ion monitoring method is substantially lower than that of the multiple ion monitoring method. Small quantities of a compound are therefore most accurately determined by adding a labelled version of the compound solely to act as a carrier, plus an internal standard giving an ion in common with the compound being measured. By this means 40 pg and 100 pg of methylated allobarbitone could be determined with coefficients of variation of 11.5 and 2.0%, respectively. Using only the labelled compound as internal standard, the corresponding values were 19.8 and 15.3% for the same quantities.
TL;DR: Choline chloride, bromide and iodide all contain a peak at m/e 118 [M + 14] in their field desorption mass spectra as mentioned in this paper, suggesting that this peak arises from an intermolecular transfer of a methyl group.
Abstract: Choline chloride, bromide and iodide all contain a peak at m/e 118 [M + 14] in their field desorption mass spectra. Comparison with choline(methyl-d9) chloride demonstrates that this peak arises from an intermolecular transfer of a methyl group. Partial exchange of hydroxyl hydrogen on choline chloride does not displace the m/e 118 peak, suggesting that this hydrogen is lost during methyl transfer. The structure of the [M + 14] species should then correspond to choline methyl ether.
TL;DR: A mass fragmentographic method for simultaneous measurement of unlabeled and deuterium labeled methadone in human plasma is described and will be of value in the study of Methadone pharmacokinetics in the steady state and in other in vivo situations where multiple drug pools must exist.
Abstract: A mass fragmentographic method for simultaneous measurement of unlabeled and deuterium labeled methadone in human plasma is described. This specific method has a lower sensitivity of about 16 pmol/ml with a coefficient of variation of less than 4%. The usefulness of the method was evaluated in studies on opiate dependent subjects undergoing methadone maintenance treatment. In one application methadone-d3 was given as a pulse dose during continuous treatment with unlabeled methadone and plasma levels of both species followed by mass fragmentography. The method will be of value in the study of methadone pharmacokinetics in the steady state and in other in vivo situations where multiple drug pools must exist.
TL;DR: In this article, a calibration curve has been established that gives an estimate of the temperature in the emission region of high temperature activated field desorption emitters, and two characteristic types of field anodes have been investigated: (1) emitter wires carrying microneedles of 25 to 30 μm length and (2) emitters with 50 to 60μm length, which are used for the investigations of polymers by pyrolysis field disorption mass spectrometry.
Abstract: Calibration curves have been established that give an estimate of the temperature in the emission region of high temperature activated field desorption emitters. Two characteristic types of field anodes have been investigated: (1) emitter wires carrying microneedles of 25 to 30 μm length, preferentially used for field desorption of organic compounds; (2) emitters with microneedles of 50 to 60 μm length, which are used for the investigations of polymers by pyrolysis field desorption mass spectrometry.
TL;DR: The identification of 6-methoxy 8-aminoquinoline as a metabolite of Primaquine, an important antimalarial drug, is described and the metabolite is present in urine, plasma and erythrocytes following drug ingestion.
Abstract: The identification of 6-methoxy 8-aminoquinoline as a metabolite of Primaquine, an important antimalarial drug, is described. The metabolite is present in urine, plasma and erythrocytes following drug ingestion. It was identified by mass fragmentography of its 1H and 2H acetate and the acetate produced from authentic material. No evidence of further metabolites was obtained.
TL;DR: In this article, the field desorption mass spectra of a tripeptide Pro-Leu-Gly-NH2, a pentapeptide CbzGlyPro-Pro Leu Gly-Pro Gly N 2 and a nonapeptides Arg-Pro Pro Gly Phe-Ser-Pro-Phe-Arg are presented, and sufficient fragmentation of the peptide backbone occurred to allow sequence determination of all three peptides.
Abstract: Field desorption mass spectra of a tripeptide Pro-Leu-Gly-NH2, a pentapeptide Cbz-Gly-Pro-Leu-Gly-Pro and a nonapeptide Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg are presented. In each case, a [M]+· or [M + 1]+ peak of the peptide is obtained. Sufficient fragmentation of the peptide backbone occurred to allow sequence determination of all three peptides. The pentapeptide produced [M]+·, [M + 1]+ and [M + 2]+· ions which also included molecules of ethylacetate, ethanol and/or water bound to the ion.
TL;DR: An ion doublet chemical ionization mass spectrometry technique was utilized for the rapid detection and elucidation of the structure of a new hydroxylated metabolite of the oral anticoagulant warfarin.
Abstract: An ion doublet chemical ionization mass spectrometry technique was utilized for the rapid detection and elucidation of the structure of a new hydroxylated metabolite of the oral anticoagulant warfarin. This technique involves the use of a 50:50 mixture of stable isotope labeled and unlabeled drug. With this procedure ions found in the mass spectrum which are associated with the administered drug can be identified unambiguously. The unknown metabolite from rat liver microsomal preparations was identified as benzylic hydroxywarfarin by reincubating the microsomes with warfarin specifically labeled in the benzylic position and observing the subsequent loss of label in the product. The ion doublet technique was also employed in a single human study, and benzylic hydroxywarfarin was detected and identified.
TL;DR: In this paper, the first three primary fragmentations of benzaldoxime were discussed and their metastable properties were obtained from deuterated analogues and their respective metastable characteristics.
Abstract: Primary fragmentations of benzaldoxime include loss of H·, OH·, HCN, CO and HCNO and this paper discusses the first three losses. The previously reported losses of H2O and O were proven to be thermal in origin. Information about the investigated fragmentations was obtained from the deuterated analogues and their metastable characteristics. The OH· elimination is complex. The loss of HCN exhibits a metastable with a composite structure. This fragmentation may occur both via a 4-centred and 5-centred mechanism. A fluorine atom at the ortho position of the phenyl ring favours the 5-centred mechanism.
TL;DR: In this paper, it was shown that decomposing [CnH2n−1]- fragments are completely or almost completely isomerised after a lifetime of a few μs.
Abstract: [C8H16]+. molecular ions from alkenes and cycloalkanes differing in their skeletal con-figuration do not in general isomerise completely to a common structure, except for the molecular ion of n-propylcyclopentane, the structure of which is identical to that of the normal octene ions. In contrast, decomposing [CnH2n−1]+ fragments are completely or almost completely isomerised after a lifetime of a few μs.
TL;DR: The electron impact mass spectrum (70 eV) of 26-trimethylsilyloxy-4-cholesten-3-one showed a base peak at m/e 196, attributable to combination of the trimethyl silyl group with a fragment of m /e 123 produced by cleavage across ring B 18O labelling.
Abstract: The electron impact mass spectrum (70 eV) of 26-trimethylsilyloxy-4-cholesten-3-one shows a base peak at m/e 196, attributable to combination of the trimethylsilyl group with a fragment of m/e 123 produced by cleavage across ring B 18O labelling confirms that the fragment of m/e 196 contains the 3-oxygen atom, and 2H labelling indicates retention of the trimethylsilyl moiety Similar ions are observed from other Δ4-3-ketones with sidechain trimethylsilyloxy groups: abundances depend on the site of substitution The corresponding enol trimethylsilyl ethers are readily separable from the keto forms by gas-liquid chromatography, and afford mass spectra in which the molecular ions are abundant, while ions of m/e 196 are of only moderate intensity
TL;DR: In this paper, chemical ionization mass spectra of eleven biomedically significant quaternary amimes are reported, which gives simple, easily identifiable spectra which are useful for the analysis of the original samples.
Abstract: Chemical ionization mass spectra of eleven biomedically significant quaternary amimes are reported. The samples are converted to volatile compounds by known thermal decompositions. Chemical ionization of the compounds gives simple, easily identifiable spectra which are useful for the analysis of the original samples.
TL;DR: The method described provides a new means whereby the 100 or so low molecular weight organic volatiles of plasma can be monitored during the dialysis procedure.
Abstract: Low molecular weight volatile organics extracted from the plasma of patients before and after hemodialysis were analyzed by high resolution capillary gas chomatographic mass spectrometric computer methods. The volatile components were collected on a polyphenyl ether solid adsorbent prior to analysis. Identification of components was achieved by mass spectrometry. Quantitaive changes were observed in both the plasma and dialysate composition with time. The method described provides a new means whereby the 100 or so low molecular weight organic volatiles of plasma can be monitored during the dialysis procedure.
TL;DR: A routine analysis for micro samples of plasma amino acids by a gas chromatography mass spectrometry computer system yields excellent precision and accuracy, as demonstrated by the analysis of a known amino acid mixture and of neonatal plasma.
Abstract: A routine analysis for micro samples of plasma amino acids by a gas chromatography mass spectrometry computer system has been developed. Isotope ratio determination was used as the quantitating technique via multiple internal standards. The speed of the analysis is increased by omitting the ion exchange purification step and its flexibility is maximized by using repetitive scanning rather than selective ion monitoring. This procedure yields excellent precision and accuracy, as demonstrated by the analysis of a known amino acid mixture and of neonatal plasma.
TL;DR: The alkaloids have been shown to originate from a spontaneous condensation of the corresponding amines with formaldehyde, this latter being formed in the first stage of the reaction by enzymatic conversion from 5-methyltetrahydrofolic acid.
Abstract: The use of thin-layer chromatography has demonstrated that incubations of indoleamines with 5-methyl[14-C]tetrahydrofolic acid and an enzyme previously described as an N-methyltransferase, do not yield Nw, N1, or O-methylated products. Further elucidation by thin-layer chromatography, gas chromatography, mass spectrometry and selected ion monitoring enabled us to identify the reaction products as tetrahydroisoquinolines and tetrahydro-beta-carbolines in mixtures incubated respectively with catecholamines and indoleamines in the presence of 5-methyl[14-C]tetrahydrofolic acid and enzyme. The alkaloids have been shown to originate from a spontaneous condensation of the corresponding amines with formaldehyde, this latter being formed in the first stage of the reaction by enzymatic conversion from 5-methyltetrahydrofolic acid.
TL;DR: In this paper, the kinetics of formation of [C3H5]-[M CH3]+, [C4H8]-· and [C2H4]-· from but-1-ene, cis-and trans-but-2-ene and 2-methylpropene, cyclobutane and methylcyclopropance following field ionisation have been determined as a function of time 20 (or 30) picoseconds to 1 nanosecond and at two points in the microsecond time-frame.
Abstract: The kinetics of formation of [C3H5]+[M CH3]+, [C3H4]+·[M CH4]+· and [C2H4]+·[M C2H4]+· from but-1-ene, cis- and trans-but-2-ene, 2-methylpropene, cyclobutane and methylcyclopropance following field ionisation have been determined as a function of time 20 (or 30) picoseconds to 1 nanosecond and at two points in the microsecond time-frame. The results are consistent with the supposition that at the shortest accessible times (20 to 30 picoseconds) the structure of the [C4H8]+· molecular ion qualitatively resembles that of its neutral precursor, but suggest that prior to decomposition within nanoseconds the various molecular ions (excepting cyclobutane where the processes are slower) attain a common structure or mixture of structures. Reaction pathways of the presumed known ion structures are delineated from the nature of decompostion at the shortest times.