Electron impact and chemical ionization mass spectral analyses of methyl esters species of free mycolic acid fraction from Rhodococcus lentifragmentus

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dc.contributor.authorIoneda, T.
dc.contributor.authorIshige, M.
dc.contributor.institutionUniversidade de São Paulo (USP)
dc.contributor.institutionUniversidade Estadual Paulista (Unesp)
dc.date.accessioned2014-05-20T15:27:59Z
dc.date.available2014-05-20T15:27:59Z
dc.date.issued1996-09-30
dc.description.abstractThe free mycolic acid fraction from Rhodococcus lentifragmentus was derivatized to methyl esters and further fractionated into saturated (F-0), monounsaturated (F-1) and diunsaturated (F-2) species using argentation-TLC. Methyl esters fractions F-0, F-1 and F-2, accounting for approximately 7.4%, 53.1% and 39.5%, respectively, were analyzed by electron impact (EI) and chemical ionization (CI) mass spectrometries. According to EI-MS, peaks observed for M(+)-18, that were prominent compared to those representing M(+)-32 and M(+)-(18 + 32), indicated that the carbon chain size ranged from C-36 to C-48. The pyrolytic cleavage of methyl mycolates (R(2)-CHOH-CH(R(1))-COOCH3), following the McLafferty rearrangement released fragment ions corresponding to, (a) the alpha-subunit, representing the fatty acid methyl ester (R(1)-CH2-COOCH3), methyl hexadecanoate, methyl tetradecanoate and methyl dodecanoate in decreasing order of relative intensity of peaks, and (b) the beta-subunit, representing the meroaldehyde moiety (R(2)-CHO). The saturated meroaldehyde species exhibited peaks representing meroaldehyde minus 18 mass units in which R(2) ranged from C19H39 to C31H63. The monunsaturated species exhibited peaks representing the meroaldehyde in which R(2) ranged from C19H37 to C31H61; peaks corresponding to meroaldehyde minus 18 mass units appeared only in the most abundant components, C29H57CHO, C27H53CHO, C25H49CHO and C31H61CHO, in a decreasing order of relative abundance. The diunsaturated species exhibited peaks essentially corresponding to meroaldehyde in which R(2) corresponded to C31H59 and C29H55; the latter displayed a relative intensity that was about one-half compared to that of the former. Fractions F-0, F-1 and F-2 showed a more intense pyrolytic fragmentation under CI-MS in contrast to results found under EI-MS. Therefore, peaks representing the alpha-subunit and the beta-subunit were more prominent than the ones representing the fragmentation of the hydrocarbon chain. Moreover, the beta-subunit of saturated species exhibited peaks corresponding to meroaldehyde plus hydrogen, and no dehydration of the beta-subunit occurred in this case. In turn, the beta-subunit of monounsaturated and diunsaturated species showed peaks representing both the meroaldehyde plus hydrogen and its dehydration product plus hydrogen. Thus, the presence of unsaturation in the meroaldehyde subunit of methyl mycolate facilitates appearance of dehydration fragment ions under chemical ionization procedure.en
dc.description.affiliationUNIV SAO PAULO,INST QUIM,BR-05508900 SAO PAULO,BRAZIL
dc.description.affiliationUNIV ESTADUAL PAULISTA JULIO MESQUITA FILHO,DEPT QUIM,BOTUCATU,SP,BRAZIL
dc.description.affiliationUnespUNIV ESTADUAL PAULISTA JULIO MESQUITA FILHO,DEPT QUIM,BOTUCATU,SP,BRAZIL
dc.format.extent93-109
dc.identifierhttp://dx.doi.org/10.1016/0009-3084(96)02597-2
dc.identifier.citationChemistry and Physics of Lipids. Clare: Elsevier Sci Ireland Ltd, v. 83, n. 2, p. 93-109, 1996.
dc.identifier.doi10.1016/0009-3084(96)02597-2
dc.identifier.issn0009-3084
dc.identifier.urihttp://hdl.handle.net/11449/37901
dc.identifier.wosWOS:A1996VQ56000001
dc.language.isoeng
dc.publisherElsevier B.V.
dc.relation.ispartofChemistry and Physics of Lipids
dc.relation.ispartofjcr2.766
dc.relation.ispartofsjr1,220
dc.rights.accessRightsAcesso restrito
dc.sourceWeb of Science
dc.subjectmycolic acidspt
dc.subjectmass spectrometrypt
dc.subjectRhodococcuspt
dc.subjectchemical ionizationpt
dc.titleElectron impact and chemical ionization mass spectral analyses of methyl esters species of free mycolic acid fraction from Rhodococcus lentifragmentusen
dc.typeArtigo
dcterms.licensehttp://www.elsevier.com/about/open-access/open-access-policies/article-posting-policy
dcterms.rightsHolderElsevier B.V.
unesp.campusUniversidade Estadual Paulista (Unesp), Instituto de Biociências, Botucatupt

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