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Article: Nucleophilic substitution by amide nitrogen in the aromatic rings of [zn − H]˙+ ions; the structures of the [b2 − H − 17]˙+ and [c1 − 17]+ ions

TitleNucleophilic substitution by amide nitrogen in the aromatic rings of [zn − H]˙+ ions; the structures of the [b2 − H − 17]˙+ and [c1 − 17]+ ions
Authors
Issue Date2016
PublisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pccp
Citation
Physical Chemistry Chemical Physics, 2016, v. 18 n. 16, p. 11168-11175 How to Cite?
AbstractPeptide radical cations that contain an aromatic amino acid residue cleave to give [zn − H]˙+ ions with [b2 − H − 17]˙+ and [c1 − 17]+ ions, the dominant products in the dissociation of [zn − H]˙+, also present in lower abundance in the CID spectra. Isotopic labeling in the aromatic ring of [Yπ˙GG]+ establishes that in the formation of [b2 − H − 17]˙+ ions a hydrogen from the δ-position of the Y residue is lost, indicating that nucleophilic substitution on the aromatic ring has occurred. A preliminary DFT investigation of nine plausible structures for the [c1 − 17]+ ion derived from [Yπ˙GG]+ shows that two structures resulting from attack on the aromatic ring by oxygen and nitrogen atoms from the peptide backbone have significantly better energies than other isomers. A detailed study of [Yπ˙GG]+ using two density functionals, B3LYP and M06-2X, with a 6-31++G(d,p) basis set gives a higher barrier for attack on the aromatic ring of the [zn − H]˙+ ion by nitrogen than by the carbonyl oxygen. However, subsequent rearrangements involving proton transfers are much higher in energy for the oxygen-substituted isomer leading to the conclusion that the [c1 − 17]+ ions are the products of nucleophilic attack by nitrogen, protonated 2,7-dihydroxyquinoline ions. The [b2 − H − 17]˙+ ions are formed by loss of glycine from the same intermediates involved in the formation of the [c1 − 17]+ ions.
Persistent Identifierhttp://hdl.handle.net/10722/229127
ISSN
2015 Impact Factor: 4.449
2015 SCImago Journal Rankings: 1.836

 

DC FieldValueLanguage
dc.contributor.authorMu, X-
dc.contributor.authorLau, JKC-
dc.contributor.authorLai, CK-
dc.contributor.authorSiu, KWM-
dc.contributor.authorHopkinson, AC-
dc.contributor.authorChu, IK-
dc.date.accessioned2016-08-23T14:09:10Z-
dc.date.available2016-08-23T14:09:10Z-
dc.date.issued2016-
dc.identifier.citationPhysical Chemistry Chemical Physics, 2016, v. 18 n. 16, p. 11168-11175-
dc.identifier.issn1463-9076-
dc.identifier.urihttp://hdl.handle.net/10722/229127-
dc.description.abstractPeptide radical cations that contain an aromatic amino acid residue cleave to give [zn − H]˙+ ions with [b2 − H − 17]˙+ and [c1 − 17]+ ions, the dominant products in the dissociation of [zn − H]˙+, also present in lower abundance in the CID spectra. Isotopic labeling in the aromatic ring of [Yπ˙GG]+ establishes that in the formation of [b2 − H − 17]˙+ ions a hydrogen from the δ-position of the Y residue is lost, indicating that nucleophilic substitution on the aromatic ring has occurred. A preliminary DFT investigation of nine plausible structures for the [c1 − 17]+ ion derived from [Yπ˙GG]+ shows that two structures resulting from attack on the aromatic ring by oxygen and nitrogen atoms from the peptide backbone have significantly better energies than other isomers. A detailed study of [Yπ˙GG]+ using two density functionals, B3LYP and M06-2X, with a 6-31++G(d,p) basis set gives a higher barrier for attack on the aromatic ring of the [zn − H]˙+ ion by nitrogen than by the carbonyl oxygen. However, subsequent rearrangements involving proton transfers are much higher in energy for the oxygen-substituted isomer leading to the conclusion that the [c1 − 17]+ ions are the products of nucleophilic attack by nitrogen, protonated 2,7-dihydroxyquinoline ions. The [b2 − H − 17]˙+ ions are formed by loss of glycine from the same intermediates involved in the formation of the [c1 − 17]+ ions.-
dc.languageeng-
dc.publisherRoyal Society of Chemistry. The Journal's web site is located at http://www.rsc.org/pccp-
dc.relation.ispartofPhysical Chemistry Chemical Physics-
dc.rightsThis work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License-
dc.titleNucleophilic substitution by amide nitrogen in the aromatic rings of [zn − H]˙+ ions; the structures of the [b2 − H − 17]˙+ and [c1 − 17]+ ions-
dc.typeArticle-
dc.identifier.emailChu, IK: ivankchu@hkucc.hku.hk-
dc.identifier.authorityChu, IK=rp00683-
dc.description.naturepostprint-
dc.identifier.doi10.1039/C6CP00405A-
dc.identifier.hkuros261915-
dc.identifier.volume18-
dc.identifier.issue16-
dc.identifier.spage11168-
dc.identifier.epage11175-
dc.publisher.placeUnited Kingdom-

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