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Article: Arginine-facilitated isomerization: Radical-induced dissociation of aliphatic radical cationic glycylarginyl(iso)leucine tripeptides

TitleArginine-facilitated isomerization: Radical-induced dissociation of aliphatic radical cationic glycylarginyl(iso)leucine tripeptides
Authors
Issue Date2012
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journal/jpcbfk
Citation
Journal Of Physical Chemistry B, 2012, v. 116 n. 26, p. 7627-7634 How to Cite?
AbstractThe gas phase fragmentations of aliphatic radical cationic glycylglycyl(iso)leucine tripeptides ([G•G(L/I)] +), with well-defined initial locations of the radical centers at their N-terminal α-carbon atoms, are significantly different from those of their basic glycylarginyl(iso)leucine ([G•R(L/I)] +) counterparts; the former lead predominantly to [b 2 - H] •+ fragment ions, whereas the latter result in the formation of characteristic product ions via the losses of •CH(CH 3) 2 from [G•RL] + and •CH 2CH 3 from [G•RI] + through C β-C γ side-chain cleavages of the (iso)leucine residues, making these two peptides distinguishable. The α-carbon-centered radical at the leucine residue is the key intermediate that triggers the subsequent C β-C γ bond cleavage, as supported by the absence of •CH(CH 3) 2 loss from the collision-induced dissociation of [G•RL α-Me] +, a radical cation for which the α-hydrogen atom of the leucine residue had been substituted by a methyl group. Density functional theory calculations at the B3LYP 6-31++G(d,p) level of theory supported the notion that the highly basic arginine residue could not only increase the energy barriers against charge-induced dissociation pathways but also decrease the energy barriers against hydrogen atom transfers in the GR(L/I) radical cations by ∼10 kcal mol -1, thereby allowing the intermediate precursors containing α- and γ-carbon-centered radicals at the (iso)leucine residues to be formed more readily prior to promoting subsequent C β-C γ and C α-C β bond cleavages. The hydrogen atom transfer barriers for the α- and γ-carbon-centered GR(L/I) radical cations (roughly in the range 29-34 kcal mol -1) are comparable with those of the competitive side-chain cleavage processes. The transition structures for the elimination of •CH(CH 3) 2 and •CH 2CH 3 from the (iso)leucine side chains possess similar structures, but slightly different dissociation barriers of 31.9 and 34.0 kcal mol -1, respectively; the energy barriers for the elimination of the alkenes CH 2=CH(CH 3) 2 and CH 3CH=CHCH 3 through C α-C β bond cleavages of γ-carbon-centered radicals at the (iso)leucine side chains are 29.1 and 32.8 kcal mol -1, respectively. © 2012 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/168653
ISSN
2015 Impact Factor: 3.187
2015 SCImago Journal Rankings: 1.414
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorHao, Qen_US
dc.contributor.authorSong, Ten_US
dc.contributor.authorNg, DCMen_US
dc.contributor.authorQuan, Qen_US
dc.contributor.authorSiu, CKen_US
dc.contributor.authorChu, IKen_US
dc.date.accessioned2012-10-08T03:24:02Z-
dc.date.available2012-10-08T03:24:02Z-
dc.date.issued2012en_US
dc.identifier.citationJournal Of Physical Chemistry B, 2012, v. 116 n. 26, p. 7627-7634en_US
dc.identifier.issn1520-6106en_US
dc.identifier.urihttp://hdl.handle.net/10722/168653-
dc.description.abstractThe gas phase fragmentations of aliphatic radical cationic glycylglycyl(iso)leucine tripeptides ([G•G(L/I)] +), with well-defined initial locations of the radical centers at their N-terminal α-carbon atoms, are significantly different from those of their basic glycylarginyl(iso)leucine ([G•R(L/I)] +) counterparts; the former lead predominantly to [b 2 - H] •+ fragment ions, whereas the latter result in the formation of characteristic product ions via the losses of •CH(CH 3) 2 from [G•RL] + and •CH 2CH 3 from [G•RI] + through C β-C γ side-chain cleavages of the (iso)leucine residues, making these two peptides distinguishable. The α-carbon-centered radical at the leucine residue is the key intermediate that triggers the subsequent C β-C γ bond cleavage, as supported by the absence of •CH(CH 3) 2 loss from the collision-induced dissociation of [G•RL α-Me] +, a radical cation for which the α-hydrogen atom of the leucine residue had been substituted by a methyl group. Density functional theory calculations at the B3LYP 6-31++G(d,p) level of theory supported the notion that the highly basic arginine residue could not only increase the energy barriers against charge-induced dissociation pathways but also decrease the energy barriers against hydrogen atom transfers in the GR(L/I) radical cations by ∼10 kcal mol -1, thereby allowing the intermediate precursors containing α- and γ-carbon-centered radicals at the (iso)leucine residues to be formed more readily prior to promoting subsequent C β-C γ and C α-C β bond cleavages. The hydrogen atom transfer barriers for the α- and γ-carbon-centered GR(L/I) radical cations (roughly in the range 29-34 kcal mol -1) are comparable with those of the competitive side-chain cleavage processes. The transition structures for the elimination of •CH(CH 3) 2 and •CH 2CH 3 from the (iso)leucine side chains possess similar structures, but slightly different dissociation barriers of 31.9 and 34.0 kcal mol -1, respectively; the energy barriers for the elimination of the alkenes CH 2=CH(CH 3) 2 and CH 3CH=CHCH 3 through C α-C β bond cleavages of γ-carbon-centered radicals at the (iso)leucine side chains are 29.1 and 32.8 kcal mol -1, respectively. © 2012 American Chemical Society.en_US
dc.languageengen_US
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/journal/jpcbfken_US
dc.relation.ispartofJournal of Physical Chemistry Ben_US
dc.titleArginine-facilitated isomerization: Radical-induced dissociation of aliphatic radical cationic glycylarginyl(iso)leucine tripeptidesen_US
dc.typeArticleen_US
dc.identifier.emailChu, IK:ivankchu@hku.hken_US
dc.identifier.authorityChu, IK=rp00683en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1021/jp301882pen_US
dc.identifier.pmid22671034-
dc.identifier.scopuseid_2-s2.0-84863622698en_US
dc.identifier.hkuros208686-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-84863622698&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume116en_US
dc.identifier.issue26en_US
dc.identifier.spage7627en_US
dc.identifier.epage7634en_US
dc.identifier.isiWOS:000305933800003-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridHao, Q=35274915300en_US
dc.identifier.scopusauthoridSong, T=36087959100en_US
dc.identifier.scopusauthoridNg, DCM=36981534500en_US
dc.identifier.scopusauthoridQuan, Q=37018675200en_US
dc.identifier.scopusauthoridSiu, CK=7006550712en_US
dc.identifier.scopusauthoridChu, IK=7103327484en_US

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