TY - JOUR
T1 - Peptide derivatization as a strategy to form fixed-charge peptide radicals
AU - Karnezis, Asimo
AU - Barlow, Christopher K.
AU - O'Hair, Richard A.J.
AU - McFadyen, W. David
PY - 2006/10/13
Y1 - 2006/10/13
N2 - As a means of generating fixed-charge peptide radicals in the gas phase we have examined the collision-induced dissociation (CID) chemistry of ternary [CuII(terpy)(TMPP-M)]2+ complexes, where terpy = 2,2′:6′2″-terpyridine and TMPP-M represents a peptide (M) modified by conversion of the N-terminal amine to a [tris(2,4,6- trimethoxyphenyl)phosphonium]acetamide (TMPP-) fixed-charge derivative. The following modified peptides were examined: oligoglycines, (Gly)n (n = 1-5), alanylglycine, glycylalanine, dialanine, trialanine and leucine-enkephaline (YGGFL). The [CuII (terpy)(TMPP-M)]2+ complexes are readily formed upon electrospray ionization (ESI) of a mixture of derivatized peptide and [CuII(terpy)(NO3)2] and generally fragment to form transient peptide radical cations, TMPP-M +., which undergo rapid decarboxylation for the simple aliphatic peptides. This is contrasted with the complexes containing the unmodified peptides, which predominantly undergo fragmentation of the coordinated peptide. These differences demonstrate the importance of proton mobility in directing fragmentation of ternary copper(II) peptide complexes. In the case of leucine-enkephaline, a sufficient yield of the radical cation was obtained to allow further CID. The TMPP-YGGFL+. ion showed a rich fragmentation chemistry, including CO2 loss, side-chain losses of an isopropyl radical, 2-methylpropene and p-quinomethide, and *a1 and *a4 sequence ion formation. In contrast, the even-electron TMPP-YGGFL+ ion fragments to form *an and *bn sequence ions as well as the [*b4+H 2O]+ rearrangement ion.
AB - As a means of generating fixed-charge peptide radicals in the gas phase we have examined the collision-induced dissociation (CID) chemistry of ternary [CuII(terpy)(TMPP-M)]2+ complexes, where terpy = 2,2′:6′2″-terpyridine and TMPP-M represents a peptide (M) modified by conversion of the N-terminal amine to a [tris(2,4,6- trimethoxyphenyl)phosphonium]acetamide (TMPP-) fixed-charge derivative. The following modified peptides were examined: oligoglycines, (Gly)n (n = 1-5), alanylglycine, glycylalanine, dialanine, trialanine and leucine-enkephaline (YGGFL). The [CuII (terpy)(TMPP-M)]2+ complexes are readily formed upon electrospray ionization (ESI) of a mixture of derivatized peptide and [CuII(terpy)(NO3)2] and generally fragment to form transient peptide radical cations, TMPP-M +., which undergo rapid decarboxylation for the simple aliphatic peptides. This is contrasted with the complexes containing the unmodified peptides, which predominantly undergo fragmentation of the coordinated peptide. These differences demonstrate the importance of proton mobility in directing fragmentation of ternary copper(II) peptide complexes. In the case of leucine-enkephaline, a sufficient yield of the radical cation was obtained to allow further CID. The TMPP-YGGFL+. ion showed a rich fragmentation chemistry, including CO2 loss, side-chain losses of an isopropyl radical, 2-methylpropene and p-quinomethide, and *a1 and *a4 sequence ion formation. In contrast, the even-electron TMPP-YGGFL+ ion fragments to form *an and *bn sequence ions as well as the [*b4+H 2O]+ rearrangement ion.
UR - http://www.scopus.com/inward/record.url?scp=33749531195&partnerID=8YFLogxK
U2 - 10.1002/rcm.2671
DO - 10.1002/rcm.2671
M3 - Article
C2 - 16941727
AN - SCOPUS:33749531195
SN - 0951-4198
VL - 20
SP - 2865
EP - 2870
JO - Rapid Communications in Mass Spectrometry
JF - Rapid Communications in Mass Spectrometry
IS - 19
ER -