title: N-Terminal Derivatization with Structures Having High Proton Affinity for Discrimination between Leu and Ile Residues in Peptides by High-Energy Collision-Induced Dissociation.
abstract: De novosequencing is still essential in the identification of peptides and proteins from unexplored organisms whose sequence information is not available. One of the remaining problems inde novosequencing is discrimination between Leu and Ile residues. The discrimination is possible based on differences in side chain fragmentation between Leu and Ile under high-energy collision-induced dissociation (HE-CID) conditions. However, this is observed only when basic residues, such as Arg and Lys, are present near the N- or C-terminal end. It has been shown that the charge derivatization at the N-terminal end by a quarternary ammonium or phosphonium moiety facilitates the side chain fragmentation by HE-CID. However, the effective backbone fragmentation by low-energy CID (LE-CID) is often hampered in those derivatives with a fixed charge. Previously, we demonstrated that the N-terminal charge derivatization with the structures having high proton affinity induced the preferential formation of b-ions under LE-CID conditions, allowing straightforward interpretation of product ion spectra. In the present study, we further investigated whether the same derivatization approach is also effective for discrimination between Leu and Ile under HE-CID conditions. Consequently, the side chain fragmentation of Leu and Ile residues was most effectively enhanced by the N-terminal derivatization with 4-(guanidinomethyl)benzoic acid among the tested structures. This derivatization approach, which is compatible with both HE- and LE-CID analysis, offers a straightforward and unambiguousde novopeptide sequencing method.
authors.affiliation: Graduate School of Agriculture, Kyoto University.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kitanaka
authors.affiliation: Graduate School of Agriculture, Kyoto University.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Miyashita
authors.affiliation: JEOL Ltd.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kubo
authors.affiliation: JEOL Ltd.
authors.forename: Takaya
authors.initials: T
authors.lastname: Satoh
authors.affiliation: Graduate School of Science, Osaka University.
authors.forename: Michisato
authors.initials: M
authors.lastname: Toyoda
authors.affiliation: Graduate School of Agriculture, Kyoto University.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Miyagawa
keywords: MALDI-TOF-TOF; de novo sequencing; ion trap-TOF; proton affinity