Molecular radical cations and fragmentation studies of nitrosylated peptides containing cysteine and tryptophan

BUTLER, M.; SIU, K.W.M; HOPKINSON, A.C.

Orillia

Conferencia; 31 Annual Trent Conference on Mass Spectrometry; 2014

Molecular radical cations and fragmentation studies of nitrosylated peptides containing Cysteine and Tryptophan Cysteine and tryptophan side-chains can be nitrosylated leading to the formation of chemically modified peptides. Upon Collision-Induced Dissociation (CID) of the protonated peptides generated by Electrospray Ionization (ESI), the labile NO group is easily lost thus generating radical cations. Copper complexation strategies combined with ESI are used as an alternative method for obtaining structurally different radical cations from the unmodified peptides. The fragmentation behavior in the positive ion mode of the radical cations prepared by the two different routes from model peptides is compared. The behavior of ?di-radical? cations generated from peptides containing two modified residues of cysteine and/or tryptophan is analyzed as well to explore the possibility of creating diradicals and ascertain their resemblance to open- or closed-shell species.