Comparative studies of 193-nm photodissociation and TOF-TOFMS analysis of bradykinin analogues: the effects of charge site(s) and fragmentation timescales.
The dissociation reactions of [M + H]+, [M + Na]+, and [M + Cu]+ ions of bradykinin (amino acid sequence RPPGFSPFR) and three bradykinin analogues (RPPGF, RPPGFSPF, PPGFSPFR) are examined by using 193-nm photodissociation and post-source decay (PSD) TOF-TOF-MS techniques. The photodissociation apparatus is equipped with a biased activation cell, which allows us to detect fragment ions that are formed by dissociation of short-lived (<1 mus) photo-excited ions. In our previously reported photodissociation studies, the fragment ions were formed from ions dissociating with lifetimes that exceeded 10 mus; thus these earlier photofragment ion spectra and post-source decay (PSD) spectra [composite of both metastable ion (MI) and collision-induced dissociation (CID)] were quite similar. On the other hand, short-lived photo-excited ions dissociate by simple bond cleavage reactions and other high-energy dissociation channels. We also show that product ion types and abundances vary with the location of the charge on the peptide ion. For example, H+ and Na+ cations can bind to multiple polar functional groups (basic amino acid side chains) of the peptide, whereas Cu+ ions preferentially bind to the guanidino group of the arginine side-chain and the N-terminal amine group. Furthermore, when Cu+ is the charge carrier, the abundances of non-sequence informative ions, especially loss of small neutral molecules (H2O and NH3) is decreased for both photofragment ion and PSD spectra relative to that observed for [M + H]+ and [M + Na]+ peptide ions.
Laboratory for Biological Mass Spectrometry, Department of Chemistry, Texas A and M University, College Station, Texas, USA.
Joseph W
JW
Morgan
David H
DH
Russell
D000595:Amino Acid Sequence; D001920:Bradykinin / Q000031:analogs & derivatives / Q000737:chemistry*; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010777:Photochemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000295:instrumentation / Q000379:methods
D001920:Bradykinin