Photodissociation at 193 nm of some singly protonated peptides and proteins with m/z 2000-9000 using a tandem time-of-flight mass spectrometer equipped with a second source for delayed extraction/post-acceleration of product ions.
A tandem time-of-flight mass spectrometer was built for photodissociation (PD) of singly protonated peptides and small proteins generated by matrix-assisted laser desorption/ionization. PD was performed in a second source after deceleration of precursor ions. The delayed extraction/post-acceleration scheme was used for the product ions. For the PD at 193 nm of small singly protonated peptides, the present instrument showed much better sensitivity and resolution for product ions than the previous one (Moon JH, Yoon SH, Kim MS, Bull. Korean Chem. Soc. 2005; 26: 763) even though the overall spectral patterns obtained with the two instruments were similar. The present instrument was inferior in precursor ion selection and background noise level. PD was achieved for precursor ions as large as the singly protonated ubiquitin (m/z 8560.63), indicating that the photoexcitation is capable of supplying a sufficient amount of internal energy to dissociate large singly protonated proteins. As the precursor ion m/z increased, however, product ion signals deteriorated rather rapidly. As in the PD of small peptide ions with m/z around 1000, the types of the product ions generated from singly protonated peptides with m/z in the range 2000-4000 were mostly determined by the positions of arginine residues. Namely, a(n) and d(n) ions dominated when an arginine residue(s) was near the N-terminus while v(n), w(n), x(n) and y(n) dominated when the same residue(s) was near the C-terminus. In addition, d(n), v(n) and w(n) ions were generated according to the correlation rules previously observed in the collisionally activated dissociation. Isoleucine and leucine isomers could be easily distinguished based on the w(n) and d(n) ions.
Moon
Jeong Hee
JH
School of Chemistry, Seoul National University, Seoul 151-742, Korea.
Shin
Young Sik
YS
Cha
Hyun Jung
HJ
Kim
Myung Soo
MS
D000054:Acceleration; D000595:Amino Acid Sequence; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007477:Ions; D007834:Lasers; D008969:Molecular Sequence Data; D010449:Peptide Mapping / Q000295:instrumentation* / Q000379:methods; D010455:Peptides / Q000032:analysis / Q000737:chemistry*; D010777:Photochemistry / Q000295:instrumentation* / Q000379:methods; D011506:Proteins / Q000032:analysis / Q000737:chemistry*; D011522:Protons; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D020539:Sequence Analysis, Protein / Q000295:instrumentation / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation* / Q000379:methods
D007477:Ions; D010455:Peptides; D011506:Proteins; D011522:Protons