14.01.2013 Views

Analytical Chemistry Chemical Cytometry Quantitates Superoxide

Analytical Chemistry Chemical Cytometry Quantitates Superoxide

Analytical Chemistry Chemical Cytometry Quantitates Superoxide

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Figure 3. (A) ESI-LTQ-CID-MS 2 product ion spectrum of the triply protonated type 2 modified Munc13-1 peptide (amino acids 3-9 connected<br />

with amino acids 10-15) at m/z 597.01. (B, C) ESI-LTQ-MS 3 product ion spectra of the modified R peptide [R +2H + Bu] 2+ at m/z 463.76 (B)<br />

and of the � peptide [� + H + Bu] + at m/z 819.48 (C).<br />

Peptides Modified with Hydrolyzed Linkers (Type 0). As<br />

with collision activation in the low-energy regime in an LTQ-CID-<br />

MS 2 product ion experiment of the type 0 modified Munc13-1<br />

peptide (Figure 1A), the MALDI-TOF/TOF-CID spectrum exhibits<br />

the 26 u doublet of product ions 6 and 7 as base peaks<br />

resulting from the highly preferential cleavage of the urea crosslinker<br />

(Figure 4, Table 1). However, due to the overall increased<br />

(40) Pittenauer, E.; Allmaier, G. Comb. Chem. High Throughput Screening 2009,<br />

12, 137–155.<br />

(41) Medzihradszky, K. F.; Campbell, J. M.; Baldwin, M. A.; Falick, A. M.; Juhasz,<br />

P.; Vestal, M. L.; Burlingame, A. L. Anal. Chem. 2000, 72, 552–558.<br />

(42) Shenar, N.; Sommerer, N.; Martinez, J.; Enjalbal, C. J. Mass Spectrom. 2009,<br />

44, 621–632.<br />

(43) Schwartz, J. C.; Senko, M. W.; Syka, J. E. J. Am. Soc. Mass Spectrom. 2002,<br />

13, 659–669.<br />

(44) Douglas, D. J. Mass Spectrom. Rev. 2009, 28, 937–960.<br />

collision activation in the TOF/TOF-CID experiment (Figure 4)<br />

compared to the LTQ-CID experiment (Figure 1A), a significant<br />

series of b and y ion signals resulting from the cleavage of peptide<br />

backbone amide bonds were additionally observed in the former.<br />

ISD-MS/MS data of primary product ions observed in Figure 4 for<br />

signals at m/z 943.6 (corresponding to a CNL of 129 u) and m/z<br />

969.6 (corresponding to a CNL of 103 u) are comparable to those of<br />

the fragmentation product of a Munc13-1 cross-link, in which Lys-4<br />

is connected with Lys-13 (Figure 3). Also, backbone fragmentation<br />

of the peptide was observed in MALDI-ISD experiments.<br />

MALDI-TOF/TOF data of a PPARR peptide comprising amino<br />

acids 259-272 exhibit a fragmentation behavior analogous to that<br />

in an ESI-CID-MS 2 experiment (Supporting Information, Figure<br />

S3).<br />

<strong>Analytical</strong> <strong>Chemistry</strong>, Vol. 82, No. 16, August 15, 2010<br />

6965

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!