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. Author manuscript; available in PMC: 2013 Feb 15.
Published in final edited form as: J Am Soc Mass Spectrom. 2011 Dec 1;23(2):201–212. doi: 10.1007/s13361-011-0288-4

Figure 3.

Figure 3

Although the crosslinker contains two intrinsic positive charges, peptides modified with DC4 are observed as singly charged ions in MALDI, most likely due to the loss of a proton from a carboxylic acid moiety and ion pair formation (not shown). Upon fragmentation of the singly charged precursor by either in-source decay or CID, the rearrangement produces two singly charged species by mobilizing an existing proton as shown. The difference between species A and C as well as B and D is 112 Da resulting from the loss of the DABCO moiety and is used as a selection filter for crosslinked peptides