Oxidized chain B insulin was studied to investigate negative ion mode in-source decay (ISD) in a matrix assisted laser desportion/time-of-flight mass spectrometer (MALDI/TOF MS). Negative ion mode is an alternate method for peptide and protein sequencing that allows scientists to study peptides that undergo deprotonation. Several matrices used include 2,5-dihydroxybenzoic acid (DHB), trans-4-hydroxy-3-methoxycinnamic acid (ferulic acid), 4,4'-dihydroxybenzophenone (DHBP), 2-aminobenzamide (2-AB), 2-aminobenzoic acid (2-AA), and 5-aminosalicylic acid (5-ASA). Different sample preparation methods were employed to optimize the negative ion mode in-source decay conditions. Numerous parameters, such as laser power, delayed extraction time, linear mode, and reflectron mode, were also varied to determine the best possible conditions. Use of the 2-aminobenzamide (2-AB) matrix produced the most fragmentation at the highest intensities allowing maximum peptide sequencing. The most common fragmentation produced using negative ion mode in-source decay is the c-ion type.

In-source decay mass spectrometry of deprotonated peptides

245th National Meeting (2013)

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