on 05-01-201210:32 AM - edited on 10-15-202111:58 AM by AnalyteGuru
Zeller M, Ueckert T, Delanghe B, Moehring T. Application Note 30179 With the introduction of electron transfer dissociation (ETD) on the Thermo Scientific LTQ Orbitrap mass spectrometers, ETD is now a widely accepted alternative dissociation technique and used together with the more traditional collision-induced dissociation (CID). ETD has shown to be complementary to CID and is mainly used to increase proteome coverage and for analysis of labile post-translation modifications (PTM) which are preserved in ETD. To make use of the complementary nature of CID and ETD, samples would have to be injected twice for each method or CID and ETD spectra have to be generated for each precursor ions which leads to an increase of cycle time. Josh Coon and co-workers have found in a large-scale study that peptides can have a higher probability of identification in a database search using either CID or ETD depending on the peptide charge state z and mass-to charge ratio (m/z). These rules have been implemented in a data-dependent decision tree (DDDT) logic in the instrument method setup. The aim of the directed fragmentation is to inject a sample only once and the dissociation method that most likely will lead to a positive
identification of the peptide will be applied.