| abstract |
The present invention relates to a new method for identifying polypeptides by deducing the amino acid sequence of the carboxy and amino termini by a mass spectrometer analysis. The method comprises the steps of dissociating highly charged peptide precursor ions (e.g., z>4) using electron transfer dissociation inducing anions followed by removal of those reagents and introduction of a second, proton transfer inducing anion type. The second PTR reaction duration is adjusted to convert the ETD products to primarily the +1 charge-state to reduce the highly charged c and z-type fragments, producing an m/z spectrum containing a series of c and z-type fragment ions that are easily interpreted to reveal the sequence of the amino and carboxy terminus, respectively. |