Correlation of kinetic energy losses in high-energy collision-induced dissociation with observed peptide product ions.

In collision-induced dissociation, some of an incident parent ion's kinetic energy is converted into internal energy upon collision with a neutral target. The kinetic energy lost is related to the amount of internal energy deposited into any individual ion. To see dissociations of different critical energies on the same time scale, different amounts of internal energy need to be deposited. This should be reflected in the kinetic energy lost by the parent ion in the formation of different product ions. Variable amounts of energy loss in the formation of different peptide product ions are reported here. It is seen that different product ion types (b, y, a) show ordered patterns of energy losses. A greater energy loss is observed for the formation of b-type product ions than for y-type, and even greater energy losses are observed for the formation of a-type product ions. A very good correlation between ion type energy loss and ion mass is observed. Thus, measuring the energy losses in the formation of product ions may provide a means for classifying the product ion type.