FIGURE 9.

The ion-source collision-induced-dissociation of CaM–RS20–Ca₄ complex (concentration ratio 1:1.5:5) in 5 mM ammonium acetate buffer, pH 5.9. (A)–(D) were measured on the sample using the ES capillary potentials from 104 V to 224 V. (A) shows the ESI-FTICR mass spectrum of the intact complex. The increase of the capillary potential from 104 V to 152 V (indicated in (B)) results in the decomposition of the complex to CaM–Ca₄ and RS20. Further increase of the capillary potential leads to the decomposition of CaM–Ca₄ (C) and fragmentation of CaM backbone (D). C represents CaM and P peptide, respectively.