To perform SID and characterize the HRas*GTP-SOS-HRas complex, the mixture was first separated using TIMS. We then isolated a narrow m/z range of interest, and 16+ HRas*GTP-SOS and 20+ HRas*GTP-SOS-HRas were isolated. These two complexes were then fragmented by SID. After SID, product ions from each precursor were mobility-aligned in the heat map, which is shown in Figure . To identify the SID fragments of 20+ HRas*GTP-SOS-HRas, we generated the SID spectrum of 20+ HRas*GTP-SOS-HRas by extracting its mobility peak (Figure ). The result shows that HRas*GTP-SOS-HRas dissociates into two species: HRas and HRas*GTP-SOS, and HRas*GTP retains on SOS after SID. This indicates that HRas*GTP binds more strongly with SOS than HRas. It's also interesting to note that HRas carried about half of the charges from the precursor after being dissociated from the complex, which was not anticipated. Typically, SID fragments carry charges proportional to the mass of the precursor. This suggests that HRas undergoes structural rearrangement to depart from the complex, which is similar to results reported for some other complexes. To understand the effect of GTP on HRas' structure stability, further study is required. Overall, by combining TIMS separation and quadrupole isolation, we were able to study the structure of HRas*GTP-SOS-HRas using SID without any interference from other complexes in the mixture.