To understand the role and function of a biomolecule in a biosystem, it is important to know both its composition and structure. Here, a mass spectrometric based approach has been proposed and applied to demonstrate that collision cross sections and high-resolution mass spectra of biomolecule ions may be obtained simultaneously by Fourier transform ion cyclotron resonance mass spectrometry. With this method, the unfolding phenomena for ubiquitin ions that possess different number of charges have been investigated, and results agree well with ion mobility measurements. In the present approach, we extend ion collision cross-section measurements to lower pressures than in prior ion cyclotron resonance (ICR)-based experiments, thereby maintaining the potentially high resolution of Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS), and enabling collision cross section (CCS) measurements for high-mass biomolecules.