Digital ion trap mass spectrometer for probing the structure of biological macromolecules by gas phase X-ray scattering.

Small-angle X-ray scattering is a technique for the characterization and structural analysis of a variety of materials including biological macromolecules and polymers. For the conformational analysis of proteins, the interaction between sample and X-rays is generally performed when the proteins are present in solution. Here a three-dimensional digital ion trap interfaced with a high intensity X-ray source is built to prove that X-ray scattering can be performed on ions isolated in gas-phase. Initial experiments on an unresolved ion population of multiply charged cytochrome C ions indicate that a small-angle X-ray scattering signal can be detected and that partial structural information can be extracted about the overall molecular structure of protein ions.