A New Scanning Atom Probe for the Mass Analysis of Biomolecules
O. Nishikawa, M. Taniguchi, A. Ikai
Kanazawa Institute of Technology, JP
Keywords: biomolecule, mass analysis, scanning atom probe, 3D mapping
Abstract:Atom probe (AP) is known to be an instrument which allows to mass analyze atom-by-atom. However, its application is mostly limited to metals and semiconductor. We introduced a micro extraction electrode which scans over a specimen surface and confine the high field to field evaporate surface atom in a narrow space between the micro open hole at the apex of the electrode and the specimen. The new AP is named as scanning atom probe (SAP). The mass analyzer of the SAP is a time-of-flight reflectron type and its mass resolution m/Dm is better than 1000. Utilizing the capability of the SAP we mass analyzed biomolecules such as leucine, methionine and cystine. Since the field evaporation is a static process, the evaporated ions reflect the binding state in the molecules. Thus, the mass spectra exhibit the major radicals of the molecules such as COOH+ of leucine and SCH3+ of methionine. The analyzed area of the present SAP is a limited to a circle with the diameter of a few nanometer. In order to analyze a broader area, a new SAP with a position sensitive ion detector with a spiral delay line is proposed.