Nanoscale analysis of frozen honey by atom probe tomography.

Three-dimensional reconstruction of the analysed volume is one of the main goals of atom probe tomography (APT) and can deliver nearly atomic resolution (~ 0.2 nm spatial resolution) and chemical information with a mass sensitivity down to the ppm range. Extending this technique to frozen biological systems would have an enormous impact on the structural analysis of biomolecules. In previous works, we have shown that it is possible to measure frozen liquids with APT. In this paper, we demonstrate the ability of APT to trace nanoscale precipitation in frozen natural honey. While the mass signals of the common sugar fragments CxHy and CxOyHz overlap with (H2O)nH from water, we achieved correct stoichiometric values via different interpretation approaches for the peaks and thus determined the water content reliably. Next, we use honey to investigate the spatial resolution capabilities as a step toward the measurement of biological molecules in solution in 3D with sub-nanometer resolution. This may take analytical techniques to a new level, since methods of chemical characterization for cryogenic samples, especially biological samples, are still limited.