1. National Centre of Excellence in Mass Spectrometry Imaging, NiCE-MSI, National Physical Laboratory, Teddington TW11 0LW, U.K.
2. Plasmion GmbH, 86167 Augsburg, Germany
3. Department of Metabolism, Digestion and Reproduction, Imperial College London, London SW7 2AZ, U.K.
4. Rosalind Franklin Institute, Didcot OX11 0FA, U.K.