1. Pharmaceutical Sciences Laboratory; Faculty of Science and Engineering; Åbo Akademi University; Turku 20520 Finland
2. Laboratory of Biophysics; Cell Biology and Anatomy; University of Turku; Turku 20520 Finland
3. Molecular Microscopy and Spectroscopy; Istituto Italiano di Tecnologia; via Morego 30 Genoa 16163 Italy
4. Nanoscopy; Istituto Italiano di Tecnologia; via Morego 30 Genoa 16163 Italy
5. Division of Pathology; Karolinska Universitetssjukhuset; Huddinge 141 86 Stockholm Sweden
6. Institute of Atomic and Molecular Sciences; Academia Sinica; Taipei 10617 Taiwan