1. Department of Anatomy, University of Helsinki, Helsinki 00014, Finland
2. Lehrstuhl für Biochemie, Photobiochemie, Universität Bayreuth, Bayreuth 95447, Germany
3. Optoelectronics and Measurement Techniques, University of Oulu, Oulu 90014, Finland
4. Lehrstuhl für Spektroskopie weicher Materie, Universität Bayreuth, Bayreuth 95447, Germany
5. College of Engineering and Physical Sciences, Aston University, Birmingham B4 7ET, U.K.
6. Department of Biological and Environmental Science, Nanoscience Center, University of Jyvaskyla, Jyvaskyla 40014, Finland