1. Institut für Chemie und Biochemie Organische Chemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin, Germany.
2. Unit 17, Influenza and Other Respiratory Viruses, Robert Koch-Institut, Seestr. 10, 13353 Berlin, Germany.
3. Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB3 0AS, UK.
4. College of Polymer Science and Engineering, State Key Laboratory of Polymer Materials Engineering, Sichuan University, Chengdu 610065, China.