1. Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, Kansas 66047, United States
2. Unidad de Biología Estructural, CIC bioGUNE, 48160 Derio, Bizkaia, Spain
3. IKERBASQUE, Basque Foundation for Science, 48011 Bilbao, Spain
4. Mass Spectrometry Laboratory, University of Kansas, Lawrence, Kansas 66045, United States