„Non-statistical 13C Franctionation Distinguishes Coincident and Divergent Steps in the Biosynthesis of the Alkanoids Nicotine and Tropine” Katarzyna M. Romek, Gérald S. Remaud, Virginie Silvestre, Piotr Paneth, Richard J. Robins J. Biol. Chem. 291, 16620-9 (2016)