1. Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
2. Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad. Universitaria, Coyoacán, Mexico City 04510, Mexico
3. Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29209, USA
4. Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA