1. Research Group SynBioC, Department of Organic Chemistry, Faculty of Bioscience Engineering, Ghent University, Coupure links 653, B-9000 Ghent, Belgium, Department of Chemistry and Biochemistry, University of Minnesota, Duluth, Minnesota 55812, and Center for Molecular Modeling, Ghent University, Proeftuinstraat 86, B-9000 Ghent, Belgium