1. Complex Carbohydrate Research Center, University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA), Fax: (+1) 706‐542‐4412
2. Present address: Institut Européen de Chimie et Biologie, Université de Bordeaux, INCIA, CNRS UMR 5287, 2 rue Robert Escarpit, 33607 Pessac (France)
3. School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA 30332 (USA)