1. Van't Hoff Institute for Molecular Sciences; University of Amsterdam; Science Park 904 1098 XH Amsterdam The Netherlands
2. Present address: Qingdao Institute of Bioenergy and Bioprocess Technology; Chinese Academy of Sciences; No. 189 Songling Road, Laoshan District Qingdao 266101 P. R. China
3. Eastman Chemical Company; P.O. Box 7444 Longview TX 75607-7444 USA