1. Laboratory of Clinical Chemistry, and Department of Internal Medicine, Medical School, University of Ioannina, 451 10, Ioannina, Greece, and Laboratoire de Chimie-Physique Macromoléculaire, UMR 7568 CNRS-INPL, Nancy-Université, 1 Rue Grandville, B.P. 20451, 54001 Nancy Cedex, France