1. Department of Chemistry, Faculty of Pharmacy, University of Istanbul, 34452 Istanbul, Turkey, Tubitak, Marmara Research Center, Department of Chemistry, P.O. Box 21, 41470, Gebze, Kocaeli, Turkey, and Department of Physical Biochemistry, Physiological Institute, University of Tübingen, Hoppe-Seyler Street 4, 72076 Tübingen, Germany