Hi, Could someone explain to me the scientific details of the protocols used in X-PLOR to (1) build explicit hydrogen atoms onto X-ray structures and (2) optimize their positions? Many thanks in advance. Greetings, Nadir -- Pr. Nadir T. Mrabet Structural& Molecular Biochemistry INSERM U-954 Nancy University, School of Medicine 9, Avenue de la Foret de Haye, BP 184 54505 Vandoeuvre-les-Nancy Cedex France Phone: +33 (0)3.83.68.32.73 Fax: +33 (0)3.83.68.32.79 E-mail: Nadir.Mrabet<at> medecine.uhp-nancy.fr