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This study presents ab initio calculations on six sialic acid derivatives (N-acetylneuraminic acid, 2-deoxy-2,3-didehydro-Nacetylneuraminic acid, N-acetyl-4-O-acetylneuraminic acid, N-glycolylneuraminic acid, N-glycolyl-4-O-acetylneuraminic acid and N-acetyl-9-O-acetylneuraminic acid). The calculations were carried out using the GAMESS-UK-Program. Since the charge distribution of a ligand has an essential impact on the specific interaction with an enzyme or a receptor, the precise results of ab initio calculations lead to significant information concerning possible roles of the different functional groups occurring on sialic acids. In correlation to this, valuable conclusions about the activities of different sialic acid-specific enzymes, such as sialidases, trans-sialidases, lyases and O-acetyl-or O-methyltransferases can be drawn, since these activities strongly depend on the presence or absence of the various functional groups. q 2004 Published by Elsevier B.V.

Ab irutro computatronson CuO were performed wttb the Hartree-Fock method and a proper dissociation Ic(C SCF procedure In partrcular the mfluence of the CT0 basrs set for Cu in molecular computattons has been studied. A potentfaf energy curve and a Mulbken populatron analysis are presented. The equdffrium bond length IS predicted reasonably we!f but the dissocratron energy 1s only a fractron of the observed value. Tire bond appears to be a sbgbtly ionic o-type bond, in which metal 3d orbrtals partrcrpate only to a small extent.

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