nitrophenols and picolinic-acid

The structures of Ce(4+) complexes that are active for DNA hydrolysis were determined for the first time by X-ray crystallography. The crystals were prepared from a 1:2 mixture of Ce(NH(4))(2)(NO(3))(6) and dipicolinic acid (2,6-pyridinedicarboxylic acid). Depending on the recrystallization conditions, three types of crystals were obtained. Some of the Ce(4+) ions in these complexes have enough coordinated water molecules that can directly and indirectly participate in the catalysis. The distances between the Ce(4+) and the dipicolinate ligand are considerably shorter than those in the corresponding La(3+) and Ce(3+) complexes. On the other hand, the distances between the Ce(4+) and its coordinated water are similar to those for the La(3+) and Ce(3+) complexes. In a proposed mechanism of DNA hydrolysis, the scissile phosphodiester linkage is notably activated by coordination to Ce(4+) and attacked by the Ce(4+)-bound hydroxide. The process is further assisted by acid catalysis of Ce(4+)-bound water.

Topics: Base Sequence; Catalysis; Cerium; Crystallography, X-Ray; DNA; Hydrolysis; Kinetics; Ligands; Nitrophenols; Oligonucleotides; Picolinic Acids; Pyridines; Water

Topics: Carbodiimides; Dicyclohexylcarbodiimide; Isonicotinic Acids; Lysine; Niacin; Nitrophenols; Ornithine; Picolinic Acids