SUPRAMOLECULAR CHEMISTRY .62. LIGAND AND COSUBSTRATE EFFECTS ON THE HYDROLYSIS OF PHOSPHATE-ESTERS AND DNA WITH LANTHANOIDS

Attempts are described to enhance the catalytic activity of lanthanide ions by providing cosubstrates with an increasing number of nucleophi lic groups or by attaching corresponding polyols covalently to stronge r metal-binding centers Like diazacrown ethers. Although the kinetic e ffects on the hydrolysis of bis(4-nitrophenyl) phosphate (BNPP) and of supercoiled plasmid DNA are only moderate, their dependence on cosubs trate structure and polyol configuration unambiguously demonstrates th at these are involved in the slow step of the reactions. Thus, additio n of gluconic acid to a LaCl3 solution leads to a marked increase of D NA cleavage from 20 to 71%. Naphthyl units covalently bound to the dia zacrown show little effect on BNPP hydrolysis, but enhance DNA hydroly sis again from e.g. 38% (RF II) to 60%. Preliminary affinity measureme nts with calf thymus DNA, using a fluorimetric assay with ethidium bro mide, show for polyamines a dependence on the number of ligand charges as observed earlier. The naphthyl compound is characterized by a high affinity; preliminary NMR data indicate that the naphthyl units inter calate into DNA.