DNA hydrolysis by cerium(IV)–saccharide complexes

Homogeneous solutions are prepared by mixing Ce(NH4)2(NO3)6 with either lyxose, ribose, xylose, gentiobiose, isomaltose, or palatinose at pH 7, under the conditions that [monomeric residue of saccharide]0/[Ce(IV)]0>1. Melibiose and dextran give homogeneous solutions of Ce(IV) when the ratio is greater than 2. Formation of Ce(IV) hydroxide gel is efficiently suppressed by these saccharides. Sugar alcohols (arabinitol, galactitol, mannitol, ribitol, glucitol, and xylitol), glucamine (1-amino-1-deoxy-d-glucitol), lyxosylamine, and N-methylglucamine (1-deoxy-1-methylamino-d-glucitol) are also effective for the solubilization of Ce(IV). In contrast, other monosaccharides (fructose, galactose, and glucose), disaccharides (cellobiose, lactose, maltose, sucrose, and trehalose), cyclodextrins [α-cyclodextrin (cyclomaltohexaose), β-cyclodextrin (cyclomaotoheptaose), and γ-cyclodextrin (cyclomaltooctaose)], and amyloses (as well as galacturonic acid and glucosamine) are poor for the solubilization. The activities of the homogeneous solutions for DNA hydrolysis are in the following order: glucamine>>gentiobiose, isomaltose, ribose, lyxosylamine>lyxose, xylose, arabinitol, galactitol, mannitol, ribitol, glucitol, xylitol, N-methylglucamine. The pseudo-first-order rate constant (5.0×10−3 h−1) for the hydrolysis of thymidylyl(3′–5′) thymidine by the Ce(IV)–glucamine system at pH 7.0 and 50 °C ([Ce(IV)]0=[glucamine]0=10 mmol L−1) is far greater than those of the Ce(IV) complexes of iminodiacetate and ethylenediaminetetraacetate.