Hydrolysis of 2-hydroxypropyl-4-nitrophenyl phosphate (HPNP), a commonly used RNA model substrate, was examined in molybdate solutions by means of (1)H, (31)P, and (95)Mo NMR, Raman, and Mo K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy. (1)H and (31)P NMR spectroscopy indicate that at 50 degrees C and pD 5.9 the cleavage of the phosphodiester bond in HPNP proceeds with a rate constant of 6.62 x 10(-6) s(-1), giving a cyclic phosphate ester and p-nitrophenol as the only products of hydrolysis. The NMR spectra did not show evidence of any paramagnetic species, excluding the possibility of Mo(VI) reduction to Mo(V), and indicating that the cleavage of the phosphodiester bond is purely hydrolytic. The Mo K-edge XANES region also did not show any sign of Mo(VI) to Mo(V) reduction during the hydrolytic reaction. The pD dependence of k(obs) exhibits a bell-shaped profile, with the fastest cleavage observed at pD 5.9. Comparison of the rate profile with the concentration profile of polyoxomolybdates shows a striking overlap of the k(obs) profile with the concentration of heptamolybdate, suggesting that the highly negatively charged [Mo(7)O(24)](6-) is the hydrolytically active species. Kinetic experiments at pD 5.9 using a fixed amount of [Mo(7)O(24)](6-) and increasing amounts of HPNP revealed slight signs of curvature at 25 molar excess of HPNP. The data fit the general Michaelis-Menten reaction scheme, permitting the calculation of the catalytic rate constant k(2) (3.02 x 10(-4) s(-1)) and K(m) (1.06 M). Variable temperature (31)P NMR spectra of a reaction mixture revealed broadening of the HPNP (31)P resonance upon increase of temperature, implying the dynamic exchange process between free and bound HPNP at higher temperatures. Addition of salts resulted in the inhibition of HPNP hydrolysis, as well as addition of dimethyl phosphate, suggesting competition for the binding to [Mo(7)O(24)](6-). The hydrolysis of 10 equiv of HPNP could be achieved in the presence of 1 equiv of [Mo(7)O(24)](6-), and the multiple turnovers demonstrate that the reaction is catalytic. (31)P NMR and Mo K-edge EXAFS spectra measured during different stages of the hydrolysis indicated that under catalytic conditions a partial conversion of [Mo(7)O(24)](6-) into [P(2)Mo(5)O(23)](6-) occurs.

Diffusion ordered NMR spectroscopy (DOSY NMR) is shown to be an excellent tool for observing reactive transients in the hydrolysis of the phosphatase model substrate (p-nitrophenyl)phosphate (NPP) promoted by polyoxomolybdate.

The first example of a phosphodiester bond cleavage promoted by a highly negatively charged polyoxometalate cluster has been discovered: the hydrolysis of the phosphodiester bond in a DNA model substrate bis(p-nitrophenyl)phosphate (BNPP) is promoted by the heptamolybdate anion [Mo7O24](6-) with rates which represent an acceleration of nearly four orders of magnitude compared to the uncatalyzed cleavage.

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Key indicators: single-crystal X-ray study; T = 100 K; mean (C-C) = 0.003 Å; R factor = 0.037; wR factor = 0.092; data-to-parameter ratio = 10.2.The title compound, [Na(NO 3 )(C 3 H 7 NO 2 )] n , was obtained unintentionally as the product of an attempted reaction of sodium molybdate in aqueous solution and the amino acid l-alanine (ala), in order to obtain a -type octamolybdate, Na 4 [Mo 8 O 26 (ala) 2 ].18H 2 O, coordinated by l-alanine. The coordination geometry around the Na atom can be considered as trigonal-bipyramidal, with three bidentate nitrate anions coordinating through their O atoms and two l-alanine molecules each coordinating through one carboxylate O atom. (1996, 1999). Related literature ExperimentalCrystal data [Na(NO 3