Studies on the stability of polyazamacrocycle-Eu (Tb) by potentiometry and its catalytic hydrolysis on phosphate diester

The stability constants and species distributions of complexes of two lanthanide ions, Eu (III) and Tb(III), with a macrocyclic ligand, 3,6, 9, 17 20, 23-hexaazo-29, 30-dihydroxy-13, 27-dimethyl-tricylco-[23,3,1,1(11,15)] triaconta-1 (28) 11,13,15 (30), 25 26-hexane (BDBPH), in 1: 1 and 2: 1 system, were determined potentiometrically in 50% ethanol solution, at 35.0 degrees C and I = 0.100 mol/L (KCl). The two metal ions could form deprotonated mono- or dinuclear complexes with BDBPH with high stability after the three protons of the ligand completely neutralized. At higher pH values, Eu(M) could not form hydroxo complexes with BDBPH, while Tb(III) could form hydroxo complexes in the types of M2L(OH) M2L(OH)(2) and M2L (OH)(2). The kinetic study on the hydrolysis reaction of his (4-nitrophenyl) phosphate (BNPP) catalyzed by Tb-BDBPH system (2:1) was carried out in aqueous solution (pH 7.0 similar to 10.0) at 35 degrees C with I = 0.1000 mol/L (KCl). The second-order rate constant k(BNPP) (2.3 x 10(-3) (mol/L)(-1)center dot s(-1)) was determined. The dinuclear monohydroxo species, L-Tb-2-OH, is kinetically active species.

Intramolecular amide hydrolysis in N-methylmaleamic acid revisited

The intramolecular amide hydrolysis of N-methylmaleamic acid have been revisited by use of density functional theory and inclusion of solvent effects. The results indicate that concerted reaction mechanism is favored over stepwise reaction mechanism. This is in agreement with the previous theoretical study. Sovlent effects have significant influence on the reaction barrier.

Binuclear lanthanide complexes as catalysts for the hydrolysis of double-stranded DNA

The efficient cleavage of plasmid DNA ( pCAT) by binuclear lanthanide complexes was investigated. At 37 degrees C and neutral pH, both Ho23+L and Er23+L promoted 100% conversion of supercoiled plasmid to the nicked circular form and linear form in 1 h. The corresponding saturation kinetics curve of cleavage of pCAT plasmid by binuclear lanthanide complexes showed the expected increase with catalyst concentration. (C) 1999 Elsevier Science S.A. All rights reserved.

Cleavage of nucleotides by Ce4+ and the lanthanide metal complexes

The cleavage of adenosine-5'-monophosphate (5'-AMP) and guanosine-5'-monophosphate (S-GMP) by Ce4+ and lanthanide complex of 2-carboxyethylgermanium sesquioxide (Ge-132) in acidic and near neutral conditions was investigated by NMR, HPLC and measuring the liberated inorganic phosphate at 37 degrees C and 50 degrees C, The results showed that 5'-GMP and 5'-AMP was converted to guanine (G), 5'-monophosphate (depurination of 5'-GMP), ribose (depurination and dephosphorylation of 5'-GMP), phosphate and adenine (A), 5'-monophosphate (depurination of 5'-AMP), ribose (depurination and dephosphorylation of 5'-AMP), phosphate respectively by Ce4+. In presence of lanthanide complexes, 5'-GMP and 5'-AMP were converted to guanosine (Guo) and phosphate and adenosine (Ado) and phosphate respectively. The mechanism of cleaving 5'-GMP and 5'-AMP is hydrolytic scission.

Cleavage of nucleotides by lanthanide metal complexes

The present work revealed that the praseodymium( II ) complex of 2-carboxyethylgermanium sesquioxide (Ge-132) promotes the hydrolysis of the phosphodiester linkages of 3',5'-cyclic adenosine monophosphate (cAMP), 3' , 5'-cyclic deoxyadenosine monophosphate (dcAMP), 5'-adenosine monophosphate(5'-AMP) and 5'-deoxyadenosine monophosphate (5'-dAMP) under mild conditions. Both cAMP and dcAMP were hydrolyzed site-specifically, yielding predominantly 3'-monophosphates, the main products of the cleavage of 5'-AMP and 5'-dAMP included adenosine (Ado). deoxyadenosine (dAdo) and free phosphates respectively. A hydrolytic mechanism was proposed for cAMP, dcAMP, 5'-AMP and 5'-dAMP.

Lanthanide metal complexes for the hydrolysis of adenosine-5'-monophosphate and deoxyadenosine-5'-monophosphate

The hydrolysis of adenosine-5'-monophosphate and deoxyadenosine-5'-monophosphate has been studied with lanthanide(III) metal complexes of 2-carboxyethylgermanium sesquioxide (Ge-132) by NMR and HPLC and by measuring the liberated inorganic phosphates.

Preparation of TiO2 Film through Hydrolysis of Titanium Butoxide and Interaction between Sensitizing Dyes and the Film

A method of preparation of stable, homogeneous and controlled thickness TiO2 film through hydrolysis of Ti(OC4H(9))(4) is introduced in detail. The structure and property of the film have been investigated by means of SEM and FT-IR techniques. The strong quenching effect between sensitizing dyes and TiO2 film is observed in their fluorescence spectra.

Lanthanide metal complexes for the hydrolysis of ribonucleoside 3',5'-cyclic phosphate and deoxyribonucleoside 3',5'-cyclic phosphate

Ytterbium(III) and praseodymium(III) complexes of 2-carboxyethylgermanium sesquioxide (Ge-132) can hydrolyze the phosphodiester linkage of 3',5'-cyclic adenosine monophosphate (cAMP) and 3',5'-cyclic deoxyadenosine monophosphate (dcAMP). Both cAMP and dcAMP are hydrolyzed with high selectivity, yielding predominantly 3'-monophosphates. The selectivity and activity for hydrolyzing cAMP and dcAMP by lanthanide metal(III) complexes and lanthanide metal ions are compared.

Efficient cleavage of ribonucleoside 3',5'-cyclic phosphates and deoxyribonucleoside 3',5'-cyclic phosphate by lanthanides

The cleavage of 3',5'-cAMP, 3',5'-cGMP and 3',5'-dcAMP by lanthanides has been investigated by HPLC and H-1 NMR. Rapid cleavage of cAMP, cGMP and dcAMP by Ce(III) under air at pH 8 and 37 degrees C has been observed. Regioselective cleavage of P-O(5') bond in cAMP, cGMP and dc;aMP tu give the corresponding 3'-AMP, 3'-GMP and 3'-dAMP by lanthanide chlorides has been achieved, and 3'-AMP and 3'-GMP are cleaved to adenosine(A) and guanosine(CT) more slowly, respectively, The notable difference in reactivity between Ce(III) and the other lanthanide ions under air has also been studied. The cleavage is enhanced with the increase in the molar fraction of Ce(IV). The fast cleavage of cAMP by Ce(III) under air at pH 8 is ascribed to the resultant Ce(IV) in the reaction mixture.

INVESTIGATIONS OF HYDROLYSIS KINETICS OF ATROPINE SULFATE BY ELECTROANALYSIS AT THE WATER NITROBENZENE INTERFACE

The hydrolysis kinetics of atropine sulphate has been investigated by cyclic voltammetry at the water/nitrobenzene interface. The transfer process is diffusion controlled and the transfer species is a 1:1 proton-atropine complex. Two main factors, pH and temperature, which have notable effects on the hydrolysis rate, are illustrated. The most suitable pH for atropine to be preserved in aqueous solution and related parameters were estimated.

Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation

The effect of inorganic salts such as sodium chloride on the hydrolysis of chitosan in a microwave field was investigated. While it is known that microwave heating is a convenient way to obtain a wide range of products of different molecular weights only by changing the reaction time and/or the radiation power, the addition of some inorganic salts was shown to effectively accelerate the degradation of chitosan under microwave irradiation. The molecular weight of the degraded chitosan obtained by microwave irradiation was considerably lower than that obtained by traditional heating. Moreover, the molecular weight of degraded chitosan obtained by microwave irradiation assisted under the conditions of added salt was considerably lower than that obtained by microwave irradiation without added salt. Furthermore, the effect of ionic strength of the added salts was not linked with the change of molecular weight. FTIR spectral analyses demonstrated that a significantly shorter time was required to obtain a satisfactory molecular weight by the microwave irradiation-assisted inorganic salt method than by microwave irradiation without inorganic salts and conventional technology. (C) 2005 Elsevier Ltd. All rights reserved.

Salt-assisted acid hydrolysis of starch to D-glucose under microwave irradiation

The effect of inorganic salts on the hydrolysis of starch in a microwave field was investigated and it was found that some inorganic salts can effectively accelerate the acid hydrolysis of starch. The yield of D-glucose reached 111 wt% (equal to the theoretical yield). (C) 2001 Published by Elsevier Science Ltd. All rights reserved.

Kinetic Analysis of Ester Hydrolysis

A two-week multi-step experiment that introduces students to mechanistic organic chemistry and substituent effects. A simple preparation of differentially substituted para-nitrophenyl benzoates is followed by ester hydrolysis with monitoring by UV-Vis spectroscopy to provide rate data for the reaction.