NOPR Collection:

Use of lanthanide metal complexes for the hydrolysis of 3',5' - and 2' , 3' - cyclic nucleotides

Tue, 01 Sep 1998 00:00:00 GMT

Title: Use of lanthanide metal complexes for the hydrolysis of 3',5' - and 2' , 3' - cyclic nucleotides Authors: Zhu, Bing; Zhao, Da-Qing; Ni, Jia-Zuan Abstract: Lutetium(III) and lanthanum(lII) complexes of 2- carboxyethylgermanium sesquioxide (Ge-132) can hydrolyze the phosphodiester linkage of 3' , 5' -cyclic adenosine monophosphate (cAMP), 3' , 5' -cyclic deoxyadenosine monophosphate (dcAMP) and 2' , 3' -cyclic adenosine monophosphate (2' ,3' - cAMP). Both cAMP and dcAMP are hydrolyzed with high selectivity, yielding predominantly 3' - monophosphates. 2',3'- cAMP is converted to 3' -AMP and 2' -AMP, the ratio of 3' - AMP to 2' -AMP produced being 1.4. Page(s): 755-758

Complex formation of cobalt(II) with 2-(imidazoleazo )benzene and 2-(2-aminoethyl)benzimidazole: A kinetic and equilibrium study

Tue, 01 Sep 1998 00:00:00 GMT

Title: Complex formation of cobalt(II) with 2-(imidazoleazo )benzene and 2-(2-aminoethyl)benzimidazole: A kinetic and equilibrium study Authors: Dash, Anadi C; Acharya, Achyutananda; Sahoo, Rama K Abstract: The reversible complexation of cobalt(II) with 2-(irnidaioleazo) benzene (lAB) and 2-(2-aminoethyl)benzimidazole (AEB) has been studied at l=0.3 mol dm^-3. At 25°C the values of log K_M (K_M is the stability constant), ∆H⁰/KJ mol^-1, and ∆S⁰/JK^-1 mol'! are 2.09±0.03, 14.4±2.4, 88±8 for Co(IAB)2+ and 2.65±0.01, 20.0±7.2, 120±21 for Co(AEB)2+ respectively. The rate constants of formation of COL2+chelate via the reaction: CO(OH₂)₆²⁺+L Co(OH₂)₄L²⁺., (10^-4 k/dm^-3 mol^-1 s^-1=11.7±0.4 (lAB), 1.01±0.03 (AEB) at 10°C) are at least 10 times smallerthan the rate constant of water exchange from Co(OH₂)₆²⁺.Data analysis further indicates that the chelate formation involves Chelation Controlled Substitution mechanism. The dissociation of Co(AEB)²⁺ is strongly acid catalysed unlike that for Co(IAB)²⁺. Page(s): 759-764

Kinetics and mechanism of iridium(III) catalysed oxidation of butan-2-ol by cerium(IV) in aqueous sulphuric acid media

Tue, 01 Sep 1998 00:00:00 GMT

Title: Kinetics and mechanism of iridium(III) catalysed oxidation of butan-2-ol by cerium(IV) in aqueous sulphuric acid media Authors: Mondal, Sudhin K; Kar, Dalia; Das, Mahua; Das, Asim K Abstract: The kinetics and mechanism of Ir(III) catalysed oxidation of butan-Z-ol by Ce(IV) in aqueous sulphuric acid media have been followed at different temperatures (20-35°C) under the conditions, [butan-2-0l]_T>>[Ce(IV)]_T. >> [Ir]_T(ca. 10^-6 mol dm^-3). In 1.0 mol dm^-3 sulphuric acid media, the observed rate law conforms to: -dln[Ce(IV)]ldt=K_obs=a[butan-2-ol]_T [Ir]_T/(b+c[butan-2-ol]_T) where, [butan-z-ol], and [Ir]Tgive the total concentrations of the substrate and catalyst respectively; a, band care constants at a particular temperature and fixed [H₂SO₄]. From the [H_SO₄·] dependence, Ce(SO₄)₂ has been found kinetically active. The proposed mechanism involves a pre-equilibrium interaction between the catalyst and substrate leading to an outer-sphere complex followed by the electron transfer at the rate determining step involving Ce(IV) and outer-sphere complex formed in pre-equilibrium step. It operates through the Ir(III)/Ir(IV) catalytic cycle. The process is acid catalysed. Activation parameters have been determined to investigate the effect of temperature. Page(s): 765-768

Quantitative aspects of intramolecular interactions in ternary complexes of purine nucleotides and amino acids

Tue, 01 Sep 1998 00:00:00 GMT

Title: Quantitative aspects of intramolecular interactions in ternary complexes of purine nucleotides and amino acids Authors: Reddy, P Rabindra; Venkatadri, E Abstract: Interaction Of bivalent metal ions (CO²⁺,Ni²⁺, Cu²⁺,Zn²⁺) with purine nucleotides (5' - guanosinemono-phosphate and 5' - inosinemonophonsphate) and amino acids (alanine, phenylalanine and tryptophan) in I: I and I: I: 1 ratios has been investigated by potentiometric pH measurements and formation constants in various systems are determined by computer program. The extra stabilization is expressed in terms of ∆logK. The hydrophobic interactions associated with different amino acids and nucleotides have been identified with parameters like ∆logK, K_l % of (MLA)_st' and ∆G^o The pH profiles of various species are generated in order to identify the stable species. Page(s): 769-774