Electron paramagnetic resonance spectroscopy and density functional theory methods were used to study the structure of a single, high-affinity Mn(II) binding site in the hammerhead ribozyme. This binding site exhibits a dissociation constant Ke of 4.4 microM in buffer solutions containing 1 M NaCl, as shown by titrations monitored by continuous wave (cw) EPR. A combination of electron spin echo...

Probabilities and correlations in EPR experiments. The EPR-Bohm-Aharonov [1] system of two correlated spin-half particles or qubits observed by spatially separated observers has often been used as an arena in which to probe fundamental questions about quantum theory. Typically there are four different configurations corresponding to four different experiments and one obtains no-go theorems on (...

Paramagnetic complexes of iron (III), manganese (II), and cobalt (II) protoporphyrins IX and apohemoproteins react with nitric oxide to form spectroscopically distinct compounds. Optical and electron paramagnetic resonance (EPR) studies suggest that a l-electron transfer between nitric oxides and metal ions which occurs in these reactions results in the formation of spin-paired complexes of the...

Paramagnetic complexes of iron (III), manganese (II), and cobalt (II) protoporphyrins IX and apohemoproteins react with nitric oxide to form spectroscopically distinct compounds. Optical and electron paramagnetic resonance (EPR) studies suggest that a l-electron transfer between nitric oxides and metal ions which occurs in these reactions results in the formation of spin-paired complexes of the...

Paramagnetic complexes of iron (III), manganese (II), and cobalt (II) protoporphyrins IX and apohemoproteins react with nitric oxide to form spectroscopically distinct compounds. Optical and electron paramagnetic resonance (EPR) studies suggest that a l-electron transfer between nitric oxides and metal ions which occurs in these reactions results in the formation of spin-paired complexes of the...

The Py(2)N(4)S(2) octadentate coordinating ligand afforded dinuclear cobalt, copper and zinc complexes and the corresponding mixed metal compounds. The overall geometry and bonding modes have been deduced on the basis of elemental analysis data, MALDI-TOF-MS, IR, UV-vis and EPR spectroscopies, single-crystal X-Ray diffraction, conductivity and magnetic susceptibility measurements. In the copper...

Oxalate decarboxylase from Bacillus subtilis is composed of two cupin domains, each of which contains a Mn(II) ion coordinated by four identical conserved residues. The similarity between the two Mn(II) sites has precluded previous attempts to distinguish them spectroscopically and complicated efforts to understand the catalytic mechanism. A multifrequency cw-EPR approach has now enabled us to ...

A set of four copper(ii) complexes, and (X = Cl, Br; = N-(l-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide), have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystals and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensio...