Magnetic circular dichroism spectroscopy studies

Cole et al. (97) studied the electronic structure of the laccase trinuclear copper active site by the use of absorption, circular dichroism, and low-temperature magnetic circular dichroism spectroscopies. The assigned ligand field transition energies indicated that all three coppers have tetragonal geometries and that the two type-3 coppers are inequivalent. 

TL2221). The mechanism of this proton transfer was also investigated using the temperature-jump relaxation technique (77JA4438). 3-Hydroxypyridine tautomer-ism has also been studied by magnetic circular dichroism spectroscopy (80BCJ3069). 

Six symmetrically disubstituted derivatives of r-tetrazine have been studied by linear dichroism spectroscopy in the UV-Vis region, magnetic circular dichroism spectroscopy, and theoretical calculations of structures and spectra <1995CPH(200)201>. A detailed discussion of the sensitivity and of the optothermal detection scheme for the study of nonfluorescing excited states of the r-tetrazine-argon van der Waals complex has been presented <2000MI183>. 

Optical Spectroscopy General principles and overview, 246, 13 absorption and circular dichroism spectroscopy of nucleic acid duplexes and triplexes, 246, 19 circular dichroism, 246, 34 bioinorganic spectroscopy, 246, 71 magnetic circular dichroism, 246, 110 low-temperature spectroscopy, 246, 131 rapid-scanning ultraviolet/visible spectroscopy applied in stopped-flow studies, 246, 168 transient absorption spectroscopy in the study of processes and dynamics in biology, 246, 201 hole burning spectroscopy and physics of proteins, 246, 226 ultraviolet/visible spectroelectrochemistry of redox proteins, 246, 701 diode array detection in liquid chromatography, 246, 749. 

Several direct methods are available to analyze the tertiary structure of ODNs like nuclear magnetic resonance (NMR) and X-ray crystallographic (XRC) techniques, which needs a sophisticated setup and infrastructure. An alternative but indirect method to study the structure and conformations of nucleic acids is circular dichroism spectroscopy (CD spectroscopy) (25, 26), where circular dichroism refers to the differential absorption of left and right circularly polarized light (27). 

Cryoreduction of ferric metalloproteins has been mostly done by y-irradiating of frozen solutions of heme proteins at 77K, unless it is specially stated otherwise. Cryoradiolytic reduction of ferric cytochrome c and its complexes with fluoride, azide, cyanide, and imidazole were studied using optical absorption spectroscopy and magnetic circular dichroism.36,39,46 44 The primary products of cryoreduction of low-... 

Molecular dynamics (MD) simulations fill a significant niche in the study of chemical structure. While nuclear magnetic resonance (NMR) yields the structure of a molecule in atomic detail, this structure is the time-averaged composite of several conformations. Electronic and vibrational circular dichroism spectroscopy and more general ultraviolet/visible and infrared (IR) spectroscopy yield the secondary structure of the molecule, but at low resolution. MD simulations, on the other hand, yield a large set of individual structures in high detail and can describe the dynamic properties of these structures in solution. Movement and energy details of individual atoms can then be easily obtained from these studies. 

Magnetic circular dichroism (MCD) is a technique for studying magnetic-field induced perturbations in the energy levels of a system. It provides additional information about the nature of the energy levels that cause a transition in optical spectroscopy. Recent reviews of iron porphyrin MCD have been written by Dawson and Dooley [10] and Cheesman et al. [29]. 

The spin Hamiltonian formalism, which is also needed to interpret, for example, electron paramagnetic resonance or magnetic circular dichroism spectra see Magnetic Circular Dichroism (MCD) Spectroscopy), was first applied to the interpretation of magnetic Mossbauer spectra by Wickmann, Klein and Shirley and was implemented into a computer program by Miinck et al. in the early 1970s. For most studies of mononuclear iron centers with electron spin quantum number S, the following electronic Hamiltonian is used ... 

Circular dichroism (CD) spectroscopy has been used to study the cleaved (73), deflavo (74), and intact (19, 60) forms of flavocytochrome 62 from S. cerevisiae and the intact enzyme from H. anomala (73, 75). Magnetic circular dichroism (MCD) has been used to probe the holo-and deflavo-cleaved enzyme from S. cerevisiae (76), as well as the cytochrome 62 core (77). It was noted that bands in the CD and MCD spectra ascribed to the heme were affected by removal of the FMN group, providing direct evidence of an interaction between the two prosthetic groups (73). Circular dichroism experiments on the intact and cleaved forms of S. cerevisiae flavocytochrome 62 led Jacq and Lederer (19) to conclude that there were differences in the heme environment between these two forms of the enzyme. 

Mascharak et al. 63) have prepared a structural BLM model PMAH containing pyrimidine, imidazole, and primary and secondary amine building blocks. The iron -PMAH complex was studied by X-ray absorption, magnetic circular dichroism, and resonance Raman spectroscopy 63). This Fe-BLM model exhibits a five-coordinate, square pyramidal geometry in the solid state and a distorted octahedral geometry in solution with a solvent molecule at the sixth position. Similar spectral features have been found for Fe -BLM. This PMAH-Fe" complex binds O2 to generate PMAH-Fe "-OOH, a low-spin hydroperoxo-iron(III) complex 64) able to promote the lipid peroxidation as BLM 65). 

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