Investigations of the roles of the distal heme environment and the proximal heme iron ligand in peroxide activation by heme enzymes via molecular engineering of myoglobin

To pursue structure-function relationships of heme enzymes in the activation of peroxides, we have chosen to use myoglobin as the framework for our molecular engineering studies. Comparison of the crystal structures of myoglobin and peroxidases reveals differences in the arrangement of amino acid residues in heme active sites. On the basis of these structural differences and the reaction mechanisms of peroxidases, we have converted myoglobin into a peroxidase-like enzyme by alternation of the heme distal pocket via site-directed mutagenesis. The replacement of the proximal histidine with cysteine and the exogenous substituted imidazoles slightly accelerates the peroxide O-O bond cleavage due to the electron donor characteristics. However, we have not observed an enhancement in the activation of peroxide by the proximal mutant with tyrosine, the exogenous phenolate, and benzoate. A clear understanding of the absolute role of the proximal ligand remains elusive.     

Measurement of activation yields for platinum group elements using Bremsstrahlung radiation with end-point energies in the range 11-14 MeV

Activation yields have been measured for (γ,n) reactions of the elements Ru, Rh, Pd, Ir and Pt. Metallic foils of natural isotopic composition were irradiated using Bremsstrahlung radiation produced from an electron linear accelerator operated with electron beam energies in the range 11-14 MeV. Activation products, including both unstable ground states and metastates were measured using a high-purity germanium detector. Cross-sections were estimated from the yield data by assuming a simple two-parameter model for the shape of the cross-section with energy.     

Silver-ion high-performance liquid chromatographic separation and identification of conjugated linoleic acid isomers

This is the first report of the application of silverion impregnated high-performance liquid chromatography (Ag⁺-HPLC) to the separation of complex mixtures of conjugated linolenic acid (CLA) isomers present in commercial CLA sources and foods and in biological specimens. This method showed a clear separation of CLA isomers into three groups related to their trans,trans, cis,trans or trans,cis, and cis,cis configuration of the conjugated double-bound system. In addition, this method separated within each geometrical isomeric group. Following Ag⁺-HPLC isolation, gas chromatography (GC)-electron impact mass spectrometry, and GC-direct deposition-Fourier transformed infrared spectroscopy were used to confirm the identity of two major positional isomers in the cis/trans region, i.e., Δ8,10- and Δ11,13-octadecadienoic acid, which had not been chromatographically resolved previously, Furthermore, the potential of this method was demonstrated by showing different Ag⁺-HPLC profiles exhibiting patterns of isomeric distributions for biological specimens from animals fed a diet containing a commerical CLA preparation, as well as for a commerical cheese product.     

Increased collateral blood flow to ischemic myocardium by estrogen replacement therapy may contribute to reduced incidence of fatal and non-fatal acute myocardial infarction in postmenopausal women

We report a case of neurosarcoidosis, which simulated a cerebral tumor located at the floor of the III ventricle, associated to an aseptic meningitis and diabetes insipidus. It was the first and only manifestation of the illness. The response to steroid therapy was very favourable, with complete clinical recuperation and radiological resolution.