Biomedical subjects

R LoBrutto

Publications and source records attributed to R LoBrutto.

39 records · Page 3Linked to original sources

PubMed1982

Spatial relationship between cytochrome a and a3.

We have studied the spatial relationship between cytochromes a and a3 by the enhancement of the spin relaxation of cytochrome a3-NO EPR signals by the paramagnetic a heme at 15 K. An Fe-Fe distance of 12-19A is estimated from the absence of dipolar broadening and from the observation of spin relaxation enhancement in the a3-NO complex. When this result is combined with resonance x-ray diffraction data reported by Blasie et al. (Blasie, J. K., Pachence, J. M., Tavormina, A., Dutton, P. L., Stamatoff, J., Eisenberger, P., and Brown, G. (1982) Biochim. Biophys. Acta 679, 188-197) and the contribution from the exchange interaction is considered, we can limit the iron-iron distance to 12-16 A and estimate the angle between the Fe-Fe vector and mitochondrial membrane normal as 30-60 degrees. We also consider the possible effects of CuA on cytochrome a3-NO.

Anaerobiosis↗

PubMedDate not supplied

Mechanistic aspects of chiral discrimination on an amylose tris(3,5-dimethylphenyl)carbamate.

The separation of [2R-[2alpha(R*),3alpha]]-5-[[2-[1-[3,5-bis-(trifluoromethyl)phenyl]ethoxy]-3(S)-4-fluorophenyl)4-morpholinyl]-methyl]-N,N-dimethyl-1H-1,2,3-triazole-4-methanamine hydrochloride from its enantiomer was achieved on an amylose tris-3,5-dimethylphenyl carbamate stationary phase. The retention of the enantiomers is dominated by weak hydrogen bonds while the enantioselectivity is governed by other kinds of interactions, e.g., inclusion in the amylose carbamate chains. Van't Hoffplots of 1nalpha vs. reciprocal temperature were non-linear and could be divided into two linear regions. One region at low temperature (5 degrees C- approximately 20 degrees C) and another one between 25 degrees C-70 degrees C with the change in slope occurring between 16 degrees C and 20 degrees C. DSC experiments suggested that the behavior can be attributed to breakage of H-bonds triggering a conformational change. Molecular simulation indicated a correlation between the interaction energies and the elution order obtained experimentally. The most retained enantiomer (R,R,S-enantiomer) interacts with the stationary phase through a hydrogen bond between the triazole proton and the C=O groups of the stationary phase, as well as through an inclusion in the cleft of the stationary phase. The other enantiomer exhibits a bifurcated H-bond between the triazolic proton and the C=O groups of the stationary phase leading to a less stable complex.

Journal Article↗

PubMedDate not supplied

Human malignant melanomas with varying degrees of melanin content in nude mice: MR imaging, histopathology, and electron paramagnetic resonance.

The etiology of the paramagnetic relaxation enhancement seen in malignant melanoma on proton magnetic resonance (MR) images has been the subject of many recent investigations and has been ascribed to iron from associated hemorrhage or chelated metal ions, rather than directly due to melanin. The purpose of this study was to correlate proton relaxation times on MR images in malignant melanomas with histopathologic features (i.e., degree of pigmentation, iron deposition, and necrosis), water content, and electron paramagnetic resonance (EPR) spectra to elucidate the etiology of the relaxation behavior demonstrated by these neoplasms. Cultured cells derived from human malignant melanoma metastases were implanted subcutaneously into nude mice. Twelve separate lesions were evaluated in 10 mice. Magnetic resonance imaging was performed in vivo at 1.9 T using spin echo and inversion recovery acquisitions for the purposes of calculating T1, T2, and proton density [N(H)]. Histopathologic examination was performed on specimens resected immediately after imaging, using hematoxylin/eosin, Prussian blue, and Fontana stains to assess tumor necrosis, and iron and melanin content. Dry/wet weight ratios and EPR spectra were also obtained on resected specimens. Our results indicate that T1 shortening correlates with increasing melanin content and not with increasing iron deposition, EPR-active metallic cations, necrosis, or water content. In fact, a presumably unrelated statistical correlation was found between increased iron and T1 prolongation. The T2 relaxation times did not correlate with the presence of any single factor other than proton density. Although the unique relaxation behavior of nonhemorrhagic malignant melanoma in vivo cannot be traced to a single cause, our data suggest that, contrary to previous investigations, it is strongly influenced by the presence of melanin rather than iron or other naturally occurring paramagnetic ions.

Animals↗