Glicemical analysis of human blood serum using FT-Raman: a new approach.

BACKGROUND DATA: Fourier transform Raman spectroscopy (FT-Raman) is a noninvasive diagnostic tool largely applied to the analysis of biological fluids and tissues. METHODS: We examined the variation of carbohydrate concentration in human blood during 180 min relative to 29 spectra of patients split into four categories: hypoglycemic, healthy, threshold, and diabetic. The main bands monitored were placed in 960, 1030, 1091, 1128, and 1205 cm(-1). These bands were respectively attributed to C-O, C-C (stretching), C-O-H and C-O-C of carbohydrates. In this study, the Raman scattering signal of the all the blood samples was collected during 360 sec. The calculated correlation coefficient (R) between the concentration of carbohydrates and the Raman intensity was 0.923. CONCLUSIONS: The obtained results are reasonable according to classical biochemical analysis. Our proposed FT-Raman-based method was shown to be suitable for the monitoring of carbohydrate concentration in human blood, and presented some advantages over classical biochemical methods, such as real-time analysis, required small sample volume, and was nondestructive, and the samples did not need any previous treatment.

Ferric species of the giant extracellular hemoglobin of Glossoscolex paulistus as function of pH: an EPR study on the irreversibility of the heme transitions.

The present article is focused on the transitions of ferric heme species of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) induced by successive alterations in pH, involving alkaline and acid mediums. Electron paramagnetic resonance (EPR) is the spectroscopy used to evaluate the transitions that occur in the first coordination sphere of ferric ion as a consequence of ligand changes in a wide range of pH, since this tool is very sensitive to slight changes that occur in the heme pocket of paramagnetic species. This approach is adequate to obtain information regarding the reversibility/irreversibility that involves the heme transitions induced by pH, since the degree of reversibility is associated to the intensity of the changes that occur in the spatial configuration of the polypeptide chains, which is clearly associated to the first coordination sphere. The results demonstrate a significant degree of irreversibility of heme transitions, since the final species, which do not present any change after 6 h of its respective formations, are quite different of the initial species. The results denote that the more stable species are the bis-histidine (hemichrome) and pentacoordinate species, due to the properties of their ligands and to the mechanical influence of the respective subunits. EPR spectra allow to distinguish the types of hemichrome species, depending on the reciprocal orientation between the histidine axial ligands, in agreement with Walker's Classification [Walker, F.A., 1999. Magnetic spectroscopic (EPR, ESEEM, Mössbauer, MCD and NMR) studies of low-spin ferriheme centers and their corresponding heme proteins. Coord. Chem. Rev. 185-186, 471-534]. However, these transitions are not completed, i.e., the appearance of a determined species does not mean the total consumption of its precursor species, implying the coexistence of several types of species, depending on pH. Furthermore, it is possible to conclude that a "pure" EPR spectrum of aquomet ferric species is an important indicator of a high level of conservation referent to the "native" configuration of whole hemoglobin, which is only encountered at pH 7.0. The results allow to infer important physico-chemical properties as well as to evaluate aspects of the structure-activity relationship of this hemoprotein, furnishing information with respect to the denaturation mechanism induced by drastic changes in pH. These data are very useful since HbGp has been proposed as prototype of substitute of blood, thus requiring wide knowledge about its structural and chemical properties.