V. A. Semionkin

Mössbauer spectroscopy with a high velocity resolution: advances in biomedical, pharmaceutical, cosmochemical and nanotechnological research.

The methodological principles of velocity resolution as additional characteristic of the quality of both Mössbauer spectrometer velocity driving system and Mössbauer spectrum were briefly considered. Significantly better quality of Mössbauer spectra measured with a high velocity resolution in comparison with those measured with a low velocity resolution was demonstrated. The main advances of recent studies of iron containing biomolecules, pharmaceutical products, meteorite samples and nanoparticles using Mössbauer spectroscopy with a high velocity resolution were considered and advantages of this technique were shown.

Mössbauer spectroscopy with a high velocity resolution in the study of iron-containing proteins and model compounds.

Mössbauer spectroscopy with a high velocity resolution was used for comparative studies of human adult, rabbit and pig oxyhemoglobins, human liver ferritin and its pharmaceutically important models Imferon and Maltofer(®) as well as liver and spleen tissues from normal and lymphoid leukemia chicken. These studies revealed small variations of Mössbauer hyperfine parameters which were related to small variations of iron electronic structure and stereochemistry in these samples.

Comparative study of the iron cores in human liver ferritin, its pharmaceutical models and ferritin in chicken liver and spleen tissues using Mössbauer spectroscopy with a high velocity resolution

Application of Mössbauer spectroscopy with a high velocity resolution (4096 channels) for comparative analysis of iron cores in a human liver ferritin and its pharmaceutically important models Imferon, Maltofer(®) and Ferrum Lek as well as in iron storage proteins in chicken liver and spleen tissues allowed to reveal small variations in the (57)Fe hyperfine parameters related to differences in the iron core structure. Moreover, it was shown that the best fit of Mössbauer spectra of these samples required different number of components. The latter may indicate that the real iron core structure is more complex than that following from a simple core-shell model. The effect of different living conditions and age on the iron core in chicken liver was also considered.

57Fe Mössbauer spectroscopy and electron paramagnetic resonance studies of human liver ferritin, Ferrum Lek and Maltofer®

A human liver ferritin, commercial Ferrum Lek and Maltofer® samples were studied using Mössbauer spectroscopy and electron paramagnetic resonance. Two Mössbauer spectrometers have been used: (i) a high velocity resolution (4096 channels) at 90 and 295K, (ii) and a low velocity resolution (250 channels) at 20 and 40 K. It is shown that the three studied materials have different superparamagnetic features at various temperatures. This may be caused by different magnetic anisotropy energy barriers, sizes (volume), structures and compositions of the iron cores. The electron paramagnetic resonance spectra of the ferritin, Ferrum Lek and Maltofer® were decomposed into multiple spectral components demonstrating the presence of minor ferro- or ferrimagnetic phases along with revealing marked differences among the studied substances. Mössbauer spectroscopy provides evidences on several components in the measured spectra which could be related to different regions, layers, nanocrystallites, etc. in the iron cores that coincides with heterogeneous and multiphase models for the ferritin iron cores.

Mossbauer spectroscopy with high velocity resolution in the study of iron-bearing minerals in meteorites

Application of Mossbauer spectroscopy with a higher velocity resolution than commonly applied appeared to be useful for obtaining hyperfine parameters of 57 Fe nuclei with a lower experimental error and for a better fit of complicated spectra. The study of iron-bearing phases in ordinary and carbonaceous chondrites as well as iron meteorite and extracted iron-nickel phosphides by Mossbauer spectroscopy with an improved velocity resolution (measurement in 4096 channels, presentation in 1024 channels) demonstrated new results which had not been obtained from Mossbauer spectra measured in 512 channels or less. In particular, it was possible to reveal spectral components related to M1 and M2 sites in olivine and pyroxene in Mossbauer spectra of bulk samples of ordinary chondrites and then to evaluate the temperatures of equilibrium cation distribution. Moreover, differences in small variations of Mossbauer hyperfine parameters were obtained for 57 Fe in M1 and M2 sites for both olivine and pyroxene.

Mössbauer spectroscopy with a high velocity resolution: Principles and applications

Principles and applications of Mossbauer spectroscopy with a high velocity resolution are considered. A comparison of the spectra quality measured using conventional and high velocity resolution Mossbauer spectrometers showed the possibility of the latter technique to fit much better the features of the absorption line shape. The limitations and problems of Mossbauer spectroscopy with a high velocity resolution are also discussed. Nevertheless, advances of this technique could be considered as a way to improve Mossbauer spectrometers and measure the high quality Mossbauer spectra permitting to excavate new results on the basis of a decrease of the instrumental (systematic) error for hyperfine parameters and better fit of the complex Mossbauer spectra.

Comparison of iron-bearing minerals in ordinary chondrites from H, L and LL groups using Mössbauer spectroscopy with a high velocity resolution.

Ordinary chondrites from H, L and LL groups were studied using Mössbauer spectroscopy with a high velocity resolution. Mössbauer parameters of spectral components were obtained using new fitting model excluding the effect of previous misfits of troilite component. Obtained parameters were related to corresponding iron-bearing minerals in ordinary chondrites. The differences of these minerals content as well as small differences in the hyperfine parameters of the same iron-bearing minerals were revealed for different meteorites. The temperatures of equilibrium cations distribution in silicates were estimated and suitable parameters for classification of H, L and LL chondrites were supposed using Mössbauer parameters.

The 57Fe hyperfine interactions in the life sciences: application of Mössbauer spectroscopy with a high velocity resolution in the study of iron-containing biomolecules and pharmaceutical compounds

The 57Fe hyperfine interactions are the useful source of information about the finest structural peculiarities in various iron-containing proteins which can be essential in the natural variety of structure and function relationship in normal biomolecules as well as in its changes in the case of molecular pathology. Mössbauer spectroscopy with a high velocity resolution as the most sensitive probe for the 57Fe hyperfine interactions demonstrates some advances in the study of various hemoglobins, ferritins and pharmaceutical products that can bring new information for the life sciences.

Different 57Fe microenvironments in the nanosized iron cores in human liver ferritin and its pharmaceutical analogues on the basis of temperature dependent Mössbauer spectroscopy

Mössbauer spectra of human liver ferritin and its pharmaceutical analogues Ferrum Lek and Maltofer® measured at various temperatures within the range of 295-83K were fitted using five quadrupole doublets related to different 57Fe microenvironments in various layers/regions of the ferrihydrite and akaganéite iron cores. The observed anomalous temperature dependences of some Mössbauer parameters were considered as a result of low temperature structural rearrangements in different layers/regions in the iron core.

Study of Iron oxide nanoparticles using Mössbauer spectroscopy with a high velocity resolution

Iron oxide (magnetite and maghemite) nanoparticles developed for magnetic fluids were studied using Mössbauer spectroscopy with a high velocity resolution at 295 and 90K. The recorded Mössbauer spectra have demonstrated that usual physical models based on octahedral and tetrahedral sites were not suitable for fitting. Alternatively, the Mössbauer spectra were nicely fitted using a large number of magnetic sextets. The obtained results showed that the Mössbauer spectra and the assessed parameters were different for nanoparticles as-prepared and dispersed in the dispersing fluid at 295K. We claim that this finding is mainly due to the interaction of polar molecules with Iron cations at nanoparticles surface or due to the surface coating using carboxylic-terminated molecules. It is assumed that the large number of spectral components may be related to complexity of the nanoparticles characteristics and deviations from stoichiometry, including in the latter the influence of the oxidation of magnetite towards maghemite.