Elena Rosseeva

An NMR Study of Biomimetic Fluorapatite : Gelatine Mesocrystals

The mesocrystal system fluoroapatite—gelatine grown by double-diffusion is characterized by hierarchical composite structure on a mesoscale. In the present work we apply solid state NMR to characterize its structure on the molecular level and provide a link between the structural organisation on the mesoscale and atomistic computer simulations. Thus, we find that the individual nanocrystals are composed of crystalline fluorapatite domains covered by a thin boundary apatite-like layer. The latter is in contact with an amorphous layer, which fills the interparticle space. The amorphous layer is comprised of the organic matrix impregnated by isolated phosphate groups, Ca3F motifs and water molecules. Our NMR data provide clear evidence for the existence of precursor complexes in the gelatine phase, which were not involved in the formation of apatite crystals, proving hence theoretical predictions on the structural pre-treatment of gelatine by ion impregnation. The interfacial interactions, which may be described as the glue holding the composite materials together, comprise hydrogen bond interactions with the apatite PO43− groups. The reported results are in a good agreement with molecular dynamics simulations, which address the mechanisms of a growth control by collagen fibers, and with experimental observations of an amorphous cover layer in biominerals.

Interconnection of Nanoparticles within 2D Superlattices of PbS/Oleic Acid Thin Films

Make it connected! 2D close-packed layers of inorganic nanoparticles are interconnected by organic fibrils of oleic acid as clearly visualized by electron holography. These fibrils can be mineralised by PbS to transform an organic-inorganic framework to a completely interconnected inorganic semiconducting 2D array.

The influence of amino acids on the formation of nanocrystalline hydroxyapatite

The influence of amino acids on the formation of particles of synthetic analogs of hydroxyapatites of renal calculi with different degrees of nonstoichiometry is investigated. It is demonstrated that the electrokinetic properties (the charge and the potential) and the dispersion composition of the synthesized hydroxyapatite sols depend on the Ca/P atomic ratio. The results obtained allow the assumption that, under the normal physiological conditions, free amino acids are natural inhibitors for the formation of renal calculi in the human organism.

Intergrowth and Interfacial Structure of Biomimetic Fluorapatite-Gelatin Nanocomposite : A Solid-State NMR Study

The model system fluorapatite-gelatin allows mimicking the formation conditions on a lower level of complexity compared to natural dental and bone tissues. Here, we report on solid-state NMR investigations to examine the structure of fluorapatite-gelatin nanocomposites on a molecular level with particular focus on organic-inorganic interactions. Using (31)P, (19)F, and (1)H MAS NMR and heteronuclear correlations, we found the nanocomposite to consist of crystalline apatite-like regions (fluorapatite and hydroxyfluorapatite) in close contact with a more dissolved (amorphous) layer containing first motifs of the apatite crystal structure as well as the organic component. A scheme of the intergrowth region in the fluorapatite-gelatin nanocomposite, where mineral domains interact with organic matrix, is presented.

Thermodynamic and experimental modeling of the formation of major mineral phases of uroliths

Solubility diagrams have been calculated for the major phases of uroliths and their binary systems with a common cation or anion at 25°C. Phase-formation laws under the conditions of healthy human urea have been experimentally studied. The adequacy of the theoretical and experimental modeling to pathogenic mineralization in humans is analyzed. The applicability limits of the thermodynamic model have been refined.

Mechanics of twisted hippuric acid crystals untwisting as they grow

Spontaneous twisting of single crystals is a common growth induced deformation. But as twisted crystals thicken they can untwist, restoring a straight form. The mechanics of this process was studied for vapor grown needle-like crystals of N-benzoylglycine (hippuric acid) and N-(2-thienylcarbonyl)glycine, and analyzed by phenomenological models. The elastic stress at the crystal tip undergoes plastic relaxation leading to the twisting deformations. As the crystal grows and thickens it partially untwists showing linear increases of the twist period with crystal thickness. Such behavior was simulated with a model that assumes the constant density of defects in successive growth layers. However, transmission electron microscopy does not reveal any dislocations or other extended defects typically associated with plastic deformation. Published data on other materials show the linear dependencies of pitch on thickness suggesting comparable untwisting mechanisms for different materials.

Refinement of apatite atomic structure of albid tissue of Late Devon conodont

The crystal structure of carbonate-containing apatite from albid tissue of Late Devon conodonts of Polygnathus species (Ozarkodinida order) has been refined by single-crystal X-ray diffraction with the application of electron-probe X-ray microanalysis and Raman spectroscopy data. This apatite-organic composite yields a diffraction pattern characteristic of a single crystal. The atomic structure of biological apatite is close to that of stoichiometric apatite-(CaF). The content of carbonate ions replacing [PO4]3− anions is very low (∼1 wt %). Channels of the structure contain not only fluorine but also OH ions (in a ratio of 3: 1); the latter are partially replaced with water molecules. The main cationic substitutions occur in the Ca2 position. The specific features of the diffraction pattern of albid tissue indicate that the apatite-organic composite under study is a nanostructured material (a biological mesocrystal).

Radioactive Elements in Bone Tissue From Freshwater Fish

The regularities of radionuclide incorporation to a bone tissue of living organisms have been regarded. Material for researches (chondral and achondral bones of freshwater fish) was collected in control reservoirs of Leningrad region, in reservoirs polluted by radioactive substances as a result of failure on the Chernobyl atomic power station (cooling pond) and technological reservoirs of ‘Mayak’ (the Chelyabinsk region). Results of comparative studying of bone fabric structure are presented in this article. The mineral component of researched bones is presented by poorly crystallized calcium deficient apatite of B-type. Apatite crystallites (~10 nm) are randomly oriented. Alternating of zones with apatite and albumen prevalence is observed in the SEM-images. Different zones in SEM images are corresponded to different ratio between albumen and apatite concentrations: dark zones contain more apatite. In SEM-images bone tissue cells were distinctly identified also. The greatest specific activity is observed in the samples from ‘Mayak’ reservoirs. The concentration of 137Cs isotope in chondral bones is usually greater, than in achondral ones, it’s connected with the greater concentration of albumen in chondral bones. The element composition of the bones of one type from different reservoirs is similar, while chondral and achondral bone of one fish have greater difference in the element composition. Thus, it is possible to draw a conclusion that the mechanism of formation of a bone and a patrimonial accessory of fishes render a greater influence on a chemical compound of a bone fabric, than growth of fish in the conditions of the raised maintenance of radioactive elements. Not only environmental pollution, but also histological features were taken into consideration. Investigation of the regularities of elements’ distribution between chondral and achondral fish bones was estimated for the first time. Work is executed with financial support of projects of the Russian Federal Property Fund No 08-05-00957, 08-05-10073, 11-05-90425-укр_ф_а.

Medical Geology in Russia and the NIS

Systematic and regular epidemiological studies on endemic diseases and the natural environment in Russia and NIS are scarce and sporadic. However, there have been some studies of the links between health of the population and the geological background. Information on fluorine, iodine, arsenic, selenium, and other elements’ behavior in natural environment and their effect on human health is presented in this chapter and is the first attempt to synthesize the interdisciplinary knowledge on some geological factors which affect human health in Russia and NIS. Also anthropogenic factors are mentioned, however, of geological origin.