Structural complexity of hexagonal prismatic crystal specimens of fluorapatite-gelatine nanocomposites: A case study in biomimetic crystal research

Hexagonal prismatic crystal-like entities of fluorapatite-gelatine nanocomposites were grown by double-diffusion in gelatine gels. The Bragg pattern of the specimens (containing 2.3(3) wt.-% gelatine) is consistent with fluorapatite. TEM images together with atomistic computer simulations reveal the material to be best described as a mosaic-dominated nanocomposite superstructure. Intrinsic electric dipole fields (detected by electron holography), generated by a non-classical crystallization process of composite nanoboards (elongated platelets), cause the integration of a meso/macroscopic pattern (symmetry: 6/m) of gelatine microfibrils into the superstructure matrix

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 P-31, F-19, and H-1 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

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

FEATURES OF ANDROGENESIS IN ANTHER CULTURES OF VARIETIES AND A PROMISING ACCESSION OF SPRING COMMON WHEAT BRED IN WEST SIBERIA DIFFERING IN THE PRESENCE OR ABSENCE OF WHEAT-ALIEN TRANSLOCATIONS

Androgenesis has been studied in anther cultures of eight cultivars and one promising accession of spring common wheat raised in West Siberia (Siberian Research Institute of Agriculture, Omsk, Russia). The varieties are close in origin but vary in the presence or absence of wheat-alien translocations (wheat–rye 1RS.1BL and wheat–couch grass 7DL-7Ai). The promising accession L-311/00-22 bears the 1RS.1BL translocation and the cytoplasm of cultivated barley Hordeum vulgare L. The main task of the study is to assess the possibility of obtaining dihaploid lines in the genotypes examined bearing wheat-alien translocations. It has been found that different accessions respond differently to anther culture conditions depending on the concentration of 2,4-D in the initial medium. Accession L-311/00-22 is best for androgenesis experiments and raise of dihaploid lines. The dependence of the effect of the genotypic environment of wheat on the effect of wheat-alien translocation on androgenesis features, is discussed

EFFECT OF CERTAIN CHROMOSOME REGIONS OF TRITICUM TIMOPHEEVII ON THE FORMATION OF PEST RESISTANCE AND QUANTITATIVE TRAITS IN COMMON WHEAT

The effects of introgression fragments from Triticum timopheevii Zhuk. (2n = 28, AtAtGG) and their combinations on resistance to leaf rust, stem rust, powdery mildew, and some quantitative traits were assessed in 15 common wheat introgression lines. Molecular and cytological analyses of the lines demonstrated an advantage of combined use of various marker types in comprehensive characterization of hybrids and detection of translocations and substitutions. Resistance tests to various fungal diseases showed that the lines containing introgression fragments of chromosome 5G were completely resistant to the West Siberian populations of leaf rust and to the stem rust population of the Omsk region. Lines 3862-5 and 3862-15, containing a fragment of the long arm of chromosome 2G, were resistant to West Siberian stem rust populations. No negative effects of the alien genetic material on yield and other quantitative traits were noted. In addition, positive effect of the 2G chromosome fragments of Triticum timopheevii on ear grain number was established. Thus, the introgression lines can be used in breeding programs as donors of resistance genes to fungal diseases