Biominerals - source and inspiration for novel advanced materials

Biomineralization seems an odd sort of word. How can you combine biology and minerals? However, a quick look around brings to light many familiar objects that are examples of biominerals. Most dramatic are the coral reefs and sea shells of the marine environment (calcium carbonate) and human bone and teeth (calcium hydroxyapatite) but there are many other examples. In the past 10 years, an increasing number of biominerals has been reported (Table 1). Interest in the biological and chemical processes that lead to biomineralization, howeyer, has only developed rather recently. Early observations were made by paleontologists who were interested in the preservation, through geological time, of the hard parts of organisms such as shells and skeletons but only in 1989 did the field really come of age with the almost simultaneous publication of three monographs covering current knowledge of the biological, biochemical, chemical and taxonomic aspects of biomineralization (Mann et al. 1989; Lowenstam & Weiner 1989; Simkiss & Wilbur 1989)

Biologically active inorganic solids: Case study of iron oxides in the marine molluscs, limpets and chitons

Biologically active inorganic solids are being used increasingly to inspire the development of new materials and novel technologies. The organization of the iron oxides present in the mineralizing teeth of the radula of limpets and chitons has been described at the sub-micron level. The magnetic and structural properties of these oxides and the iron core of the transport protein ferritin have been analysed in detail. The organization of the organic fibres within the teeth appears well suited to the role of the fibres as 'shock absorbers' during feeding on the rocky substrate. At the molecular level, these fibres are involved in the selective control of mineralization of iron and calcium in different regions of the teeth

The effect of temperature on the radial distribution function for iron in native horse spleen ferritin

Iron K-edge X-ray absorption spectra were recorded for a sample of freeze-dried horse spleen ferritin over a range of temperatures from 40 to 300 K. Gaussian-type radial distribution functions were fitted to the data from all temperatures simultaneously and the obtained mean-square relative displacements σ2 (EXAFS Debye-Waller factors) were fitted using an Einstein model. For iron atoms in the second and/or third coordination shell an Einstein temperature of 330 ± 20 K was obtained. If oxygen was assumed in the second or third shell, its Einstein temperature was 460 ± 20 K. This indicates that the core of ferritin may have a somewhat more rigid structure than those of previously studied ferritin analogues (polysaccharide iron complexes)

Non-stoichiometric magnetite and maghemite in the mature teeth of the chiton Acanthopleura hirtosa

Mature radula pieces from the chiton Acanthopleura hirtosa were studied using Mössbauer spectroscopy. The magnetite present in the radulae was found to have a distribution of Verwey transition temperatures in the range 85-100K. It was deduced that the magnetite was non-stoichiometric with an average formula Fe 2.98O 3. About 10% of the Fe in the radulae was in the form of maghemite and about 19% was in the form of paramagnetic or superparamagnetic phases

The effect of europium (Ⅲ) on iron uptake by apoferritin

In order to explore the posibility using apoferritin as a cage to synthesize inorganicnanosize particles containing rare earth ions the effect of europium(Ⅲ)on the iron uptake byhorse spleen apoferritin was studied by using absorption spectra. The inhibition of europium(Ⅲ)on iron uptake only affects the initial rate. In the presence of europium(Ⅲ), ferritincan be formed from apoferritin and iron(Ⅱ)in air

A low-spin iron complex in human melanoma and rat hepatoma cells and a high-spin iron(II) complex in rat hepatoma cells

Human melanoma and rat hepatoma cells cultured in the presence of low concentrations (2.5 μM) of low-molecular-weight iron (Fe) chelates and Fe-transferrin complexes have been studied with 57Fe Mössbauer spectroscopy. The spectra show that holoferritin is only a minor fraction of the total iron present in the cells. The major form of Fe was in a low-spin state unlike the high-spin Fe(III) found in ferritin. Only about 10% of the Fe could be attributed to ferritin. In addition, the hepatoma cells had a high-spin Fe(II) spectral component which made up about 20% of the Fe present

A Mössbauer spectroscopic study of the forms of storage iron in the larval and adult stages of the lamprey,Geotria australis

The principal forms of storage-iron in the lamprey, Geotria australis, are haemosiderin in the nephric fold of the larval animal and ferritin in the liver of the adult. Mössbauer spectroscopy of the larval haemosiderin showed that about half of the iron was in the form of ferrihydrite (5Fe2O3.9H2O) with the remainder being in the form of a non-crystalline iron oxyhydroxide, suggesting two modes of biomineralization. The cores of the adult liver ferritin gave spectral parameters indicating the iron to be predominantly in the form of ferrihydrite with about 10% being in a non-crystalline phase