Biomineralisation by earthworms - an investigation into the stability and distribution of amorphous XXXX .

@entity1522 @entity13359 @entity4959 @entity16415 @entity3689 @entity8450 @entity72960
BACKGROUND: Many biominerals form from amorphous @entity4959 ( @entity72960 ), but this phase is highly unstable when synthesised in its pure form inorganically. Several species of earthworm secrete @entity4959 granules which contain highly stable @entity72960 . We analysed the milky fluid from which granules form and solid granules for @entity3689 (by liquid chromatography) and functional group (by Fourier transform infrared (FTIR) spectroscopy) compositions. Granule elemental composition was determined using @entity8450 ( @entity13359 ) and electron microprobe analysis (EMPA). Mass of @entity72960 present in solid granules was quantified using FTIR and compared to granule elemental and @entity3689 compositions. Bulk analysis of granules was of powdered bulk material. Spatially resolved analysis was of thin sections of granules using synchrotron-based  -FTIR and EMPA electron microprobe analysis. RESULTS: The milky fluid from which granules form is @entity3689 -rich ( <= 136    3 nmol mg(-1) (n = 3;    std dev) per individual @entity3689 ); the @entity16415 phase present is @entity72960 . Even four years after production, granules contain @entity72960 . No correlation exists between mass of @entity72960 present and granule elemental composition. Granule @entity3689 concentrations correlate well with @entity72960 content (r >=  0.7, p  <= 0.05) consistent with a role for @entity1522 (or the proteins they make up) in @entity72960 stabilisation. Intra-granule variation in @entity72960 (RSD = 16%) and @entity3689 concentration (RSD = 22-35%) was high for granules produced by the same earthworm. Maps of @entity72960 distribution produced using synchrotron-based  -FTIR mapping of granule thin sections and the relative intensity of the   2:   4 peak ratio, cluster analysis and component regression using @entity72960 and calcite standards showed similar spatial distributions of likely @entity72960 -rich and calcite-rich areas. We could not identify organic peaks in the  -FTIR spectra and thus could not determine whether @entity72960 -rich domains also had relatively high @entity3689 concentrations. No correlation exists between @entity72960 distribution and elemental concentrations determined by EMPA. CONCLUSIONS: @entity72960 present in earthworm @entity16415 granules is highly stable. Our results suggest a role for @entity1522 (or proteins) in this stability. We see no evidence for stabilisation of @entity72960 by incorporation of inorganic components. Graphical abstractSynchrotron-based  -FTIR mapping was used to determine the spatial distribution of amorphous @entity4959 in earthworm-produced @entity16415 granules.
