Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 13: Topical Session Nanoanalytics using Small-Angle Scattering I
MM 13.4: Vortrag
Dienstag, 24. März 2009, 11:15–11:30, IFW A
Lots wife problem in biomineralization: An exploration of colloidal protein-minerals particles with SANS — Alexander Heiß1,2, Vitaliy Pipich1, Willi Jahnen-Dechent2, and •Dietmar Schwahn1 — 1IFF des Helmholtz Forschungszentrum Jülich — 2IBMT der RWTH Aachen
The serum protein fetuin-A is an important inhibitor of calcification in mammals. In vitro experiments using SANS and TEM demonstrated, that fetuin-A mediates the formation of colloidal protein-mineral composites (CPP) in aqueous supersaturated calcium phosphate solutions. Colloidal particles, very similar to those in vitro synthesized secondary CPPs, were also found in ascites from a patient with calcifying peritonitis, a rare clinical complication. Here we show that SANS contrast variation provides detailed information on the topology and the composition of protein-mineral colloids.
Fetuin-A gives rise to a two-stage process of colloid formation. The primary CPPs are spherical and have a diameter of 50 nm, whereas the secondary CPPs have an ellipsoidal shape and a diameter of 200x100 nm. Contrast variation SANS in combination with singular value decomposition technique revealed that the primary CPPs appear as a homogeneous protein-mineral composite whereas the secondary CPPs consist of a compact octacalcium phosphate nucleus covered by a fetuin-A monolayer. Moreover, the analysis of the SANS data indicated that in fact most fetuin-A was still in solution as monomers loaded with calcium and phosphate ions.