Biointerphases

Journal for Biophysical Chemistry

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Open Access

Structural dynamics of a colloidal protein-mineral complex bestowing on calcium phosphate a high solubility in biological fluids

Biointerphases2:20100016

https://doi.org/10.1116/1.2714924

Received: 12 January 2007

Accepted: 13 January 2007

Abstract

The concentration of mineral solutes in mammalian blood is considerably higher than that predicted by their solubility product. The plasma protein fetuin-A inhibits calcium phosphate deposition by forming colloidal calciprotein particles (CPPs). In this article the authors present a detailed small angle neutron scattering study including contrast variation analysis providing detailed quantitative information on the three-dimensional topology of the CPPs and on their morphogenesis. In detail the authors found the following: (i) A two stage growth process showing spontaneously formed primary particles with a size of about 500 Å diameter that subsequently transformed to 1000 Å sized particles which were stable for at least 24 h. (ii) A particular shielding topology was observed for the second CPP state, namely, that a densely packed fetuin-A monolayer covers a mineral core and thereby prevents further crystal growth. (iii) Transmission electron microscopy analysis of in vitro synthesized second state CPPs revealed striking similarities to material retrieved from a human peritonitis patient. This latter finding underscores the importance of short- and long-term stabilizations of CPPs by fetuin-A to enable clearing of mineral debris in the body.