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Issue 4, 2012
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Mechanism of inhibition of calcium oxalate crystal growth by an osteopontin phosphopeptide

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Abstract

Osteopontin (OPN) inhibits the nucleation and/or growth of several biominerals, including hydroxyapatite (HA) and calcium oxalate monohydrate (COM), and is thought to function in the prevention of soft-tissue calcification. In previous studies, pOPAR, a peptide corresponding to amino acids 65–80 of rat bone OPN (pSHDHMDDDDDDDDDGD), was shown to be a potent inhibitor of HA crystal growth. We now show that formation of COM in the presence of this peptide results in plate-shaped crystals with rounded ends and scalloped {100} faces. Measurement of crystal dimensions revealed that the pOPAR inhibits growth of COM faces in the order {100} > {121} > {010}. Crystal growth inhibitors are believed to act by adsorbing to growth steps, sites at which lattice-ion addition is energetically favoured. To test this hypothesis, we performed molecular dynamics (MD) simulations of pOPAR adsorption to {121} steps on a {100} face and {121} steps on an {010} face. In the former case, the peptide adsorbs to the {100} (terrace) plane in preference to the {121} (riser) plane; in the latter, the peptide adsorbs to the {121} (riser) plane in preference to the {010} (terrace) plane. These studies represent the first use of MD to study the interaction between an inhibitor and crystal steps. Contrary to the prevailing belief that crystal growth inhibitors adsorb to both lattice planes of a step, we show that pOPAR interacts preferentially to either the terrace or the riser, depending on which is more cationic.

Graphical abstract: Mechanism of inhibition of calcium oxalate crystal growth by an osteopontin phosphopeptide

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Publication details

The article was received on 30 Jun 2011, accepted on 16 Nov 2011 and first published on 08 Dec 2011


Article type: Paper
DOI: 10.1039/C1SM06232H
Citation: Soft Matter, 2012,8, 1226-1233
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    Mechanism of inhibition of calcium oxalate crystal growth by an osteopontin phosphopeptide

    S. Hug, B. Grohe, J. Jalkanen, B. Chan, B. Galarreta, K. Vincent, F. Lagugné-Labarthet, G. Lajoie, H. A. Goldberg, M. Karttunen and G. K. Hunter, Soft Matter, 2012, 8, 1226
    DOI: 10.1039/C1SM06232H

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