Role of molecular charge and hydrophilicity in regulating the kinetics of crystal growth
- S. Elhadj*,†,
- J. J. De Yoreo‡,
- J. R. Hoyer‡,§, and
- P. M. Dove*,†
- *Department of Geosciences, Virginia Tech, Blacksburg, VA 24061;
- ‡Department of Chemistry and Materials Science, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551; and
- §Department of Pediatrics, University of Pennsylvania School of Medicine and Children's Hospital of Philadelphia, Philadelphia, PA 19104
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Edited by Joanna Aizenberg, Lucent, Murray Hill, NJ, and accepted by the Editorial Board November 1, 2006 (received for review July 9, 2006)
Abstract
The composition of biologic molecules isolated from biominerals suggests that control of mineral growth is linked to biochemical features. Here, we define a systematic relationship between the ability of biomolecules in solution to promote the growth of calcite (CaCO3) and their net negative molecular charge and hydrophilicity. The degree of enhancement depends on peptide composition, but not on peptide sequence. Data analysis shows that this rate enhancement arises from an increase in the kinetic coefficient. We interpret the mechanism of growth enhancement to be a catalytic process whereby biomolecules reduce the magnitude of the diffusive barrier, E k, by perturbations that displace water molecules. The result is a decrease in the energy barrier for attachment of solutes to the solid phase. This previously unrecognized relationship also rationalizes recently reported data showing acceleration of calcite growth rates over rates measured in the pure system by nanomolar levels of abalone nacre proteins. These findings show that the growth-modifying properties of small model peptides may be scaled up to analyze mineralization processes that are mediated by more complex proteins. We suggest that enhancement of calcite growth may now be estimated a priori from the composition of peptide sequences and the calculated values of hydrophilicity and net molecular charge. This insight may contribute to an improved understanding of diverse systems of biomineralization and design of new synthetic growth modulators.
Footnotes
- †To whom correspondence may be addressed. E-mail: elhadj2{at}llnl.gov or dove{at}vt.edu
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Author contributions: S.E. and P.M.D. designed research; S.E. performed research; J.R.H. contributed new reagents/analytic tools; S.E., J.J.D.Y., and P.M.D. analyzed data; and S.E., J.J.D.Y., J.R.H., and P.M.D. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS direct submission. J.A. is a guest editor invited by the Editorial Board.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0605748103/DC1.
- Abbreviation:
- AFM,
- atomic force microscopy.
- © 2006 by The National Academy of Sciences of the USA
