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Review article

https://doi.org/10.5562/cca1809

Kinetic Approach to Biomineralization: Interactions of Synthetic Polypeptides with Calcium Carbonate Polymorphs

Branka Njegić-Džakula ; Laboratory for Precipitation Processes, Ruđer Bošković Institute, P. O. Box 180, HR–10002 Zagreb, Croatia
Ljerka Brečević ; Laboratory for Precipitation Processes, Ruđer Bošković Institute, P. O. Box 180, HR–10002 Zagreb, Croatia
Giuseppe Falini ; Dipartimento di Chimica "G. Ciamician", Università di Bologna, via Selmi 2, 40126 Bologna, Italy
Damir Kralj ; Laboratory for Precipitation Processes, Ruđer Bošković Institute, P. O. Box 180, HR–10002 Zagreb, Croatia


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Abstract

Biomineralization processes are the subject of numerous investigations. This article gives a review
of the study on interactions between the charged polypeptides and the mineral surfaces involved in
biomineralization, with an additional kinetic approach. The influence of polypeptides on two types of precipitation
processes is discussed: the spontaneous precipitation from supersaturated solution and the
growth kinetics of calcite seed crystals. In the first case the phenomenon of the formation and stabilization
of metastable phases was found while in the second case the influence of the applied polypeptides on the
kinetics and mechanisms of calcite crystal growth was investigated. Calcium carbonate polymorphs, calcite
and vaterite, were used as biomineral substrates and acidic polypeptides, poly-L-aspartic (pAsp) acid
and poly-L-glutamic (pGlu) acid, as simplified models of naturally occurring soluble acidic proteins. A
basic polypeptide, poly-L-lysine (pLys), was also used in experiments in order to find out whether conformity
between the crystal surface and the adsorbed polypeptide, or just the electrostatic interactions,
have a decisive role in these processes. The addition of a particular polypeptide into the precipitation system
caused a significant inhibition of nucleation and growth of vaterite, the extent of inhibition being in
the order InhpAsp > InhpGlu >> InhpLys. In addition to the inhibition of precipitation, the change of the polymorphic
composition and the crystal morphology of the precipitate were also achieved. The explanation of
such acidic polypeptide behaviour is a consequence of kinetic constraints through the diverse efficiency of
inhibition of both calcite nucleation and vaterite growth caused by adsorption of acidic polypeptides. The
acidic polypeptides also caused the inhibition of calcite crystal growth, the effect being pAsp > pGlu, and
changed the observed mechanism of growth controlled by the integration of ions into the spiral steps, as
found for the model systems, to the surface nucleation rate-determining mechanism. Nonselective, weak
and electrostatic adsorption of pLys at the crystal surface was probably responsible for increasing the calcite
crystal growth rate when pLys was present at low concentrations and for inhibiting it at pLys higher
concentrations. The strongest interactions between the crystal surfaces and the polypeptides, observed for
the calcite/pAsp system, can account for coordinative interactions between the side chain carboxylic
groups of the predominantly planar arrangement of the pAsp structure (β-pleated sheet) and Ca2+ ions
from the crystal surface. (doi: 10.5562/cca1809)

Keywords

calcium carbonate, calcite, vaterite, amorphous calcium carbonate, poly-L-aspartic acid, poly-L-glutamic acid, poly-L-lysine

Hrčak ID:

71993

URI

https://hrcak.srce.hr/71993

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