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ePaper created 2015-05-08, 15:29:13 | version 1.38.0
1,2 µm 1 µm 0,8 µm 0,6 µm 0,4 µm 0,2 µm {006} {012} {104} 54 GENETIC ENGINEERING OF INORGANIC CRYSTALS Pure mineral crystals are commonly obtained from salt solutions. In many cases, the morphologies and microstructures of such crys- tals can be predicted only under precisely controlled conditions of crystallization. When it occurs in presence of organic additives, the morphologies of the crystals are unpredictable. Yet, the atomic struc- tures of such synthetic crystal composites are usually the same as in the pure mineral phase. In natural biominerals, outer morphologies and atomic structures of composite crystals are extremely well defined. It still remains a mystery how such crystals form in the presence of biomolecules, or how crystals are even directed by them. One would expect that proteins act as “impurities”, disturb the ordered alignment of nanoparticle precursors, and interfere with crystallization. In 2014, it was demonstrated that genetically engineered proteins derived from nacre induce directional lattice distortions in synthetic calcite crystals [1]. A few micrograms of the protein GFP-perlucin (Fig. 1) were sufficient to also reduce the grain size of the composite material (Fig. 2). The observed phenomenon represents a first unequivocal case study which revolutionizes the functional classi- fication of so-called biomineralization proteins opening up a new era for “applied biomineralization” in view of bioinspired crystal engineering and materials science. In combination with new analytical tools [2], biomolecular crystal engineering has become a method that enables new ways of fine-tuning the internal characteristics of advanced organic-inorganic interfaces at atomic length scales. HIGHLIGHTS I. M. WEISS Fig. 1: Computational overlay model of recombinant mollusc shell proteins, inducing lattice distortions in inorganic crystals. Fig. 2: Comparison of grain sizes in minerals precipitated in presence of various concentrations of control protein (green circle) and mollusc shell protein (blue circle). Schematically reproduced from Ref. [1]. BIOMINERALIZATION