Abstract
In situ atomic force microscopy was utilized to study the relation between crystal structure, surface morphology, and growth mechanisms of faces of macromolecular crystals that have screw axes perpendicular to them. It was found that the {0 0 1} faces of orthorhombic catalase, trigonal trypsin, and tetragonal Bence-Jones protein (BJP) crystals grow by successive deposition of n alternating, symmetry-related layers with a thickness of d 0 0 n = 1 n |c| . These layers are associated with two-, three- and four-fold screw-axes in the crystal structure of catalase ( n=2), trypsin ( n=3) and BJP ( n=4) crystals, respectively. Implications for growth rates and three-dimensional morphological development are discussed.
Highlights
Correlation between crystal structure and morphology has been the subject of intensive studies for more than a century
The step height of the nuclei is equal to 11.570.2 nm, which corresponds to half of the unit cell dimension d0 0 2 along c: Each successive layer derived from a 2D island is related by a 1801, 2-fold rotation to the preceding layer (Fig. 1a)
The anisotropy within a d0 0 2 layer itself can be explained by the fact that the symmetry axes of the catalase tetramers do not coincide with the crystallographic directions, molecules forming step edges moving in opposite crystallographic directions expose different parts of their surfaces
Summary
Correlation between crystal structure and morphology has been the subject of intensive studies for more than a century. The Bravais Friedel Donnay Harker (BFDH) criterion [1,2] couples the interplanar distance dh k l of a face (h k l) to its growth rate R: Based on geometrical considerations and growth rates, it was demonstrated that the larger the interplanar distance dh k l; the lower the growth rate of the face (h k l) This results in a higher relative statistical frequency of occurrence of (h k l) as well as a higher relative size of the (h k l) face occurring on a crystal, i.e. a larger morphological importance (MI) of the (h k l) face [1,3]. Macromolecular crystals contain multiple asymmetric units per unit cell [5], and the thickness of the
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