The development of effective protocols for the control of crystal structure, size and morphology attracts considerable interest given the requirement for particles of modal size and shape in many areas of particle processing and the importance of crystallochemical selectivity in determining the exploitable properties of crystalline solids. In biological systems there are many examples of advanced “crystal engineering” in which materials are deposited in a highly controlled manner to produce crystal phases that are unique with respect to their structure, habit, uniformity of size and texture. A review of biomineralisation will show that while a complex array of strategies have evolved for regulating crystal growth, one feature is common to the biological paradigm. Interactions between supramolecular organic structures and the nascent inorganic solids play a fundamental role in controlling the deposition of the biominerals and ordering the assembly of these units into hierarchical structures. In order to gain a better understanding of the molecular recognition events, which take place at the organic-inorganic interface, a bio-inspired crystal chemical approach has been adopted. For this work organised organic assemblies (e.g. surfactant aggregates, peptide mimics, dendrimers) of precise molecular design (head group identity, packing conformation, primary sequence etc.) are being assayed for their effectiveness in controlling the nucleation and growth of crystals. It is evident from these studies that the chemical organisation of the polymeric microenvironment operates at the molecular level to control certain aspects of the nucleation, growth and stabilisation of inorganic particles. By systematically changing the molecular motif of the organic template we have established that the size, crystallographic orientation, growth and assembly of the mineral phase can be tailored to function. These results have relevance not only to our understanding of biomineralisation but also suggest a multiplicity of exploitable opportunities for the engineering of crystals.

The application of genetic and molecular biological methods to the engineering of proteins, the engine of the biotechnology revolution, has become increasingly dependent on knowledge of protein, nucleic acid and virus molecular structure. Structural information of high precision, essential to this enterprise, can only be obtained through X-ray crystallographic techniques. The quality of this information is directly a function of the properties and degree of perfection of the crucial intermediates, the macromolecular crystals. As a consequence, there is now broad and intense interest in developing new methods, procedures and reagents for the nucleation and growth of such crystals. There is, in addition, an expanded interest in the properties of biological crystals and the use of physical measurements in improving approaches to growing better and larger crystals. Here some of the fundamentals of macromolecular crystal growth will be reviewed, and some current trends in the field remarked upon, including the new initiative to develop a national structural genomics program.

Magnesium is a key determinant in CaCO3 biomineral formation and has recently emerged as an important paleotemperature proxy. Atomic force microscopy (AFM) was used to determine the fundamental thermodynamic and kinetic controls of Mg2+ on calcite morphology and growth. Comparison of directly measured monomolecular step velocities (vs±) to theoretical crystal growth impurity models demonstrated calcite inhibition due to enhanced mineral solubility through Mg2+ incorporation. Terrace width (λ) measurements independently supported an incorporation mechanism by indicating a shift in the effective supersaturation (σeff) of the growth solutions in the presence of Mg2+. This study resolves the controversy over the molecular-scale mechanism of calcite inhibition by Mg2+ and provides an unambiguous model for the thermodynamic and kinetic consequences of impurity incorporation into CaCO3 biominerals.