Advanced Biocrystallogenesis

Nowadays, X-ray crystallography is one of the most popular structural biology methods. Successful crystallization depends not only on the quality of the protein sample, precipitant composition, pH or other biophysical and biochemical parameters, but also largely on the use of crystallization technique. Some proteins are difficult to be crystallized using basic crystallization methods; therefore, several advanced methods for macromolecular crystallization have been developed. This chapter briefly reviews the most promising advanced crystallization techniques and strategies as one of the efficient tools for crystallization of macromolecules. Crystallization in capillaries, gels, microfluidic chips, electric and magnetic fields as well as crystallization under microgravity condition and crystallization in living cells are briefly described.

Mössbauer and magnetic studies of FeCoNiCuNbSiB nanocrystalline alloys

Nanocrystalline Fe80-x-yCoxNiyCu1Nb3Si4B12 alloys were prepared by the annealing of amorphous ribbons. Primary crystallization of the alloys annealed at temperatures of between 500 and 550°C was studied by X-ray diffraction and Mössbauer spectroscopy. Magnetic properties of the alloys were investigated using a hysteresis loop tracer and vibrating sample magnetometer. The annealed ribbons are composed of a two-phase nanostructure consisting of bcc Fe-based grains embedded in an amorphous matrix. Conversion electron Mössbauer spectroscopy (CEMS) measurements reveal a more advanced crystallization process in the surface layers when compared with the volume of the ribbons. The degree of saturation magnetization of the nanocrystalline alloys is of about 1.5 T. The coercive field varies from 1.0 to 6.5 A/m and peaks at an annealing temperature of 525°C. Magnetic softening of the nanocrystalline alloys observed after annealing at 550°C is correlated with a volume fraction of the nanocrystalline bcc phase.

Increasing the probability of successful crystallization by using symmetric tag

Recent progress in the techniques of bio-macromolecular crystallography makes crystal structure analysis more powerful and useful for life science. The structure analysis of huge super-molecular (eukaryotic Ribosome, Vault etc.) and membrane proteins related to diseases were successful. Moreover, the structure/fragment drug design using crystal structure analysis method is also becoming reliable. However, crystallization still remains as a major bottleneck for determining bio-macromolecular structures, although many methods have been developed such as crystallization kits, crystallization robot, crystallizing in gel, space, and magnetic field, laser excitation, using antibody, modification of protein surface, and so forth. The current situation of crystallization is still dependent on the accidental method searching for a crystallization reagent and the growth environment since the methodology for obtaining a quality crystal for structure analysis is not established yet. Therefore, further development of more advanced crystallization methods is required to increase the probability of successful crystallization. In principal, probability of successful crystallization could be increased by polymerized molecules with 2 or 3-fold rotation symmetry [1]. We have solved more than 100 structures, and found some fragments which is isolated from core structure, and seem to contribute to form high quality crystal by forming a polymer with 2 or 3-fold axial symmetry. Thus, we developed a novel method by fussing target protein with crystallization tags named 2/3RS-tag. These 2/3RS-tags polymerize target proteins with 2 or 3-fold axial symmetry, and consequently accelerate formation of crystal. We will report and discuss this new method in this presentation.

Komatiites and other high-magnesia lavas: some problems

Criteria for the recognition of high-magnesia liquids, among which the absence of phenocrysts is the most important, are discussed. Some high-magnesia lava sequences are strongly porphyritic but it can be demonstrated that their character is not due to the accumulation of ferromagnesian phenocrysts in normal basaltic magmas. The term primitive porphyritic magma is introduced to describe the magmas from which such sequences crystallize. Possible origins of primitive porphyritic magmas include advanced crystallization of high-magnesia liquids without loss of phenocrysts. The occurrence of Phanerozoic high-magnesia lavas associated with continental break-up is described and comparison is made with Archaean komatiite vulcanism. Low levels of incompatible elements are characteristic of the Archaean rocks but high CaO/Al 2 O 3 is not a specifically Archaean feature. Phanerozoic liquids with MgO much above 20 % have yet to be identified but may possibly have existed. Major-element data for komatiites are discussed with a view to the constraints they put on the composition of the source material. Several interpretations, which also have widely varying implications for depth of origin and degree of melting, are presently possible. A new model involving the complete mobilization of source material after a comparatively low degree of partial melting is presented. Bulk compositions of magmas produced lie on a mixing line between the composition of the source and the composition of the liquid fraction at the moment of mobilization.