Crystals Of Satellite Tobacco Mosaic Virus Research Articles

Brillouin light scattering spectroscopy as a versatile probe of hypersound in diverse materials systems

An overview of the inelastic laser light scattering technique of Brillouin spectroscopy and its application to the study of hypersound in a diverse set of materials systems will be presented. In particular, results obtained from recent Brillouin scattering experiments on natural gastropod mucus, layered high temperature superconductor Bi2Sr2CaCu2O8+δ, biotite micas, and satellite tobacco mosaic virus crystals will be highlighted. Collectively, these results demonstrate the utility of Brillouin light scattering spectroscopy as a sensitive non-destructive probe of hypersound velocity and attenuation in the vicinity of structural phase transitions, the influence of chemical composition and incommensurate structure on material elasticity, and of phonon dynamics in challenging materials classes.

Elastic Properties of Viruses

Viruses are compact biological nanoparticles whose elastic and dynamical properties are hardly known. Inelastic (Brillouin) light scattering was used to characterize these properties, from microcrystals of the Satellite Tobacco Mosaic Virus, a nearly spherical plant virus of 17-nm diameter. Longitudinal sound velocities in wet and dry Satellite Tobacco Mosaic Virus crystals were determined and compared to that of the well-known protein crystal, lysozyme. Localized vibrational modes of the viral particles (i.e., particle modes) were sought in the relevant frequency ranges, as derived assuming the viruses as full free nanospheres. Despite very favorable conditions, regarding virus concentration and expected low damping in dry microcrystals, no firm evidence of virus particle modes could be detected.

Electron microscopy of satellite tobacco mosaic virus crystals: metal-coated, negatively stained and stereo pairs.

Highly purified virions of satellite tobacco mosaic virus (STMV) were found to crystallize at relatively low concentrations (300-500 microg ml(-1)) in pure water. Small crystals of these preparations were examined in the transmission electron microscope after either being rotary shadowcast with metal or negatively stained with 4% uranyl acetate. Stereo views were also obtained of both types of preparations. Stereo pairs of metal-coated crystals provided good three-dimensional images. When stereo pairs of negatively stained crystals were printed from second negatives, they provided striking images although the three-dimensional aspect was not so pronounced. Images of both types of preparations were compared with a computer-generated model of the virus. This model was based on data obtained in earlier X-ray diffraction crystallographic studies. Measurements of crystal axes on the EM images were somewhat lower than those of the computer model. It is assumed the reason for this is the dehydration of crystals during preparation for electron microscopy. The EM images did verify the type of crystal lattice determined in the X-ray diffraction studies. Conversely, knowing the exact unit cell parameters and the distribution of virions in the crystal from X-ray diffraction data aids in the further interpretation of electron micrographs of virus crystals.

Protein and virus crystal growth on international microgravity laboratory-2

Two T = 1 and one T = 3 plant viruses, along with a protein, were crystallized in microgravity during the International Microgravity Laboratory-2 (IML-2) mission in July of 1994. The method used was liquid-liquid diffusion in the European Space Agency's Advanced Protein Crystallization Facility (APCF). Distinctive alterations in the habits of Turnip Yellow Mosaic Virus (TYMV) crystals and hexagonal canavalin crystals were observed. Crystals of cubic Satellite Tobacco Mosaic Virus (STMV) more than 30 times the volume of crystals grown in the laboratory were produced in microgravity. X-ray diffraction analysis demonstrated that both crystal forms of canavalin and the cubic STMV crystals diffracted to significantly higher resolution and had superior diffraction properties as judged by relative Wilson plots. It is postulated that the establishment of quasi-stable depletion zones around crystals growing in microgravity are responsible for self-regulated and more ordered growth.

Macromolecular crystal growth experiments on International Microgravity Laboratory--1.

Macromolecular crystal growth experiments, using satellite tobacco mosaic virus (STMV) and canavalin from jack beans as samples, were conducted on a US Space Shuttle mission designated International Microgravity Laboratory--1 (IML-1), flown January 22-29, 1992. Parallel experiments using identical samples were carried out in both a vapor diffusion-based device (PCG) and a liquid-liquid diffusion-based instrument (CRYOSTAT). The experiments in each device were run at 20-22 degrees C and at colder temperatures. Crystals were grown in virtually every trial, but the characteristics of the crystals were highly dependent on the crystallization technique employed and the temperature experience of the sample. In general, very good results, based on visual inspection of the crystals, were obtained in both PCG and CRYOSTAT. Unusually impressive results were, however, achieved for STMV in the CRYOSTAT instrument. STMV crystals grown in microgravity by liquid-liquid diffusion were more than 10-fold greater in total volume than any STMV crystals previously grown in the laboratory. X-ray diffraction data collected from eight STMV crystals grown in CRYOSTAT demonstrated a substantial improvement in diffraction quality over the entire resolution range when compared to data from crystals grown on Earth. In addition, the extent of the diffraction pattern for the STMV crystals grown in space extended to 1.8 A resolution, whereas the best crystals that were ever grown under conditions of Earth's gravity produced data limited to 2.3 A resolution. Other observations indicate that the growth of macromolecular crystals is indeed influenced by the presence or absence of gravity. These observations further suggest, consistent with earlier results, that the elimination of gravity provides a more favorable environment for such processes.