Tobacco mosaic virus crystals

More than half a century ago, Bawden and Pirie [77] found that aqueous solutions of tobacco mosaic virus (TMV), a charged rodlike virus, formed a liquid crystal phase at as very low a concentration as 2%. To explain such remarkable liquid crystallinity was one of the central themes in the famous 1949 paper of Onsager [2], However, systematic experimental studies on the phase behavior in stiff polyelectrolyte solutions have begun only recently. At present, phase equilibrium data on aqueous solutions qualified for quantitative discussion are available for four stiff polyelectrolytes, TMV, DNA, xanthan (a double helical polysaccharide), and fd-virus. 

Stanley first crystallized a virus, tobacco mosaic virus. 1937... 

Keywords wrinkling Thin-film Elastomeric polymer Polydimethylsiloxane Patterns Deformation Surfaces Self-assembly Polyelectrolyte multilayer films Thin-films Polymer brushes Colloidal crystallization Mechanical-properties Assembled monolayers Buckling instability Elastomeric polymer Tobacco-mosaic-virus Soft lithography Arrays... 

Both X-ray and neutron fiber diffraction (as well as electron microscopy) techniques have been applied to filamentous viruses, for which the prospect of three-dimensional crystals is poor. By combining neutron and X-ray fiber diffraction, NMR, circular dichroism, and Raman and infrared spectroscopies, an atomic model for the filamentous bacteriophage Pfl has been derived (Liu and Day, 1994). Other studies concerning Pfl have relied on purely X-ray fiber diffraction data, together with molecular modeling, to provide detailed filament structures (Pederson et at, 2001 Welsh et at, 1998a,b, 2000). Eiber diffraction was also used to solve the structure of the rodlike helical tobacco mosaic virus (TMV), where all of the coat protein and three genomic nucleotides... 

Some colloids consist of well-defined molecules, with constant molecular weight and definite molecular shape, permitting them to be piled in a crystalline array. Crystalline proteins include egg albumin (MW 43000) and hemoglobin (MW 68000). Even viruses, such as, tobacco-mosaic virus, have been crystallized their molecular weights are in the neighborhood of 10,000,000 (bushy-stunt virus) to 2,000,-000,000 (vaccinia virus). 

Although the technical applications of low molar mass liquid crystals (LC) and liquid crystalline polymers (LCP) are relatively recent developments, liquid crystalline behavior has been known since 1888 when Reinitzer (1) observed that cholesteryl benzoate melted to form a turbid melt that eventually cleared at a higher temperature. The term liquid crystal was coined by Lehmann (2) to describe these materials. The first reference to a polymeric mesophase was in 1937 when Bawden and Pirie (2) observed that above a critical concentration, a solution of tobacco mosaic virus formed two phases, one of which was bireffingent. A liquid crystalline phase for a solution of a synthetic polymer, poly(7-benzyl-L-glutamate), was reported by Elliot and Ambrose (4) in 1950. 

FIGURE 3.1 Crystals of a variety of macromolecules. In (a), clusters of needle crystals of bacterial a amylase in (b), crystals of a protease from pineapple, in (c), a crystal of satellite tobacco mosaic virus and in (d), a crystal of the sweet protein thaumatin. 

A few non-amphiphilic molecules are able to show liquid crystallinity in solution at a certain range of concentration, such as PBLG, DNA, the tobacco mosaic virus, etc. They are of great molecular mass, very rigid, rod-like and have a very long anisotropic shape. They are typical macromolecules and are lyotropic liquid crystals. This class of liquid crystals does not aggregate to form sphere, column or laminar structures. These lyotropic systems depend on the properties of the solvent. They are one of major interest of this book and will be discussed in detail later. 

Some viruses such as the tobacco mosaic virus (TMV) can form lyotropic cholesteric liquid crystals. TMV contains 94% protein and 6% RNA. In TMV the proteins and RNA are stacked regularly, see Figure 6.26. It looks like a long rod of average length 300 nm and of diameter 15 nm. The molecular mass is as high as 4 x 107. 

As early as 1938, Langmuir observed the phase separation of clay suspensions into an isotropic phase and a birefringent gel at the macroscopic level in test-tubes [9]. However, in the same report, he noted that this property of phase separation was gradually lost with time, which he tentatively explained by the incorporation of impurities diffusing from the glass tubes. He also compared this system to normal liquid crystals. Later, in 1956, Emerson observed a banded texture similar to that displayed by the Tobacco Mosaic Virus [48]. The investigation of clay suspensions from the structural point of view has been recently resumed. However, the study of the nematic order of suspensions of montmorillonite clays is in fact complicated by their gel properties. In spite of sustained efforts to understand its nature, the gelation mechanism has not yet been fully elucidated [49]. 

Several plant viruses have been studied using X-ray crystallography and conventional X-ray sources. These are, in no particular order, TBSV (tomato bushy stunt virus), SBMV (southern bean mosaic virus) and STN V (satellite tobacco necrosis virus) - all spherical viruses - and TMV (tobacco mosaic virus) - a cylindrical virus. These virus crystals diffract relatively well and are reasonably stable to radiation. 

It has been already pointed out that the energy of interaction between dispersed particles depends on the particle size. As a result, for large particles, and especially for anisometric ones, oriented in a certain way with respect to each other, the presence of a secondary minimum may be of importance. For such particles this secondary minimum may be sufficiently deep in comparison with kT. In some cases these systems may experience a peculiar colloid phase transition from a free disperse system (at low concentrations of dispersed phase) to crystal-like periodic structures consisting of colloidal particles in equilibrium with the dilute sol consisting of single particles. Such periodic structures are observed in some biological systems, e.g. in tobacco mosaic virus, in V205 sols and in latexes. 

Wendell Stanley shared the Nobel Prize in chemistry in 1946 with John Northrop, awarded to them for their preparation of enzymes and virus proteins in a pure form, and with James Sumner for his discovery that enzymes can be crystallized. In 1926 Sumner had crystallized the enzyme urease in 1930 Northrop had crystallized pepsin and in 1935 Stanley had crystallized tobacco mosaic virus. Stanley s result and subsequent findings... 

Sumner s analytical studies convinced him that urease was a protein. This conclusion was resisted by the chemical community but John H. Northrop s (1891-1987) crystallization of pepsin in 1930 at the Rockefeller Institute in New York City and its unambiguous decomposition into amino acids fully vindicated Sumner. Sumner and Northrop were able to make use of the ultracentrifiige developed by Svedberg and the electrophoresis technique developed by his student Tiselius to fully establish purities and molecular weights of their enzymes. Sumner and his coworkers then crystallized trypsin and chymotrypsin. Sumner and Northrop shared the 1946 Nobel Prize in chemistry with Wendell M. Stanley (1904—71), who in 1935 crystallized the tobacco mosaic virus in his laboratory at the Rockefeller Institute. 

In 1935, Wendell M. Stanley (1904—1971), working at Rockefeller University, crystallized tobacco mosaic virus (TMV) and conducted its chemical analysis just like any other pure crystalline chemical substance. He demonstrated that crystalline TMV becomes fully active as a virus when bioassayed. For this work, Stanley shared the 1946 Nobel Prize in chemistry with James B. Sumner and John H. Northrop, who had established in the 1920s that all enzymes are proteins (see chapter 3). 

Somewhat later, even biological systems were investigated from a liquid crystal research point of view (e.g., the tobacco-mosaic-virus) [26], see also Chap. VIII of this volume. The main progress of lyotropic liquid crystal research in these times is connected to works on soap/water mixtures [27, 28] and the investigation of thermotropic mesophases of soaps [29]. The amphotropic character of such compounds was also studied. In such systems, no continuous transitions were observed between thermotropic and lyotropic mesophases, but always biphasic regions could be seen [30, 31]. Thereafter, the interest in understanding biological cell membranes inspired research-... 

It fits nicely into the picture of dual structure-phase views of biomesogenic organizations that objects of rod-like appearance , for instance the little world of the tobacco mosaic virus (which - its overall design reduced to a simple rod-like entity - became the starting point of Onsager s theory [37]), as well as much simpler protein and nucleic acid helices are typical mesophase formers in the classical liquid-crystal phase... 

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