Cylindrical viruses

The solution conditions enter the description through the pH, AB, and AD. Expression (19) provides an explanation for why self-assembled protein structures become more stable with increasing concentration of salt, which seems to be true for a wide variety of systems, including spherical and cylindrical viruses (Kegel and van der Schoot, 2004, 2006). 

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. 

In this chapter we consider theories of scattering by particles that are either inhomogeneous, anisotropic, or nonspherical. No attempt will be made to be comprehensive our choice of examples is guided solely by personal taste. First we consider a special example of inhomogeneity, a layered sphere. Then we briefly discuss anisotropic spheres, including an exactly soluble problem. Isotropic optically active particles, ones with mirror asymmetry, are then considered. Cylindrical particles are not uncommon in nature—spider webs, viruses, various fibers—and we therefore devote considerable space to scattering by a right circular cylinder. 

The other major type of symmetry found in oligomers, helical symmetry, also occurs in capsids. Tobacco mosaic virus is a right-handed helical filament made up of 2,130 identical subunits (Fig. 4-25b). This cylindrical structure encloses the viral RNA. Proteins with subunits arranged in helical filaments can also form long, fibrous structures such as the actin filaments of muscle (see Fig. 5-30). 

At the present time, there is no accepted chelating agent which can be used against common influenza viruses in humans. A virus has a core of either DNA or RNA and a protective coat of many identical protein units. All viruses are either rods or spheres, that is the protein coats are cylindrical shells having helical symmetry or spherical shells having icosahedral symmetry. Viruses reproduce inside living cells, where each viral nucleic acid directs the synthesis of about 1000 fresh viruses. These are then released and the host cell may die. 

A plant virus was examined by the electron microscope and was found to consist of uniform cylindrical particles 15.0 nm in diameter and 300 nm long. The virus has a specific volume of 0.73 cm3/g. If the virus particle is considered to be one molecule, what is its molar mass ... 

Figure 12 Diagram of assembled states of the coat protein of tobacco mosaic virus M free monomers, BD cylindrical disks, LW/H protohelices and helices. Symbols results from differential scanning microscopy DSC, titration, and sedimentation experiments, lines theory. The theory is based on binding energy Equation (9) and presumes competing repulsive Coulomb and attractive hydrophobic interactions (Kegel and van der Schoot, 2006).

TMV consists of a cylindrical coat of 2,130 identical protein subunits enclosing a long RNA molecule of 6,400 nucleotides. In 1955, it was shown that the coat protein subunits and the RNA could be dissociated but would, under appropriate conditions, spontaneously self-assemble to reform fully active virus particles. This process is multistage, the critical intermediate being a 34-unit two-layered protein disc which, upon binding the RNA, is converted to a helical structure with 16.33 protein subunits per turn (Fig. 5-2). In the absence of the RNA, the protein may be polymerized into helical tubes of indefinite length. The presence of the RNA aids the polymerization process and results in a virus particle with a fixed length of 300 nm. 

Multiple interactions in the same plane can lead to the formation of sheets where, for example, each monomer can interact with six neighbors in a hexagonal close-packing arrangement (Fig. 5-8). Sheets can, with a slight readjustment, be converted into cylindrical tubes (Fig. 5-8) or even into spheres. These closed structures can provide even greater stability since they maximize the number of interactions that can be made. The protein coats of certain viruses are excellent examples of this. Microtubules, which consist of the protein tubulin, can be converted readily between sheet and tubular forms, at least in the purified form. 

Fig. 12. Mass spectra of Rice Yellow Mottle Virus (RYMV) and Tobacco Mosaic Virus (TMV) particles analyzed with an electrospray ionization charge detection time-of-flight mass spectrometer. Inset, electron micrographs of the icosahedral RYMV (diameter 28.8 nm) and the cylindrical TMV (-300 nm long and 17 nm in diameter). The known molecular weight of RYMV and TMV are 6.5X106 and 40.5X106 Daltons,respectively...

Cylindrical (nucleocapsid) Baculoviridae 80-180 Spodoptera Utura granulosis virus (SLGV) Autographa califomica nuclear polyhedrosis virus (AcMNPV)... 

A) Rigid ovaloid folymers without charge. — A number of poljmer molecules are ovaloid-shaped. For instance, the tobacco mosaic virus is cylindrical, and the hemoglobin molecule is ellipsoidal. For such rigid... 

Jenner CE, Sanchez F, Nettleship SB, et al. The cylindrical inclusion gene of Turnip mosaic virus encodes a pathogenic determinant to the Brassica resistance gene TuRBOl. Mol. Plant Microbe Interact., 2000 13(10) 1102-1108. 

A simple virus particle consists of an outer coat made of protein, perhaps itself covered by a membrane, and an inner core of DNA or RNA. The two common structures of the coat proteins are either a cylindrical (helical) shell or a spherical shell with icosohedral symmetry. The proteins on the surface of the virus can undergo relatively rapid mutation as a result of the large number of generations of virus produced. These changes on the surface of the virus are not recognised by the host s antibodies and therefore the virus avoids rejection as an invader. 

Other anisometric viruses have rod-like helical or cylindrical structures, such as tobacco mosaic virus [495,496,509,533] or alfalfa mosaic virus [551,561,562]. Thus cross-sectional parameters can be determined using / xs Q) Q q->o addition to Rq d I 0) data [537,550]. Stuhrmann plots of the / xs data lead to information on the cross-sectional distribution of protein and RNA. Shell models for the cross-section can likewise be made by analogy with the isometric viruses [550,561,562]. The radial scattering density of the cross-section can be calculated by applying the Hankel transformation to the scattering curve [509]. 

Certain macromolecular species are modeled more accurately as a cylinder rather than an ellipsoid. Examples include short DNA fragments and rodlike viruses such as tobacco mosaic virus (TMV). Extensive theoretical studies of the hydrodynamic properties of cylindrical particles have been carried out. These have been recently reviewed by Ortega and de la Torre [2003], who have extended prior calculations using the bead-shell model to short cylinders and disks. Eor long cylinders of length L and cross-sectional diameter d, and hence axial ratio J=Lid, such analysis leads to... 

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