TMV

Flard spherocylinders (cylinders witli hemispherical end caps) were studied using computer simulations [118]. In addition to a nematic phase, such particles also display a smectic-A phase, in which tire particles are arranged in liquid-like layers. To observe tliis transition, ratlier monodisperse particles are needed. The smectic-A phase was indeed observed in suspensions of TMV particles [17]. 

Vimses are also detectable with imprinted sensor materials thus leading to the first tme rapid on-line analysis for these species that are too small for e.g. light scattering experiments. So we e.g. succeeded in determining the tobacco mosaic vims (TMV) in plant saps as well as the Human Rhinovims (HRV). 

Extracts from 152 plant species, representing 46 different families, were screened for effects on tobacco mosaic virus (TMV) replication in cucumber cotyledons. Twenty species have shown enough activity to warrant further study. Several members of the Caprifoliaceae family increased virus replication. An extract of Lonicera involucrata enlarged the virus lesions in local lesion hosts and produced a thirty fold increase in virus titer, but had no effect on virus replication in systemic hosts. The active material appears to affect the virus defense mechanism of local lesion hosts. An extract of common geranium is an active virus inhibitor. It inactivates TMV and TMV-RNA (ribonucleic acid) in vitro by forming non-infectious complexes. In vivo, it also inhibited starch lesion formation in cucumber cotyledons incited by TMV infection. 

Cucumber cotyledons were inoculated with purified tobacco mosaic virus (TMV) 20 to 24 hours before vacuum infiltration with different concentrations of crude water extracts of plant leaves (4). After 7 days, inoculated leaves were harvested and stored 24 hours in the dark in a moist chamber to remove excess starch. Starch lesions were counted after clearing with alcohol and staining with an iodine-potassium iodide-lactic acid mixture. The inhibitory effects of various extracts were demonstrated by comparing lesion counts of treated cotyledons to counts on control cotyledons. 

A twinberry (Lonicera involucrata) extract, as well as snow-berry (Symphoricarpas albus) and several other species of common honeysuckle (Lonicera spp.), markedly increased the TMV lesion... 

Figure 1. Effect of twinberry leaf extract infiltrated 24 hours after virus inoculation on TMV starch lesion development on cucumber cotyledons...

Aqueous geranium extract inhibited TMV starch lesion formation in cucumber cotyledons. Starch lesions were completely inhibited by vacuum infiltrating effective dosages at any time between 1 and 33 hours after virus inoculation. Between 33 and 72 hours, inhibition decreased progressively. The active ingredient in the geranium extract was identified by means of ultraviolet absorption spectrum and... 

Active TMV starch lesion-inhibiting component isolated from geranium leaves on paper chromatograms... 

However, in a systemic host of TMV (P. floridana) the infiltration of tannic acid (0.034%) 24 hours after virus inoculation reduced virus titer about 75% during the first week after infection. After two weeks there was no significant difference in total virus content between tannic acid-treated and water-treated samples. Thus tannic acid does interfere with virus synthesis at an early stage in a temporary way. 

Therefore, in the cucumber-TMV system, tannic acid treatment had no effect on the establishment of infection it merely suppressed the expression of starch lesions and at the same time interfered with the defense mechanism of the host, permitting systemic spread of the virus. 

Tannic acid is a strong inhibitor of virus particles in vitro. It inactivated both TMV and TMV-RNA by forming noninfectious complexes (1). TMV-RNA was much more sensitive to inactivation than was whole TMV. It would thus appear that tannic acid could possibly inactivate TMV by reacting with either the protein coat or the RNA core. 

In both cases, a seeming virus stimulator (twinberry extract) and a virus inhibitor (tannic acid) operated in a more or less similar way in the cucumber-TMV system. They both affect the host defense mechanism against virus infection. The active component in twin-berry extract exhibits a mild and temporary interference, thus permitting virus to make further rounds of gain (ringlike patterns) while tannic acid produces a strong and permanent interference. 

Hooft van Huijsduijnen, R.A.M., Van Loon, L.C. Bol, J.F. (1986). cDNA cloning of six mRNAs induced by TMV infection of tobacco and a characterization of their translation products. EMBO Journal, 5, 2057-61. 

Some virus particles have their protein subunits symmetrically packed in a helical array, forming hollow cylinders. The tobacco mosaic virus (TMV) is the classic example. X-ray diffraction data and electron micrographs have revealed that 16 subunits per turn of the helix project from a central axial hole that runs the length of the particle. The nucleic acid does not lie in this hole, but is embedded into ridges on the inside of each subunit and describes its own helix from one end of the particle to the other. 

Helical symmetry was thought at one time to exist only in plant viruses. It is now known, however, to occur in a number of animal virus particles. The influenza and mumps viruses, for example, which were first seen in early electron micrographs as roughly spherical particles, have now been observed as enveloped particles within the envelope, the capsids themselves are helically symmetrical and appear similar to the rods of TMV, except that they are more flexible and are wound like coils of rope in the centre of the particle. 

TMVS Text-mining based virtual screening... 

The synthesized CPMV-alkyne 42 was subjected to the CuAAC reaction with 38. Due to the strong fluorescence of the cycloaddition product 43 as low as 0.5 nM, it could be detected without the interference of starting materials. TMV was initially subjected to an electrophilic substitution reaction at the ortho-position of the phenol ring of tyrosine-139 residues with diazonium salts to insert the alkyne functionality, giving derivative 44 [100]. The sequential CuAAC reaction was achieved with greatest efficiency yielding compound 45, and it was found that the TMV remained intact and stable throughout the reaction. 

A typical virus with helical symmetry is the tobacco mosaic virus (TMV). This is an RNA virus in which the 2130 identical protein subunits (each 158 amino acids in length) are arranged in a helix. In TMV, the helix has 16 1/2 subunits per turn and the overall dimensions of the virus particle are 18 X 300 nm. The lengths of helical viruses are determined by the length of the nucleic acid, but the width of the helical virus particle is determined by the size and packing of the protein subunits. 

Completely different mechanisms are involved in the self-assembly of the tobacco mosaic virus (TMV). This virus consists of single-strand RNA, which is surrounded by 2,130 identical protein units, each of which consists of 158 amino acid residues. A virus particle, which requires the tobacco plant as a host, has a rodlike structure with helical symmetry ( Stanley needles ). It is 300 nm long, with a diameter of 18nm. The protein and RNA fractions can be separated, and the viral... 

Balias, N., Zakay, N., Sela, I., and Loyter, A., Liposome bearing a quaternary ammonium detergent as an efficient vehicle for functional transfer of TMV-RNA into plant protoplast, Biochimica et Biophysica Acta, 1988, 939, 8-18. 

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