Icosahedral particles

Adenoviruses Adenovirus Icosahedral particles 80nm in diameter Commonly cause upper respiratory tract infections tend to produce latent infections in tonsils and adenoids will produce tumours on injection into hamsters, rats or mice... 

Cytomegalovirus (CMV) Enveloped, icosahedral particles 150nm in diameter CMV is generally acquired in childhood as a subclinical infection. About 50% of adults carry the virus in a dormant state in white blood cells. The virus can cause severe disease (pneumonia, hepatitis, encephalitis) in immunocompromised patients. Primary infections during pregnancy can induce serious congenital abnormalities in the fetus... 

Epstein-Barr virus (EBV) Enveloped, icosahedral particles 150nm in diameter Infections occur by salivary exchange. In young children they are commonly asymptomatic but the virus persists in a latent form in lymphocytes. Infection delayed until adolescence often results in glandularfever. In tropical Africa, a severe EBV infection early in life predisposes the child to malignant facial tumours (Burkitt s lymphoma)... 

Picomaviruses Poliovirus Naked icosahedral particles 28 nm in diameter One of a group of enteroviruses common in the gut of humans. The primary site of multiplication is the lymphoid tissue of the alimentary tract. Only rarely do they cause systemic infections or serious neurological conditions like encephalitis or poliomyelitis... 

Particles of face-centered cubic metals of diameter 5 nm of more have been studied extensively by high resolution electron microscopy, diffraction and other methods. It has been shown that such particles are usually multiply twinned, often conforming approximately the idealized models of decahedral and icosahedral particles consisting of clusters of five or twenty tetrahedrally... 

For enveloped viruses such as the influenza viruses it has been shown that similar binding affinities are found for the hemagglutinin (HA) Hg-and sialic acid using either isolated HA or the whole virus [37,40] using simple H NMR titration experiments. In contrast to structural proteins of non-enveloped viruses, HA is a membrane protein and thus not as rigid as proteins as part of, e.g., icosahedral particles. For the application of STD NMR... 

Several structures of icosahedral particles with diameters in the range of 300-1250 A have been reported to reach a subnanometer resolution to date. Different methods of data collection and analyses were used. Table I summarizes the characteristics of the data acquisition and data processing... 

Using the procedure illustrated in Fig. 4, we have determined several subnanometer-resolution structures of icosahedral particles (Zhou et al, 2000, 2001, 2003 Viang et al, 2001a, 2003 Liang et al, 2002). In this section, we discuss each of the steps in our procedure and mention the specific modular programs (in italics) employed. 

The data set for structure determination of an icosahedral particle of a moderate size (300—1200 A in diameter) at suhnanometer resolution typically needs 30—200 focal pairs of micrographs containing several thousands of particle images (Table 1). For example, the number of particles increased about 40 times, from 159 to 5900, to improve the herpesvirus capsid reconstruction from 25 A (Zhou et al., 1994) to 8.5 A (Zhou et al., 2000). Table 11 shows the size of the data sets for various particle diameters for four targeted resolutions. Notably, the amount of data involved for a near atomic resolution reconstruction of a 1200-A particle is nearly 1 terabytes (TB) and is almost 1 million times more than that needed for a low-resolution small particle reconstruction. 

The typical strategy for processing and 3D reconstruction of icosahedral particles consists ofthe following steps First, a series of micro-... 

Figure 6.5 Icosahedral particles formed during the initial st es of nickel electrodeposition (6.66J.

Sastri, M. Kekuuda, R. Gopinath, K. Kunar. C.T.R. Jagath, J.R. Savithri, H.S. Assembly of Physalis mottle viras capsid protein in Escherichia coli and the role of amino acid carboxy termini in the formation of icosahedral particles. J. Mol. Biol. 1997, 272, 541-552. 

Puller, S.D., Butcher, S.J., Cheng, R.H., and Baker T.S. (1996). Three-dimensional reconstruction of icosahedral particles - The uncommon line. J. Structural Biol. 116, 48-55. 

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