## What is quasi-equivalence?

Quasi-equivalence can be defined as the extent of similarity between these structurally unique environments occupied by the chemically identical subunits in the virus capsid. Quasi-equivalent capsids should contain 60T subunits, however, there are exceptions.

## Why do viruses have icosahedral symmetry?

However, we have found that the presence of a small compression of the capsid (caused, for instance, by an external pressure, or a genome size smaller that the preferred size of the capsid protein shell, or a longer-range attractive interaction between capsomers) systematically facilitates the appearance of icosahedral …

**What is H and K in triangulation number?**

The triangulation number is defined as the square of the distance between 2 adjacents 5-fold vertices. Point O corresponds to a 5-fold vertex and the first neighbouring 5-fold vertex,at point M has coodinates (H,K).

**What is the advantage of icosahedral symmetry?**

Thus, the advantages of icosahedral symmetry come with costs – subunit geometry must be ideal, subunit interaction energies have a relatively narrow window, and the resulting capsids’ resistance to dissociation makes them peculiarly unresponsive to its environment.

### Is influenza helical or icosahedral?

In fact, most plant viruses are helical, and it is very uncommon that a helical plant virus is enveloped. In contrast, all helical animal viruses are enveloped. These include well-known viruses such as influenza virus, measles virus, mumps virus, rabies virus, and Ebola virus (Fig. 2.5 ).

### What is symmetry virus?

Self assembly of virus capsids follows two basic patterns: helical symmetry, in which the protein subunits and the nucleic acid are arranged in a helix, and icosahedral symmetry, in which the protein subunits assemble into a symmetric shell that covers the nucleic acid-containing core.

**What is t number virus?**

The capsid is composed 60 asymmetric units made of 1 protein (T=1), for a total of 60 capsid proteins. Icosahedric triangulation number is calculated following Caspar and Klug system. Physical principles in the construction of regular viruses.

**What is the difference between helical and icosahedral viruses?**

A helix is mathematically defined by amplitude and pitch. An icosahedron is a geometric shape with 20 sides, each composed of an equilateral triangle. The sides are composed of viral protein subunits that create a structural unit, which is repeated to form a larger side and the other sides of the icosahedron.

#### How many edges does the icosahedral virus have?

30 edges

The 20 faces of the icosahedron are equilateral triangles; they meet in 30 edges and 12 vertices.