# T=21 icosahedral capsid

The capsid is composed 60 asymmetric units made of 21 proteins (T=21), for a total of 1260 capsid proteins. These capsids are skewed, and are therefore described as either right- (dextro) or left- (laevo) handed.

Icosahedric triangulation number is calculated following Caspar and Klug system

**Physical principles in the construction of regular viruses**

D. L. Caspar, A. Klug

Cold Spring Harb. Symp. Quant. Biol. 1962; 27: 1?24