EM of adenovirus (red). The Adenovirus is a group of viruses associated with the common cold, also with the transformation of healthy cellsto cancerous cells. The capsid or protein coat surrounding the virions is isochedral. In most complete virus particles, the capsids containing the nucleic acid are enclosed in an envelope of glycoprotein and lipid which recognizes the membrane of the host cell, fuses with it and empties the capsids into the cell. Magnification x300,000.