Cleavage by formamide of intercapsomer bonds in adenovirus types 4 and 7 virions and hemagglutinins

Disruption of adenovirus type 7 by lithium iodide resulting in the release of viral deoxyribonucleic acid

Adenovirus type 7 exposed to solutions of LiI was progressively converted into slower sedimenting deoxyribonucleic acid (DNA)-containing particles, and, ultimately, under proper conditions, DNA free or almost free from protein was released from the virus. The degree of viral degradation was dependent on the time of treatment, on the temperature, and on the concentration of the reagent.

Effect of formamide on the capsid morphology of adenovirus types 4 and 7

Treatment of adenovirus types 4 and 7 with formamide disrupted the virions, degrading the capsids into predominantly single capsomers. As shown by electron microscopic observation, disruption proceeded in the following sequence: (i) reduction of the electron density of the virions, suggesting release of an internal component; (ii) progressive cleavage of the capsid into two or more segments and the formation (type 7 only) of capsomer "sheets"; (iii) final cleavage of the capsid into single or groups of a few capsomers. The sequence appeared similar for both adenoviruses; for both types, the rate and extent of disruption were dependent on the formamide concentration, but type 7 was more easily disrupted than type 4 by short-term (5 to 10 sec) treatment at the low (10%) concentration. At 30% formamide, the intercapsomer bonds of either type were fully cleaved, and the capsids were completely degraded into predominantly single capsomers. Pretreatment with formaldehyde did not prevent this degradation. Under suitable conditions, virus-derived remnants can be observed among the breakdown products. These remnants have been shorn of capsomers and presumably represent intact internal nucleoprotein.