Phase Transition of Virus' DNA

Many double stranded DNA viruses infect their host cells by injecting their genetic information into the host body. But the virus' DNA is usually rigid and packed inside the shell of a virus. In two separate studies done by biophysicist Alex Evilevitch from Carnegie Mellon University it was shown that a phase transition at the time of infection aids the transfer.

The genetic material of virus forms repulsive forces that exert a large amount of pressure on the capsid, and according to previous research done by Evilevitch, this pressure propels DNA out of a small porthole in the virus's capsid at the temperature of infection. Also, the rigid crystalline structure of the DNA is changed to fluid-like structure, at the temperature of infection which passes through the hole in the capsid.

A solid-to-fluid transition of the DNA within the virus' capsid

To see how these DNA could pass so easily through such a tiny opening in the capsid, Evilevitch did separate studies on Herpes Simplex virus type 1 (HSV-1), which infects humans, and bacteriophage lambda, which infects bacteria.

In the HSV-1 study, Evilevitch used atomic force microscopy and small angle x-ray scattering (SAXS) to see what physical conditions affected the fluidity and mobility of the DNA virus. He found that DNA was more fluid towards the  temperature of infection (37 degree Celsius) and ionic conditions were similar to the epithelial and neuronal cell (cell affected by HSV-1 virus). In the bacteriophage lambda study, Evilevitch used ultra-sensitive microcalorimetry and SAXS to confirm that at the temperature of infection the phage underwent a solid-to-fluid change which aids the DNA mobility.

Most of the antiviral drugs work by deactivating the viral proteins, but viruses often evolve and became drug resistant. But now according to Evilevitch, the researchers have a possible way to prevent the viral infection - by blocking the phase transition. "This could lead to a therapy that isn't linked to the virus' gene sequence or protein structure, which would make developing resistance to the therapy highly unlikely" says Evilevitch.

I think this is a great breakthrough for the researchers in the  field of medicine and science. The number of viral diseases/infections prevalent in our society have increased a lot. The very recent break out of ebola virus is an example of how deadly these virus' are if not taken care of at right time.


Article: http://www.sciencedaily.com/releases/2014/09/140929154545.htm
Related Article: Viral Infection - http://www.merckmanuals.com/home/infections/viral_infections/overview_of_viral_infections.html