Effects of salt concentrations and bending energy on the extent of ejection of phage genomes

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Recent work has shown that pressures inside dsDNA phage capsids can be as high as many tens of atmospheres; it
is this pressure that is responsible for initiation of the delivery of phage genomes to host cells. The forces driving ejection of the
genome have been shown to decrease monotonically as ejection proceeds, and hence to be strongly dependent on the genome
length. Here we investigate the effects of ambient salts on the pressures inside phage-l, for the cases of mono-, di-, and tetravalent
cations, and measure how the extent of ejection against a fixed osmotic pressure (mimicking the bacterial cytoplasm) varies with
cation concentration. We find, for example, that the ejection fraction is halved in 30 mM Mg21 and is decreased by a factor of 10
upon addition of 1 mM spermine. These effects are calculated from a simple model of genome packaging, using DNA-DNA
repulsion energies as determined independently from x-ray diffraction measurements on bulk DNA solutions. By comparing the
measured ejection fractions with values implied from the bulk DNA solution data, we predict that the bending energy makes the d-
spacings inside the capsid larger than those for bulk DNA at the same osmotic pressure.


  • Alex Evilevitch
  • Li Tai Fang
  • Aron Yoffe
  • Martin Castelnovo
  • Donald C. Rau
  • V. Adrian Parsegian
  • William M. Gelbart
  • Charles M. Knobler
Enheter & grupper

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Biofysik
Sidor (från-till)1110-1120
TidskriftBiophysical Journal
Utgåva nummer3
StatusPublished - 2008
Peer review utfördJa