Dynamic and static light scattering analysis of DNA ejection from the phage lambda.
With the aid of time-resolved dynamic light scattering (DLS) and static light scattering (SLS), we have analyzed the ejection kinetics from the bacterial virus bacteriophage (or phage) lambda , triggered in vitro by its receptor. We have used DLS to investigate the kinetics in such a system. Furthermore, we have shown that both SLS and DLS can be interchangeably used to study the process of phage DNA release. DLS is superior to SLS in that it also allows the change in the light scattering arising from each of the components in the system to be monitored under conditions such that the relaxation times are separable. With help of these two methods we present a model explaining the reason for the observed decrease in the scattering intensity accompanying DNA ejection from phage. We emphasize that ejection from phage capsid occurs through a very long tail (which is nearly three times longer than the capsid diameter), which significantly separates ejected DNA from the scattering volume of the capsid. The scattering intensity recorded during the DNA ejection process is the result of a change in the form factor of the phage particle, i.e., the change in the interference effects between the phage capsid and the DNA confined in the phage particle. When the DNA molecule is completely ejected it remains in the proximity of the phage for some time, thus contributing to the scattering signal as it diffuses away from the phage capsid, into the scattering volume and returns to its unperturbed chain conformation in bulk solution. The free DNA chain does not contribute to the scattered intensity, when measured at a large angle, due to the DNA form factor and the low concentration. Although the final diffusion-controlled step can lead to overestimation of the real ejection time, we can still use both scattering methods to estimate the initial DNA ejection rates, which are mainly dependent on the pressure-driven DNA ejection from the phage, allowing studies of the effects of various parameters affecting the ejection.
Löf
David
D
Division of Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden.
Schillén
Karin
K
Jönsson
Bengt
B
Evilevitch
Alex
A
D010582:Bacteriophage lambda / Q000737:chemistry* / Q000235:genetics*; D003198:Computer Simulation; D042003:DNA Packaging / Q000502:physiology*; D004279:DNA, Viral / Q000737:chemistry* / Q000502:physiology*; D008954:Models, Biological; D008956:Models, Chemical; D012031:Refractometry / Q000379:methods*
D004279:DNA, Viral