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BP: Fachverband Biologische Physik

BP 13: DNA/RNA and Related Enzymes

BP 13.3: Vortrag

Mittwoch, 28. März 2012, 10:15–10:30, H 1058

Nematic ordering due to intrinsic chain stiffness causes DNA molecules packed in phage capsids to preferentially form torus knots — Daniel Reith¹, Andrzej Stasiak², Peter Cifra³, and •Peter Virnau¹ — ¹Department of Physics, Uni Mainz — ²Center for Integrative Genomics, UNIL, Lausanne, Switzerland — ³Polymer Institute, Slovak Academy of Sciences, Bratislava, Slovakia

When mature bacteriophages such as P2 or P4 are assembled in infected cells, a long linear DNA molecule is loaded into the phage capsid and arranges itself in a toroidal, nematic phase. Intriguingly, experiments show that the DNA is not only highly knotted, but also exhibits a rather uncommon knot spectrum. Observation that DNA molecules in bacteriophage capsids preferentially form torus knots provide a sensitive gauge to evaluate various models of DNA arrangement in phage heads. We demonstrate with computer simulations of a simple bead-spring model that an increasing chain stiffness not only leads to nematic ordering and a (somewhat counter-intuitive) increase of knottedness, it is also the decisive factor in promoting formation of DNA torus knots in phage capsids.