How can DNA bend or circularize with a persistence length of 150 bp?

[karthik3k]

The persistence length of a double stranded DNA is reported to be ~ 150 bp.


If so how can DNA of ~100 bp and less bend or circularize?

Or is the definition of persistence length wrong ?

 

[pattylou]

What is the definition of persistence length?

The ORI is pretty long itself, so I'd suspect 100 bp would be too short.

 

[karthik3k]

whats ORI ?

 

[pattylou]

What's the definition of persistence length?

The ori is the origin of replication. I have no idea if it's relevant to the topic, because I'm not sure what "persistence length" means.

 

[Monique]

from the net:

Persistence length (P): A lengthscale for polymer stiffness. The distance over which the direction of a polymer segment persists, in the time or ensemble average, owing to limited flexibility of the polymer. For DNA the persistence length is ~50 nm, i.e., ~150 bp. Chains Ł P in length require a lot of work (free energy) to bend much, yet in nucleosomes roughly one persistence length of DNA is bent in nearly two full turns.

Or: the length of the DNA along which a thermally excited bend of 1 radian typically occurs (the DNA is essentially straight over shorter distances). Since the persistance length is based on just thermal fluxuations, it should be possible to bend it further with binding energies for instance (wrapping DNA around histones).