Comment on `Nanoconfinement-enhanced conformational response of single   DNA molecules to changes in ionic environment'
  In the present Comment we show that, contrary to the recent findings of Reisner et al. [Phys. Rev. Lett. 99, 058302 (2007)], the excluded volume effect does not play an important role in determining DNA behavior in nanochannels at low ionic strength. We argue that the DNA extension data are described very well without the notion of an effective polymer width using the entropic depletion theory due to Odijk. 
Madhavi Krishnan and Eugene P. Petrov