DOI: 10.1140/epje/e2003-00023-0
Osmotic force resisting chain insertion in a colloidal suspension
M. Castelnovo, R.K. Bowles, H. Reiss and W.M. GelbartDepartment of Chemistry and Biochemistry, University of California Los Angeles, Los Angeles, California 90095, USA castel@chem.ucla.edu
(Received 18 December 2002 Published online: 16 April 2003 )
Abstract
We consider the problem of inserting a stiff chain into a colloidal suspension of particles that interact with it through
excluded volume forces. The free energy of insertion is associated with the work of creating a cavity devoid of colloid and
sufficiently large to accommodate the chain. The corresponding work per unit length is the force that resists the entry of
the chain into the colloidal suspension. In the case of a hard sphere fluid, this work can be calculated straightforwardly
within the scaled particle theory; for solutions of flexible polymers, on the other hand, we employ simple scaling arguments.
The forces computed in these ways are shown, for nanometer chain and colloid diameters, to be of the order of tens of
pN for solution volume fractions of a few tenths. These magnitudes are argued to be important for biophysical processes such
as the ejection of DNA from viral capsids into the cell cytoplasm.
82.35.Pq - Biopolymers, biopolymerization.
82.60.Qr - Thermodynamics of nanoparticles.
82.70.Dd - Colloids.
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2003
