Hard-wall entropic effect accelerates detachment of adsorbed polymer chains.
Physical review. E
American Physical Society
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Lee, C., & Terentjev, E. (2019). Hard-wall entropic effect accelerates detachment of adsorbed polymer chains.. Physical review. E, 100 (3-1), 032501. https://doi.org/10.1103/physreve.100.032501
Many previous studies of unbinding kinetics have focused on a two-state model, with fully-bonded and free states, which may not extend to more complicated biopolymer dynamics involving other reactions. Here we address the kinetic rate of this process at the segment level, as it is influenced by a growing dangling end of the chain. We use the mean fi rst-passage time approach, and treat the polymer as a chain attached to a wall through a succession of spring potentials, with two distinct regions of bonded and free segments. The interaction between the wall and free-moving chain end adds an entropic repulsion to this process. We estimate the average monomer detachment rate K as a function of the free dangling length L. For flexible polymer, we fi nd an acceleration factor in the average detachment rate depending on L and the details of the spring bond; when L is long, this factor is a simple ratio of its breaking distance to the natural bond length. For semi-flexible lament, we examine the regime where L is shorter than persistence length Lp, as the limit opposite to the flexible chain. An enhancing factor also appears, speeding up the lament unbinding when free length grows; for a long rigid rod, this factor becomes 2, independently of the bond details. We also examine the total unbinding time of an irreversible detaching process by integrating (1/K) over polymer length, and discover that its power-law scaling with chain length is smaller than one, over the commonly-seen range of polymer size.
This work is funded by the Theory of Condensed Matter Critical Mass Grant from EPSRC (EP/J017639).
External DOI: https://doi.org/10.1103/physreve.100.032501
This record's URL: https://www.repository.cam.ac.uk/handle/1810/296151
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