title: Physics of size selectivity.
abstract: We demonstrate that two mechanisms used by biological ion channels to select particles by size are driven by entropy. With uncharged particles in an infinite cylinder, we show that a channel that attracts particles is small-particle selective and that a channel that repels water from the wall is large-particle selective. Comparing against the extensive density-functional theory calculations of our model, we find that the main physics can be understood with surprisingly simple bulk models that neglect the confining geometry of the channel completely.
authors.affiliation: Max-Planck-Institut für Metallforschung, Heisenbergstrasse 3, D-70569 Stuttgart, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Roth
authors.forename: Dirk
authors.initials: D
authors.lastname: Gillespie
mesh_terms: D000465:Algorithms; D055592:Biophysical Phenomena; D001703:Biophysics; D019277:Entropy; D007473:Ion Channels / Q000502:physiology*; D010316:Particle Size; D015221:Potassium Channels / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology; D012997:Solvents; D014867:Water / Q000378:metabolism
chemical_list: D007473:Ion Channels; D015221:Potassium Channels; D015222:Sodium Channels; D012997:Solvents; D014867:Water