title: Correlated trapping of sugar molecules by the trimeric protein channel  chitoporin.
abstract: The protein channel chitoporin (ChiP), which is used by marine bacteria to translocate selected sugar molecules through the outer cell membrane, is studied via single channel current measurements in water and heavy water sugar solutions. The dynamic trapping and escape probabilities of sugar molecules from different monomers in the trimeric channel are characterized, including their dependence on channel orientation and sensitivity to a deuterium isotope effect. A detailed analysis of stochastic current fluctuations reveals that the trapping properties of chitoporin exhibit memory effects: the rate of trapping transitions depends on the previous sequence of transitions; and intermonomer correlations: the average trapping rate of an unblocked monomer is larger when its neighboring monomers are blocked. The latter, likely resulting from rapid re-trapping of recently escaped sugar molecules, is considered as a possible design strategy to enhance sugar transport.
authors.affiliation: Biochemistry-Electrochemistry Research Unit, School of Chemistry, Institute of Science, Center of Excellence in Advanced Functional Materials, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand.
authors.forename: Wipa
authors.initials: W
authors.lastname: Suginta
authors.affiliation: School of Engineering and Science, Jacobs University Bremen, Bremen, Germany.
authors.forename: Mathias
authors.initials: M
authors.lastname: Winterhalter
authors.affiliation: School of Physics, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand. Electronic address: mfsmith@g.sut.ac.th.
authors.forename: M F
authors.initials: MF
authors.lastname: Smith
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D003903:Deuterium; D018272:Porins / Q000737:chemistry*; D055503:Protein Multimerization
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002241:Carbohydrates; D018272:Porins; D003903:Deuterium
keywords: Chitoporin; Passive transport; Protein channel transport; Single channel current measurement