IonChannelsRicam：离子通道ricam.pptVIP

Physical Characteristics of Ion ChannelsNatural Nanodevices Single Channel Currents have little variance Lipid Bilayer SetupRecordings from a Single Molecule Current depends on type of ionSelectivity Charge Mutation in Porin James Clerk Maxwell  “I carefully abstain from asking molecules where they start… I only count them…., avoiding all personal enquiries which would only get me into trouble.” Royal Society of London, 1879, Archives no. 188 In Maxwell on Heat and Statistical Mechanics, Garber, Brush and Everitt, 1995 I fear Biologists indulge themselves with verbal models of molecules where Maxwell abstained Verbal Models areVagueandDifficult to Test Verbal Modelslead to Interminable Argument and  Interminable Investigation thus,to Interminable Funding Charge Mutation in Porin Fit of 1D PNP Current-Voltage 100 mM KCl Net Charge Difference= 0.13 ? 1.1= ? 0.97e Conditional PNP Sensitivity to Parameters Trade-offs ‘1.5’ adjustable parameters Binding CurvesSensitivity to Parameters At Large Volumes Electrical Potential can Reverse Best Result to Date with Atomic Detail Monte Carlo, including Dielectric Boundary Force Cl? Selective Channel Selective for Larger Anions The Dilute Channel Wolfgang Nonner Dirk Gillespie Chloride Channel Channel prefers large anions in experiments, Low Density of Charge (several partial charges in 0.75 nm3) Selectivity Filter contains hydrophobic groups these are modeled to (slightly) repel water this results in large-ion selectivity Conducts only anions at low concentrations Conducts both anions and cations at high concentration Current depends on anion type and concentration Wolfgang NonnerDirk GillespieDoug HendersonDezso Boda Biological Case Chloride ChannelSelectivity depends Qualitatively on concentration Wolfgang Nonner Dirk Gillespie The Dilute Channel: Anion Selective Channel protein creates a Pressure difference between bath and channel Large ions like Cl– are Pushed into the channel