ion channels as natural nanodevices 1 project goals: develop measurement, simulation, and...
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Ion Channels as Natural NanoDevices 1
• Project Goals: Develop measurement, simulation, and fabrication tools needed to make ion channels into practical devices that can be controlled for our use.
• Technical Approach – Measure currents from single protein molecules of known and modified
ATOMIC structure, in a wide range of solutions– Compare measurements with currents predicted from mean field theories and
transport Monte Carlo, so we understand the PHYSICAL BASIS OF SELECTIVITY and permeation.
– Fabricate sheets of channels as strong as SaranWrap that generate microamps of signal. Channel Sheets might be the silicon wafer of ionic transistors.
Porins Gramicidin
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Cl Channel AgonistChannel
Ion Channels as Natural NanoDevices 2
Technical Approach
– Compare measurements with currents predicted from mean field theories and transport Monte Carlo, so we understand the PHYSICAL BASIS OF SELECTIVITY and Permeation.
Calcium Channel Na Channel
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Figure from Mashl/Jakobsson
Single molecule detection Power of protein engineering Current flow changed by binding Frequency reveals concentration Amplitude reveals identity Durable only in lab setting
Biomimetics: Functionality of ion channels into nanopores (CNTs)
Ideal for IC based chips
Fundamental issues: Transport of water, electrolytes and analytes through CNT
Ion Channels, Nanopore Sensors, Aluru et al 3
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Nature 414, 188 - 190 (2001) Our Simulations
Occupancy of Water in SWCNT 4
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Drift-Diffusion Simulation with Prophet 5 Umberto Ravaioli et al
• It is straightforward to include several multi-valent species in PROPHET without modifying the source-code.
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50mM:50mM CaCl2 in ompF
D(Ca++)=0.206x10-5cm2/sec
D(Cl-)=0.528x10-5cm2/sec
experiment
experiment
3DPNP D(Ca++)=0.68x10-6cm2/sec
D(Cl-)=1.74x10 -6cm2/sec
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1M:1M CaCl2 in ompF
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25 50 75 100
Example: CaCl2 in ompF porin
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Monte Carlo Particle Simulation of Channels 6
Umberto Ravaioli et al
Gramicidin - Successful Na+ trajectory – Point particle model
The charged particle trajectories are evaluated froma detailed electric field distribution in space, obtained by solving the Poisson equation.
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Ion Channels as Natural
NanoDevices 7
Technical Approach
– Fabricate sheets of channels as strong as SaranWrap that generate microamps of signal. Channel Sheets might be the silicon wafer of ionic transistors.