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

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

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

Nature 414, 188 - 190 (2001) Our Simulations

Occupancy of Water in SWCNT 4

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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Example: CaCl2 in ompF porin

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.

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.