2015-12-2 Dynamics of single-file water chains inside nanoscale
channels: physics, biological significance and applications
(particularly on clear water problem) Fang Haiping ( Shanghai
Institute of Applied Physics Chinese Academy of Sciences ( ) Slide
2 2015-12-2 Outline 1.Introduction Clear water &
nanotechnology/ biological water/anomaly 2.Simulation and results
Mechanical and electrical gating Nanochannels inspired by the
structures of Aquaprins 3. Summary Slide 3 Water shortage threatens
humanity particularly in China Most of the developing countries :
insufficient safe water Nature 422, 252 (2003) Atlas of a thirsty
planet Slide 4 2015-12-2 Water Pollution in Taihu Lake : The
blue-green algae ( outbreak in Taihu Lake has affected daily water
supply in Wuxi (2007)
http://english.cri.cn/4426/2007/06/05/[email protected] Slide 5
Desalination( ) ( the process of removing salts and suspended
solids from brackish water and seawater) may be best hope to slake
world's thirst. New Scientist, 30 June 2006 Science313,1088 (2006);
Nature 452, 301 (2008) Desalination plant in Ashkelon, Israel
Problem: high cost Key: Semipermeable membrane to dilute a chemical
solution on the other side Basically, [membrane] technology hasnt
changed much in the last 40 years, says Thomas Mayer, a
desalination expert at Sandia. Key part: Channels Slide 6 2015-12-2
Nanotechnology is already being used to remove contaminants from
drinking water and increase the availability of fresh water, but
there is still a long way to go.----- Hillie and Hlophe,
Nanotechnology and the challenge of clean water,COMMENTARY, Nature
Nanotech. 2, 663 (2007) Nanotechnology & water
http://www.merid.org/nano/waterworkshop Nanofluidic Slide 7
2015-12-2 Clapham Cell 115,641(2003) 2003 Noble Prizer in chemistry
Key part of the semipermeable membrane---pores, allow fast
transportation of water but stops ion permeation Nanochannel
desalination Aquaporin---A biological water channel allows water to
get in and out of cells but blocks the nimble proton Single-file
water Slide 8 2015-12-2 Bio-inspired: Aquaporin is too complex, CNT
with appropriate radius can be a good candidate Desalination based
on carbon nanotube (CNT) Single-file water Hummer found,
unexpectedly, there are water molecules inside the hydrophobic
single-walled carbon nanotube, Nature 414,188 2001 Slide 9
2015-12-2 Common: Wet-dry transition induced by a minor change of
the water-channel interaction Biophys. J. 86,2883 (2004) Water:
cyan sticks small mechano-sensitive channel MscS Hummer, Nature
414,188 2001 Slide 10 Experimental measurement on water across
narrow CNT Enhanced about 1,000 times Holt et al. Science 2006,
312, 1003 Many applications in nanotechnology: desalination of
seawater, and the filtration of polluted water. Numerical
simulation plays an important role! Slide 11 Individual
Water-Filled Single-Walled Carbon Nanotubes as Hydroelectric Power
Converters Chen Wang, Sishen Xie and Lianfeng Sun et al Adv. Mater.
2008,20,1 / A water flow induced inside the SWNT which is driven by
the applied current and causes one part of the device to act as a
motor. Experiment Slide 12 Questions: How to control the
nanochannels----- Mechanical and Electrical? Are there more
inspired by the structures of Aquaprins beside the single-file
water? 1.Mechanical gating 2.Electrical gating 3.Water nanopump
inspired by the charge structures of Aquaprins We: Slide 13
Confined water is importance on the structures and functions of
biomolecules 1.DNA conformation Nature 171, 740 (1953) Fengshou
Zhang PRL100, 088104 (2008) 2.Water-mediated interactions
facilitates native-like packing of surpersecondary structural
elements of a protein PNAS, 101,3352 (2004) 3.Dynamically ordered
water on the surface of DNA PNAS,100, 8113 2003 4.Hydrophobic
interaction mediates the collapsing of a two- domain protein
Science 305, 1605 (2004) High Humidity B-DNA Low humidity A-DNA
Biological Water Slide 14 2015-12-2 High melting and boiling
temperatures. - They should be lower according to its molecular
weight. Density maximum at 4 o C (H 2 O). High heat capacity. Large
among energy stored in the system . T(K) Known water Anomalies ( )
Unique property of water Slide 15 2015-12-2 Water Anomalies
originates from hydrogen-bonds between water molecules O H H
Hydrogen bond H-bond network Slide 16 Mechanical Response Carbon
nanotube is deformed due to external force F on an atom A F B Red:
Water molecules, Green: carbon atoms Carbon nanotube diameter: 8.1
length:13.4 Osmotic pressure ( up- bottom Effective pore size:
8.1-3.4=4.8 Water radius: 2.8 R.Z. Wan, J.Y Li, H.Y. Lu, H.P. Fang,
J. Am. Chem. Soc. 127, 7166 (2005) Slide 17 2015-12-2 Simulation
results N : Number of water molecules inside the tube Water flux:
Difference of the numbers of water molecules entered the SWNT from
bottom and upper ends, left on the other sides, per nanosecond.
T=216 ns; Transient: 16 ns; flux is averaged by each 18 ns
Effective pore size: 4.8 Water radius: 2.8 Slide 18 N: Number of
water molecules inside the channel Excellent gating Effectively
resistant to noisy deformation Sensitive to available signals
Osmotic pressure up-bottom Carbon nanotube Radius= 8.1, Length=13.4
Flux red line does not decrease Our Observation Wan JACS 2005 Slide
19 2015-12-2 Applications ( Force 1.8 nN from open to closed In the
force range of many experimental facilities. Possible nanosensor,
i.e., nanoscale syringe ( Slide 20 Why excellent gating??? Press
here Wavelike structure of water density distribution 0 2.0 . Phase
shift to accommodate the effect due to channel deformations
Dipole-dipole interaction of water plays an important role
positions of carbon atoms Wan et al. JACS 2005 Lu et al., PRB Slide
21 Wavelike water density distribution in Biological channel GlpF
Tajkhorshid et al. Science 2002, 296, 525 Biological channels are
expected to share this excellent gating due to similar wavelike
water density distribution Wan et al JACS 2005 Slide 22 2015-12-2
Electrical Response Tajkhorshid et al. Science 2002, 296, 525 How
do the charges on Aquporins influence the water permeation? Partial
charges here Water chain Slide 23 2015-12-2 Simulation system Green
sphere: the imposed charge. Osmotic pressure radius= 8.1,
length=13.4 J.Y. Li, H.P. Fang et al, Proc. Natl. Acad. Sci. USA,
104, 3687 (2007). Slide 24 Excellent gating , too Effectively
resistant to noisy charge signals Sensitive to available charge
signals Li et al., PNAS, 2007 Flow=all water penetrating through
Flux= up down (for water penetrates through) > 0.85 : Flux is
very close to the system without any charge (dashed) Slide 25
2015-12-2 Water-charge interaction shows local property. Slide 26
2015-12-2 Why water-charge interaction show local property? z
Dipole Slide 27 P C WC : Interaction energy of the water molecule
facing the imposed charge with the imposed charge. P C WW :
Interaction energy of the water molecule facing the imposed charge
with its neighbored water molecules. At the transition point: ~
0.85 , P C WC = P C WW Why excellent gating? Competition: charge-
water interaction --- STRONG hydrogen- bonging interactions
transition point Slide 28 2015-12-2 Orientation transitoion of
water molecules z Dipole Slide 29 2015-12-2 Flow and the net flux
decreases e xponentially with respect of (P C WW P C WC ) in the
interval of 0.25 0.75 . P C WW : interaction energy of the water
molecule facing the imposed charge with the imposed charge P C WC :
interaction energy of the water molecule facing the imposed charge
with its neighbored water molecules Li et al., PNAS, 2007 Slide 30
In AQPs, the bipolar water order stops proton permeation but not
water transport. Net flux = 1.9 /ns (21% of those of the fully
opened state), comparable to the measured 3.9 0.6 /ns = 0.5 Bipolar
or water transport Slide 31 A charge driven molecular water pump
inspired by the charge distribution of conserved regions in
biological channels called aquaporins Net flux 2.8/nanose cond
Aquaprins X.J. Gong, H.P. Fang et al., Nature Nanotechnology 2, 709
(2007) Slide 32 A charge driven molecular water pump ( Why )
Hydrogen bonds in quasi-one- dimensional water chain External
charge fields induces definite HB orientations, making water easy
to be driven by electric fields A combination of charge makes
relative low potential barriers Asymmetry charge distribution
drives water from one end to the other end Bottom: only charge
left
