Adventures in nanoscale mechanics. Peter M. Hoffmann Department of Physics & Astronomy Wayne State University

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1 Adventures in nanoscale mechanics Peter M. Hoffmann Department of Physics & Astronomy Wayne State University

2 What s so special about the nanoscale? Na no tech nol o gy Noun, From the Greek, for give me money for funding.

3 What is so special about the nanoscale? Breakdown of continuum picture Silicon

4 What is so special about the nanoscale? Convergence of energy scales Energy transduction and Conversion: chemical-electrostatic-mechanical-thermal Rob Philips, Steven Quake, Physics Today May 2006

5 What is so special about the nanoscale? Can see onset of collaborative effects which lead to long times scales Slow Fast

6 Nanosystem examples Nanoconfined liquids Single biomolecules Molecular machines

7 (Nano)Confined liquids- Why? Biology: Biomolecular structure, biochemical processes, thermal reservoir, thermal noise (molecular machines) Interactions with biological surfaces Origin of Life Nanoscience: Local order creation influence on self-assembly Flow through narrow channels, nanofluidics Nanotribology Colloid science Phase transformations on surfaces Wetting Oil & gas extraction

8 Water, water everywhere: The crowded cell David Goodsell: The machinery of life

9 Water and Life All known life relies on water Solvent for biologically important molecules Determines structure of macromolecules (hydrophilic, hydrophobic) Drives self-assembly, protein folding etc. Transport medium, dissolves ions Thermal reservoir & source of thermal noise

10 Geology, 2005

11 Water in porous rock, oil recovery

12 What happens when you squeeze a liquid to just a few nanometers?

Measuring mechanics at the nanoscale: The Atomic Force Microscope (AFM) What kind of forces could we expect at the nanoscale (molecules)?..and how could we measure such forces?

13 Measuring mechanics at the nanoscale: The Atomic Force Microscope (AFM) What kind of forces could we expect at the nanoscale (molecules)?..and how could we measure such forces? Need: Back-of-the-envelope calculation Energy of a weak bond 0.1 ev J Length of a bond: a few Angstrom = 0.1 nm = m Work to break a bond = Energy of bond = Force x Distance, Therefore: Force = Energy/Length of bond J/10-10 m = N = 100 pn Stiffness of spring of bond: Hooke s law: F = - k x Therefore: k N/(10-10 m) = 1 N/m! 13

14 Homebuilt AFM

15 Measurement procedure Measure amplitude & phase Move at low speed: nm/s Oscillate at small amplitude: nm

16 Our measurements: Probing dynamics Measure amplitude & phase R Stiffness & damping h Mechanical relaxation time: low for liquid, high for solid t R h R

17 2 Å/s = 1 ft/50yrs 8 Å/s 14 Å/s

18 What is so special about the nanoscale? Breakdown of continuum picture Silicon

19 Collective dynamics gives long relaxation times When liquid is confined, motion is restricted to quasi 2D For liquid to move out of the way, many molecules have to move collectively. A simple argument 0 N 10 0 p 14 N s 1 s N 47molecules p 1 p N N

20 What is so special about the nanoscale? Can see onset of collaborative effects which lead to long times scales Slow Fast

24 Viscosity (Pa s) Viscosity (Pa s) Water, compressed at 0.2 nm/s 4.00E E E E E E E E E E E E E E E-09 Tip-surface separation (m) Water, compressed at 1.4 nm/s 1.60E E E E E E E E E E E E E E E-09 Tip-surface separation (m)

25 Changing gear.

26 1.75 m A few cm X x nm 1000 X 20 microns

27 Single molecule AFM: Pulling Molecules Polymer linker (PEG) k 0 W diss Measurable Parameters: Activation barrier height, E* Position of activation barrier, x* Shape of potential around E b Change in free energy/depth of energy well, DG Stiffness of bond/ curvature of energy, k i Off-rate at zero force, k 0 Diffusion, friction, metastable states Dissipated work, W dis E b k i E A DG x* 27

28 Single molecule Protein Interactions Mechanics, dynamics and regulation of biological macromolecules and molecular assemblies 600 pn) distance(nm) 28

29 Single molecule Effect of applied force: Lowering of activation barrier x* U max 29

31 Monte-Carlo simulations of rupture events Which tail is it? Multiple bonding? Heterogeneous bonding?

Single protein force measurements on live cancer cells pn -1 0.0018 0.0016 0.0014 0.0012 0.0010 0.0008 0.0006 0.0004 0.0002 a pn -1 0.0000 0 500 1000 1500 2000 2500 3000 Unbinding force (pn) 0.0014 0.0012 0.0010 0.0008 0.0006 0.0004 0.0002 b 0.

re X1: AFM measurements of binding between TIMP1 (Fig. a) and TIMP 2 (Fig. b) on live cells expressing MT1-MMP (inset to Fig.

32 Single protein force measurements on live cancer cells pn a pn Unbinding force (pn) b Unibinding force (pn) Figure X1: AFM measurements of binding between TIMP1 (Fig. a) and TIMP 2 (Fig. b) on live cells expressing MT1-MMP (inset to Fig. b). Fig. a shows predominantly non-specific binding (maximum probability for zero force) of TIMP1, while b shows strong affinity of TIMP2 to MT1-MMP (most probable force ~500 pn). Inset a: Control: Binding probability for TIMP2 on cells without MMP (EV) and with MMP (GPI) shows that about 60-70% of binding events are specific. For TIMP1 no significant difference is observed.

33 A new instrument Olympus IX-81 Fluorescence microscope w. epifluorescence, TIRF, phase, DIC, lasers: 405, 488, 561, 640 nm, two cameras, one very high resolution, dual view Bruker Catalyst AFM w. peak force imaging, perfusion capability, EasyAlign setup etc.

36 Force (recognition) imaging of (PS + LBP) membranes using a cantilever functionalized with MEMO-linker molecules and αlbp antibodies. Roes S et al. J. Biol. Chem. 2006;281: by American Society for Biochemistry and Molecular Biology

37 Single molecule Total Internal Reflection Fluorescence (TIRF) Single myosin, imaged with TIRF:

38 When a molecule becomes a machine Fastest AFM in the World: Toshio Ando, Kanazawa University, Japan ~ 100 nm 150 ms/frame

39 What is so special about the nanoscale? (4) Predominance of thermal noise

40 Feynman s Ratchet

41 The ratchet, the reset, and the second law

42 Needs a reset step powered by a supply of energy... and an asymmetric energy landscape.

43 Do actual molecular machines really work like this? Hill 1938, Frog muscle Simulation of damped diffusion on an oscillatory tilting sawtooth potential (stochastic differential equation, Markov process) Speed v

Conclusions and Acknowledgments AFM is a versatile tool to measure nanomechanical properties of nanosystems Liquids deviate strongly from bulk behavior

for single-molecule studies on live cells and can be combined with optical methods.

45 Conclusions and Acknowledgments AFM is a versatile tool to measure nanomechanical properties of nanosystems Liquids deviate strongly from bulk behavior when nanoconfined : Ordering Divergence of relaxation time scales Altered viscoelastic behavior New, surprisingly complex phenomena AFM is a useful tool for single-molecule studies on live cells and can be combined with optical methods. Acknowledgments: My students: Shah Khan, Venkatesh Subba-Rao, Essa Mayyas, George Matei, Ed Kramkowski, David Wilson, Anwesha Sakar. Post-docs: Shivprasad Patil, Mircea Pantea. Funding: NSF-DMR , WSU Nano@Wayne 45

AFM Imaging In Liquids. W. Travis Johnson PhD Agilent Technologies Nanomeasurements Division

AFM Imaging In Liquids. W. Travis Johnson PhD Agilent Technologies Nanomeasurements Division AFM Imaging In Liquids W. Travis Johnson PhD Agilent Technologies Nanomeasurements Division Imaging Techniques: Scales Proteins 10 nm Bacteria 1μm Red Blood Cell 5μm Human Hair 75μm Si Atom Spacing 0.4nm