麻省理工大学：《生物材料的分子结构》教学讲义（英文版）Lecture 13：Molecular Devices Last time

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 13: Molecular Devices Last time biological strategies for inorganic templating by organic materials Biomimetic organic template materials Biomimesis of bone Today Reading V Vogel, 'Reverse engineering: Learning from proteins how to enhance the performance of synthetic nanosystems, MRS Bull. Dec. 972-978(2002) Overview to date Current Road Map of the course: Started with degradable synthetic polymers-structural and controlled release materials Discussed modifying degradable materials for biological recognition Moved to controlled release devices fabricated from degradable polymers Next, hydrogel materials for drug delivery, tissue engineering and lab-on-a-chip applications o Structure, what are they made of o Theory of gel swelling for neutral and ionic gels Biomineralization: approaches used by biology and how we are trying to mimic them o Future materials for hard tissue engineering So far, largely looking at macroscopic materials MOk o Materials from which micron-sized or larger scaffolds, drug delivery devices and gels are fabricated Moving to smaller length scales: molecules and aggregates of molecules, we come to some new applications Performing molecular-level fund o Delivering molecular cargos to cells(labeling or treating cells) Application areas we'll focus on: Molecular devices o Length scale of one or a few molecules) o Single-molecule switches o Molecular motors Nano-to micro-scale drug carriers and detection reagents o(Length scale of supramolecular aggregates to many-molecule aggregates) Drug targeting Molecular Devices Current Approaches to Molecular Devices based on Protein-polymer h 3 examples we'll discuss 1. Use synthetic polymers to control 'on' and off state of a protein 2. Use engineered surfaces to direct the function of proteins 3. Use engineered proteins to build nano-motorized devices on surfaces Lecture 13-Hybrid macromolecules 1 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Lecture 13: Molecular Devices Last time: biological strategies for inorganic templating by organic materials Biomimetic organic template materials Biomimesis of bone Today: molecular devices Reading: V. Vogel, ‘Reverse engineering: Learning from proteins how to enhance the performance of synthetic nanosystems,’ MRS Bull. Dec. 972-978 (2002) Overview to date Current Road Map of the course: ƒ Started with degradable synthetic polymers – structural and controlled release materials ƒ Discussed modifying degradable materials for biological recognition ƒ Moved to controlled release devices fabricated from degradable polymers ƒ Next, hydrogel materials for drug delivery, tissue engineering, and lab-on-a-chip applications o Structure, what are they made of o Theory of gel swelling for neutral and ionic gels ƒ Biomineralization: approaches used by biology and how we are trying to mimic them o Future materials for hard tissue engineering ƒ So far, largely looking at ‘macroscopic’ materials o Materials from which micron-sized or larger scaffolds, drug delivery devices and gels are fabricated ƒ Moving to smaller length scales: molecules and aggregates of molecules, we come to some new applications o Performing molecular-level functions o Delivering molecular cargos to cells (labeling or treating cells) Application areas we’ll focus on: ƒ Molecular devices o (Length scale of one or a few molecules) o Single-molecule switches o Molecular motors ƒ Nano- to micro-scale drug carriers and detection reagents o (Length scale of supramolecular aggregates to many-molecule aggregates) ƒ Drug targeting Molecular Devices Current Approaches to Molecular Devices based on Protein-polymer hybrids ƒ 3 examples we’ll discuss: 1. Use synthetic polymers to control ‘on’ and ‘off state of a protein 2. Use engineered surfaces to direct the function of proteins 3. Use engineered proteins to build nano-motorized devices on surfaces Lecture 13 – Hybrid macromolecules 1 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Single-molecule switches Using LCST polymers as the basis of a molecular switch o LCST polymers show sharp volume change at the transition temperature as they transform from swollen coil to globule Poly (N-isopropylacrylamide) 4/1 cm T/℃ Finain t x sat th nelms b wf astv mie ge nd t(r, a ordered water molecules (minimize water-hydrophobe contacts) /nm Dehydration allows water to FIG, I. Typical hydrody nan polyIN-isopropylacrylamide) chains in deionized water disorder(entropically-driven) At359 ws the argular △S=S 0 (Wu and Wang, 1998) A temperature-sensitive streptavidin m o Chime animation of streptavidin with biotin bound to tetrameric pockets http://www.chem.uwec.edu/webpapers2001/barkacs/pages/steptavidin.html Poly(N, N-diethylacrylamide) -(CH2-CH) Mutatation introducing cysteine ydrates with increasing temperature-analogous to PEG- PPO-PEG triblock copolymers T Hydrodynamic STREPTAVIDIN.EIlt T(ic) Ding et al. 2001) o Blockade of access to biotin-binding pocket is dependent on the size of the biotinylated target Small protein G is not sterically blocked by the hydrated PDEAAm chain arge biotinylated IgG cant access pocket even when PDEAAm chain is collapsed o Varying the length of the thermally-responsive chain allows the degree of binding blockade to be tuned (Figure 4) Lecture 13-Hybrid macromolecules 2 of 13

-- BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Single-molecule switches ƒ Using LCST polymers as the basis of a molecular switch1 o LCST polymers show sharp volume change at the transition temperature as they transform from swollen coil to globule Dehydration allows water to disorder ( ) 'S = Sdehydrated - Shydrated > 0 Poly(N-isopropylacrylamide) ordered water molecules (minimize water-hydrophobe contacts) entropically-driven (Wu and Wang, 1998) 2-4 ƒ A temperature-sensitive streptavidin mutant o Chime animation of streptavidin with biotin bound to tetrameric pockets: http://www.chem.uwec.edu/Webpapers2001/barkacs/Pages/Steptavidin.html - TLCST Rh,0 Hydrodynamic radius (related to 1/2) ~Rh,0/3 T (¡C) (Ding et al. 2001) o Blockade of access to biotin-binding pocket is dependent on the size of the biotinylated target: ƒ Small protein G is not sterically blocked by the hydrated PDEAAm chain ƒ Large biotinylated IgG can’t access pocket even when PDEAAm chain is collapsed o Varying the length of the thermally-responsive chain allows the degree of binding blockade to be tuned (Figure 4) Lecture 13 – Hybrid macromolecules 2 of 13 Poly(N,N-diethylacrylamide): -(CH2-CH)n Mutatation introducing cysteine C=O dehydrates with increasing temperature- analogous to PEG- near binding pocket PPO-PEG triblock copolymers N HC 3 2 C H H -C 2-CH3

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Polymer switch shows B-protein G size-selective blockade of streptavidin binding pocket B-BSA a:: Figure 1 sheldig of binny ated proten bndng D BIN118K-PDENmc bindng of biotinylated BSA ( B-BSA b the E51KN118K-PDEAAm-12 E51NNl18K-PDEAAm-12 8k conjugate (open circles ef cient over the who terperature range estimated, while the binding of the lage proten B-lgg to the rature range Uhor he bindng conditons used (see Meto), the E51KN118K- PDEAm- 12. 8k corium has an LaST df C fopen triangles Also the basis for triggered release switches o Expose biotin-loaded conjugates to successive cycles of T TLcsT through T> TLCST 4 cycles kick out all bound biotin All bound biotin released by 4 temperature cycles 37ic E116C.pP 图E16c ST 24i c 374374374374 4i c Figure 8. Cumulative release of bound bi duplicate experiments. Magnetic beac mobilized with 5.4 x 10-10 mol of E116C assay. Sodium phosphate buffer, PH 7.4 (Ding et al., 1999) Mechanisms for controlling access by large or small ligands o Small ligands have access to binding pocket next to immobilized chain blocked when chain is collapsed but can access the pocket when the chain is hydrated Conversely, if biotin binds in the pocket, collapse of the chain can eject the bound small ligand Lecture 13-Hybrid macromolecules 3 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 size-selective blockade of streptavidin binding Polymer switch shows pocket: ƒ Also the basis for triggered release switches o Expose biotin-loaded conjugates to successive cycles of T TLCST ƒ 4 cycles ‘kick out’ all bound biotin All bound biotin released by 4 temperature cycles: (Ding et al., 1999) TLCST 37¡C 4¡C = 24¡C ƒ Mechanisms for controlling access by large or small ligands o Small ligands have access to binding pocket next to immobilized chain blocked when chain is collapsed, but can access the pocket when the chain is hydrated ƒ Conversely, if biotin binds in the pocket, collapse of the chain can eject the bound small ligand Lecture 13 – Hybrid macromolecules 3 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Larger igands are always prevented from accessing the pocket next to the immobilized chain ctive access occurs for the second binding pocket 20 a away- when the chain is collapsed it does not prevent access to the second pocket, but when hydrated, long chains can prevent ccess to the neighboring pocket and block protein binding Mechanisms of Biotin Smart switch operation Blocked T>LCST T< LCST Accessible Fabrication of capture and release devices o Conjugation to magnetic micro-or nano-spheres Affinity purification Affinity purification Responsive drug release Conjugation to magnetic microspheres/nanospheres Generality of concept o Switch temperature can be tuned by copolymerizing with more hydrophilic monomers such as hydroxyethyl methacrylate Lecture 13-Hybrid macromolecules 4 of 13

B B BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 o Larger protein ligands are always prevented from accessing the pocket next to the immobilized chain ƒ Selective access occurs for the second binding pocket 20 Å away- when the chain is collapsed it does not prevent access to the second pocket, but when hydrated, long chains can prevent Mechanisms of switch operation: access to the neighboring pocket and block protein binding ƒ Fabrication of capture and release devices3,5 o Conjugation to magnetic micro- or nano-spheres ƒ Affinity purification QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. Applications: • Affinity purification 1) QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. 3) B B QuickTime™ and a Graphics decompressor are needed to see this picture. B B B B Conjugation to magnetic microspheres/nanospheres B B B 2) B B B B • Cell-surface labeling • Responsive drug release QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. QuickTime™ and a Graphics decompressor are needed to see this picture. ƒ Generality of concept o Switch temperature can be tuned by copolymerizing with more hydrophilic monomers such as hydroxyethyl methacrylate Lecture 13 – Hybrid macromolecules 4 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 o Other temperature-responsive polymers that could be used Poly(N-isopropylacrylamide) o pH-responsive switches copolymers of PNIPAAm and AAc Copolymerization allows switch Switches can also be synthesized for temperature to be varied light or pH triggering -(CH2-CH) M0cr2fc2/c2分H C-OCH, CH, OH Rudom Copolar on NIPAAID-AAc PONIPAAmAAc DEAAm HEMA H7. 4 and 6.0 pH5.0 pH 4.0 SA 7. 4 and 6.0 pH5.0 PH 4.0 igure 6. Proposed conformations of the polymer chatn col Molecular motors 6 Engineering principles on which macroscopic engines/motors are based fail at the nano-scale How to miniaturize controlled force-generating devices cell-manipulating devices, nanobots, etc. o Molecular motors driven by single-molecule fuels, photons, etc Protein motors used by nature for force generation and motion Motor proteins convert chemical energy into mechanical force via conformational changes o Generation of protein motion along guide-wires: protein filaments o Driven by energy released on hydrolysis of adenosine 5-triphosphate o Myosin and kinesin are two examples of ubiquitous motor proteins found in eukaryotic cells o Motor protein translates along 25nm-diameter rigid rods(microtubules, up to 100 um in length possible in o Transport of molecular cargos through cells Small membrane organelles or protein complexes E.g. encapsulated neurotransmitters from nerve cell nucleus to the synapse to excite neighboring o Coordination of two heads allows continuous walking along microtubules with 80 A steps Efficient processive motion allows long-range transport by one or a few motor proteins Motion is directional toward plus end of microtubule Myosins o Motor protein moves along actin filaments o Enables contractile cell functions such as cell motility and muscle contraction Operates in a large array of motors to produce large-scale motions/forces Lecture 13-Hybrid macromolecules 5 of 13

-- BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 o Other temperature-responsive polymers that could be used: ƒ Poly(N-isopropylacrylamide) o pH-responsive switches ƒ copolymers of PNIPAAm and AAc Copolymerization allows switch Switches can also be synthesized for temperature to be varied: light or pH triggering: -(CH2-CH)n￾C=O N 2 C H H -C 2-C HC 3 H3 HEMA DEAAm Molecular Motors6 ƒ Engineering principles on which macroscopic engines/motors are based fail at the nano-scale ƒ How to miniaturize controlled force-generating devices cell-manipulating devices, nanobots, etc.? o Molecular motors driven by single-molecule fuels, photons, etc. 7 Protein motors used by nature for force generation and motion ƒ Motor proteins convert chemical energy into mechanical force via conformational changes o Generation of protein motion along guide-wires: protein filaments o Driven by energy released on hydrolysis of adenosine 5’-triphosphate o Myosin and kinesin are two examples of ubiquitous motor proteins found in eukaryotic cells ƒ Kinesin o Motor protein translates along 25nm-diameter rigid rods (microtubules, up to 100 µm in length possible in vitro) o Transport of molecular cargos through cells ƒ Small membrane organelles or protein complexes ƒ E.g. encapsulated neurotransmitters from nerve cell nucleus to the synapse to excite neighboring cells o Coordination of two heads allows continuous ‘walking’ along microtubules with 80 Å steps ƒ Efficient processive motion allows long-range transport by one or a few motor proteins ƒ Motion is directional toward ‘plus’ end of microtubule ƒ Myosins o Motor protein moves along actin filaments o Enables contractile cell functions such as cell motility and muscle contraction ƒ Operates in a large array of motors to produce large-scale motions/forces Lecture 13 – Hybrid macromolecules 5 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 o -100 A per ATP hydrolysis step o Two heads act independently of one another- single stroke then release from actin polymer Can't continuously march along polymer by kinesin Muscle motor protein, transport along transport along microtubules actin fibers Limitations for use in bioengineering applications unidirectional motion AControlling orientation of dable Gand oarO (Vale and Milligan, 2000) Energy source for these molecular motors o AtP hydrolysis cycle linked to conformational change cycle o Energy gained by binding ATP moves kinesin neck linker from rearward-facing position forward to dock against catalytic core of head Motion of one neck pulls other free from previous microtubule binding site and throws it forward to the next site(-80 A) o Origin or directionality: myosin goes opposite direction from kinesin Directionality comes from conformation matching of head to polymers in one direction combined with time sequence of head release from polymer Both motors have an upstroke on binding ATP, downstroke on hydrolysis Kinesin neck docks onto head on upstroke Myosin: tight binding of head to polymer in ATP-free state o Forward motion on upstroke when head releases from polymer inesin: tight binding in ATP-bound state o Reverse motion on downstroke when head releases from polymer Lecture 13-Hybrid macromolecules 6 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 o ~100 Å per ATP hydrolysis step o Two heads act independently of one another- single stroke then release from actin polymer ƒ Can’t continuously march along polymer by itself Myosin kinesin Muscle motor protein, transport along transport along microtubules actin fibers QuickTime™ and a Video decompressor are needed to see this picture. QuickTime™ and a Video decompressor are needed to see this picture. Limitations for use in bioengineering applications: ¥unidirectional motion ¥Controlling orientation of Ô carÕ cableÕand Ô (Vale and Milligan, 2000) ƒ Energy source for these molecular motors o ATP hydrolysis cycle linked to conformational change cycle o Energy gained by binding ATP moves kinesin neck linker from rearward-facing position forward to dock against catalytic core of head ƒ Motion of one neck pulls other free from previous microtubule binding site and throws it forward to the next site (~80 Å) o Origin or directionality: myosin goes opposite direction from kinesin ƒ Directionality comes from conformation matching of head to polymers in one direction combined with time sequence of head release from polymer ƒ Both motors have an upstroke on binding ATP, downstroke on hydrolysis x Kinesin neck docks onto head on upstroke x Myosin: tight binding of head to polymer in ATP-free state o Forward motion on upstroke when head releases from polymer x Kinesin: tight binding in ATP-bound state o Reverse motion on downstroke when head releases from polymer Lecture 13 – Hybrid macromolecules 6 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 SHOW SCHEMATICALLY ON BOARD Fig. 4. A model for the "power strokes"of myosin and kinesin motors complexed with MyosIn heir polymer tracks. In myosin, a -100A ADP-PI motion of the lever arm domain is generated when the motor undergoes a transition from an ADP-Pi-bound state to an ADP/nucleotide-free conformation(78). This figure was generated by superimposing the structures of smooth 100 A muscle myosin(ADP-AlF4 )and the nucleotide free chicken skeletal myosin. Shown are the converter/lever arm positions in ADP-Pi bel low)and nucleotide-free(red )states, the sim ilar catalytic cores(blue), and the actin fila- ment (gray: "pointed end"toward the top). In the motility cycle of a kinesin dimer(only one ADP /nucleotide-free head shown here)along a microtubule(a single protofilament is shown in gray: "plus end"to ward the top), the neck linker swings from a Kinesin rearward-pointing position (ADP/nucleotide free: red)to a forward-pointing position (ATP/ ATP/ADP. ADP-Pi; yellow ) The"ATP/ADP-Pi"state is rat conventional kinesin, whereas the "ADP/nucle otide-free"position of the neck linker was modeled on the basis of cryo-electron micros- 80A opy from Rice et al. (26). Myosin and kinesin uctures were superimposed using their P loops, showing that they bind in similar orien- ations to their tracks.( Note: The actin fila- ADP/nucleotide-free ment runs parallel to the plane of the image. protofilament but the microtubule is tilted -20 with respect to the plane of the image. )Although the me ements are sim nesin an the power strokes occur in opposite directions(arrows)because of the different polymer binding cycles of the two motors(see text for details). Scale bar, 80A. Some of matt lang s work? Engineering devices for nanoscale assembly using nature's motors(Hess et al. 2001) Question: How can we manipulate, move, and assemble objects with nanoscale sizes? E.g. individual proteins, nanocrystals, etc o AFM probe tip- one by one- too slow to be really useful in biosensors, lab-on-a-chip or other materials applications Alternatives? Surfaces with microtubule nano-cargo carriers(Hiratsuka et al.) o Discovered that kinesin molecules adsorbed to a surface could be used to drive random motion of Researchers sought to use photolithographically patterned surfaces to gain control over motion and develop nano-carriers with directed motion Lecture 13-Hybrid macromolecules 7 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 SHOW SCHEMATICALLY ON BOARD: Some of Matt Lang’s work? Engineering devices for nanoscale assembly using nature’s motors (Hess et al. 2001) ƒ Question: How can we manipulate, move, and assemble objects with nanoscale sizes? E.g. individual proteins, nanocrystals, etc. o AFM probe tip- one by one- too slow to be really useful in biosensors, lab-on-a-chip or other materials applications o Alternatives? ƒ Surfaces with microtubule nano-cargo carriers (Hiratsuka et al.8 ) o Discovered that kinesin molecules adsorbed to a surface could be used to drive random motion of microtubules in 2D ƒ Researchers sought to use photolithographically patterned surfaces to gain control over motion and develop nano-carriers with directed motion Lecture 13 – Hybrid macromolecules 7 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Gass S i Photomask (3) Absorption of motor molecules c Protein solution madly i un in ni 1 wothgnaph: Imine ns, kinesin (Hiratsuka et al, 2001) o Simple approach: tracks etched in a photoresist, exposing glass Kinesin motors adsorbed randomly onto exposed glass under conditions where adsorption to resist was minimal(high ionic strength and 0. 1% tween surfactant present during adsorption Circular tracks Tracks confine motion of microtubules approximately linearly forward or backward No arrowheads: microtubules walk in both directions around circles With arrowheads: microtubules on inside track move counter-clockwise microtubules on outer track move clockwise o Arrowheads act as directional rectifiers, moving against direction of arrow, high probability of microtubule striking wall and reversing direction as it jumps to new set of kinesin molecules o Steady motion observed up to 2 hrs in the presence of ATP FIGURE 4 Achve transport between two pools of micrometer scales. A Lecture 13-Hybrid macromolecules 8 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 Random transport of microtubules over randomly oriented surface-bound kinesin molecules: QuickTime™ and a ÉVÉlÉpÉbÉN decompressor are needed to see this picture. (Hiratsuka et al, 2001) o Simple approach: tracks etched in a photoresist, exposing glass ƒ Kinesin motors adsorbed randomly onto exposed glass under conditions where adsorption to resist was minimal (high ionic strength and 0.1% tween surfactant present during adsorption) ƒ Circular tracks: x Tracks confine motion of microtubules approximately linearly forward or backward x No arrowheads: microtubules walk in both directions around circles x With arrowheads: microtubules on inside track move counter-clockwise, microtubules on outer track move clockwise o Arrowheads act as directional rectifiers, moving against direction of arrow, high probability of microtubule striking wall and reversing direction as it jumps to new set of kinesin molecules o Steady motion observed up to 2 hrs in the presence of ATP 20 µm Lecture 13 – Hybrid macromolecules 8 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 The soace betweer the kinesin ain to prevent nonspecific surface adsorpton of the indicate the paths af indvidual mcrotwbu (Vogel, 2002) We don't yet understand the physicochemical principles controlling molecular motor speed, unloading/loading of cargo A molecular rotor built from atPase Question: how do we create engines to provide piconewton forces for nanodevices? o One answer: engineered materials based on protein motor-based engines Work of the group of Carlo Montemagno at UCLA (Dept of Bioengineering) o Role of this protein in cell ATPase complex No-load rotational velocity of -17 revolutions per second o Generates >80 pNnm work o Approximately 100% efficient! o -10 nm diameter Lecture 13-Hybrid macromolecules 9 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 (Vogel, 2002) ƒ We don’t yet understand the physicochemical principles controlling molecular motor speed, unloading/loading of cargo A molecular rotor built from ATPase ƒ Question: how do we create engines to provide piconewton forces for nanodevices? o One answer: engineered materials based on protein motor-based engines ƒ Work of the group of Carlo Montemagno at UCLA (Dept. of Bioengineering)9-13 ƒ F1 fragment of adenosine triphosphate synthase (F1-ATPase) o Role of this protein in cell o Rotary motion during ATP hydrolysis as J subunit transitions between 3 equidistant positions around the ATPase complex ƒ No-load rotational velocity of ~17 revolutions per second o Generates > 80 pN•nm work o Approximately 100% efficient! o ~10 nm diameter Lecture 13 – Hybrid macromolecules 9 of 13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 F, fragment of adenosine triphophate synthase(F-ATPase) Figure 14-25 ATP synthase. As foamed finan muliple subunits GReed tters), as is the transmembrane H' Montemagno's group prepared mutants of this protein to use as ATP-fueled molecular motors for nanodevices 750-1400nm Biotinylated cysteine @@f the motor Geetabind Ni-capped post Teetor immobilization of motor hong et al., 2000) Hybrid ATPase Figure l. Schematic diagram()and CCD photomicrograph(B) of fluorescent microspheres attached to the y subunit of individual(Bachand et al., 2000) lized on nickel dot arrays that were created using electron beam lithography Lecture 13- Hybrid macromolecules 10of13

BEH.462/3.962J Molecular Principles of Biomaterials Spring 2003 F1 fragment of adenosine triphophate synthase (F1-ATPase) ƒ Montemagno’s group prepared mutants of this protein to use as ATP-fueled molecular motors for nanodevices 750-1400 nm Ô Ô Ô 80 nm Hybrid ATPase Fluorescent microsphere axleÕof the motor feetÕfor immobilization of motor feetÕbind Ni-capped posts (Soong et al., 2000) (Bachand et al., 2000) Lecture 13 – Hybrid macromolecules 10 of 13