Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session P18: Focus Session: Biological-Synthetic Hybrid Materials I |
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Sponsoring Units: DPOLY DBP Chair: Francis Starr, Wesleyan University Room: B117 |
Wednesday, March 17, 2010 8:00AM - 8:12AM |
P18.00001: Phase Behavior of DNA-Functionalized Nanoparticles: Dependence on Number and Orientation of Attached DNA strands Wei Dai, Chia Wei Hsu, Francesco Sciortino, Francis Starr Nanoparticles (NP) functionalized with single-stranded DNA (ssDNA) offer a route to custom-designed, self-assembled nanomaterials. The large length scale of the DNA links relative to the core NP size allows the formation of interpenetrating networks that give rise to unusual phase behavior. Among 3-, 4-, and 5-functionalized NP, we find phase diagrams with up to four amorphous phases (i.e., polyamorphism) which consist of interpenetrating networks. Our work demonstrates that regular symmetry of the functionalized NP is not a prerequisite for interpenetration. For the particular case of 6-functionalized NP with octahedral symmetry, the system forms (at least) six distinct crystalline structures (i.e., polymorphism), consisting of up to six interpenetrating simple cubic (sc) lattices. [Preview Abstract] |
Wednesday, March 17, 2010 8:12AM - 8:24AM |
P18.00002: Stability of DNA-linked Nanoparticle Crystals: Effect of Number of Strands Olivia Padovan-Merhar, Fernando Vargas Lara, Francis Starr Three-dimensional lattices of DNA-functionalized nanoparticles (NP) have potential application to novel devices and materials, but most experimental attempts to form crystals result in amorphous packing. Molecular models of DNA-functionalized NP have focused mainly on a small ($\sim$10) number of DNA strands, while the experimental particles have a large ($>$50) number of attached strands. Here we study crystal formation of DNA-linked NP using a coarse-grained molecular model in which ss-DNA are attached to spherical core NP. We examine the effect of strand number on crystal stability by using the method of thermodynamic integration to compute the free energy and entropy of BCC and FCC lattices, as well as determine the thermodynamic melting point of these structures. Additionally, it has been argued that the surface of gold NP have significant mobility, possibly resulting in DNA tethers which are not localized at specific points on the NP surface. We show that such strand mobility results in a crystal that is less stable than one formed when strands are rigidly attached. [Preview Abstract] |
Wednesday, March 17, 2010 8:24AM - 8:36AM |
P18.00003: Relative Stability of DNA-Linked Nanoparticle Crystals Fernando Vargas Lara, Francis Starr The creation of three-dimensional, crystalline ordered nanoparticle (NP) structures linked by DNA has proved experimentally challenging. Here we aim to systematically study parameters that influence the relative thermodynamic stability of such crystals. We carry out molecular dynamics simulations of a coarse-grained model in which DNA strands are tethered to a core icosahedral NP and examine the influence of strand length, fraction of linking bases in the strand, and strand stiffness on crystal stability. We use the thermodynamic integration method to compute the free energy, entropy, and melting point for BCC and FCC lattices formed for a broad range of parameter choices. We rationalize our findings using a simple model for the entropy difference due to hybridization, which suggests that the stability, measured by the heat of melting, can be expressed as a simple function of the fraction of linking base pairs. [Preview Abstract] |
Wednesday, March 17, 2010 8:36AM - 9:12AM |
P18.00004: Nanoparticles with DNA-mediated interactions: from Mess to Order and Complexity Invited Speaker: By decorating colloids and nanoparticles with various biomolecules, one can introduce highly selective key-lock interactions between them. This leads to a new class of systems and problems in soft condensed matter physics. In my talk, I will review a number of theoretical possibilities and recent experimental achievements in this new field. First, I will discuss DNA-mediated self-assembly of nanostructures and nanoclusters. The specificity and tunability of the interactions result in a remarkable morphological diversity of in such systems. In some of the proposed schemes, DNA can be used to essentially ``program'' the self-assembly of a desired structure. The colloids with type-dependent interactions can also be used for experimental realization of one of the simplest self-replicating system. Its study may shed some light onto such important problems as prebiotic evolution and origin of life. [Preview Abstract] |
Wednesday, March 17, 2010 9:12AM - 9:24AM |
P18.00005: Theoretical Description of the Self-Assembly Dynamics of DNA-functionalized Nanoparticles Chia Wei Hsu, Francesco Sciortino, Francis Starr Nanoparticles (NP) functionalized with DNA strands can assemble into networks with unusual structure and phase behavior. Properties of such materials are known from computational studies, but a deeper understanding requires a theoretical description of the assembly process. As a step toward this goal, we show that the kinetics of self-assembly of a mixture of NP functionalized by two or three DNA strands can be quantitatively described by the Flory-Stockmayer (FS) theory of gelation. Below the percolation threshold for the DNA-linked NP network, the FS theory also accurately describes the cluster size distribution. These results rely on the formation of nearly loopless structures; a more general theoretical description remains to be developed. In addition, we show that at equilibrium, the diffusion of nanoparticles is connected to the formation of bonds through a simple relation. [Preview Abstract] |
Wednesday, March 17, 2010 9:24AM - 9:36AM |
P18.00006: Improving the compatibility of DNA-functionalized nanoparticles and DNA scaffolds in solutions of divalent cations William Sherman, Mudalige Kumara, Oleg Gang With the construction of increasingly intricate nanometer scale assemblies from DNA, there is a push to use these structures as scaffolds for the precise arrangement of functional guests. Gold nanoparticles (AuNPs), with their size-tunable plasmon resonances, and convenient oxidation resistance have been the archetypical functional guests. Unfortunately, DNA nanostructures are generally only stable in a buffer with $\sim$10 mM concentration of divalent cations such as Mg$^{+2}$. These cations, however, induce the aggregation of DNA-functionalized AuNPs, which prevents their attachment to DNA scaffolds. Here we describe an approach in which AuNPs are covered by heterogeneous self-assembled monolayers consisting of thiolated DNA strands and thiolated zwitterions. These monolayers serve the dual function of allowing the AuNPs to attach to the DNA scaffolds via Watson-Crick base-pairing, while also allowing the AuNPs to resist aggregation for at least 7 weeks in buffer with 10 mM MgCl$_{2}$. This approach is thus more broadly applicable than previous methods for scaffolding particles on DNA constructs. [Preview Abstract] |
Wednesday, March 17, 2010 9:36AM - 9:48AM |
P18.00007: Assembly of DNA-Linked Nanoscale Platonic Solid Fang Lu, Yugang Zhang, Daniel van der Lelie, Oleg Gang A self-assembly strategy based on DNA-hybridization has been demonstrated as a promising platform for creation new types of materials via incorporating the nano-particles functionalities into well-define structures. However, the phase behavior dependence of such systems on the nanoparticles geometric anisotropy has not been explored yet. Here we report a study on assembly and packing of three kinds of nanoscale objects with shapes of platonic solids, including cubes, octahedral and rhombic dodecahedrons. Via DNA-linker-assisted programmable assembly, three-dimensional superlattices of DNA-capped nano-objects have been formed and probed using in-situ structural and spectroscopic methods. The superlattices can exhibit phase transformations, which are not attainable for systems built from spherical objects. The correlation between particle geometric anisotropy and the kinetics of phase formation has been also investigated. [Preview Abstract] |
Wednesday, March 17, 2010 9:48AM - 10:00AM |
P18.00008: Crystallization Dynamics of DNA-functionalized Nanoparticles Francis W. Starr, Wei Dai, Sanat Kumar As a step toward understanding techniques to create crystalline ordered arrays of DNA -linked nanoparticles (NP), we examine the dynamics of a model system of NP functionalized with six complementary strands of DNA that readily crystalizes. The octahedral geometry of the NP units naturally gives rise to cubic order; the length of the DNA linkers results in a NP lattice spacing that is large compared to the NP size, so that it also possible to form interpenetrating cubic crystals. We show that the formation of either single or interpenetrating crystals must preceded by a dense amorphous cluster, even in the absence of a metastable liquid-liquid transition. In this case, clustering is facilitated by the natural self-assembly of the DNA links. We detail the nucleation process through numerical simulations. [Preview Abstract] |
Wednesday, March 17, 2010 10:00AM - 10:12AM |
P18.00009: Dynamically Tunable 3D Nanosystems: From Structural to Optical Switching Oleg Gang, Mathew Maye, Huiming Xiong, Dmytro Nykypanchuk, Mudalige Thilak Kumara, William Sherman, Matthew Sfeir The structural plasticity of biomolecules and the reversibility of their interactions can be exploited for creation of nano-systems that are dynamic, reconfigurable and responsive. Here we report a study on 3D nanoparticle systems with discrete and continuous structural tunability endowed by DNA motifs. In the first example we demonstrate an assembly of nanoparticles in 3D superlattices, incorporating a reconfigurable DNA device. The interparticle distances in the superlattices have been modified by adding molecular stimuli, DNA strands. The superlattices were found to switch between two discrete rigid states, whilst a transition to a flexible device configuration showed a significant hysteresis, attributed to molecular trapping within the superlattice. In the second example, we present the successful realization of multi-component superlattices that incorporate metallic nanoparticles and chromophores interconnected by DNA. As the distances between the nano-components were regulated continuously, we have quantified, using small angle x-ray scattering and time-resolved microscopy, the relationship between in-situ determined superlattice structure and fluorescence lifetime. [Preview Abstract] |
Wednesday, March 17, 2010 10:12AM - 10:24AM |
P18.00010: Specific Templating of Inorganic Materials on Self-Assembled Clathrin Proteins Sarah Heilshorn Nature has evolved numerous methods for the reproducible self-assembly of nanoscale architectures that are ideal templates for patterning inorganic nanostructures. For example, the protein clathrin assembles into a variety of 2D and 3D structures depending on environmental conditions during assembly. The ability of this single protein to form multiple architectures makes clathrin an ideal model system for investigating the kinetic and thermodynamic principles of self-assembly, which will lead to the ability to predictably control template architecture. We design bi-functional peptide linkers to serve as molecular bridges between distinct sites on the clathrin monomers and specific inorganic materials including gold, titania, and cobalt oxide. By generating a family of bi-functional peptides, we develop a flexible, modular system that enables the rapid development of multiple inorganic nanostructures from a single protein template without requiring re-design of the template. We present examples of gold and anatase titania catalysts fabricated through this method. [Preview Abstract] |
Wednesday, March 17, 2010 10:24AM - 10:36AM |
P18.00011: Non-classical assembly pathways of anisotropic particles Stephen Whitelam Advances in inorganic synthesis and synthetic biology have spawned an array of nanoparticles and bio-inspired components of diverse shapes and interaction geometries. Recent computational and experimental work indicates that such anisotropic particles exhibit a variety of ``non-classical'' growth pathways, forming ordered assemblies via intermediates that do not share the architecture of the bulk material. Here we apply self-consistent mean field theory to a prototypical model of interacting anisotropic particles. We find that the impetus for non-classical ordering is in some regimes of parameter space thermodynamic in origin, and in other regimes of parameter space driven chiefly by considerations of particle mobility. We also introduce a molecular model of bacterial S-layer crystallization in order to illustrate features of non-classical assembly inaccessible to mean field theory. [Preview Abstract] |
Wednesday, March 17, 2010 10:36AM - 10:48AM |
P18.00012: Responsive micelles, vesicles and organogels from poly(lysine)-containing block copolymers Daniel Savin, Sandeep Naik, Jacob Ray, Ashley Montgomery In these studies, amphiphilic AB diblock and ABA triblock copolymers containing poly(lysine) (P(Lys)) were synthesized and their solution assembly studied using dynamic light scattering, circular dichroism spectroscopy and transmission electron microscopy. Rod-coil block copolymers containing P(Lys) are able to self-assemble into responsive micelles and vesicles, as well as organogels and liquid crystals. The hydrophobic block used was poly(propylene oxide), which exhibits a tunable critical point below which the block copolymer is in the ``double hydrophilic'' limit. In these multiply-responsive materials, we exploit secondary structure changes that occur within the P(Lys) chain to observe changes in solution morphology as a function of solution conditions. This talk will present some recent results on the pH responsiveness of P(Lys)-based ABA triblock copolymers and A$_{2}$B 3-arm star copolymers in aqueous media as well as ionic liquids. The effect of morphology changes due to secondary structure transitions will be discussed in the context of the interfacial curvature changes with pH and temperature. These dynamic materials have potential applications as viscosity modifiers, liquid crystals and gels. [Preview Abstract] |
Wednesday, March 17, 2010 10:48AM - 11:00AM |
P18.00013: Bionanoelectronic devices based on 1d-lipid bilayers on nanotube and nanowire templates Aleksandr Noy Biological molecules perform sophisticated functions in living systems with complexity often far exceeding most of man-made devices and objects. Direct integration of biological components with electronic circuits could drastically increase their efficiency, complexity, and capabilities and result in novel sensing and signaling architectures. Yet, one of the obstacles for this vision of a bionanoelectronic circuit is the absence of a versatile interface that facilitates communication between biomolecules and electronic materials. We have been building platforms that integrates membrane proteins with one-dimensional inorganic materials such as carbon nanotubes and silicon nanowires. In our devices, a nanotube of nanowire is covered by a lipid bilayer that serves both as a universal membrane protein matrix and an insulating shield. We will discuss the fabrication and properties of these ``shielded'' nanowires and of their use in bionanoelectronic devices that incorporate working membrane proteins in an electronic circuit. [Preview Abstract] |
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