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Poster Abstracts

Active and Adaptive Materials
October 22nd and 23rd 2015, ASRC

Invited Speakers

Bio-Inspired Supramolecular Materials

Samuel I. Stupp Northwestern University

Thursday Oct 22nd 2015, 9:45-10:30

Supramolecular soft matter has the potential to mimic the structures and dynamics of biological systems, and it is therefore a rich platform for the development of bio-inspired materials. The interesting features of supramolecular soft materials include, nanoscale control of dynamics, highly responsive behavior to external stimuli, capacity to self-heal defects, noncovalent co-localization of functional domains, and the use of self-assembly to optimize function, among many others. This lecture will first describe supramolecular soft materials that mimic the photosynthetic machinery of plants by integrating the necessary functions to generate solar fuels. In these systems light harvesting structures are co-localized with catalysts for hydrogen production in highly hydrated environments that enhance their function. Other energy relevant examples will be described in which supramolecular systems integrate electron donors and acceptors for photovoltaic behavior or ferroelectric response. As a third topic, the lecture will discuss the development of highly dynamic bioactive supramolecular materials designed to interact with cells in order to trigger biological adhesion and signaling pathways relevant to regenerative medicine.

Can Chemistry go MENTAL*?

Lee Cronin University of Glasgow

Thursday Oct 22nd 2015, 2:10-2:55

What is life? How did life start on planet earth ca. 3.5 billion years ago, and which molecules / chemical systems lead to biology? Is there are general theory of evolution that extends to all matter? Can we make or evolve life from scratch in a matter of hours? These are fantastically interesting questions but in this lecture, rather than look back into the past, we will look to the future and discuss how chemists may go about creating new types of truly synthetic (artificial life, new or 'inorganic' biology). In embarking upon this quest we will be asking the question "What is the minimal chemical system that can undergo Darwinian evolution?" and in doing so looking towards the concept of 'adaptive matter' and evolvable materials and chemical systems. The aim is inorganic biology, or more simply, a living system that does not the current chemical infrastructure utilized by biology.

Abstract Image

Figure. A picture of one of our 'networked' evolutionary chemical systems.

This lecture describes our work towards the development of inorganic systems capable of evolution as a fundamentally less complex 'emergent' model of prebiotic evolution that pre- dates the RNA / DNA world. In synergy we are also developing a new paradigm for evolution outside of biology, towards an experimental framework leading to the search for minimal evolvable inorganic chemical entities. This is because minimal self-assembling inorganic systems capable of catalysis and replication may provide a route to cross the information threshold where the number of evolvable bits (Eb) exceeds that required to start the process (Ib). Ultimately this approach could allow us to (re)discover biology relevant to life in earth as it is today or to develop a totally new 'inorganic biology'. We postulate that the evolvable inorganic systems could be used as an efficient route to the realization of functional nanotechnology that does not need atom-by-atom positioning as suggested by people like Drexler.

* MENTAL = Molecularly Evolved Nanotechnology for Artificial Life

Out-of-equilibrium BIOMIMETIC Systems by Dynamic and Dissipative Self-assembly

Jan H. van Esch Delft University of Technology

Thursday Oct 22nd 2015, 10:30-11:00

The self-assembly of small molecules, polymers, proteins, nanoparticles and colloids under thermodynamic equilibrium conditions has been a powerful approach for the construction of a variety of structures of nano- to micrometer dimensions, like vesicles, capsules, and nanotubules. Despite these advances, the permanent nature of these synthetic self-assembled structures does not compare well to the complex spatiotemporally confined self-assembly processes seen in natural systems, which for instance allow the dynamic compartmentalization of incompatible processes, responsiveness, and self-healing. It remains a challenge to develop out-of-equilibrium systems through spatio- and temporal control over self-assembly. In our research we focus on molecular approaches which allow control over self-assembly processes through covalent bond formation: (i) the development of dynamic covalent gelators, which allow spatial and temporal control over self-assembly by use of catalysts,[1,2] and (ii) dissipative self-assembly driven by a chemical fuel[3,4]. I will discuss the background of our approaches together with recent results, and will suggest how dynamic self-assembling systems may lead to the next generation of responsive, nanostructured and self-healing materials.

[1] J. Boekhoven, J.M. Poolman, C. Maity, Feng Li, L. van der Mee, C.B. Minkenberg, E. Mendes, J.H. van Esch, R. Eelkema; Nature Chemistry 5 (2013) DOI:10.1038/nchem.1617
[2] A.G.L. Olive, N. Hakimin Abdullah, I. Ziemecka, E. Mendes, R. Eelkema, J.H. van Esch, Angew. Chem. 53 (2014), DOI:10.1002/anie.201310776
[3] J. Boekhoven, A.M. Brizard, K.N. Kowlgi, G.J. Koper, R. Eelkema, J.H. van Esch, Angew. Chem. Int. Ed. 49 (2010) DOI: 10.1002/anie.201001511.
[4] J. Boekhoven, W. Hendriksen, G. Koper, R. Eelkema, J.H. van Esch, Science, 349 (2015) DOI: 10.1126/science.aac6103

Dual-phase Evolution and the Emergence of Materials Genomes

David G. Lynn Emory University

Thursday Oct 22nd 2015, 5:00-5:30

Life may best be understood as molecular information flowing at the nanometer scale. The diversity of DNA sequences, both known and yet to be characterized throughout Earth's realms, along with the vast repertoire of catalytic and structural forms of proteins, constitute the dynamic evolving molecular network that underpins our tree of life. Most remarkably, information flow is achieved with two foundational biopolymers locked in mutualistic synergy through three hierarchical dimensions, ultimately yielding life as we currently know it.[1,2] We will show how covalent macromolecular synthesis can be tied to non-covalent folding and supramolecular associations in a single molecular scaffold, and define critical chemical and physical functions emerging from tension created from combining dynamic chemical/physical networks. Feedback processes, both chemical and physical, are expressed across all dimensions of the network.[3-5] These results establish that the range and degree of order accessible to various materials can yield diverse functional phases, from compartments to metabolism and informational polymers, and demonstrate that specific phases can be propagated, selected, and exploited for their unique structural and chemical functions. Further, mutualistic scaffolds are available for the creation of cooperative functions and supramolecular order. Taken together, there is an emerging space for autonomous dynamic networks poised to expand access to materials genomes.

Abstract Image

[1] Goodwin JT; Lynn DG. 2014. Alternative Chemistries of Life - Empirical Approaches. Emory University, ISBN: 978-0-692-24992-5.
[2] Goodwin JT, Mehta AK, Lynn DG. 2012 Digital and Analog Chemical Evolution. Acc Chem Res. 45, 2189-99. DOI: 10.1021/ar300214w
[3] Liang, C; Smith-Carpenter, J; Ni, R.; Childers, W.S.; Mehta, A.K.; Lynn, D.G. 2014 Kinetic Intermediates in Amyloid Assembly, J. Am. Chem. Soc. 136: 15146-9. DOI: 10.1021/ja508621b.
[4] Anthony NR, Mehta AK, Lynn DG, Berland KM 2014 Mapping amyloid-β (16-22) nucleation pathways using fluorescence lifetime imaging microscopy. Soft Matter, 10: 4162-4172. DOI: 10.1039/C4SM00361F
[5] Guo, Q, Mehta, AK, Grover, MA, W. Chen, W., Lynn, DG, Chen, Z. 2014. Shape Selection and Multi-stability in Helical Ribbons, App Phys Letts, 104: 211901, DOI: 10.1063/1.4878941

Elasticity and Friction of 1D and 2D Systems: from DNA to Graphene

Elisa Riedo CUNY Advanced Science Research Center & City College of New York

Friday Oct 23rd 2015, 9:15-9-45

The scope of this research is to understand, predict and manipulate the relationship between mechanical properties and size, chemistry and structure of matter with reduced dimensions, such as 1D and 2D materials. Two-dimensional (2D) materials, such as graphene and MoS2, are few-atomic-layer thick films with strong in-plane bonds and weak interactions between the layers. The in-plane elasticity has been widely studied in bending experiments where a suspended film is deformed substantially; however, little is known about the films' elastic modulus perpendicular to the planes, as the measurement of the out-of-plane elasticity of supported 2D films requires indentation depths smaller than the films' interlayer distance. Here, we report[1] on sub-Å-resolution indentation measurements of the perpendicular-to-the-plane elasticity of 2D materials. Our indentation data, combined with semi-analytical models and density functional theory are then used to study the perpendicular elasticity of a few-layers thick graphene and graphene oxide films. We find that the perpendicular Young’s modulus of graphene oxide films reaches a maximum when one complete water layer is intercalated between the graphitic planes. This non-destructive methodology can map interlayer coupling and intercalation in 2D films. In the second part of the seminar we will discuss our recent results of the stretching elastic modulus of short DNA molecules with RNA intrusions[2].

[1] Yang Gao, Si Zhou, Suenne Kim, Hsian-Chih Chiu, Daniel Nélias, Claire Berger, Walt de Heer, Laura Polloni, Roman Sordan, Angelo Bongiorno and Elisa Riedo, "Elastic coupling between layers in two-dimensional materials", Nature Materials 14, 714–721 (2015), DOI: 10.1038/nmat4322
[2] Hsiang-Chih Chiu, Kyung Duk Koh, Marina Evich, Annie L. Lesiak, Markus W. Germann, Angelo Bongiorno, Elisa Riedo and Francesca Storici "How RNA intrusions change DNA structure and elastic properties", Nanoscale 6 (17), 10009-10017 (2014) DOI: 10.1039/C4NR01794C.

Seek, Destroy and Heal: Enzyme-Responsive Nanoparticles as In Vivo Targeted Delivery Systems

Nathan C. Gianneschi UC San Diego

Friday Oct 23rd 2015, 11.45-12:15

The goal of targeted therapeutics and molecular diagnostics is to accumulate drugs or probes at the site of disease in higher quantities relative to other locations in the body. To achieve this, there is tremendous interest in the development of nanomaterials capable of acting as carriers or reservoirs of therapeutics and diagnostics in vivo.[1] Generally, nanoscale particles are favored for this task as they can be large enough to function as carriers of multiple copies of a given small molecule, can display multiple targeting functionalities, and can be small enough to be safely injected into the blood stream. The general goal is that particles will either target passively via the enhanced permeability and retention (EPR) effect, actively by incorporation of targeting groups, or by a combination of both.[2] Nanoparticle targeting strategies have largely relied on the use of surface conjugated ligands designed to bind overexpressed cell-membrane receptors associated with a given cell-type.[3] We envisioned a targeting strategy that would lead to an active accumulation of nanoparticles by virtue of a supramolecular assembly event specific to tumor tissue, occurring in response to a specific signal. The most desirable approach to stimuli-induced targeting would be to utilize an endogenous signal, specific to the diseased tissue itself, capable of actively targeting materials introduced via intravenous (IV) injection. We present the development of nanoparticles capable of assembling in vivo in response to selective, endogenous, biomolecular signals. For this purpose, we utilize enzymes as stimuli, rather than other recognition events, because they are uniquely capable of propagating a signal via catalytic amplification. We will describe the preparation of highly functionalized polymer scaffolds utilizing ring opening metathesis polymerization, their development as in vivo probes and their utility as a multimodal imaging platform and as drug carriers capable of targeting tissue via a new mechanism.

Abstract Image

[1] J. A. Hubbell, A. Chilkoti, Science, 337, 303-305.
[2] a) Y. Matsumura, H. Maeda, Cancer Res 1986, 46, 6387-6392; b) D. Peer, J. M. Karp, S. Hong, O. C. Farokhzad, R. Margalit, R. Langer, Nat. Nanotechnol. 2007, 2, 751-760.
[3] a) W. Arap, R. Pasqualini, E. Ruoslllahti, Science 1998, 279, 377-380; b) D. Pan, J. L. Turner, K. L. Wooley, Chem. Commun. 2003, 2400-2401; c) A. R. Hilgenbrink, P. S. Low, J. Pharm. Sci. 2005, 94, 2135-2146. .

Correlated Structure and Photophysics in Supramolecular Polymer Films

Adam B. Braunschweig University of Miami

Thursday Oct 22nd 2015, 12:15-12:45

Synthetic supramolecular systems provide insight into how complex biological systems organize as well as produce self-organized systems with functionality comparable to their biological counterparts. The assembly of a system composed of diketopyrrolopyrrole (DPP) donors with chiral and achiral side chains and perylene diimide (PDI) acceptors into supramolecular polymers will be described. These donor-acceptor polymers incorporate singlet fission electron donors into active layer films in an attempt to increase substantially the efficiencies of charge generation, but challenges related to film preparation and the characterization and spin and charge interactions within electron donors and acceptors remain. Using transient absorption spectroscopy, we report that films of several DPP donors[1,2] undergo singlet fission (Figure). Upon combination with PDI acceptors into hierarchical films, singlet fission is outcompeted by charge separation to [mDPP⚫+-PDI⚫-]1 that undergoes radical pair intersystem crossing to [mDPP⚫+-PDI⚫-]3 followed by spin-selective charge recombination to 3*mDPP.[3] We describe how film formation is guided by orthogonal noncovalent interactions, thereby simplifying the film preparation, and how recombination lifetimes increase a thousand fold because of charge and spin delocalization or charge hopping through the film.[3] Active layer design, where structure and spin dynamics are considered synergistically, could lead to a new understanding of emergent spin dynamics and breakthroughs in organic optoelectronics.

Abstract Image

Figure. PDI and mDPP assemble into supramolecular polymer ropes as a result of complementary a) H-bonding, and b) π-stacking along an orthogonal axis drives the formation of homochiral superstructures that c) undergo photoinduced charge separation to produce long-lived charge carriers.

[1] S. Rieth, et al. J. Phys. Chem. C 2013, 117, 11347-11356.
[2] D. Ley, et al. J. Am. Chem. Soc. 2014, 136, 7809-7812.
[3] C. X. Guzman, et al. J. Phys. Chem. C 2015, 119, 19584-19589.

Random Organization, Hyperuniformity and Photonic Bandgaps

Paul Chaikin New York University

Thursday Oct 22nd 2015, 11:30-12:00

A periodically sheared non-Brownian suspension undergoes collisions which allow the particles to explore new configurations. Below a critical strain the system evolves and arranges itself until collisions no longer occur and an absorbing state is reached. A simple model “Random Organization” well describes the process. We have studied similar phenomena in granular systems where limit cycles rather than reversible paths are found as absorbing states. Recent work by Hexmer and Levine show that at criticality absorbing state systems produce hyperniform particle correlations. Together we have most recently found that reactivating, "kicking", the absorbing state leads to the most hyperuniform configuration possible equivalent to the uniformity of a crystal but with no periodicity or long range order.

Hyperuniform systems have particle number fluctuations which decrease more rapidly with window size than do random systems. Torquato and Steinhardt suggested that hyperuniformity rather than periodicity is responsible for spectral gaps in wavelike materials. We have constructed Hyperuniform disordered systems (HUDS) on a cm (microwave) and micron (IR) scale and find large isotropic photonic bandgaps. Further we have shown that such HUDS photonic materials can be modified to allow arbitrary waveguides, switching and resonant cavities.

Time-Programmed Self-Assemblies and Dynamic Materials

Andreas Walther Aachen University

Friday Oct 23rd 2015, 9:45-10:15

We present a generic concept to program lifetimes of self-assemblies in closed systems. The key concept relies on separating the kinetic steps of formation and destruction of self-assemblies by controlling the availability of chemicals needed (i) to promote the assembly from the disassembled state A to the self-assembled state B (promoter) and (ii) its subsequent decay (deactivator; from B to A, Scheme 1). We conceive dormant deactivators that slowly chemically degrade, or are activated by introduction of the promoter, to furnish the active deactivator. The combination of fast promoters and dormant deactivators in a single injection enables a kinetic balance to establish a rationally designed, autonomously self-regulating, transient pH-state. Coupling of this non-equilibrium state to fuel pH-switchable self-assemblies allows predicting their assembly/disassembly fate in time - similar to a precise self-destruction mechanism.[1,2] The duration of this transient state can be tuned over four orders of magnitude: from minutes to days. We demonstrate the versatility of this platform approach by programming the lifetimes of self-assemblies of block copolymers, nanoparticles and peptides. Programming such autonomously self-regulating, transient states into switchable self-assemblies enables a new level of control in switchable materials and allows advancements towards dynamic materials, spawning self-regulation and transient memory functions.

[1] Heuser, T.; Weyandt, E.; Walther, A. Biocatalytic Feedback-Driven Temporal Programming of Self-Regulating Non-Equilibrium Peptide Hydrogels Angew. Chem. Int. Ed., accepted doi: 10.1002/anie.201505013 (2015).
[2] Heuser, T.; Steppert, A.-K.; Molano-Lopez, C.; Zhu, B.; Walther, A.: A Generic Concept to Program the Time Domain of Self-Assemblies with a Self-Regulation Mechanism Nano Lett., 15, 2213, (2015).

Geometrical Basis for Symmetry Breaking and Multi-functionality

Stoyan Smoukov University of Cambridge

Friday Oct 23rd 2015, 3:15-3:45

Symmetry breaking in living systems is often achieved by coupling of chemical reactions and selective growth to achieve shape change. In many systems, however, novel mechanisms are discovered, such as nonlinearities in material properties that can cause the symmetry breaking. It is important to understand such new mechanisms as they could help us direct growth, shape change, and be a source of morphogenesis and adaptability in artificial systems.

Active materials, exhibiting dynamic shape-change behaviour, have shown much promise for engineering multi-functionality. They are useful for developing novel artificial muscles, adaptable structures, and for bringing insights into the processes or morphogenesis.

We show examples of engineering the symmetry breaking and dynamics for multiple structures and processes, on multiple lengthscales – from nanometers to centimeters. We demonstrate the formation of Janus and other asymmetric particles, which form as a result of coupling of chemical reactions to non-linear mechanical properties of materials[1,2]. We also demonstrate the opposite effects – how mechanical deformations and molecular interactions can help one simplify chemical syntheses[3].Further, we also demonstrate that even without reactions, the material properties and geometry alone could cause symmetry breaking. By bending a spherical cap and a cone shell, we characterize the instabilities and show novel behaviors, both static and dynamic.

Abstract Image

Upon inversion of the magnetic spherical cap, for example, using high speed video, we have captured an intermediate asymmetric quasi-stable state. The results are reproduced faithfully by a finite element model analysis where we only put in the material properties and the remote forces exerted on the cap by a magnetic field[4]. Equilibrium deformations also show symmetry breaking. We have focused on another simple shape – a conical shell. Upon deformation one can achieve in a controlled way symmetry breaking with 2-, 3-, 4- and 5- sided polygonal shapes. We explore the energetics of these transitions.

Finally, we have achieved combinatorial multifunctionality by foregoing pure chemical approaches to introduce multiple functions only at the molecular level. Instead, we use controlled internal phase separation in a material to introduce existing materials with already optimized functions, and interweave them into one. We show how this spatial separation of just 3 phases and 20 functions would lead to over 8000 trifunctional materials. We demonstrate such materials and in addition to the separate material functions of the phases we show emerging effects.

[1] Ding T, Baumberg J, Smoukov SK, Harnessing Nonlinear Rubber Swelling for Bulk Synthesis of Anisotropic Hybrid Nanoparticles with Tunable Metal-Polymer Ratios, J. Mater. Chem. C, 2, 8745-8749 (2014) DOI: 10.1039/c4tc01660b
[2] Wang Y, Ding T, Baumberg J, Smoukov SK, Symmetry Breaking Polymerization: One-Pot Synthesis of Plasmonic Hybrid Janus Nanoparticles, Nanoscale 7, 10344-10349 (2015) DOI: 10.1039/c5nr01999k
[3] Marshall, JE, Gallagher S, Terentjev EM, Smoukov SK, Anisotropic Colloidal Micromuscles from Liquid Crystal Elastomers, J. Am. Chem. Soc., 136 (1), 474-479 (2014), DOI: 10.1021/ja410930g
[4] Loukaides E, Seffen KA, Smoukov SK, Magnetic Actuation and Transition Shapes of a Bistable Spherical Cap, Intl. J. Smart & Nano Mater. (2015) DOI: 10.1080/19475411.2014.997322
[5] Khaldi Khaldi A, Plesse C, Vidal F, Smoukov SK, Designing Smarter Materials with Interpenetrating Polymer Networks, accepted in Adv. Mater. 27 (30), 4418–4422 (2015) DOI: 10.1002/adma.201500209

Contributing Speakers

Engineering with biomolecular motors

Henry Hess Columbia University

Thursday Oct 22nd 2015, 4:30-5:00

Motor proteins, such as kinesin, can serve as biological components in engineered nanosystems. A proof-of-principle application is a 'smart dust' biosensor for the remote detection of biological and chemical agents, which is enabled by the integration of recognition, transport and detection into a submillimeter-sized microfabricated device. The development of this system has revealed a number of challenges in engineering at the nanoscale, particularly in the guiding, activation, and loading of kinesin-powered molecular shuttles. Overcoming these challenges requires the integration of a diverse set of technologies, illustrates the complexity of biophysical mechanisms, and enables the formulation of general principles for nanoscale engineering.

Molecular motors also introduce an interesting new element into self-assembly processes by accelerating transport, reducing unwanted connections, and enabling the formation of non-equilibrium structures. The formation of nanowires and nanospools from microtubules transported by kinesin motors strikingly illustrates these aspects of motor-driven self-assembly.

On Probing Molecular Conformation of Microtubules by Second Harmonic Generation

Hyungsik Lim Hunter College, The City University of New York

Thursday Oct 22nd 2015, 12:20-12:40

Microtubule (MT) is a component of cytoskeleton playing an important role in a variety of cellular processes. Altering the structure of MT is a crucial mechanism of modulating the function, but it is difficult to measure the in vivo conformation. We present here the use of second-harmonic generation (SHG) for acquiring information about the architecture of MTs in living tissue. Axonal MTs were imaged by polarization-resolved SHG and anisotropy in the molecular structure was determined by means of the second-order tensor analysis. The feasibility of the second-order tensor analysis was studied for measuring the conformational changes induced by MT-stabilizing drug. It demonstrates that the new optical contrast may be useful for investigating the dynamics of MT cytoskeleton in vivo.

Quantifying Signal Propagation and Conformational Changes in Allosteric Proteins

Vanessa Ortiz Columbia University

Friday Oct 23rd 2015, 10:35-10:55

Allostery connects subtle changes in a protein's potential energy surface to significant changes in its function. Understanding this phenomenon and predicting its occurrence are major goals of current research in biophysics and molecular biology. At the microscopic level, protein energetics is characterized by a balance between different inter-atomic interactions, with small perturbations at specific sites potentially leading to major changes in conformational distributions. Therefore, a thorough characterization of allostery requires understanding of two aspects: (1) how energy propagates through the protein structure, and (2) which regions of the protein are likely to suffer structural deformations as a response to the applied perturbation.

On the first aspect, we have developed a new energy-based network analysis method, which allows characterization of signaling pathways in proteins. The method assumes that signals travel more efficiently through residues that have strong inter-atomic interactions, and is able to correctly identify important residues for allosteric signal propagation in the allosteric enzyme imidazole glycerol phosphate synthase. In addition, we introduce a quantity named energetic coupling, which is able to discriminate allosterically active mutants of a known allosterically regulated protein, the lactose repressor (LacI). Commonly used protein structure networks based on correlation coefficients or number of inter-residue contacts, are not able to reproduce our results.

On the second aspect, we show that the calculation and analysis of atomic elastic constants of LacI, highlights regions that are particularly prone to suffer structural deformation, and are experimentally linked to allosteric function. The calculations are based on a high resolution, all-atom description of the protein, but are computationally inexpensive when compared to methods employing the same resolution. Lower resolution models are shown to yield qualitatively different results, indicating the importance of adequately describing the local environment surrounding the different parts of the protein.

Enzymatic Synthesis of Size Controlled, Water Soluble Quantum Dots

Bryan W. Berger Lehigh University

Thursday Oct 22nd 2015, 2:55-3:15

Biological systems have evolved several unique mechanisms to produce inorganic nanomaterials of commercial interest. Furthermore, bio-based methods for nanomaterial synthesis are inherently "green", enabling low-cost and scalable production of nanomaterials under benign conditions in aqueous solutions. However, achieving regulated control of the biological processes necessary for reproducible, scalable biosynthesis of nanomaterials remains a central challenge. This is especially true of quantum dots (QDs), which are nanocrystals made from seminconducting metals whose diameter is smaller than the size of its exciton Bohr radius, leading to size-dependent changes in their optical properties. Several studies have described production of QDs from biological systems, but without control over particle size or composition.

In this work, we describe the isolation, selection and characterization of an enzyme capable of metal sulfide QD synthesis with control over nanocrystal size.

We estimate yields on the order of grams per liter from batch cultures under optimized conditions, and are able to reproduce the entire size range of CdS QDs described in literature. Furthermore, we are able to generalize this approach to not only cadmium, but PbS QDs as well. Investigation of purified QDs using ESI-MS reveals several putative proteins that may be involved in biosynthesis, and current work is aimed at improving photoluminescent properties as well as long-term aqueous stability. Nonetheless, our approach clearly demonstrates the ability of biological systems to produce advanced, functional nanomaterials, and provides a template for engineering biological systems to high-value materials such as QDs at cost and scale.

Catalytic Shakers and Swimmers: Control of Vesicle Membrane Permeability and Chemotaxis of "Matchstick" Colloids

Corinna M. Preuss The University of Warwick

Friday Oct 23rd 2015, 12:40-1:00

In this talk we will present two of our latest findings on the fabrication and out of equilibrium behavior of supracolloidal soft matter systems which contain catalytic manganese oxide. In the first example we will show that the membrane permeability of polymer vesicles which contain manganese oxide particles in their membrane can be regulated upon their response to hydrogen peroxide. We will demonstrate that we can fine-tune the release profiles of encapsulated ingredients. In the second example we will describe in detail the synthesis of anisotropic matchstick shaped particles which have a catalytically enriched head of manganese oxide. We will show that these particles can self-propel upon exposure to hydrogen peroxide, and more importantly, have the ability to undergo chemotaxis when exposed to a gradient of this fuel.

Active Colloids via Controlled Dewetting

Stefano Sacanna New York University

Friday Oct 23rd 2015, 10:55-11:15

Anisotropic colloids with complex shapes and tunable compositions, are synthesized in bulk via an emulsion-based method. Solid particles are systematically dewetted from polymerizable micro-droplets yielding a whole new class of asymmetric colloids. We demonstrate that the method is applicable to a broad spectrum of materials, from polymer particles to inorganic semiconductors and magnetic materials. This synthetic methodology represent a new and general tool for designing functional colloids, such as micro swimmers, colloidal surfactants and self-assembling building blocks.

Light-emitting Self-assembled Peptide Nucleic Acids Exhibit Both Stacking Interactions and Watson-Crick Base Pairing

Or Berger Tel Aviv University

Friday Oct 23rd 2015, 10:15-10:35

The two main branches of bionanotechnology involve the self-assembly of either peptides or DNA. Peptide scaffolds offer chemical versatility, architectural flexibility and structural complexity, but they lack the precise base pairing and molecular recognition available with nucleic acid assemblies. Here, inspired by the ability of aromatic dipeptides to form ordered nanostructures with unique physical properties, we explore the assembly of peptide nucleic acids (PNAs), which are short DNA mimics that have an amide backbone. All 16 combinations of the very short di-PNA building blocks were synthesized and assayed for their ability to self-associate. Only three guanine-containing di-PNAs-CG, GC and GG-could form ordered assemblies, as observed by electron microscopy, and these di-PNAs efficiently assembled into discrete architectures within a few minutes. The X-ray crystal structure of the GC di-PNA showed the occurrence of both stacking interactions and Watson-Crick base pairing. The assemblies were also found to exhibit optical properties including wide-range excitation-dependent fluorescence in the visible region.

A Supramolecular Shield to Overcome Aβ42 Toxicity

Silvia Sonzini University of Cambridge

Thursday Oct 22nd 2015, 12:00-12:20

Interactions between peptides and proteins are at the base of several biological processes both physiological, such as enzyme catalysis and recognition at the cell membrane, and pathogenic, as protein aggregation.[1,2] Being able to mimic and improve the understanding of these interactions via a synthetic host-guest system is a great challenge within the field of supramolecular chemistry. Through a biophysical approach, we were able to unveil the rules of binding interactions between peptides, particularly aromatic residues, and CB[8], one of the macrocyclic hosts within the cucurbit[n]uril family.[3,4] Amongst the possible applications, we specifically focused on investigating the aggregation of Aβ42 sequence, one of the peptides involved in the onset of Alzheimer's disease, whose mechanism of toxicity still remains elusive.[2,5] Our supramolecular strategy, involving CB[8] specifically encapsulating aromatic residues in Aβ42 , was able to alter the structural mobility and exposure of hydrophobic residues at the peptide surface.[6] The data obtained by ThT assay, circular dichroism, transmission electron microscopy and dynamic light scattering suggested that the oligomers formed by Aβ42-CB[8] complexes exhibit an increased aggregation rate, still retaining amyloid features. Furthermore, Aβ42 exhibited a significant decrease in toxicity in the neuronal cell line SH-SY5Y in the presence of CB[8] and fluorescence imaging suggested a limited cell uptake of Aβ42 administrated in conjunction with CB[8]. Hence, by specifically shielding the aromatic residues through a supramolecular approach, we overcame the harmful stage of the aggregation of Aβ42 and disclosed the connection between the peptide toxicity and structural features, thus supplying a new specific target to counterattack Alzheimer's disease.

[1] C. M. Dobson "Protein misfolding, evolution and disease" Trends Biochem. Sci. (1999) 24, 329-332.
[2] C. M. Dobson "Protein folding and misfolding" Nature (2003) 426, 884-890. [3] S. Sonzini, S. T. J. Ryan and O. A. Scherman "Supramolecular dimerisation of middle-chain Phe pentapeptides via CB[8] host-guest homoternary complex formation" Chem. Commun. (2013) 49, 8779-8781.
[4] S. Sonzini, A. Marcozzi, R. J. Gubeli, P. Ravn, C. F. Van Der Walle, A. Herrmann and O. A. Scherman "Recognition of an internal protein motif by CB[8] heteroternary complexation" Manuscript in preparation.
[5] D. Eisenberg and M. Jucker "The Amyloid State of Proteins in Human Diseases" Cell (2012) 148, 1188-1203.
[6] S. Sonzini, H. F. Stanyon and O. A. Scherman "A supramolecular host unveils the connection between structure and toxicity of Aβ42" Manuscript submitted

Transient Peptide Nanostructures

Charalampos G. Pappas University of Strathclyde and CUNY Advanced Science Research Center

Thursday Oct 22nd 2015, 4:15-4:30

Living systems are exceptionally capable of changing their structures in response to changing situations, largely through molecular assembly and dis-assembly via competing pathways under the influence of chemical fuels. Dynamic processes in living systems are regulated by balancing thermodynamic and kinetic aspects. The rapid responses required for biological survival are achieved through catalytic amplification, which enables dynamic change under otherwise constant conditions. Indeed, enzymes are increasingly used to activate or deactivate a variety of functions in designed, peptide-based nanostructures, including self-assembly. There is tremendous interest in developing man-made analogues of non-equilibrium, transient nanostructures, which provides insights into the workings of biology's remarkable ability to adapt to changing environments and may find use in future adaptive nanotechnologies. Herein, we report on two different ways to trigger transience. First, the use of ultrasonic waves (80 KHz), to achieve transient reorganization of supramolecular peptide nanostructures (from fibres to micelles and twisted fibres according to the peptide sequence used), which revert back to the original state when sound is switched off. The changes observed were due to an altered balance between H-bonding and π-stacking, giving rise in changes in chiral organisation of peptide building blocks.[1] Second, we demonstrate peptide sequence dependent formation of supramolecular nanostructures based on biocatalytic assembly and hydrolysis in chemically fuelled tripeptides using chymotrypsin.[2] We sought to achieve control of the kinetics and consequent lifetime of the nanostructures formed by chemical design.

[1] Pappas et al. Mater. Horiz., 2015, 2, 198-202.
[2] Pappas et al. Angew. Chem. Int. Ed., 2015, 54, 8119-8123.

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Grant funding provided by Army Research Office
Sponsor: Army Research Office