California NanoSystems Institute
CNSI
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March 16, 2004

Angela Belcher
Massachusetts Institute of Technology
Virus-Based Genetic Toolkit for the Directed Synthesis of Magnetic and Semiconducting Nanowires
Abstract:

The exploitation of the self-assembly motifs employed by the M13 bacteriophage to produce a biological scaffold provides a means of generating a complex, highly ordered, and economical template for the general synthesis of single crystal nanowires. By introducing programmable genetic control over the composition, phase and assembly of nanoparticles, a generic template for the universal synthesis of a variety of materials can be realized. Further advances in the fabrication of nanoscale materials and devices can be achieved through modification of the remaining four proteins in the virus to incorporate device-assembly directors. The ability of viruses to form liquid crystal systems, based on their shape anisotropy, is another promising route for the assembly of virus-based nanowires into well ordered arrays on multiple length scales.

We report a virus-based scaffold for the synthesis of single crystal ZnS, CdS and free-standing L10 CoPt and FePt nanowires, with the means of modifying substrate specificity through standard biological methods. Peptides selected through an evolutionary screening process that exhibit control of composition, size, and phase during nanoparticle nucleation have been expressed on the highly ordered filamentous capsid of the M13 bacteriophage. The incorporation of specific, nucleating peptides into the generic scaffold of the M13 coat structure provides a viable template for the directed synthesis of semiconducting and magnetic materials. Removal of the viral template via annealing promoted oriented aggregation-based crystal growth, forming individual crystalline nanowires. The unique ability to interchange substrate specific peptides into the linear self-assembled filamentous construct of the M13 virus introduces a material tunability not seen in previous synthetic routes. Therefore this system provides a genetic tool kit for growing and organizing nanowires from semiconducting and magnetic materials.

March 09, 2004

Carlos Bustamante
UC Berkeley
Grabbing the Cat by the Tail: Studies of DNA Packaging by Single 029 Bacteriophage Particles Using Optical Tweezers
Abstract:

I will present our recent results on the packaging of DNA by the connector motor at the base of the head of bacteriophage Ø29. As part of their infection cycle, many viruses must package their newly replicated genomes inside a protein capsid to insure its proper transport and delivery to other host cells. Bacteriophage Ø29 packages its 6.6 mm long double-stranded DNA into a 42 nm dia. x 54 nm high capsid via a portal complex that hydrolyses ATP. This process is remarkable because entropic, electrostatic, and bending energies of the DNA must be overcome to package the DNA to near-crystalline density. We have used optical tweezers to pull on single DNA molecules as they are packaged, thus demonstrating that the portal complex is a force generating motor. We find that this motor can work against loads of up to ~57 picoNewtons on average, making it one of the strongest molecular motors ever reported. Movements of over 5 mm are observed, indicating high processivity. Pauses and slips also occur, particularly at higher forces. We establish the force-velocity relationship of the motor and find that the rate-limiting step of the motor's cycle is force dependent even at low loads. Interestingly, the packaging rate decreases as the prohead is filled, indicating that an internal pressure builds up due to DNA compression. We estimate that at the end of the packaging the capsid pressure is ~15 MegaPascals, corresponding to an internal force of ~50 pN acting on the motor. The biological implications of this internal pressure and the mechano-chemical efficiency of the engine are discussed.

March 02, 2004

Xiang Zhang
UCLA
Engineering Sub-Wavelength Photonic Meta-Structures: A Route Toward Nano-Plasmonics and Superlensing
Abstract:

Recent theory predicted a new class of meta structures made of engineered sub wavelength entities - meta "atoms" and "molecules" which enable the unprecedented electromagnetic properties that do not exist in the nature. For example, artificial plasma and artificial magnetism, and super lens that focuses far below the diffraction limit. If the theory is correct and these unique properties can be realized, it will have profound impact in wide range of applications such as nano-scale imaging, nanolithography, and integrated nano photonics. These photonic "atoms" usually form highly complex structures which present a critical need in developing truly 3D micro and nano-manufacturing techniques which are not available presently.

In the first part of this presentation, I’ll discuss a few micro and nano fabrication technologies that we developed for engineering complex meta-structures. In the second part, I’ll discuss sub-? photonic "atoms" and "molecules" and the potential applications in nano-scale imaging and lithography. We demonstrated, for the first time, the high frequency magnetic activity at THz generated by artificially structured "molecule resonance", as well as the artificial plasma. Our experiment also confirmed the key proposition of super lens theory by using surface plasmon. We indeed observed preliminary superlensing at near-field. The surface plasmon indeed promises an exciting engineering paradigm of "optical frequency and x-ray wavelength". This talk will be concluded with a vision of the nano-manufacturing that will enable the new nano plasmonics and other applications.

February 24, 2004

Todd Yeates
UCLA
Principles of Protein Assembly in Nature, Disease, and Designed Structures
Abstract:

One of the hallmarks of biological macromolecules is their ability to recognize and bind specifically to other macromolecules of distinct or like identity. Natural protein self-assembly leads to a wide range of biological architectures. Spontaneous or unnatural protein self-assembly underlies critical laboratory phenomena such as protein crystallization, as well as numerous amyloid diseases. Symmetric protein assembly also provides new strategies for designing novel protein-based materials with sizes or length scales in the mid-nanometer range. Principles and progress will be described in the areas of protein assembly, aggregation, and design.

References:

Padilla, JE, Colovos, C, and Yeates, TO. (2001). Nanohedra: using symmetry to design self assembling protein cages, layers, crystals, and filaments. PNAS 98, 2217-21.

Yeates TO, Padilla JE. (2002). Designing supramolecular protein assemblies. Curr. Opin. Struct. Biol. 12, 464-70.

February 17, 2004

Carlo Montemagno
UCLA
Integrative Technology - 21st Century Technology for 21st Century Engineers
Abstract:

Integrative technology, the merging of nanotechnology, biotechnology and informatics offers an opportunity for realizing true advances in the manner in which technology interacts with humanity. Using the power of nanotechnology to manipulate matter, that is the placing of molecule’s where we want, when we want, to perform functions that we want. Using the inspiration of biotechnology both to co-opt the tools of molecular manufacturing and to provide a baseline understanding of the way nature manipulates matter and information. And finally, using Informatics to create a robust framework for transforming the information implicit in molecular and larger scale interactions to engineer Complex Adaptive Systems that exhibit embedded higher-order behavior. Collectively these technologies established the basis for Integrative Technology, a new IT. The first examples of the implementation of Integrated Technology are manifested in the synthesis of a new class of smart materials. These materials have the potential to emulate much of the functionality associated with living systems such as the active transport and transformation of matter and information and, the transduction of energy into different forms. We will present the details of the technological demands and the results of efforts associated with the production of these new functional materials. Elements of the discussion will include the genetic engineering of active biological molecules into engineering building blocks, the precision assembly of these molecules into a stable, "active" material and, the promise of embedding intelligent behavior into the matrix of the assembled matter.

February 10, 2004

Uri Banin
The Hebrew University, Jerusalem
Semiconductor Quantum Rods: Synthesis, Properties and Applications
Abstract:

Semiconductor nanocrystals manifest unique size, shape and composition dependent properties with both basic and applied significance and are emerging building blocks of devices in Nanotechnology. Modifications of the colloidal synthesis conditions provide shape control allowing for the preparation of rod shaped particles, quantum rods. The talk will describe methods to prepare semiconductor rods of different materials comparing seeded and surfactant-controlled growth methods. Such length controlled rods manifest the transition from a zero dimensional quantum dot, to a one-dimensional quantum wire, which was studied by a combination of optical and tunneling spectroscopies. We will also discuss advantages or the rod architecture over dots, in relation to optical gain.

References:

ShiHai Kan, Taleb Mokari, Eli Rothenberg, and Uri Banin "Synthesis and properties of semiconductor quantum rods with cubic lattice" Nature Materials 2, 155-158 (2003).

David Katz, Tommer Wizansky, Oded Millo, Eli Rothenberg, Taleb Mokari and Uri Banin "Size dependent tunneling and optical spectroscopy of CdSe quantum rods" Phys Rev. Lett. 89, 086801, (2002).

Miri Kazes, David Y. Lewis, Yuval Ebenstein, Taleb Mokari and Uri Banin "Lasing from semiconductor quantum rods in a cylindrical microcavity" Adv. Mat. 14, 317-321 (2002).

February 03, 2004

Kevin Plaxco
UCSB
Better Living Through Biosensors
Abstract:

Contemporary analytical techniques can, given sufficient time, money and resources, detect trace amounts of almost any analyte. In contrast there exists no general solution to the problem of analyte detection in settings, such as civil defense and in the developing world, where speed, cost and convenience are critical constraints. In order to meet the challenge of analyte detection that is not only sensitive and selective, but also convenient and cost-effective, we are developing optical and electronic biosensor platforms based on the binding-induced folding of peptides, proteins and DNA. Our protein folding-based optical sensors provide a rapid, sensitive detection architecture generalizable to a wide range of macromolecular analytes. Our analogous electronic DNA sensor is reagentless, reusable, highly miniaturizable and combines picomolar sensitivity with greater than million-fold selectivity. The sensitivity, gain and background suppression of these folding-based sensors suggest that they may provide a means for the inexpensive and operationally convenient detection of a wide range of clinically, defense and environmentally relevant materials.

January 29, 2004

Julius Rebek, Jr.
Scripps Research Institute
The Inner Space of Molecules
Abstract:

Molecular recognition is the science of weak, intermolecular forces acting on complementary surfaces. This lecture follows the course of research that elaborates synthetic structures with concave surfaces into receptors. Complementarity of size, shape and chemical surface makes possible the recognition of smaller convex target molecules. Concave receptors outfitted with additional functionality are shown to give rise to high reactivity; an example of an amine in a cavitand bearing an inwardly-directed carboxyl group is shown below. The receptors make contact with increasingly larger fractions of the targets surfaces. Eventually, the target is completely encapsulated by the receptor. The use of capsules with nanoscale dimensions in recognition, assembly and polymerization is described.

References:

A.R. Renslo, J. Rebek, Jr. Molecular Recognition and Introverted Functionality. Angew. Chemie., Int. Ed., Engl. 2000, 39, 3281-3283.

R.K. Castellano, C. Nuckolls, S.H. Holger Eichorn, M.R. Wood, A.J. Lovinger, and J. Rebek, Jr. Hierarchy of Order in Liquid-Crystalline Polycaps. Angew. Chem. Int. Ed. Engl. 1999, 38, 2603-2606.

R.K. Castellano, S.L. Craig, C. Nuckolls, J. Rebek, Jr. Detection and Mechanistic Studies of Multi-Component Assembly by Fluorescence Resonance Energy Transfer. J. Am. Chem. Soc., 2000, 122, 7876-7822.

R.K. Castellano, R. Clark, S.L. Craig, C. Nuckolls, J. Rebek, Jr. Emergent Mechanical Properties of Self-Assembled Polymeric Capsules. Proc. Natl. Acad. Sci., U.S.A., 2000, 97, 12418-12421.

January 20, 2004

Luisa de Cola
University of Amsterdam
Photo-and Electroresponsive Materials
Abstract:

Electro(chemi)luminescent materials based on metal complexes for electronic or diagnostic applications will be described. We have recently shown that is possible to obtain materials that can switch the color of the emission between green and red changing the applied voltage. The use of zeolite as hosting unit for dyes in combination with energy donor molecules (metal complexes) used as stoppers will be illustrated. Photoresponsive dendrimers and dendrons and their assembly with metal complexes or on surfaces will be shown.

References:

Electroluminescent device with reversible switching between red and green emission S. Welter*, K. Brunner†, J. W. Hofstraat*† & L. De Cola*
*Molecular Photonics Group, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WVAmsterdam, The Netherlands
† Philips Natuurkundig Laboratorium, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands

Dendritic nanodevices Photo-induced processes in dendrimers Anouk Dirksen, Luisa De Cola *
Universiteit van Amsterdam, IMC, Molecular Photonic Group, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands Received 12 May 2003; accepted 18 August 2003
January 13, 2004

Mark Ratner
Northwestern University
Molecular Electronics: Transport, and a Bit Beyond
Abstract:

Using molecules as electronic components is a challenge to our understanding of matter at both the continuum and the molecular levels. This talk will discuss some simple notions for how to make a cylindrical micelle by self - assembly, and then will move to the general theme of transport in molecular junctions. Some mechanistic ideas will be discussed, and a possible device structure using stereochemical change will be outlined.