Nanoscience NY

CUNY NY Skyline logo

Event Home


Speaker Biographies


Poster Abstracts

Soft Nano
June 18th 2015, ASRC


1. MMP-9 responsive peptides for tumor associated formation of doxorubicin releasing nanofibers

Daniela Kalafatovic*, Max Nobis, Kurt I. Anderson and Rein V. Ulijn
CUNY's Advanced Science Research Center

Expression levels of enzymes dictate the difference between health and disease in many cases, including cancer. This leads to explore strategies to incorporate enzyme sensitivity in materials where the goal is to achieve dynamic and targeted changes in material properties. Peptide amphiphiles were designed, that upon cleavage by a disease-associated enzyme reconfigure from micellar aggregates to fibres. Upon this morphological change, a doxorubicin payload could be retained in the fibres formed, which makes them valuable carriers for localised formation of fibre depots for slow release of hydrophobic anticancer drugs.

The designed PhAc-FFAGLDD and GFFLGLDD and its expected product of enzyme cleavage PhAc-FFAG and GFFLG were synthesized and characterized by AFM, FTIR, DLS, rheology and fluorescence. After the designed peptides were shown to be successful for controlling the morphology of the supramolecular aggregates based on the peptide length i.e. hydrophobicity, the enzyme triggered micelle to fibre transition was explored. Following this it was investigated whether the micelles were capable to perform as mobile vehicles for encapsulation and release of hydrophobic drugs. It was observed that the assembled fibres provide a new scaffold for prolonged drug delivery due to the partial entrapment of the drug and the intrinsic biodegradable nature of peptide carriers themselves.

Being purely peptidic these systems have the advantage of being not toxic to cells (MTT assay) and can be used as carriers for doxorubicin in vivo. When tested on animal models, the cancer growth in slowed down by administration of doxorubicin loaded peptides compared to doxorubicin only. This approach opens up the possibility of developing new (enzyme responsive) drug delivery vehicles designed to release drug payload only in the presence of the desired enzyme with potential application in cancer therapy.

2. Packing behavior manipulation of colloids

Xiao Zhong*, Michael D. Ward
New York University

Inspired by our group's work on using colloids to mimic molecular crystals, we are studying the packing behavior of spherical and disk-shaped colloids near corners with different angles using dielectrophoresis. The aim for this project is to investigate the angular effect on crystal's packing behavior. Based on the conclusion in our group's recent publication, which suggests that the packing behavior can transcend length scales from the molecular to the colloidal scale, we hope this study will shed light on understanding the angular effect on molecular crystal's packing behavior. Finally, it will help us control polymorphs of a given crystal system.

3. Synthesizing and Self-Assembling a Periodically Sequenced Polypeptide

Matthew B. Kubilius* and Raymond S. Tu
The City College of New York

Synthesizing a periodically-sequenced, useful, amphipathic peptide is challenging due to the polydispersity index increases of large molecular weight polypeptide systems. To overcome this, we designed synthetic amino acid dimers that are both amphipathic and water-soluble. When polymerized, these dimers give rise to a peptide with alternating hydrophilic/hydrophobic side groups: the typical periodicity for beta-sheet forming polypeptides. Using this approach, we can influence polydispersity in the growing polypeptide chains, controlling the kinetics of growth through transport-limited chain elongation. Our experiments show that in the absence of a micellular interface, standard bulk-phase condensation polymerization occurs. The amphipathic character of the peptide chain increases with increasing molecular weight, resulting in a polypeptide that partitions into surfactant micelles as a function of the degree of polymerization. This type of kinetically-limited growth serves to narrow the polydispersity of our periodically-sequenced polypeptide. We quantify the dynamics of chain elongation and interfacial assembly using multi-angle light scattering and mass spectrometry and define the evolving sheet-like secondary structure using circular dichroism for various peptides of differing amino acid pairs. Our results show that the peptides grown in the presence of micelles show significantly enhanced self-assembly and a narrowed polydispersity index. From this, we conclude that the transport-limited chain elongation polymerization method shows great promise in the manufacture of low-cost, interfacially assembling polypeptides.

4. Compartmentalization of Non-orthogonal Catalytic Transformations for Tandem Catalysis

Jie Lu*, Jonas Dimroth and Marcus Weck
New York University

In Nature, incompatible catalytic transformations are being carried out simultaneously by compartmentalizing each reaction. This strategy can be used for the combination of non-orthogonal artificial catalysts in tandem reactions. Herein, we take the compartmentalization concept to the synthetic realm and present an approach that allows two incompatible transition metal catalyzed transformations to proceed in one pot in tandem. Key is the site isolation of both catalysts through compartmentalization using a core-shell micellar support in an aqueous environment. The micellar support is based on amphiphilic triblock copolymers of poly(2-oxazoline)s with orthogonal functional groups on the side-chain that can be used to covalently crosslink the micelle and to conjugate two metal catalysts in different domains of the micelle. The micelle core and shell provide different microenvironments in levels of hydrophobicity for the reactions: Co-catalyzed hydration of an alkyne to form a methyl ketone proceeds in the hydrophobic core while the Rh-catalyzed asymmetric transfer hydrogenation (ATH) of the intermediate ketone into a chiral alcohol occurs in the hydrophilic shell. The catalytic reaction reaches up to 95% conversion and above 96% ee.

5. Stepwise orthogonal self-assembly of DNA-functionalized patchy particles

Xiaolong Zheng,* Yufeng Wang, Yu Wang, David J. Pine, and Marcus Weck
New York University

We site-specifically functionalize patchy colloids with oligonucleotides bearing orthogonal sticky ends, demonstrating reversible, stepwise, and orthogonal colloidal self-assembly via DNA hybridization. The colloidal particles, possessing azide moieties on the surfaces of the patch and carboxylic acids on the shell, are synthesized via a cluster-encapsulation method that affords multiple shapes and geometries, including linear, triangular, tetrahedral and trigonal dipyramidal. Two types of DNA with distinct terminal sequences are conjugated to the particle patches or shell employing two orthogonal coupling strategies: strain-promoted alkyne-azide cycloaddition and carbodiimide-mediated amidation. By fine-tuning the temperature, we can sequentially activate and deactivate the DNA-driven self-assembly on the patches and/or the shell, enabling the formation of multi-functionalized colloidal molecules and polymers.

6. Multicompartment Micelles as Catalytic Scaffolds

Aaron Cohen*, Professor Marcus Weck
New York University

This poster will discuss the synthesis and self-assembly of triphilic triblock co-polymers, which in an aqueous environment should be able to form multicompartment micelles featuring microphase separation within the hydrophobic core. In this system, each of the blocks possesses a functional "handle" and can undergo a series of orthogonal post-polymerization reactions. Using such a design, three different catalysts can be attached to the polymer, ultimately enabling one to carry out a variety of multi-step catalytic tandem reactions in one pot.

7. A coumarin-based molecular rotor as a tool to investigate the nanoscopic self-assembly

Silvio Panettieri*, Giovanni Signore, Julian Silverman, Ranieri Bizzarri, George John
The City College of New York

This work focuses on the development of a novel fluorophore belonging to the 'molecular rotor' family. Molecular rotors are compounds whose fluorescent emission is strongly affected by environmental viscosity and they represent a remarkable tool to probe viscosity non-destructively and at high spatiotemporal resolution in biological specimens as well as in polymerization reactions.

The fluorophore developed is a coumarin-based molecular rotor that displays viscosity-dependent photophysical behavior as well as a marked solvatochromism. This unique combination of environmental responses has been thoroughly investigated via both NMR spectroscopy to unravel interesting structural features and fluorescence spectroscopy with the goal of characterizing its photophysical features in various conditions (i.e. in high viscous solutions at both high and low polarity).

The molecular rotor was then employed to probe the gelation process of an amphiphilic glucoside (i.e. raspberry ketone glucoside). Gelation consists of the self-assembly of amphiphilic molecules via weak intermolecular interactions that eventually result in the formation of an ordered network and a macroscopically solid-like material. In order for the molecular rotor to be incorporated in this network and report on variations at a molecular level, we tailored it by introducing either a long-alkyl fatty acid or a glucose portion. Unexpected and interesting results were obtained confirming the capability of this probe at sensing variations at a molecular level in the surrounding environment.

Daniel Roxbury*, Prakrit V. Jena, Ryan M. Williams, and Daniel A. Heller
Memorial Sloan Kettering Cancer Center

The intrinsic photoluminescence of single-walled carbon nanotubes (SWCNTs) exhibits unique photostability, narrow bandwidth, near-infrared penetration of biological media, and environmental sensitivity. Advanced biological applications will require the spectral and spatial resolution of individual (n,m) SWCNT species' photoluminescence and its modulation within live cells and tissues. We present a wide-field hyperspectral imaging approach to resolve SWCNTs with single molecule resolution in live mammalian cells, in murine tissues ex vivo, and in live zebrafish endothelium. Taking advantage of the narrow-band emission of SWCNTs, simultaneous multicolor imaging was used to resolve 17 nanotube chiralities in the 900-1400 nm nIR spectral region, including 12 distinct fluorescent species within live cells. We used this method to identify chirality-resolved optical properties of single SWCNTs in tissues and to precisely quantify fluorescent nanotubes in live cells.

9. Transient peptide nanostructures

Charalampos G. Pappas1,2 and Rein V. Ulijn1,2
1WestChem, Department of Pure and Applied Chemistry, University of Strathclyde
2CUNY Advanced Science Research Center

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. Non-equilibrium, transient nanostructures, that only exist away from thermodynamic equilibrium are increasingly of interest. 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 (Figure 1a). The changes observed were due to an altered balance between H-bonding and ?-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. We sought to achieve control of the kinetics and consequent lifetime of the nanostructures formed by chemical design, producing nanostructures with different supramolecular chirality and hydrogen bonding.2

1. Pappas et al., Mat. Horiz., 2015
2. Pappas et al., Angewandte Chemie, In press.

10. Theoretical investigation of resonance energy transfer dynamics in oligofluorene-C60

Hiroko Ajiki,* Lei Yang, Seogjoo Jang
Queens College

Theoretical studies are conducted on the intramolecular excitation energy transfer for oligofluorene-C60

11. Main-Chain ABC Triblock Copolymers: Synthesis and Morphology Studies

Diane S. Lye*, Marcus Weck
New York University

Block copolymers have attracted much attention for use in a variety of applications over the last few decades. Choice of monomer and composition ratio of each block are known to influence resulting material properties. We engineered an ABC main-chain triblock copolymer, based on poly(styrene)-b-poly(norbornene)-b-poly(methyl methacrylate), polymerized via ring-opening metathesis polymerization and atom transfer radical polymerization; their morphology was also studied. In addition, we installed supramolecular end-groups via functionalized initiators during polymerization, imbuing complexity in the design of our multiblock copolymers.

12. Designing a High-Sensitivity Biosensor Using Enhanced Localized Surface Plasmon Resonance

Peter Schnatz*, Ronald Koder
The City College of New York, CUNY

The need for a rapid and highly sensitive detection system for biological toxins grows more urgent with each passing year. We propose a project that will build upon current techniques being used to accurately identify harmful substances common in bioterrorism. By modifying a protein to bind to a biotoxin and charging the structure, we intend to be able to improve the sensitivity of existing biosensing methods. These surface-attached proteins will inherently go through a conformational change upon binding and measurements of the surface plasmon resonance will show a marked difference in the angle of minimum reflection of a monochromatic source. We expect this signal will be enhanced due to surface charges on the protein, thereby increasing the sensitivity of the biosensing device and detecting toxins at safer concentrations than what was required previously for similar assays.

13. Selection of Aptamers Targeting T-Cell Receptor (TCR) and B-Cell Receptor (BCR) Using a Novel Cell-SELEX Method

Hasan E. Zumrut*, Mst. Naznin Ara, Shami Chakrabarti, Prabodhika Mallikaratchy
Lehman College

Nucleic acid aptamers are single stranded DNA or RNA molecules that have stable three-dimensional structures and can form stable complexes with various targets, such as proteins. Aptamers can be generated by a process named 'systematic evolution of ligands by exponential enrichment' (SELEX). Since they can bind specifically to their targets; aptamers are considered as antibody analogues and are being investigated to develop therapeutic molecules for cancer. In order to develop successful therapeutic molecules based on aptamers, it is necessary to generate aptamers for known specific targets. Currently, target specific aptamers are selected using over-expressed proteins either on a cell surface or in purified form, which may not recognize its targeting epitope when the protein is being expressed at its native levels or in its native environment. A recent method named cell-SELEX allows generation of aptamers towards membrane targets in their native state by using whole cells. We are introducing a novel cell-SELEX method for generating specific aptamers for pre-determined epitopes of a receptor molecule in its native state guided by antibody-antigen interactions. Using cultured cell lines, we performed and completed two different aptamer selections; (1) against T-cell receptor complex expressed in T-cells and (2) against B-cell receptor complex expressed in B-cells. Evolved pools were sequenced, analyzed and synthesized. Currently, we are screening potential aptamer candidates to find specific aptamers for these target receptors. Future work will include analyzing potential therapeutic applications of the generated aptamers and their biological effect on cancer cells.

14. Directional Self-Assembly of Polymeric Colloids

Elizabeth Elacqua*, Xiaolong Zheng, and Marcus Weck
New York University

The introduction and exploitation of directional supramolecular interactions within colloidal self-assembly has the potential to fabricate open 3D architectures that can function in applications ranging from photonics and plasmonics to biomaterials and catalysis. The use of colloidal self-assembly as a potent bottom-up technique to construct materials is motivated, in part, by the utility of colloidal particles as highly tunable inexpensive platforms that exhibit unique long- and short-range order, as well as multiple specific orientations. As such, colloidal self-assembly is dynamic and offers the potential for modular fabrication, resulting in well-defined and diverse structures and/or morphologies (e.g., clusters, crystals, chains) via simple modification of intermolecular interactions. While the vast majority of colloidal assemblies have been limited to either non-directional self-assembly or DNA hybridization as a key feature, we have expanded our approach to investigate other supramolecular elements based upon directional self-assembly. In this presentation, we will introduce methodologies based upon directional interactions to achieve open colloidal lattices using patchy particles. In particular, we will introduce host-guest interactions using cucurbit[8]uril to facilitate open colloidal lattices.

15. Functionalization of ZnO nanowires for potential p-nitrophenol sensing applications

Bruce Kim, Saikat Mondal*
The City College of New York

In this work, we demonstrate the functionalization of zinc oxide nanowires with carboxylic acid moieties and investigate their potential application as p-nitrophenol sensors. First, synthesis of high quality zinc oxide nanowires along with appropriate characterization results is discussed. Subsequently, oleic acid, as a model system, is used to examine functionalization behavior of nanowire surface. Vibrational spectroscopic techniques are employed to determine nature of bonding and orientation of oleic acid molecule at nanowire surface. Photoluminescence properties of modified- and unmodified ZnO nanowires with oleic acid were investigated. Based on these results, an appropriate receptor capable of sensitive optical detection of p-nitrophenol is proposed. In addition, results on sensing mechanism of the receptor based on fluorescence quenching are reported, which highlight the capability of selective and sensitive detection of p-nitrophenol analyte using the receptor.

16. Photocatalytic degradation pathways of mustard gas surrogate on zinc hydroxide and zinc oxide nanoparticles: The role of the surface features

Dimitrios A. Giannakoudakis*, Javier A. Arcibar-Orozco and Teresa J. Bandosz
The City College of New York and the Graduate Center of New York, CUNY

Flower-like ZnO nano-particles and rhombic zinc hydroxide particles were synthesized using a controlled precipitation method. Commercial zinc oxide was used as a reference material. The materials were characterized by XRD, FTIR, potentiometric titration, nitrogen adsorption, TA- MS, MS-MS, SEM and UV-vis-NIR. While a slow addition of NaOH to the ZnCl2 solution resulted in formation of hydroxyl groups on the surface, a rapid addition of the base, led to zinc oxide formation. The surface area of Zn(OH)2 was higher (350%) than that of ZnO nanoparticles. A band gap of Zn(OH)2 was 3.22 eV compared to 3.05 eV for ZnO. The materials were used as reactive adsorbents of mustard gas surrogate, 2-chloroethyl ethyl sulfide (CEES). The performance of Zn(OH)2 was better than those of the synthesized and commercial ZnO. Moreover, Zn(OH)2 exhibited a higher adsorption and degradation efficiency under a visible light exposure than in dark. The results indicated the paramount role of terminal OH groups and porosity in the reactive adsorption process. Ethyl vinyl sulfide (EVS) was detected on the surfaces of all samples. Hydroxyethyl ethyl sulfide (HEES) was detected only on Zn(OH)2, under visible light irradiation. The formed ethyl ethyl sulfide (EES) cation by the adsorption of photons is further transforming to less toxic EVS by dehydrohalogenation. Hydroxyl groups and water on the surface promote the formation of hydroxyl radicals under light. They react with EES radicals and form HEES via a hydrolysis pathway. No degradation of CEES was found in the dark.

17. Utilizing a Sugar Glass-Matrix to Stabilize Soft Supramolecular Nanotubes

Sarah J. Belh,1,2* Nicolás N. Yehya,1 Grayson Huffman,1 Mohammad Molla,1 and Dorthe M. Eisele1,2
1Department of Chemistry, City College of New York, City University of New York
2Graduate Center of The City University of New York

Research on synthetic supramolecular nanostructures has been inspired by nature's highly efficient photosynthetic systems, such as those found in sulfur bacteria. Nature's masterpieces contain thousands of molecules, which are self-assembled into supramolecular nanostructures. The molecular subunits within the supramolecular assembly are bonded via weak noncovalent interactions that cause the materials soft structural properties to be highly sensitive to minute alterations in their chemical environment. Furthermore, prevention of any destructive oxidation processes is essential for applications of synthetic supramolecular assemblies in the context of artificial photosynthesis. Therefore, experimental techniques to stabilize the soft nanostructures and to prevent photooxidation processes are pivotal to enable further fundamental investigations as well as future applications.

Sugar glass-matrices are commonly used to study protein structures allowing the proteins' delicate structure to be maintained even after extreme alterations in their environments. Here we discuss utilizing a sugar glass-matrix to further develop a sample preparation technique for supramolecular assemblies, specifically for soft light-harvesting nanotubes self-assembled from synthetic cyanine dye derivatives in aqueous solution. This sample preparation method is highly promising as it can be used not only to stabilize the assemblies soft supramolecular structure but also to prevent damaging photooxidation processes, which is key to enable further experimental studies for this material system, as well as potential applications.

18. Models of globular protein evolution indicate that pI differences between subcellular environments results from selection for stability

Kaiser Loell*, Vikas Nanda
Center for Advanced Biotechnology and Medicine, Rutgers University

Proteome surveys have demonstrated significant differences in acidity between proteins from different subcellular compartments. In this study, we confirm the presence of an acidic bias among proteins associated with the lysosome and a basic bias among proteins associated with the mitochondrion. However, the magnitudes of these biases are less than suggested by previous studies. We also attempt to explain the biases with models of evolution based on selection for either solubility or stability of the folded state, factoring in the external pH of the subcellular environment. We find that models based on selection for stability predict patterns in line with observations, while models based on selection for solubility predict changes opposite to those observed.

19. Functional Bioinorganic Supramolecular Materials

Lee Solomon*, H. Christopher Fry
Argonne National Laboratories

Nature employs a variety of functional inorganic coordination complexes to move electrons from one site to another in well controlled electron transfer processes. These cofactors are precisely arranged in protein frameworks to facilitate the mobility of the electrons through the protein environment. Furthermore, cofactors like hemin, can change function (E.g. oxygen carrier, oxidase, electron transfer) depending on their coordination environment. With the ever rising interest in self-assembled, peptide based materials, we feel the peptide construct itself is underutilized as a functional material. It is therefore our goal to incorporate both biologically relevant cofactors like hemin as well as bio-inspired cofactors like metallo-macrocycles to engineer natural and non-natural function to peptide-amphiphilic networks. We are exploring how the peptide material structure influences the function and application of the inorganic cofactor molecules. For example, we are able to control the morphology of the peptide amphiphile c16-H2L3K3-CO2H by varying the buffer and controlling the pH. At high pH, fibers form and at neutral pH in HEPES buffer, micelles form. Yet, both constructs coordinate hemin in a bis-histidine coordination environment. Thus, we wish to address how these different morphologies yielded from peptide amphiphiles that incorporate metalloporphyrin cofactors function as electronic materials, O2-carriers, sensors, and scaffolds for tissue engineering.

20. Predicting Electrophoretic Mobilities of Proteins

Daniel Grisham* and Vikas Nanda
Rutgers University

The zeta potential of a charged molecule provides a measure of its long-range electrostatic interactions in a particular ionic environment. It is an effective potential that accelerates a molecule during an ionic perturbation (e.g. an applied electric field). The charged molecule's electrophoretic mobility is a measure of its ability to move in response to the ionic perturbation and is defined by a competition between its zeta potential and the surrounding solution's hindrance by friction. The objective of this work is to provide a background of the electrokinetic phenomena associated with electrophoresis and its basis for modeling. Available software can calculate charge and electrostatic potential distributions for computationally generated molecular structures and solve the standard electrokinetic model. The rationale for modeling electrophoretic mobilities of proteins is to advance protein design for drug delivery and tissue engineering applications by elucidating the relationship between structure and long-range charge interactions.

21. A multifunctional Lipoprotein/Polymer Hybrid Nanoparticle for Controllef Release Drug Delivery to Atherosclerotic Plaques

Brenda L Sanchez-Gaytan*, Francois Fay, Mark E Lobatto, Jun Tang, Mireille Ouimet, YongTae Kim, Susanne EM van der Staay, Sarian M van Rijs, Bram Priem, Liangfang Zhang, Edward A Fisher, Kathryn J Moore, Robert Langer, Zahi A Fayad, Willem JM Mulder
Icahn School of Medicine at Mount Sinai

Hybrid HDL-polymer nanoparticles (HDL-PLGA), with poly(lactic-co-glycolic acid) (PLGA) in the core and HDL-like coating were synthesized using microfluidics. HDL natural targeting capability as well as the option to incorporate hydrophobic payloads in both the hydrophobic core and the phospholipid corona make the HDL platform an attractive nanocarrier. The polymeric core provides the NP with controlled release properties. This novel HDL-like nanoparticle displayed natural HDL characteristics, including preferential uptake by macrophages and cholesterol efflux capacities, combined with a typical PLGA nanoparticle slow release profile. In vivo studies carried out with an ApoE knockout mouse model of atherosclerosis showed clear accumulation of PLGA-HDL nanoparticles in atherosclerotic plaques, which colocalized with plaque macrophages. This biomimetic platform combines the targeting capacities of HDL-like nanoparticles with the properties of PLGA-based nanocarriers.

22. The Differential Impact of Arginine and Lysine on Directing Higher Order Self-Assembly

Jose James*, Avanish S. Parmar, Daniel Grisham, Douglas Pike, and Vikas Nanda
Rutgers University

Programming higher order assembly into peptide structure is of tremendous interest for biological and medical nanotechnology. With 20 naturally occurring amino acids, the potential sequence space to search for ideal residue patterns that can direct peptides toward self-assembly is computationally overwhelming; however this search can be simplified by identifying residues that promote or limit interpeptide interactions. While hydrophobic amino acids are an obvious way of producing interaction interfaces, in peptide systems their introduction may pose concerns with solubility in an aqueous environment and be difficult to tune a precise pattern of assembly. On the other hand, arranging charged amino acids on collagen mimetic peptides (CMPs) have been shown by our lab to direct specific and tunable higher order assembly through long range electrostatics. In order to further understand the differences in charged amino acid patterning on higher order assembly we tested the aggregation propensities of arginine versus lysine on CMPs. We demonstrate the unique ability for arginine to facilitate interhelical electrostatic interactions with aspartate or glutamate resulting in the formation of nanosheets or fibrils in contrast to the absence of detectable aggregates with lysine. This difference can potentially be attributed to the lower energetic penalty for desolvation of arginine as well as the multi-valency of its guanidinium moiety. Consequently we have found unique roles of arginine and lysine for directing long range electrostatic interactions which can then be used to engineer self-assembly pathways onto peptide sequence and control aggregation.

23. pH-sensitive elastin-like RGD-functionalized liposomes for anticancer drug delivery

Eleftheria Veneti*, Raymond Tu, Debra Auguste
The City College of New York

Integrin overexpression has been shown to be a method for accumulation within breast cancer tumors. RGD is employed as a targeting ligand for breast cancer cell binding and uptake. The strategy for coupling RGD to drug delivery vehicles usually utilizes a short PEG chain polymer. Here we employed an elastin-like polypeptide (ELP) that can change its secondary structure in order to identify how the tether mechanics may be employed in cell uptake behavior. The ELP sequence (VPGVG)n is characterized by 'near ideal' elasticity and has been exploited to further enhance the accumulation of anticancer drugs in heated tumors, due to its thermally triggered phase transition. Here, we present a novel delivery vehicle that can drive pH-triggered elastin conformational shift in a similar way and consequently, affect binding efficiency.

24. Characterization of Jammed Colloidal Particles using Fluorescent Imaging Techniques

Eru Kyeyune-Nyombi*, M. Lane Gilchrist, Hernán Makse
The City College of New York

Crystalline solids exhibit a periodic arrangement of molecular units that allows mechanical, electrical, optical and other behavioral properties to be directly correlated to the solids' molecular and microscopic structure. However, disordered solids like glasses and granular matter have random arrangements of their molecular or microscopic units that hinder efforts to correlate their structure to their behavior. Several scientists have resorted to using a volume-based ensemble to develop statistical mechanics for disordered solids. This volume-based ensemble along with simulations by Makse and collaborators have produced a phase diagram for packings of mono-disperse particles. The phase diagram is constructed from measurements of the average coordination number and packing density of jammed mono-disperse spheres. The work herein experimentally tests this phase diagram by preparing packings of fluorescently labeled colloidal particles at different packing densities and using the particles' fluorescent signal to measure coordination number.

25. Adaptive and Nonlinear Optics with Alcohol-Water Binary Mixtures

Steven Vallone*, Luat Vuong
Queens College

The visible-light properties of binary aqueous mixtures involving polar organic solutes are far from well understood. Here we review and discuss the theory behind the highly concentration dependent interactions between the solute molecules and water as well as due to molecular self-interactions and make note of the major challenges which exist and influence the optical behavior in relevant mixtures. We provide a discussion of the index of refraction in mixtures of organic solvents with particular attention given to the volume ratio between the components of the mixture. We provide experimental reflectance data for both the thickness and index of refraction of ultrathin films of non-linear binary mixtures.

26. De novo designed, copper-binding peptide assemblies are capable of oxygen activation

Olga V Makhlynets*, Pallavi M Gosavi, Ivan V Korendovych
Syracuse University

We have designed 7-residue copper binding peptides that are capable oxygen activation. Addition of Cu(II) to the designed peptides leads to peptide assembly into amyloid-like fibrils that are capable of catalytically oxidize dimethoxyphenol (DMP) using dioxygen or hydrogen peroxide.

These results indicate that prion-like fibrils are able to not only catalyze their own formation they also can catalyze chemical reactions. Thus, they might have served as intermediates in the evolution of modern-day metalloenzymes. These results also have implications for the design of self-assembling nanostructured catalysts including ones containing a variety of biological and nonbiological metal ions.

27. Generic Phase Diagram of Binary Superlattices

Alexei Tkachenko
Brookhaven National Laboratory

We study a phase behavior of a binary system of small (S) and large (L) "sticky" spheres, with mutual attraction between different types, and hard core repulsion between same type particles. The proposed analytic theory predicts the phase diagram of this mixture, as function of its composition and the ratio of particle diameters. In the limit of strong enough attraction, or equivalently very low overall volume fraction, the problem is purely geometric one: one needs to find the state with maximum number of SL contacts, subject to the excluded volume constraints. The resulting phase behavior is remarkably rich: it features most of the superlattices discovered in recent years in a wide variety of colloidal and nanoparticle systems (such as elecrostatic, DNA-functionalized and others). The model itself can be easily modified to add system specific features, such as finite interaction range, same-type attraction, etc. In general, it complements classical hard sphere problem by providing a generic description of the regime dominated by interparticle binding rather than entropy.

28. Photocatalytic degradation pathways of mustard's gas surrogate on zinc hydroxide and zinc oxide nanoparticles: The role of the surface features

Dimitrios A. Giannakoudakis*, Javier A. Arcibar-Orozco, and Teresa J. Bandosz
City University of New York

Flower-like ZnO nano-particles and rhombic zinc hydroxide particles were synthesized using a controlled precipitation method. Commercial zinc oxide was used as a reference material. The materials were characterized by XRD, FTIR, potentiometric titration, nitrogen adsorption, TA- MS, MS-MS, SEM and UV-vis-NIR. While a slow addition of NaOH to the ZnCl2 solution resulted in formation of hydroxyl groups on the surface, a rapid addition of the base, led to zinc oxide formation. The surface area of Zn(OH)2 was higher (350%) than that of ZnO nanoparticles. A band gap of Zn(OH)2 was 3.22 eV compared to 3.05 eV for ZnO. The materials were used as reactive adsorbents of mustard gas surrogate, 2-chloroethyl ethyl sulfide (CEES). The performance of Zn(OH)2 was better than those of the synthesized and commercial ZnO. Moreover, Zn(OH)2 exhibited a higher adsorption and degradation efficiency under a visible light exposure than in dark. The results indicated the paramount role of terminal OH groups and porosity in the reactive adsorption process. Ethyl vinyl sulfide (EVS) was detected on the surfaces of all samples. Hydroxyethyl ethyl sulfide (HEES) was detected only on Zn(OH)2, under visible light irradiation. The formed ethyl ethyl sulfide (EES) cation by the adsorption of photons is further transforming to less toxic EVS by dehydrohalogenation. Hydroxyl groups and water on the surface promote the formation of hydroxyl radicals under light. They react with EES radicals and form HEES via a hydrolysis pathway. No degradation of CEES was found in the dark.

29. It takes two to stagger - a minimalist fibril just got shorter

FangFang Chen*, Rebecca Strawn, Anne Arias, Monique De Leeuw, Sam Wong, Yujia Xu
Hunter College

We recently reported the self-assembly of a collagen-like, periodic min-fibril having a d-periodicity of 35 nm from a designed triple helix Col108. Our study further suggested that the d-period of the mini-fibril is related to the periodicity in the amino acid sequence of Col108. The triple helix domain of Col108 consists of three pseudo-identical units of amino acid sequence arranged in tandem. A mutual staggering of one sequence unit of the associating Col108 triple helices would produce fibrils having alternating gap and overlap zones consistent with the 35 nm repeating banding pattern observed by electron microscope. Based on this 1-unit staggering model a triple helix with only two-sequence units should also have the potential to form the same d-periodic mini-fibrils. Indeed, when fibril studies were carried out on such a triple helix, the 2U-Col108, mini-fibrils having the same d-period of 35 nm were observed. We also studied the self-assembly of another triple helix consisting of only one sequence unit, the 1U-Col108, but found no fibril' like assemblies. All three triple helices are produced from an E. coli expression system using artificial genes. The mini-fibrils exemplify the 'minimalist fibrils' since they lack both Hyp and the telopeptides; two factors may be involved in the fibrillogenesis of collagens. The findings of the periodic mini-fibrils of Col108 and 2U-Col108 accentuated the potential roles of the sequence periodicity in the formation of the periodic fibrils of the triple helix, and suggest new approaches to create collagen-mimetic materials for biomedical and industrial applications.

Sponsor: CEM Peptides Sponsor: Leica Microsystems Sponsor: PerkinElmer Sponsor: VWR