Paul Russo - US grants

Nuclear Magnetic Resonance (NMR) spectroscopy is the most powerful tool available to the chemist for the elucidation of the structure of molecules. Chemists can now study substances in the solid-state and thereby gain information in addition to that accessable from traditional solution studies. State-of-the-art NMR spectrometry is essential to chemists who are carrying out frontier research. The Department of Chemistry at Louisiana State University will use an award from the Chemistry Shared Instrumentation Program and the Instrumentation for Materials Research Program to help purchase a 200 MHz solid-state NMR spectrometer. The areas of chemistry that will be enhanced by the acquisition of the instrument include: 1) Solid-state deuterium NMR and ADLF spectroscopy: Applications to organometallic chemistry and polymers 2) Solid-state NMR of biomolecules 3) Applications of pulsed field gradient NMR to polymer dynamics 4) Characterization of chitin-protein complexes 5) Characterization of cement/hazardous waste systems 6) High pressure NMR to investigate capillary condensation from supercritical fluids

This research focuses on dynamical aspects of rod-bearing polymer solutions. Tracer self-diffusivities of fluorescently tagged rodlike polymers will be measured by fluorescence photobleaching recovery to verify the large data set already obtained via light-scattering methods, and to test existing theories of self diffusion and its relationship to mutual diffusion. Solvent mobility in such solutions will be measured by pulsed-field-gradient nuclear magnetic resonance techniques, in order to account for the increasing resistance offered by solvent as polymer concentration is increased. This will, enable a comparison with theoretical predictions made by Doi and Edwards a decade ago, as well as more recent developments. The diffusion of rigid asymmetric probes through solutions of less stiff polymers will be measured. Finally, an initiative into the behavior of rods with long, flexible sidechains-"furry rods"-is planned. These experiments will open research into the molecular dynamics of rods in the molten state, which relates to the processing of thermotropic liquid crystals.

Polypeptides will be synthesized as "fuzzy rods" and "star rods". Fuzzy rods have a stiff backbone but many flexible sidechains. They are the largest, most rigid materials known to form liquid crystals in solution and upon heating. This plus a narrow size distribution makes them ideally suited to establish the flow characteristics of molten rods, which is one objective. The versatile sidechain chemistry can also lead to completely new materials. For example, crosslinking of the liquid crystals will yield covalent fuzzy rod networks, leading to oriented polymeric aerogels. Star rods made by attaching several fuzzy rods to a central core exhibit unusual structures in both solution and melt. They are not really rigid, but the arms are nearly so. More uniform arm distribution is a major objective of the research. Star rods will elucidate important features of polymer solutions, such as the approach to semidilute conditions in rods. They will also contribute to the understanding of molten rods. This almost completely ignored macromolecular architecture may also facilitate production of molecular level composites, nonlinear optical materials, biaxially oriented films, and perhaps micromotors, materials with automatic temperature compensation, or optical switches.

Rodlike polymers are the basic components of various high -- temperature, high -- strength materials. Conventional processing methods are often inadequate for rods, so they must be processed from concentrated solutions -- most often into fibers and films. However, the solution behavior or rodlike polymers remains poorly studied compared to random coil polymers. Additionally, it is important to understand the dynamics of mixtures of rodlike and random coil polymers, as these mixtures are the precursors to composite materials in which rodlike polymers reinforce a conventional random coil matrix. Optical studies of the diffusion of helical polypeptides have already revealed much about concentrated, isotropic solutions. These studies will be extended to mixtures with random coils and also to liquid crystalline solutions. A special class of polypeptide, the poly(alkylglutamate)s, will facilitate these studies. Thermoreversible gelation of rodlike polymers is a baffling phenomenon, but an important one if rodlike polymers are to be developed into three -- dimensional materials and not just fibers and films. Poly(alkylglutamate)s and other polypeptides will be used to study the gelation of rodlike polymers. Light scattering and tracer diffusion measurements will help to establish the relative importance of aggregation and phase separation in gelation.

A Beckman Optima XL-A analytical ultracentrifuge will be purchased for use in multidisciplinary research in the Biochemistry and Chemistry Departments at Louisiana State University. The ultracentrifuge will be used to characterize peptides, rodlike synthetic polymers, proteins, and nucleic acids. Molecular weights, aggregation states, and mutual friction coefficients of these molecules will be determined. This information will be used in studies of the mechanism of action of lytic peptides, transport in semidilute solutions, protein structure and stability, and DNA dynamics.

Description: This project supports a collaboration by Dr. Paul S. Russo, of the Chemistry Department at Louisiana State University (LSU) and Dr. Zuhal Kucukyavuz and Dr. Savas Kucukyavuz of the Chemistry Department at the Middle East Technical University (METU) in Ankara, Turkey. In this collaboration they will study the phase stability and dynamics of ternary polymer solutions. The specific classes to be investigated will be systems where rigid rodlike polymers and flexible polymers are mixed together in a common solvent. Such systems represent precursors to molecular composites wherein a random coil polymer is strengthened by the fibrous, rodlike polymer. Light scattering studies will be conducted on specially selected prototype systems, with special attention given to `fuzzy rods` made from polypeptides with long alkyl sidechains. The long sidechains impart good stability to the fuzzy rods, which will be studied in tetrahydrofuran when they scatter strongly. The random coil component will be polydimethysiloxanes, which scatters only weakly in tetrahydrofuran. Polydimethylsiloxanes will be prepared and characterized at the METU in Ankara. Light scattering measurements will be performed at LSU in Baton Rouge. Scope : The collaboration to be supported in this project is useful to the US and to Turkey because it allows the two scientists to use their complementary capabilities to enhance the effectiveness of their research. Dr. Russo is currently supported by NSF's Division of Material Research for the primary research. The funds provided by INT will be used for the incremental costs resulting from the collaboration.

The project will lead to improved understanding of entanglements and tenuous structures in complex fluids containing rigid components. It will include a study of the rotation and translation of rigid rods in entangling and non-entangling polymer solutions. The model system here is composed of tobacco mosaic virus and linear or globular dextran. Related experiments concern diffusive transport in liquid crystals, emphasizing synthetic polypeptides of variable length to determine the effects of flexibility. Characterization of poly(stearylglutamate in dodecane will illuminate the unique properties of this, perhaps the simplest of all reversible gels. Studies of self-assembling, two-directional arborols will emphasize basic properties such as stability. Equally important are the mechanisms by which the self-assembly can be controlled. Techniques include static and dynamic light scattering, fluorescence photobleaching recovery, pulsed field gradient NMR spectroscopy, and to-be-developed birefringence methods.

Complex fluids with rigid, extended components are important precursors to high-strength fibers and films. They also pose very challenging fundamental questions, such as the nature of entanglements. The experiments will provide the observations to support theoretical developments elsewhere, creating together the underpinnings for rational design and processing of better materials. Good chances for serendipitous discovery exist, particularly in the self-assembling arborols, which show preliminary signs of unusual long-range structures. Potential applications include diffraction gratings and other optical devices, superior stationary phases for enhanced throughput in analytical separations, and more efficient systems for control of polymer/colloid stability, which is important in environmental remediation and nanofabrication. Students and others will work in an atmosphere that blends classroom and practical laboratory education with fundamental research and partnership with industrial and other off-campus scientists.

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Paul Russo - Louisiana State University
IGERT: Teaching Craft for Macromolecular Creativity

This Integrative Graduate Education and Research Training (IGERT) award supports the establishment of a multidisciplinary graduate training program of education and research on the synthesis, characterization, processing and theory of macromolecules. Students in eight departments will participate in this IGERT experiment. After research-driven formal training in the above topical areas, the students will join an interdisciplinary team including other students, faculty and off-campus participants. The research mix includes engineering plus curiosity-driven and applied science. An Apprentice-Artisan-Craftsperson ladder is adapted from the trade arts to develop skills, creativity, ethics, responsibility and philosophy. Students will arrive early for a summer of research discovery and ethics training. Based on demonstrated merit, they will be elected to apprenticeships. Apprentices will work side by side with professors and off-campus "research master craftspersons" for 2 to 6 weeks-long enough to demonstrate first-hand the responsible and ethical conduct of research, but short enough that the student can still flourish independently. Upon completion of a written report and advancement to Ph.D. candidacy, Apprentices become Artisans. Among other privileges and responsibilities, Artisans may write minigrants in support of original ideas. After a successful data defense, Artisans will be declared Craftspersons and become eligible for up to six months of "finishing school" at another university, government or industrial site. Excellent opportunities have been pre-arranged, but Craftspersons might design their own based on preliminary data from their independent minigrants. The core curriculum will be revised to serve a more interdisciplinary clientele. Team-taught, integrated lab/lectures will pay special attention to practical skills, including those required for equipment building, programming and troubleshooting. Training in the ethical conduct of science and technology, plus business issues, will be provided in two courses available to graduate and undergraduate students across campus. Students must perform a community service project and participate in a new, interdepartmental seminar. A strong reward structure will maintain student and faculty interest in this demanding experiment. The member departments and off-campus participants will share their different strengths in gender, cultural and racial diversity. More than 30 students will participate overall. Successful aspects of the experiment will spread throughout the campus, guided by a new sociometrics project to assess its effectiveness.

IGERT is an NSF-wide program intended to meet the challenges of educating Ph.D. scientists and engineers with the multidisciplinary backgrounds and the technical, professional, and personal skills needed for the career demands of the future. The program is intended to catalyze a cultural change in graduate education by establishing new, innovative models for graduate education and training in a fertile environment for collaborative research that transcends traditional disciplinary boundaries. In the third year of the program, awards are being made to nineteen institutions for programs that collectively span all areas of science and engineering supported by NSF. The intellectual foci of this specific award reside in the Directorates for Mathematical and Physical Sciences, Engineering, and Education and Human Resources.

Technical Abstract. An asymmetric field flow fractionation device with on-line light scattering detectors, both static and dynamic, will permit high-resolution measurements of the size and molecular weight distributions of particles and assemblies. The system, which can handle aqueous or non-aqueous samples, will benefit these primary projects: formation of amyloid fibrils, which is a key process in Alzheimer's disease; responsive dendrimer superstructures designed to trap and release guests, such as drugs, toxins, and reagents, on command; early assembly of precursors to noncovalently stabilized polymer gels with potential as nanoscale scaffolds; evaluation of silica-polypeptide composite particles designed to produce responsive colloidal crystals; and, interactions in polymer-clay composites being developed for artificial skin applications. Secondary projects include characterization in support of virus preparation and function, physicochemical behavior of polyelectrolytes, and novel cone-shaped vesicles. The large size and often-delicate nature of the particles of interest makes them difficult or impossible to characterize by gel permeation chromatography. Other competing methods, such as cryo electron microscopy, are sometimes subject to preparation artifacts or undersampling errors. Most of the particles to be investigated carry an electrical charge; therefore, the request includes equipment to measure zeta potential, which is related to the effective charge on a molecule or particle in solution. This also permits routine biophysical measurements, such as the isoelectric point of proteins and subtle changes in their size under biologically relevant conditions. The new equipment will permit an older light scattering device to be retired and then reborn in the hands of student designers. The outcome will be an instrument that transcends commercially available designs for applications such as microrheology and rapid self-assembly.

Non-technical Abstract. The requested equipment can measure the size and mass of nanoparticles, polymers and their aggregates, both synthetic and naturally occurring. For example, Alzheimer's disease is thought to progress through the accretion of very small protein fragments into huge structures. The requested equipment will help assess the efficacy of drug candidates designed to intercept this process. The very same equipment will be used to characterize new synthetic materials that have the potential to carry drugs, remove environmental toxins, or isolate new materials in optically pure form. One component of the request is not widely available in publicly accessible laboratories. Its presence on the Louisiana State University campus leverages growing programs to improve both industrial outreach and diversity of our student body. The equipment adds significantly to the Louisiana Applied Polymer Technology Extension Consortium, a statewide university coalition whose primary mission is economic development in one of the poorest regions of the United States. The paucity of similar equipment in academic laboratories makes the equipment appealing to a wider audience of students, including summer interns supported by NSF-REU and a new, NIH-funded initiative targeting under-represented groups. The equipment supports a new research partnership with the University of Texas-Pan American, which trains a largely Latino student body. The equipment will play a key role in a new, interdepartmental, team-taught course, the first at Louisiana State University to address colloid science and its interface to nanoscale research and macromolecules.

TECHNICAL SUMMARY:

Silica core-polypeptide shell composite particles will be synthesized with various core sizes, shell thicknesses and surface densities. This will permit the controlled investigation of thermal coil-to-helix transitions in a single organic solvent. Related transitions are known to destabilize cell membranes when influenza virus particles attack. It is hypothesized that when synthetic particles are mixed with other polymers, a conformational transition may be able to act as a phase stability switch to produce responsive materials. The nature of such phases will be explored by mixing rodlike polypeptides with the core-shell particles. The literature on mixtures of naturally occurring rods and spherical latex particles suggests that new, entropically driven phases may result; however, the size and functionality of the constituent rods and spheres has not been continuously variable as it will be in the proposed work. The core-shell particles can be prepared with a magnetic component, providing another means to initiate or destabilize new phases.
NON-TECHNICAL SUMMARY:
Particles having a glass-like core and a protein-like surface can be configured to capture, purify or deliver pharmaceuticals. Magnetic inclusions permit the particles to be manipulated simply, enhancing these functions. The particles form liquid crystals with light-diffracting properties that are of interest in the production of inexpensive blue lasers, which are essential for high-density data storage. A key factor here is increasing the uniformity of the crystal structure, which may be accomplished by a combination of magnetic and structural transitions. The particles can be used to emulate bio-mineralization, the process by which some sea animals make elegant nanostructures. This bio-inspired project stands near the confluence of fundamental and applied science, which is fertile ground for training young researchers. It poses challenging problems in synthesis, characterization and structure determination. The program will assist faculty and students at target colleges and universities with their research whenever possible; as a result, student interns will return to an interested local science coach who will be able to integrate the gains of an intense summer experience over at least one academic year of further research and coursework.

TECHNICAL:

Submicron hybrid particles will be developed. Each particle will have a silica core and covalently attached polypeptide shell. The shell confers the interesting chemical properties; it can be tailored to respond to temperature, even in an organic solvent where powerful ionic forces are absent, or to pH in aqueous environments where those forces predominate. The size, surface density and surface thickness of the particles will be controlled, enabling a study of how these parameters affect conformational transitions. The limits of making the particles by an "attach to" mechanism (fully formed polymers are connected to the silica cores) will be explored. The particles feature a number of useful physical functions. Either core or shell may bear fluorescent moieties to facilitate visualization of magnetic alignment, equilibrium structures or phase separation. The polypeptides comprising the shell are capable of forming liquid crystals when not tethered to a core, raising the possibility that "local liquid crystals" will form where particles covered with these molecules touch, elevating the local concentration of mesogens. This will be explored by chaining together superparamagnetic variants of the particles using an applied magnetic field. While held in these chains, reactions on the particles or their precursor cores will be explored, possibly leading to particles wearing a polypeptide belt or to poly(colloids) that may be able to undergo muscle-like expansions and contractions, even in an organic solvent.


NON-TECHNICAL:

Polypeptide-coated particles provide an excellent platform for applied discovery because they merge the characteristics of proteins' chemical versatility, ability to recognize markers for disease, switchable size and shape with ease of manipulation using gravitational or magnetic fields. The particles look a bit like porcupines, with "prickles" coating a central core. It is hoped that variants built with magnetic inclusions can be connected, leading to artificial "cilia" that respond to stimuli such as acidity or temperature. Related materials in the future are anticipated to have optoelectronic uses, such as light harvesting or sensing of amino acids related to disease. Researchers associated with the project team will train for a long career, emphasizing technical skills, critical thinking, ethical awareness and communication. Team members are expected to be factual advocates for their craft and for science in general. An important venue for such expression will be the Chemical Education Foundation's You Be the Chemist Challenge competition, a "quiz bow" for middle school students. Graduate student and postdoctoral team members will assist with the competition and/or training of students. Selected young scholars who perform well in the competition will actively participate in the proposed research, erasing the major deficiency of a structured question-and-answer competition, i.e. that it provides no practical training. The Chemical Education Foundation attempts to follow the careers of its young challengers, which provides at no cost to NSF a way to track the efficacy of competition-based science training. It is hoped that additional middle school students will be engaged in active learning, using a technical hobby as a starting point.

TECHNICAL SUMMARY:

The proposed research activities will develop and explore submicron particles having synthetic polypeptide shells atop silica cores, sometimes with magnetic inclusions. The polypeptide shells render the particles responsive to temperature and good sensors of molecular asymmetry, while the silica cores make it possible to direct these functions to a particular location. Whole particles and their individual polypeptide and silica components will be studied. Specifically, the following work will be performed: 1) The effects of core radius, shell polymer coverage, and shell polymer molecular weight on a thermally driven coil-to-helix transition will be assessed by small-angle X-ray and neutron scattering, static and dynamic light scattering, optical rotatory dispersion, and NMR; 2) The particles, acting as very large monomers, will be polymerized into nearly uniform chains by using a magnetic field to align them perpendicular to a striped optical pattern that will initiate a photochemical crosslinking reaction originally developed for proteins; 3) Better understanding of silica core structure, including newly discovered variants, will be achieved by chromatography with fractionation and scattering of X-ray or visible radiation; 4) The stiffness of a water-soluble, uncharged polypeptide will be determined by combined chromatographic and scattering methods; 5) A big difference between the mobility of rigid rods and polypeptide semiflexible filaments will be explored by an optical tracer method; 6) A long-standing problem with the measurement of rigid rod diffusion using pulsed-gradient NMR will be re-assessed using a very high-field-gradient facility.


NON-TECHNICAL SUMMARY:

Some of nature's most important building blocks and functional engines are made of proteins. Synthetic polypeptides, which can be made in large amounts by simple methods, borrow the protein structure and retain many protein-like features, such as the ability to rotate light and respond to thermal or chemical changes in the environment. The problem is that, even though they are very large molecules, polypeptides are still very small things. This makes them hard to manipulate. The proposed work marries the functionality of bio-inspired polypeptides to the easy manipulation of larger particles using gravitational or magnetic fields. This will be accomplished by placing the polypeptides onto colloidal silica, essentially little balls of glass, resulting in core-shell particles. By adjusting the temperature, the shape of the polypeptide shell will be altered. This will provide information on shape transitions similar to those used by influenza virus to penetrate the human body. Chains of particles crosslinked by the action of light will result in nearly uniform filaments that bring polymer science into the visible regime for easier inspection, while facilitating the creation of even larger structures. Studies on a particularly attractive water-soluble polypeptide will lead to improved understanding of the kinds of polymers used to make high-strength fibers, such as those woven into bullet-proof vests. In terms of societal impact, a middle school chemistry competition will be further expanded in minority-serving districts, thanks to successful attempts to woo professional educators to this cause. New outreach initiatives with a public science & technology middle school will ensue, integrated with real world experience and laboratory research.

Nontechnical: This SusChEM award by the Biomaterials program in the Division of Materials Research to Georgia Institute of Technology is to investigate how natural materials combine structural stability with elegant function, and how that ability may be harnessed for the production of superior semiconducting polymer assemblies for flexible/stretchable electronics. These polymers, which transport charge or harvest photons to produce charge, depend upon organization into ideally defect-free macromolecular structures. The vision presented in this proposal is to exploit the ability of some fungal proteins to encapsulate and induce the self-assembly of semiconducting polymers into organized architectures that are expected to have exceptional electronic characteristics. These features will provide access to low-cost, high performance, flexible, stretchable electronics, which could transform technology as we know it today. This SusChEM project provides opportunities to integrate research and education in technologies that will impact society. Robust, flexible and stretchable electronic systems may enable affordable sensors for applications in monitoring the environment and personal health, flexible and conformal displays and many more. The students participating in this research will be cross-trained in multiple areas to expand their knowledge and experience for professional growth and career opportunities. Further, based upon Georgia Tech's Invention Studio, the investigators plan to adopt the model of student-led training to Materials Science & Engineering through creation of a new Materials Innovation Studio to champion problem-solving and creative applications of material sciences and engineering.

Technical: This proposal will investigate how the structural stability and elegant functional properties of natural biomaterials could be harnessed for the production of superior and value added optoelectronic, and other high performance materials. These molecular or supramolecular entities depend upon organization and alignment of them into ideally defect-free, tightly stacked assemblies on a macromolecular scale. Using a class of amphiphilic fungal proteins known as hydrophobins, this proposal will exploit their ability to encapsulate and induce self-assembly of polymers into organized architectures with enhanced stacking and therefore unprecedented performance. These features are expected to provide access to low-cost, high performance, flexible, stretchable materials for many applications. Hydrophobins are powerful natural surfactants, known to form aqueous dispersions and even encapsulate gases, organic solvents, and polymer solutions. Using these fungal proteins, this project will study factors that control the maximum capsule loading, and explore the impact of crystal structure on electronic characteristics and design appropriate protocols to prepare high performance, flexible and stretchable optoelectronic materials for fabrication of devices and circuits. Students participating in this study will benefit from this multidisciplinary and collaborative environment to expand their knowledge and experience. The investigators plan a strong and long-running commitment to broadened participation of students in science and engineering, and in serving the community. Additionally, these researchers plan to expand Georgia Tech's Invention Studio with its student-led training to Materials Science & Engineering areas, and to take a leading role in problem-solving and creative applications of material sciences and engineering.