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Dr. David Boatright

 

Phase-transfer catalysis (PTC) is a powerful technique that is applied to an ever increasing array of chemical reactions in 40 reaction categories. The most important parameters which determine the reactivity and selectivity of PTC systems are catalyst, solvent and hydration. Although much empirical work has been performed characterizing the effects of catalyst structure, solvent and hydration on reactivity, very little work has been performed to elucidate the underlying fundamental structure-activity relationships (SAR’s). Empirical guidelines have been suggested for choosing catalyst structure, solvent and hydration, however, in the absence of a deep understanding of the underlying fundamentals, these guidelines are rough at best. This leads to the loss of valuable time and money for businesses trying to apply PTC to their commercial processes.

 

Through a close collaboration with PTC Organics, Inc., I am investigating the relationships between catalyst structure, solvent and hydration and reaction efficiency.  The goals of this research are to: [1] gain a deep understanding of the SAR’s for catalyst structure, solvent and hydration, [2] use the added understanding to improve upon the existing empirical guidelines for choosing catalyst structure, solvent and hydration to enable the more efficient PTC process development for industrial applications.

 

 

 

 

Dr. Sharmistha Basu-Dutt

 

I am interested in inter-disciplinary projects in applied science relevant to the Engineering Studies major.  In one project, students study factors that control the efficiency of solar cells.  In another project, students build fuel cells and manipulate design parameters to study their effects on the operation of these cells.

 

I am involved in developing nanotechnology based activities that can be used in lower and upper level chemistry courses.  One activity currently being developed involves using spectroscopy to study structural characteristics of single walled nanotubes.

 

I am actively participating in science education projects.  In collaboration with Dr. Gail Marshall in the Department of Curriculum and Instruction, professional development workshops are offered for K-12 teachers in the area of learning and teaching science by the inquiry method. 

 

 

 

Dr. Megumi Fujita

 

My research interest is transition metal-catalyzed environmentally friendly organic reactions. My current research focus is to develop transition metal complexes that catalyze selective oxidation of organic compounds by nitrous oxide (N2O) and hydrogen peroxide (H2O2). These "green" oxidants would generate only non-toxic byproducts, nitrogen (N2) and water (H2O), respectively, after consumption as oxidants. We synthesize new tridentate and tetradentate ligands as scaffolds for selected first-row, late transition metal ions to create N2O- and H2O2-activation site.

 

 

 

 

Dr. Anne Gaquere-Parker

 

My background is in organic chemistry, however during my PhD I started to look at the use of ultrasounds to enhance the reaction rates. Since it gave me good results, I am very keen on this technique and now I am using ultrasounds everywhere! In my research laboratory, students study how ultrasounds can be used to accelerate the degradation rate of persistent harmful pollutants. As you can see, little by little I have become a sonochemist with an emphasis on environmental chemistry. Nothing is set in stone... I am also very interested in nanotechnology and especially the study of fullerenes, carbon nanotubes, their behavior in organic solvents and their possible chemical functionalization.

 

 

 

 

Dr. Lucille B. Garmon

 

I am a physical chemist with interests in general chemical education as well as in the history and philosophy of science.  My research right now is in the field of chemical education.  In the Fall of 1998,  I started a project on using a “Workshop” format to help students master general chemistry.  The workshops are groups of 8 or 9 students who meet weekly to go over sets of assigned questions and problems.  A number of undergraduate students are involved as peer leaders of the workshops.  Results of the project will be used to improve student understanding of material, attitudes toward chemistry, and retention in future chemistry courses.

 

 

 

 

Dr. Victoria J. Geisler

 

Generating Enthusiasm in Math & Science (GEMS)

 

When people try to pass a verbal message to others the words and sometimes the meaning of the message often gets distorted. It might seem surprising, then, that molecules inside our body allows cells to constantly communicate with one another without distorting the relayed information. Actually, no one could survive without such precise signaling. Over the past 15 years, great progress has been made in unlocking the code that cells use for their communication and advances in research are suggesting new strategies for attacking diseases that are caused by faulty signaling in cells. 

 

Cancer involves abnormalities in the rate of proliferation of cells marked by uncontrollable cell division and migration. One way this can be achieved is by the over activity of proteins in signal-relaying pathways. Most of these complex signaling pathways involve a chemical messenger that binds to a cell surface receptor causing a signal to be transduced within the cell. Transduction of the signal typically involves a second messenger that produces a response inside the cell. An example of this is the phosphoinositide pathway. Here, ligand binding to the receptor activates an intracellular G-protein whose subunit, complexed with guanidine triphosphate (GTP), activates the membrane bound enzyme phospholipase C. The activated enzyme catalyzes the hydrolysis of phosphatidylinositol-4,5-bisphosphate to inositol-1,4,5-triphosphate (IP3) and diacylgylcerol (DAG). IP3 mobilizes calcium ions from the endoplasmic reticulum. Diacylglycerol, Ca2+, and phosohatidylserine (PS) are secondary messengers required for full activation of Protein Kinase C (PKC) to phosphorylate and thereby regulate the activities of several different cellular proteins. PKC effectively passes information from the membrane of the cell to its nucleus.

 

If there is a continuous activation of PKC, the normal regulation of cell growth and division is changed so that growth of a tumor is promoted. In fact, PKC over-expression has been discovered in several malignant cell types. The inhibition of PKC may hold the key to controlling the proliferation of malignant tumors. Sphingosine, the backbone component of sphingolipids, is a natural repressor of PKC, and inhibits cancer and tumor-causing phosphorylation.1 Sphingosine prevents the formation of an active lipid-enzyme complex by displacement of the activator (DAG or phorol ester) from the complex.2 Mechanistically, it is believed that sphingosine inhibits PKC by disrupting Ca2+ association with DAG and PS at the activation site. Sphingosine is an amino alcohol of 18 carbons with a trans configuration at its double bond. It is generally believed that PKC is inhibited by long-chain bases that are positively charged.3 In this research a series of analogs of sphingosine will be synthesized to determine the mechanistic role of the 3-hydroxyl group, the trans-double bond and the effect of additional nitrogen moieties.

 

 

 

 

The synthetic approach, which has been adopted for the preparation of these compounds, is outlined in Scheme 1.  This procedure is a modification of the synthesis of sphingosine by Liotta and coworkers.4 To date this procedure has been carried out using 1-tetradecylamine. We plan on using a number of amines including polyamines in the synthesis of our analogs. These compounds will be tested for biological activity at Emory University.  In order to characterize intermediates formed and their purity, standard 1D and 2D 1H-NMR and 13C-NMR spectra will be obtained routinely.

 

Scheme 1

 

NMR has become as excellent tool for obtaining information about ionization processes. We will determine the pKa’s of the compounds synthesized using 1H and 13C NMR titrations. Bottega et al. has determined the pKa of sphingosine in Triton micelles using proton NMR spectroscopy. The pKa values can be determined on the basis of the pH dependence of the chemical shifts if unique signals for the protonated and unprotonated species can be observed. The protonation of the amino group in sphingosine leads to an approximate 5 ppm upfield shift of the 13C resonances of the C-2 and C-3 carbon atoms and we have determined the pKa of sphingosine in Triton micelles to be 7.8 which compares with that obtained by Bottega.6 A similar method will be used to determine the pKas of the analogs synthesized.

 

 

 

 

Dr. John E. Hansen

 

I am an experimental physical chemist interested in studying the dynamics of chemical and biological systems using optical and laser spectroscopy.  A major focus in my group is to determine the folding pathway a polypeptide chain will follow to finally arrive at a unique three dimensional protein structure. 

 

Examining the process of protein folding raises a fascinating paradox.  It is known that a polypeptide will spontaneously fold to the correct, unique three-dimensional protein structure within a test tube outside a cell.  The average-sized protein consists of 270 amino acids.  Each amino acid can adopt around 10 different conformations, so the average-sized protein could assume up to 10270 different three-dimensional structures.  To give this number some meaning, realize that astronomers estimate the number of atoms in the universe to be 1087.  Also consider that the fastest chemical event is a molecular vibration, which occurs in one-tenth of a picosecond (10-13 s).  If a polypeptide chain were to sample each of the available conformations for a duration of only one-tenth of a picosecond, it would take longer than the history of the universe to arrive at the correct three-dimensional structure for the average-sized protein!  Yet, we know polypeptides can fold to the correct structure in a test tube in less than a second – sometimes a few milliseconds.

 

Although protein folding is an extremely interesting theoretical problem, its study will answer important medical questions. A number of diseases result from misfolded proteins: Alzheimer’s, bovine spongiform encephalopathy (“mad cow” disease), Jacob-Kreutzfeld disease (the human equivalent of mad cow disease), amyloidosis, cystic fibrosis, sickle cell anemia and osteogenesis imperfecta (brittle bone disease). Understanding the process of protein folding, and those forces that stabilize a protein structure will yield beneficial insights that will help society.

 

 

 

 

Dr. Farooq A. Khan

 

A physical chemist by training, I am working in two broad areas, reactivity of carbon cluster ions using a time-of-flight mass spectrometer, and reactivity of carbon nanotubes and fullerenes using optical and mass spectrometric techniques.  While the goal of this work is to carry out publishable work on current problems, there is considerable emphasis on providing undergraduate students a meaningful experience in current, cross-disciplinary work with modern instrumentation. 

 

Reactivity of carbon Cluster Anions (with Dr. Andrew J. Leavitt)

A variety of atmospheric reactions occur on the surface of soot, a ubiquitous pollutant.  We are exploring the reactivity of carbon cluster cations and anions (pictured below) with oxides of sulfur to experimentally and computationally model atmospheric reactions. 

 

Functionalization of Carbon Nanotubes and Fullerenes (with Dr. Anne C. Gaquere)

Carbon nanotubes are of considerable interest because of their unique physical and chemical properties.  While these novel materials are of interest in their own right, they are also potentially useful in a wide array of applications, e.g., nanoelectronic devices, composite materials that may be used in automobiles, and miniaturized chemical sensors.  An important element in processing materials is the ability to manipulate them physically or chemically.  As such, carbon nanotubes are not soluble in water or common organic solvents.  We have carried out a number of studies with the active participation of undergraduate students, wherein surfactants enable us to make suspensions of nanotubes in a variety of solvents.  These are easily characterized by UV-Vis spectroscopy. 

 

The chemical modification of carbon nanotubes would afford the possibilities of altering the structural and electronic properties, and also provide new avenues wherein increased solubility also enhances the ability to process these materials and therefore increase their potential use for practical applications.  While the ultimate goal of our research is to functionalize carbon nanotubes, we re also working on the structurally similar fullerene C60 for functionalization as well.  The first type of functionalization is a cyclopropanation with a dichlorocarbene.  We are particularly interested in enhancing the rates of the reaction by applying the powerful and proven techniques of ultrasounds.  The characterization of the products is carried out using LC-MS, in collaboration with Dr. Swamy-Mruthinti in Biology. 

 

 

 

 

 

 

 

 

Dr. Partha S. Ray

 

I am an Organic Chemist with research interests in medicinal and synthetic chemistry.  The ultimate goal in my research is to discover new anti-tumor and anti-microbial agents by chemical synthesis.  We have undertaken this exciting and challenging journey with the anticipation that along the way to our destination we will discover and develop new synthetic methods and establish structure-activity relationships.  We are particularly interested in the design and synthesis of novel inhibitors of folate requiring enzymes, which play critical roles in the biosynthesis of DNA.  

 

 

 

 

Dr. Spencer J. Slattery

 

Transition metal molecules are essential components in fundamental biological processes such as cellular respiration, photosynthesis, as well as in a variety of enzymatic activity.  They are the backbone of catalytic process which can be utilized in not only the biological sense, but also in light harvesting systems, fuel cells, and molecular electronics.  What's particularly key about these molecules and what triggers the specific behavior necessary in these various processes, however, is the structural position which surrounds the metal.  The coordinated molecules (ligands) are active players in dictating the characteristic behavior of the metal center.  Our lab has previously observed regulated redox and spin state properties due to systematic inductive and steric modifications of the coordinated ligands on monometallic first row transition metal complexes.  We have also synthesized novel ligands which contain an ionizable proton site in order to study proton coupled electron transfer behavior in first and second row transition metal complexes.  Utilizing this knowledge, my current research directive has become multifaceted.   One, we want to develop first row metal complexes which utilize these novel ligands in order to reversibly manipulate spin transition by the loss/gain of an acidic hydrogen.  Secondly, we are studying the extent that ligand substituent inductive effects influence the absorbance and fluorescing properties of chromium systems.   In addition, we are also developing novel bridging ligands with ionizable proton sites which will be used to link first row transition metals, to study the extent of spin-spin coupling between the metal centers, as well as how the coupling properties can be regulated via subtle changes in the bridge structure.  The ionizable proton sites may likewise act as a 'switching' mechanism in the extent that the ligand acts as an extension of the metal orbitals, thereby, shifting the nature of coupling, or communication, between the metals by reversible protonation/deprotonation (see picture below).  Understanding and being able to regulate these systems provide valuable insight for design in molecular electronics, more specifically molecular switches as well as in multi-electron/proton catalysis.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Dr. Douglas Stuart

 

I am a bioanlytical chemist with a research focus on the development and design of novel nanoparticle based methods of ultra-sensitive biomedical and environmental detection and analysis. Specifically, I exploit the unique optical properties of gold and silver structures such as intense absorption, wavelength selective photon scattering, localized surface plasmon resonance (LSPR), and the ability to support surface-enhanced Raman scattering (SERS). An important part of this research is the systematic investigation of the fundamental relationships between a particle’s physical properties (size, shape, composition) and its observed optical properties.  

The sensitivity of the LSPR to the dielectric environment enables us to create sensors capable of measuring binding events by monitoring shifts in the UV-Vis spectrum of the nanomaterial. The nanoparticles are functionalized –e.g. with capture antibodies – to make them sensitive only to specific target molecules. Single particle experiments have demonstrated zeptomole sensitivities.

The intense electric fields generated localized surface plasmon are  the  single most  important factor in observing the surface-enhanced Raman phenomenon.  SERS is an attractive –but under utilized- analytical technique because it generates unique vibrational spectra that can be used for unambiguous determination of analytes.   In that regard, Raman spectroscopy is similar to infra-red absorbance spectroscopy, but enjoys the advantages of being able to operate in aqueous environments,  and on  opaque surfaces and  materials (e.g. pharmaceutical tablets and coatings). In SERS, the analyte is placed at or near a nanoscale roughened noble metal surface, yielding an increase in intensity of ten to a million fold over standard Raman scattering. SERS position as the only vibrational spectroscopy capable of single-molecule is due to these enormous gains in signal.

 

 

Figure 1.  

Wavelength selective scattering from silver nanoparticles observed by dark-field microscopy.  Properly conjugated to a capture molecule, these particles can be made into very sensitive sensors.

 

 

 

 

 

Figure 2.

An array of nanopyramids.  These particles can support SERS.

 

Departmental Research Interests

 

Medicinal Synthetic Chemistry

'Green' Catalysts

Proton Coupled Spin Transition

Sonochemistry

Transition Metal Chemistry

Protein Folding & Recognition

Carbon Nanotubes

Surface Chemistry

Phase Transfer Catalysis

Synthesis Sphingosine Analogs

Solar & Fuel Cells

Nanoparticle Optical Behavior

High Spin Metal Center
Low Spin Metal Center