Current Research Activities
The Department of Chemistry, Geosciences, and Environmental Science at Tarleton State University is fortunate to be the recipient of a Chemistry Departmental Research Grant from The Robert A. Welch Foundation of Houston, Texas. A portion of these funds is used to provide undergraduate students with stipends to assist in this research.
Five faculty members are currently involved in basic chemical research projects sponsored by this grant. They are Dr. Peter Bell (Organic Chemistry), Dr. Stephen Field (Geochemistry), Dr. Arthur Low (Theoretical Chemistry), Dr. Harold Rathburn (Biochemistry), and Dr. Linda Schultz (Inorganic Chemistry).
Research Presentations Presented by Tarleton State University Welch Undergraduate Scholars in 2004
J.R. Andreatta, E.T. Davis, R.A. Oliver, and Linda D. Schultz, "Raman Spectroscopy of Potassium Polytellurides in Nonaqueous Solvents," presented at 227th ACS National Meeting, Anaheim, CA, March 29, 2004.
A.A. Low, "Nature of Metal-metal Bonds in Complexes with p-acid Ligands," presented at 227th ACS National Meeting, Anaheim, CA, March 31, 2004.
R.A. Oliver, J.R. Andreatta, and A. Charlton, "Chemvention: Detecting Increases and Decreases of Oxygen in the Atmosphere," presented at 227th ACS National Meeting, Anaheim, CA, March 29, 2004.
Research Presentations Presented by Tarleton State University Welch Undergraduate Scholars in 2005
A.K. Charlton, R.O. Glenn, J.R. Andreatta, and L.D. Schultz, "The Blue Bottle: New Applications of an Old Demonstration," presented at 229th ACS National Meeting, San Diego, CA, March 14, 2005.
A.A. Low, "Bimetallic Complexes with Bridging p-acid Ligands," presented at 60th Southwest Regional ACS Meeting, Ft. Worth, TX, September 30, 2004.
A.K. Charlton and R.S. Sevcik, "Chemvention: Colorimetric Determination of Albumin in Powdered Egg Whites with Bromophenol Blue," presented at 229th ACS National Meeting, San Diego, CA, March 14, 2005.
A.K Charlton and H.B. Rathburn, "Development of a Purification Scheme for a Trypsin Inhibitor from a Native Texas Legume", presented at 2nd Annual TAMUS Pathways Research Symposium, Texas A&M University--Corpus Christi, TX, October 15-16, 2004.
Research Presentations Presented by Tarleton State University Welch Undergraduate Scholars in 2006
O’dell Hicks and Peter T. Bell, "Abnormal Buffer Region Observed for Silica Attached to 3-aminopropyl-trimethoxysilane," Abatracts of 231st ACS National Meeting, Atlanta, GA, March 27, 2006.
Richard S. Sevcik, Jeremy R. Andreatta, and Linda D. Schultz, "Comparison of Potassium Polytellurides in Liquid Ammonia and Dimethylformamide Solution," Abstracts of 231st ACS National Meeting, Atlanta, GA, March 27, 2006.
O’Dell Hicks, Elizabet Martinez, Ragan L. McGinty, and R.S. Sevcik, "Chemvention: Toys for Chemical Education," Abstracts of 231st ACS National Meeting, Atlanta, GA, March 27, 2006.
Amanda K. Charlton and Harold B. Rathburn, "Development of a Purification Scheme for a Trypsin Inhibitor from a Native Texas Legume", Abstracts of 3rd Annual Texas A&M System Pathways Research Symposium, Texas A&M University-Kingsville, November 4, 2005.
Research Presentations Presented by Tarleton State University Faculty and/or Welch Undergraduate Scholars in 2007
“A Green Quantitative NMR Experiment: Acetone and Ethyl Alcohol in D2O,” Peter T. Bell and Linda D. Schultz, 232nd ACS National Meeting, San Francisco, CA, September 10, 2006.
“Equilibrium Among Potassium Polytellurides in Dimethylformamide Solution,” Richard S. Sevcik, Peter D. Poulsen, and Linda D. Schultz, 62nd ACS Southwest Regional Meeting, Houston, TX, October 20, 2006.
“Analysis of Purity of Common Solvents using Quantitative NMR,” Peter T. Bell, Alyssa D. Adkins, and Linda D. Schultz, 233rd ACS National Meeting, Chicago, IL, March 26, 2007.
“Recycled Paper as a Plywood Component,” Adrian Dunson, O’dell Hicks, Elizabet Martinez, and Ragan McGinty, 233rd ACS National Meeting, Chicago, IL, March 26, 2007. This was a finalist in an American Chemical Society national competition.
Dr. Peter Bell (Organic Chemistry)
I) Solid Supported O-alkyl isourea:
One of our research projects involves the development of a mild, environmentally friendly solid supported medium for alkylation of carboxylic acids to afford esters. This methodology can be extended to alkylation of other suitable species such as amines, sulfur and phosphorous nucleophiles among others. An example of the basic scheme for the ester synthesis case is illustrated in scheme 1 below.
Our research group has succeeded in synthesizing the critical intermediates 1a, 1b, and 3a (via 2a) as shown below:
Future work will involve attachment of 3a to silica gel (step iii in scheme 1) to generate the solid supported O-methyl isourea. Finally its alkylation ability will be assessed with standard carboxylic acids.
II) Green Quantitative NMR Experiment Development:
In conjunction with Dr.Linda Schultz we developed and implemented quantitative 1H-NMR experiments to assess the purity/composition of common organic solvents using D2O.
Dr. Arthur Low (Inorganic/Theoretical Chemistry)
A collaborative effort was begun with Dr. Tom Cundari of University of North Texas during this year. The first project concerns performing theoretical ab initio DFT-level solid state calculations on a number of triimine platinum TCNQ (TCNQ =7,7,8,8-tetracyanoquinodi-methane) complexes, [Pt(tbrpy)(XH)][TCNQ] (tbrpy=4,4’,4”-tBu3-2,2’,6’,2”-terpyridine, X = O or S). These complexes form Pt-TCNQ chains in the solid state that exhibit metallic behavior. It is thought that there is a large contribution from the π and π* bands of the TCNQ ligand to the valence band. From the calculations, a density of states (DOS) analysis will be performed to analyze the individual contributions to metallic behavior.
Figure 1 Structure of [Pt(tbrpy)(OH)][TCNQ]1. The water molecules in the crystal structure are omitted.
Another project concerns calculations simulating metal-organic frameworks2 that form crystalline porous materials. Such materials have many applications such as safe hydrogen or methane storage materials for fuel cells,3 or in gas separations, namely the non-cryogenic separation of air. The material that we are currently investigating is a silver complex with the perfluorinated ligand 3,5-bis(trifluoromethyl)-1,2,4-triazole (shown below in Figure 2).
Figure 2 3,5-bis(trifluoromethyl)-1,2,4-triazole ligand
When this ligand is reacted with silver nitrate in methanol, it forms a compound with the formula of {Ag2[Ag4L6]}n that consists of 6-connected tetranuclear [Ag4L6] clusters linked by 3-coordinate Ag(I) atoms. The 3D framework possesses hydrophobic internal cavities into which the CF3 groups point into. These cavities are semi-rectangular in shape with 12 × 7.3 Ĺ dimensions.
Currently our studies are investigating the gas storage capabilities of these cavities as to the possibility for their use in the non-cryogenic separation of air. A number of adsorbents have been used to accomplish the separation of O2 and N2 from air using pressure swing absorption processes.4 Our studies are focusing on the interaction of N2, O2, and Ar with the silver complex to determine whether these complexes are good candidates for gas separation studies.
In publications, I have a contribution submitted to a special issue of Theoretical Chemistry Accounts dedicated to Nino Russo entitled "Theoretical Study of the Biologically Important Dioxo Diiron Diamond Core Structures." by Lisa M. Perez, Charles Edwin Webster, Arthur A. Low and Michael B. Hall.
References
1Chen. W.-H; Reinheimer, E. W.; Dunbar, K. R; Omary, M. A. Inorg. Chem. 2006, 45, 2770
2For example, see Yaghi, O. M.; O’Keefe, M.; Ockwig, N. W.; Chai, H. K.; Eddauoudi, M.; Kim. J. Nature 2003, 423, 705
3Schalpbach, L. Züttel, A. Nature 2001, 414, 353
4Jasra, R. V., Choudary, N. V., Bhatt, S. G. T. Separation Science and Technology 1991, 26, 885
Dr. Stephen Field (Geochemistry)
Most of 2006-2007 was spent analyzing data collected from previous years and preparing papers for journal submission. Mineral chemical data from symplectite-bearing peridotites was gathered into spread sheets. Programs were written to convert the weight percent oxide data into cation data and to calculate bulk chemical compositions of fine-grained symplectite intergrowths. Mineral, chemical, and bulk rock data were used to construct various chemical plots. A manuscript titled "Diffusion, discontinuous precipitation, metamorphism, and metasomatism: The complex history of South African upper-symplectites" was written and submitted to the journal American Mineralogist. Reviews have been received, and revisions are currently underway. A rough draft of a second paper, tentatively titled "An unusual garnet-kyanite-corundum symplectite in eclogite" has been written. The paper will be submitted to the journal Geology at the end of August 2007.
Dr. Harold Rathburn (Biochemistry)
Research in my laboratory has focused on the isolation and characterization of a trypsin inhibitor (TI) from Sesbania vesicaria. Sesbania vesicaria (Jacq.), a legume native to the coastal states, including Texas, has been reported to be toxic to livestock (Kingsbury, 1964). Small molecules have been isolated and shown to contribute to this toxicity (Powell et al., 1984; Powell et al., 1990; Kim et al., 1992) and other interesting activities. However, the existence and possible role of TI in Sesbania sp. toxicity has never been explored. Research completed in my laboratory at Tarleton State University strongly indicates the existence of proteinaceous TI in the seeds of S. vesicaria.
Naturally
occurring inhibitors of trypsin are proteins. Plants have been a rich source of
proteinaceous TI, especially the seeds of Leguminosae species (Ryan, 1981).
Kunitz (1946) reported the crystallization of one of the first proteins, a TI of
soybean. Since Green and Ryan (1972) first suggested a defensive function for
these molecules, a body of evidence has indicated that this relationship does
indeed exist. Ryan (1990) summarized several studies exploring the
relationships between trypsin and TI of several animals and plants. The studies
assayed TI as a component in an artificial diet against insect larvae, resulting
in reduced larval weight. Transformation of crops with TI genes from other
plants has also been successful (Hilder et al.,1987; Johnson et al., 1989),
further supporting the hypothesis of Green and Ryan (1972).
Crude aqueous extracts of S. vesicaria seeds have been
prepared by undergraduate students in my laboratory with activities ranging from
4.01 to 97µg, the amount of protein required to inhibit 5µg bovine trypsin by
50% in a spectrophotometric assay modified from Houseman et al. (1985). To
further purify the TI, contaminating proteins were removed from the crude
extract by ammonium sulfate precipitation. Adding the salt to 55% saturation at
0C increased the activity in the resulting supernatant to a range of 2.74 to
9.8µg, a fold purification of about 5. Plant TIs tend to be resistant to heat -
some stable at 100C for at least 30 min. The ammonium sulfate supernatant was
heated at various temperatures up to 100C to remove denatured proteins.
However, our studies indicate that S. vesicaria TI is heat labile at
temperatures of 50C.
Since 2002, attempts to purify the TI have involved acid
precipitation of the crude extract. However, some data obtained have been
conflicting. In this purification method, as contaminating proteins are
denatured and precipitated by the addition of HCl, the activity increases until
TI itself is denatured. At that point, TI activity will decrease. Amanda
Charlton joined our group in 2004 and successfully established the pH range that
destroys TI activity. She determined this pH range to be 4 to 5. Endra Sookoor
was able to reproduce much of this work during the summer of 2006.
The next goal for our laboratory is to use HPLC to analyze the supernatant from the HCl precipitation. If time allows, SDS-PAGE (Laemmeli, 1970) will be employed to ascertain the purity of the TI of the various fractions, as well as an in gel activity of the TI of the various fractions by the method of Uriel and Berges (1968).
Dr. Linda Schultz (Inorganic Chemistry/Analytical Chemistry)
Research efforts in my laboratory have involved three very different projects, as detailed below.
1. Alkali metals in nonaqueous solvents
The major focus of the research in my laboratory for several years has been the investigation of alkali metal polytellurides in nonaqueous solvents - liquid ammonia and dimethylformamide – primarily using spectroscopic techniques. Our studies have shown that the behavior of potassium polytellurides in the two solvents differs. In liquid ammonia solution the monotelluride is insoluble, the ditelluride and tritelluride are spectroscopically identifiable entities, and the tetratelluride is not formed. By contrast, in dimethylformamide (DMF) an equilibrium exists among the monotelluride, ditelluride, and tritelluride, similar to that reported by Sharp and Koehler (Inorg. Chem., 16 (1977) 2258) for polyselenides in liquid ammonia solution. The absence of this equilibrium for the polytellurides in liquid ammonia seems to be due to the insolubility of the monotelluride in this solvent, and its presence in DMF due to the solubility of the monotelluride in this solvent. However, all of the polytellurides are extremely air-sensitive, and some data obtained was inconsistent.
Additional spectra of potassium/tellurium species in DMF solutions obtained by Richard Sevcik and Neil Tilly during 2005 seemed to indicate the possible presence of a tetratelluride. This would be consistent with the synthesis of a substituted metal carbonyl compound containing a bidentate tetratelluride ligand in DMF reported by Kolis, et. al. (Inorg. Chem., 27 (1988) 969. During the spring of 2006, Richard Sevcik prepared new solutions of all previously studied potassium/tellurium stoichiometries in DMF, obtained UV-visible spectra of them, subjected all spectra to curve resolution analysis, and obtained ICP data on all solutions. His data were in agreement with our previous observations regarding the presence of the equilibrium and also supported the presence of the tetratelluride in DMF solution.
Peter Poulsen repeated much of this work during the summer of 2006, focusing on the presence of the monotelluride in the DMF solutions. Spectral data of decomposition reactions verified earlier conclusions. This study was presented as the poster: “Equilibrium Among Potassium Polytellurides in Dimethylformamide Solution,” Richard S. Sevcik, Peter D. Poulsen, and Linda D. Schultz, 62nd ACS Southwest Regional Meeting, Houston, TX, October 20, 2006. This project is essentially complete, and a manuscript is being prepared for submission, probably to Inorganica Chimica Acta, this fall.
2. Determination of solvent purity using quantitative NMR (QNMR)
This project began as a cooperative effort between myself and Dr. Peter Bell to develop a better quantitative NMR experiment for my Instrumental Analysis class. The experiment worked much better than we had anticipated, and we presented the following poster: “A Green Quantitative NMR Experiment: Acetone and Ethyl Alcohol in D2O,” Peter T. Bell and Linda D. Schultz, 232nd ACS National Meeting, San Francisco, CA, September 10, 2006.
Further investigation revealed that this could be further developed into a useful and rapid technique for determining the purity of common solvents, such as acetonitrile, dimethylformamide, ethyl alcohol, methyl alcohol, and tetrahydrofuran. Preliminary results were presented as a poster: “Analysis of Purity of Common Solvents using Quantitative NMR,” Peter T. Bell, Alyssa D. Adkins, and Linda D. Schultz, 233rd ACS National Meeting, Chicago, IL, March 26, 2007. Unfortunately, a catastrophic quench of our NMR in early February prevented further development of this project. However, the instrument has now been repaired and we hope to complete this project and have a manuscript ready for submission to Analytical Chemistry in the spring of 2008.
3. Chemical Education publications
Although Chemical Education is not a research activity directly funded by the Robert A. Welch Foundation, student recipients of Welch Undergraduate Research Stipends have participated in the American Chemical Society Chemvention competition for the past four years. This is a national competition to solve some chemical problem in an original manner and within a limited budget. The Tarleton State University Student Affiliate Chapter has been a finalist each year, and their submissions have been presented each year at the spring National ACS Meeting, where they have been well received, and we have been encouraged to develop them into a format suitable for publication in the Jouenal of Chemical Education. This has proven to be very challenging, as the development of a simple demonstration into an activity suitable for an entire class or lab section is not unlike that of developing a small synthesis into a commercial process.
At the current time, four publications have been submitted. Their status is as follows.
A.K. Charlton, R.S. Sevcik, D.A. Tucker, and L.D. Schultz, “A Colorimetric Analysis Experiment Not Requiring a Spectrophotometer: Quantitative Determination of Albumin in Powdered Egg White,” J. Chem. Educ., 84 (2007) 826.
Richard S. Sevcik, Ragan L. McGinty, Susan V. Alexander, and Linda D. Schultz, “Periodic Table Target – A Game/Activity”, J. Chem. Educ. – accepted.
Richard S. Sevcik, O’dell Hicks, Susan V. Alexander, and Linda D. Schultz, “Elements – A Card Game”, J. Chem. Educ. – accepted.
Richard S. Sevcik, Rex Gamble, Elizabet Martinez, Susan V. Alexander, and Linda D. Schultz, “Ionic Blocks”, J. Chem. Educ. – resubmitted after review.
Because students involved in the projects were receiving financial support from the Welch Foundation at the time the work was done, Welch Foundation support has been acknowledged for these publications.