Lecturer — General Chemistry
Research and/or Creative Works
“Tell me and I’ll forget. Show me and I’ll remember. Involve me and I’ll understand.”
Student involvement and feedback are the cornerstones of my teaching philosophy. As a teacher I try to not only impart the axioms and rules of a subject to the student, but also help them to build a set of skills they can use to solve problems independently. By teaching students to do more than just memorize concepts, they will be better prepared when they encounter chemical problems on an examination, in the laboratory, or on the job. Listening to a lecture solely, does not actively impart the skills necessary to solve those problems alone. I believe a multifaceted approach utilizing technological advancements and group problem sessions are a more effective way to achieve this goal.
Chemistry is a complex subject with its own language of nomenclature, mathematical concepts, and processes. It requires the ability to draw and interpret molecular structures in both two and three dimensions, calculate physical properties, and also follow the process of how one molecule turns into another molecule. In these aspects, chemistry is a language course, an art course, and a science course combined. I like to use computer based technologies to complement chalk-talk lecture presentations as a method to better visualize important course content. This allows for the inclusion of 3D models and animation to further illustrate a concept as well as sample homework videos. As an educator I must continue to adapt to the way my students learn and not simply teach to the lowest common denominator.
I strive to help students to build problem-solving skills, not by asking students to memorize and regurgitate examples presented in lecture, but by applying earlier concepts to the current problem. I find it useful to take the time during lectures to set up a series of problems, such as the mathematical determination of an unknown structure and its physical properties, and then work through the strategy necessary for solving the problem. Also by doing this in a small group setting, such as during recitation/review, the instructor-student and student-student exchange of ideas and strategies enhances the learning process. Students then have a better ability to approach other chemical problems of varying complexity.
One of the most powerful tools that can be used for teaching chemistry is physical demonstrations. In-class demos when properly planned, give practical examples of the principles being taught in the course. Involving the students in these activities further reinforces their link to the subject matter and encourages them to understand the material at a level far above the lecture setting. Also, the laboratory environment allows for concepts from lecture to be revisited on a more individual level. I have had the pleasure on several occasions with students when they finally get a concept, or they grasp the practicality of material covered in lecture, while working in the lab. It truly is a wonderful feeling to get such positive feedback from students.
Confucius said it succinctly. I believe that in teaching chemistry, telling students is not enough. Through effective use of technology and well-prepared lectures one can show students chemistry that may be difficult for them to conceptualize. Also by involving the students through class problem sessions, demonstrations, and laboratory experimentation students will understand chemistry’s charisma. As a result more enjoyment and enthusiasm will be felt among the student body, due to a better appreciation of the subject material. I believe that this will serve the academic community well by helping to disband the myth that chemistry is simply a difficult subject that all science majors must get through.
New Methodologies for the Construction of Amino Acid Isosteres. The areas of research listed below are synthetic organic and physical organic subsets to the impressive projects found within Dr. Hondal’s group here at the University of Vermont. My research in synthetic organic chemistry has two main parts. The first involves the elucidation of new methodologies for the construction of amino acid isosteres with particular emphasis on oxidized vicinal cysteinyl cysteine dyads and oxidized vicinal cysteinyl selenocysteine dyads. These oxidized vicinal dyads form an eight-membered disulfide ring with multiple conformations and are rare substructural element in proteins. They are often found in specific γ-turn types and this unit is of functional importance to those few that possess its structure such as with the thioredoxin reductases (TRs). During construction of these dyads elements of flexibility and rigidity are installed so that we can come to an understanding of how substitution affects conformation of the vicinal disulfide ring and how it affects activity within TRs. Unrelated to TR, this research has elucidated a number of possible γ-turn mimics that have been hitherto unknown.
The second involves the construction of sulfur- or selenium-containing amino acid isosteres and other small molecules to reach a chemical understanding of why an enzyme would utilize selenium as opposed to sulfur. While these chalcogens are similar, it is much harder for an enzyme to incorporate selenium, when compared to sulfur, so there must be a chemical explanation as to why an enzyme would use selenium as opposed to sulfur. Through studies involving Thioredoxin Reductase we have come to understand that a potential reason for biology to use selenium, is its ability to be reduced even when it is in the over-oxidized selenenic (RSeO2H) form by exogenous thiol. For sulfur this over-oxidized form (sulfinic; RSO2H) cannot be reduced. For the enzyme this means that use of selenium confers protection from oxidative stress. If the enzyme is oxidized at a selenocysteine (Sec) residue and made inactive, exogenous thiol can convert it from the inactive Sec-SeO2H form into the active Sec-SeH form of the enzyme. This cannot be said for the sulfur-homolog since if it is oxidized at a cysteine (Cys) residue and made inactive, exogenous thiol cannot convert it from the inactive Cys-SO2H form into the active Cys-SH form of the enzyme.
My research in physical organic chemistry deals with determining how conformation of the vicinal disulfide or selenosulfide ring affects its redox potential. Thiol-disulfide and thiol-selenosulfide exchange reactions are monitored via HPLC or NMR, which allow these potentials to be determined. The ability to relate conformation of the ring to redox potential provides a guide as to what types of ring structure prefer to be in the reduced or oxidized state. This can then provide insight as to what type of conformations are needed for redox cycling to occur in the TRs. Similarly, rates of reduction of oxidized and over-oxidized forms of selenium (RSeOH; RSeO2H; RSeO3H) and sulfur (RSOH; RSO2H; RSO3H) are measured by HPLC and NMR to determine how fast or slow these processes occur. This provides a chemical rationale as to why selenium would be utilized over sulfur, since selenium confers stability by not becoming inactive under events of oxidative stress.
- Payne, N. C.; Barber, D.; Ruggles, E. L.; Hondal, R. J. “Can dimedone be used to study selenoproteins? An investigation into the reactivity of dimedone toward oxidized forms of selenocysteine”, Protein Sci. 2018, 28, 41-55.
Payne, N. C.; Geissler, A.; Button, A.; Sasuclark, A. R.; Schroll, A. L.; Ruggles, E. L.; Gladyshev, V. N.; Hondal, R. J. “Comparison of the redox chemistry of sulfur and selenium containing analogs of uracil”, Free Rad. Biol. Med. 2017, 104, 249-261.
St. Marie, E.; Ruggles, E. L.; Hondal, R. J. “Removal of the 5-nitro-2-pyridine-sulfenyl protecting group from selenocysteine and cysteine by ascorbolysis”, J. Pept. Sci., 2016, 22, 571-576.
Ruggles, E. L.; Deker, P. B.; Hondal, R. J. “Conformational analysis of oxidized peptide fragments of the C-terminal redox center in thioredoxin reductases by NMR spectroscopy”, J. Pept. Sci. 2014, 20, 349-360.
Lothrop, A. P.; Snider, G. W.; Flemer, S. Jr.; Ruggles, E. L.; Davidson, R. S.; Lamb, A.; Hondal, R. J. “Compensating for the absence of selenocysteine in high Mr thioredoxin reductases: The electrophilic activation hypothesis”, Biochemistry, 2014, 53, 664-674.
Areas of Expertise and/or Research
Synthesis of new, non-natural amino-acid derivatives
- B.S., Ithaca College, Ithaca, NY, 1994
- M.S., Bucknell University, Lewisburg, PA, 1996
- Ph.D., Michigan State University, E. Lansing, MI, 2003
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Innovation Hall E333
CHEM 031 and 032