Research Interests

I generally have opportunities for undergraduate and graduate students, pending resource availability. Undergraduate students can get course credit or work for pay (when available). Graduate students in the chemistry or biology departments who are interested in research can come by and talk to me to discuss opportunities and funding status. All interested students are invited to come by my office or e-mail me.

Summary: My research interests are diverse but focus primarily on DNA damage and/or protein binding by drugs and toxic substances. Experimentally, we use a variety of techniques, including: basic organic and inorganic synthesis, NMR spectroscopy, mass spectrometry, gel electrophoresis, HPLC, and computer (molecular mechanics) calculations.

Project 1: Interaction of platinum compounds with DNA and/or protein residues

Cisplatin, cis-Pt(NH₃)₂Cl₂, is a widely used anticancer drug. It has shown remarkable success with certain types of cancers, namely testicular and ovarian cancers. Additionally, platinum compounds that are structurally similar to cisplatin have been found to cleave proteins selectively after methionine or histidine residues, which could make them useful in a variety of biochemical applications. Thus, the reactions of platinum compounds are of significant biological interest. Reaction can occur with DNA, RNA, or proteins, the former being the key target responsible for anticancer activity. Cross-linking between adjacent guanine residues of DNA leads to distortion of the DNA helix and is considered to be primarily responsible for the toxicity and potency of the drug. Protein binding may be a detoxification pathway that leads to resistance to the drug’s activity.

We are studying the effects of the size and shape of the platinum complex on the formation of DNA and protein adducts. We have developed parameters that will allow us to use molecular mechanics calculations to generate computer models of complexes between platinum and methionine residues (a key amino acid target in proteins), and we are using parameters developed previously for platinum and guanine (the primary site of platinum reaction in DNA). These calculations are being used to predict the effect of the size of the platinum complex on the stability of guanine and methionine complexes.

Experimentally, we have synthesized selected cisplatin analogs. We have reacted these analogs with amino acid and nucleotide derivatives and characterized the products, primarily with NMR spectroscopy and HPLC, with future LC/MS work planned. We are also beginning to use enzyme inhibition assays to study the reaction profile of these platinum complexes with intact proteins

Current researchers:

Nilesh Sahi [Honors student]

Stephanie Robey

Amy Poynter [Honors student]

Ginny Martin [Honors student]

Alyssa Amonett

Celia Whelan [Academy student]

Cynthia Tope [Academy student]

Previous students (and post-graduation situation, if known):

Arcentra Beasley

Sam Bradley (Pikeville College School of Osteopathic Medicine)

Donald Chapman [Honors student] (M.S., Notre Dame University)

Steve Chmely (Ph.D. program, Vanderbilt University)

Kalpana Gollapudi [Graduate student] (cellular therapy specialist)

Fred Gransee

Carrie Haare (optometry school)

Allan Lam (preparing for medical school)

Jami Leckie (preparing for medical school)

Sondra Massey (research assistant, Vanderbilt University)

Jeremiah Mitchell (R & D chemist, Cytech products, Elizabethtown, KY)

Richard Pape [High school student]

Carrie Rowan (high school teacher)

Eli Xhaferi (preparing for medical school)

Becca Sandlin (Ph.D. program, Vanderbilt University)

Rebekkah Lively [Honors student] (Ph.D. program, University of South Carolina)

Seth King

Nayna Kotadia [Graduate student] (Ph.D. program, University of Tennessee, Knoxville)

Jennifer Adams

Emily Harper

Heidi Steinhaus

Justin Howell [Gatton Academy of Math and Science student] (University of Louisville)

Michael Starling (Ph.D. program, Vanderbilt University)

Carol Liao [Graduate student]

Kevin Kerian (Ph.D. program, Purdue University)

Khaja Muneeruddin [Graduate student] (Ph.D. program, University of Massachusetts at Amherst)

Rebecca Brock [Gatton Academy of Math and Science student] (University of Kentucky)

Dhatri Ravipati [graduate student]

Chaitanya Rapolu [graduate student]

Project 2: Reactions of cysteine thiolates as enzyme and protein models

Cysteine is an amino acid with a thiol functional group. The pK_a of cysteine is typically ~8.5 for the free amino acid, although hydrogen bonding and other interactions can lower this pK_a by up to 3-4 units in proteins. Thus, the dominant form of the cysteine residue is often the deprotonated thiolate, a good nucleophile that is used by a variety of proteins and enzymes, including proteases and DNA repair proteins.

We are interested in the reactions of free cysteine under basic conditions in which the thiolate form of cysteine is dominant. We are investigating the ability of deprotonated cysteine to promote reactions that resemble those catalyzed by enzymes using thiolates in the active site. Because cysteine is inexpensive and easy to work with, these experiments may be useful in teaching laboratories in biochemistry or biophysical chemistry. Also, reactions catalyzed by enzymes that are difficult to isolate could be studied by the use of cysteine at high pH. A variety of different instrumental techniques can be used to characterize the reactions, including NMR spectroscopy, UV-Visible spectroscopy, and HPLC.

Current students:

Brittany Morgan [Honors student]

Former students:

Emily Turner [Honors student] (dental school, University of Kentucky)

Project 3: Stabilization of polyunsaturated fatty acids

In collaboration with Dr. John Khouryieh, we are looking at methods to stabilize polyunsaturated fatty acids for food applications. This project will utilize a number of different techniques combining both chemistry and food science research areas.

Current students:

Goutham Puli [Graduate student]

Praneeth Papishetty [Graduate student]

Project 4: Dielectric and impedance analysis of biomolecules

Note: This project is not currently active.

In collaboration with Dr. Stuart Burris (analytical chemistry), Dr. Wei-Ping Pan (physical chemistry), and Dr. Alan Riga (adjunct faculty, physical chemistry), we investigated the use of dielectric and impedance methods to study biologically relevant molecules. These methods are utilized to determine the response of materials to electromagnetic fields. Often utilized to study polymers and materials, the methods are also applicable to biological systems.

We have utilized dielectric thermal analysis to study selected fatty acids and protein samples. Future studies involving more complex systems are planned.

Project 5: Reaction of ruthenium complexes with proteins

Note: This project is not currently active.

Selected ruthenium complexes have also shown anticancer activity, most likely due to their interaction with DNA. Reaction of ruthenium complexes with proteins appears to occur primarily at histidine residues, unlike platinum, which reacts with methionine and cysteine. Several properties of ruthenium are similar to platinum, such as the relatively slow kinetics of reactions. However, other properties of ruthenium complexes are significantly different. For example, ruthenium complexes often adopt an octahedral geometry instead of the square planar geometry that predominates for platinum(II). Ruthenium(III) complexes are also paramagnetic. These and other properties lead to the use of a variety of techniques for studying ruthenium complexes, including UV-Vis spectroscopy, IR, and paramagnetic NMR methods. We are studying the interactions of selected ruthenium complexes with histidine and histidine-containing proteins in order to better understand the interactions that are possible.

Previous researchers:

Stephen Gibson (Ph.D. program, University of Tennessee-Knoxville)

Nitin Jhamb

Bethany Alicie (M.S., Purdue University)

Megan McKeever

Amanda Moore (medical school)

Kelli Burton

Callie White