Brown Research Group
Research within the Brown group is focused on two areas of analytical chemistry: electroanalytical chemistry and separation science.
Electrochemical Preparation and Characterization of Chemically Modified Electrodes
In the area of electroanalytical chemistry, the Brown group studies the electrochemical preparation and characterization of chemically modified electrodes. A variety of compounds have been investigated as monomers for oxidative electropolymerization feasibility and these include: 3,4 ethylenedioxythiophene (EDOT), Fe(II) and Ru(II)-tris(5-amino-1,10 phenanthroline) and metal(II)-tetraaminophthalocyanine. A joint collaboration with Professor Elizabeth Sanford and research students is devoted towards preparing organic conducting polymer films using monomers of EDOT. The polymer films are formed via oxidative electropolymerization using cyclic voltammetry (CV) and are being used on different electrode surfaces for sensing applications of metals, and biologically and environmentally important molecules. The CV shown below is the electropolymerization of an EDOT-based compound which is fluorinated.
Another major aspect of the research program is devoted to understanding the mechanisms of charge transfer within the polymeric films by various electrochemical characterization techniques. This involves calculating the apparent diffusion coefficients using electrochemical techniques, and thin film thickness using ion beam techniques or atomic force microscopy. The students involved in this research will gain a fundamental understanding in a variety of electrochemical (CV and chronocoulometry) hyphenated techniques (spectroelectrochemistry).
The CV on the left is the characterization of the fluorinated EDOT compound. When the polymer film is exposed to aqueous solutions, the electrochemical activity diminishes, but is restored with return to an organic-based supporting electrolyte solution. The CV characterization on the right depicts the reversible charge transfer occurring within the Ru-based film.
A more thorough examination and characterization of the films is accomplished using electrochemical impedance spectroscopy. The figure shown on the right is a nyquist plot of Ru(II)-tris(5-amino-1,10 phenanthroline). Mixed kinetic and mass transfer impedances are present in the polymer film as evidenced by the semicircle and a 45o warburg diagonal at high and low frequencies, respectively.
Chemical Aspects of Ethnobotany and Plant Physiology
Most medicinal compounds currently used in industrialized nations are chemically synthesized, but a large number of medicines can trace their origin to specific compounds isolated from plants. In many cases, these biologically active compounds were first discovered because of their use by native peoples. Ethnobotanical studies aim to examine how the people of a particular region utilize the plants around them. Plant physiology is the study of how plants function. Plants are such amazing biochemical factories that are continuously adapting to new selection pressures. As a result, they are evolving continuously at the chemical level. The fields of ethnobotany and pharmacology rely upon the evolution of these chemical novelties to treat new medicinal problems in our modern society. Very little is known about how plants can be manipulated under certain environmental and biotic cues to produce effective quantities of these medicinal chemicals. The central plant physiological theme is to gain knowledge about how plants allocate resources to various chemical pools of interest in response to environmental and biotic cues during plant growth, development and survival.
The methods used to study the chemical properties of compounds involved in certain plants at the cellular level will be drawn primarily from analytical chemistry and organic chemistry. Various instrumental techniques in the area of separation science and spectroscopy are used to understand the dynamic and synergistic impact of environmental and biotic manipulative implants of chemicals on animal growth, animal development and animal survival. Each of these areas are monitored using modern methods in high-performance liquid chromatography (HPLC) with UV and electrochemical detection, and gas chromatography-mass spectrometry. Students working on this research will utilize chemical information from literature resources to acquire background information about the utilization of analytical chemistry techniques applied to medicinal chemistry.
Several different groundnut Apios species obtained from various locations in China and North America were evaluated for genistein and total protein content. This preliminary research was conducted to determine the viability of these species as potential food sources. HPLC instrumentation was used for the determination of genistein in Apios (Fabaceae) species including A. carnea and A. fortunei from China and A. americana from North America. The extracts of 80% ethanol were analyzed under HPLC isocratic conditions at a wavelength of 270 nm and the Lowry Protein Assay at 650 nm was utilized to determine the amount of protein in the samples. A linear calibration range of 0 ppm–340 ppm for genistein was obtained and presence of genistein in the samples were confirmed using LC-MS (M+, m/z 271). Genistein was present from 15-393 µg genistein/g plant, with the most genistein found within the groundnut tuber system. Of the samples analyzed, the A. americana plant contained the largest amount of genistein. The protein content ranged from 14–30 mg/g plant.
This research is focused on:
- Establishing a living repository of Apios species from North America and Asia
- Testing the adaptive capacity of diploid and polyploid populations
- Obtaining genomic DNA of all species, examining their genetic structures, and elucidating the origin and relationships among species of Apios
- Analyzing chemical compositions of different organs of each species
- Breeding new varieties of food and medicine of high quality via hybridization among species
HLPC with UV-Vis detection is the primary method used in the Brown lab to investigate the chemical composition of the plant species. Shown below is a chromatogram of an extract of the groundnut tuber, which was tested for the presence of genistein. The peak near 23 minutes occurs with pure standards of genistein as was confirmed using LC-MS. Current research is exploring the use of electrochemical detection of genistein and several other compounds of medicinal importance in this plant species.
Students interested in this project or similar projects should contact Professor Brown.
A. Paul Schaap Science Center35 East 12th StreetRoom 3101Holland, MI 49423