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Investigations of Solvation Using Property Modulation
Acetonitrile/water
and methanol/water mixtures are far and away the most commonly used solvent
systems in reversed phase liquid chromatography.
The goal of this project is to achieve an improved understanding of these
liquids and their solvation interactions with compounds that need to be
separated, leading to quantitative prediction of the separation characteristics
of a liquid chromatography method.
Although these solvent mixtures have been studied extensively in the
past, a detailed understanding of the interactions in these liquids is still
lacking. In
this work, a suite of complementary methodologies are used to characterize these
mixtures by modulation of a number of the experimental conditions, including
mole fraction composition of the mixtures, temperature, and solute identity and
concentration. Infrared spectroscopy, with both transmission and attenuated
total reflectance sampling, and Raman spectroscopy are used to study these
mixtures. The
resulting spectra are analyzed using several techniques, including
two-dimensional correlation analysis and alternating least squares analysis, to
elucidate structural information about the components in the mixtures.
These results are analyzed in the context of several theoretical and
simulation techniques, including ab initio structure calculations, and
Monte Carlo and cellular automata simulations.
Collaborators: Lemont B. Kier and Sally S. Hunnicutt
This work has been funded by the National Science Foundation (CHE-0076290).
Characterization of Drug Metabolism Using Chemometrics
Traditionally, metabolic studies have been limited to the characterization of single pathways, and the complex relationships between overlapping and competing metabolic reactions are not considered. This project is focused on the development of approaches for identifying metabolic pathways, following metabolite dynamics, and quantifying rate constants in complex reaction systems. Due to their central roles in the metabolism of many endogenous and exogenous compounds, the enzymes cytochrome P450 and uridinediphosphoglucuronosyl-transferase are of primary interest. Drugs such as dextromethorophan and illicit amphetamines are currently under investigation. Liquid chromatography coupled with UV-visible and mass spectrometric detection are used to analyze the small molecule substrates, and the corresponding intermediates and products. The kinetics for all reaction pathways are quantified using an alternating least squares algorithm. Studies will include single enzymes, and enzyme and substrate mixtures of increasing complexity. These studies are leading to new mechanistic insights regarding the interactions among simultaneous enzymatic pathways, as well as providing a fundamental understanding of the methodologies required for the analysis of a broad range of complex metabolic pathways.
This
work is funded by Research Corporation (RA0344).