Raman and fluorescence investigations of hydrophobic solvation
Abstract
This thesis details the development of Raman scattering methods to investigate hydrophobic solvation in aqueous solutions. Chapter One describes the second-derivative variance minimization (SDVM) method for automated spectral subtraction. Synthetic data showed that SDVM method performed the best of the five methods tested. Solvent subtraction was demonstrated on experimental data of dilute solutions of benzene in n-hexane. SDVM method was utilized further to show spectral changes induced by water on the solvation shell of acetone. Chapters Two and Three detail progress that was made towards global thermodynamic analysis of partitioning, and exploration of hydrophobic association of various solutes in aqueous solution. Specifically, Chapter Two establishes Raman spectroscopy as a viable technique for measuring partition coefficients. Alcohols, amino acid, and rhodamine dyes in various two-phase liquid-liquid systems were studied. Chapter Three discusses investigations of self-association of alcohols and the formation of solute-cyclodextrin (CD) inclusion complexes in aqueous solution using Raman measurements. Dimerization constants for alcohols in aqueous solution were calculated using multivariate analysis of spectral changes. Partitioning of those alcohols in octanol-water revealed solute association in the organic phase, and those dimerization constants were calculated. In addition, spectral evidence was observed for solute-CD inclusion complexes. Predictions of the Raman solute signal increase upon complex formation were evaluated. Chapter Four describes protein quantification in two-dimensional gels of fluorescently labeled proteins, using water Raman band as internal standard. The proteins were covalently labeled with a rhodamine dye (TAMRA), or the gels were passively stained with Sypro Ruby. The fluorescence/Raman results were compared to images from a fluorescence scanner. The water internal standard method enabled dye quantification and protein estimation. Chapter Five describes the application of curve resolution analysis to solvation shell spectroscopy. Solutes with different polar moments, namely acetonitrile and cyclohexane, were shown to affect the structure of the solvent, 1,2-dichloroethane. The resulting spectral changes were analyzed by peak height comparison, SDVM method, and curve resolution analysis. Acetonitrile induced more gauche conformations of 1,2-dichloroethane, while cyclohexane enhanced trans conformations. Moreover, multivariate curve resolution (MCR) analysis enabled extraction of two spectra, the bulk solvent spectrum and the solvent shell with the solute spectrum.
Degree
Ph.D.
Advisors
Ben-Amotz, Purdue University.
Subject Area
Analytical chemistry|Chemistry
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