Browsing by Author "Dan Feldheim, Committee Member"

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    Investigations of Liposome/Water Partitioning Using Electrokinetic Chromatography
    (2005-08-03) Barker, Jason Alan; Charles Boss, Committee Member; Morteza Khaledi, Committee Chair; Edmond Bowden, Committee Member; Dan Feldheim, Committee Member
    In this two-part investigation, Linear Solvation Energy Relationship (LSER) models were applied to liposome/water partitioning data determined by liposome electrokinetic chromatography (LEKC). In the first part of the study, LEKC retention factors were determined for a set of 71 solutes including 50 neutral aromatic solutes and 21 neutral drugs using the liposome phases mM DPPG20DPPC80, 15 mM DPPG20DPPC80/3 mM cholesterol, and 15 mM DPPG20DPPC80/6 mM cholesterol. These retention factors were used to determine linear solvation energy relationships (LSER) models for each of the three lipid phases for the set of 50 neutral aromatic solutes and the entire set of 71 solutes. The predictive ability of the LSER model was tested by using the model generated for the set of 50 neutral aromatic solutes to predict retention factors for the 21 neutral drugs. The descriptive ability of the LSER model was tested and used to examine the interactions that control liposome/water partitioning for the set of 50 neutral aromatic solutes and the set of 71 solutes including 21 neutral drugs. In the second part of the study, wo liposome electrokinetic chromatography (LEKC) lipid phases were introduced that approximate the lipid composition of the cell membrane of monkey intestinal epithelial cells. 15 mM PI10DPPS10DPPC30DPPE30SPM20/9.75 mM cholesterol most nearly approximates the lipid composition of the cell membrane of monkey intestinal epithelial cells. 15 mM DPPG20DPPC80/9.75 mM cholesterol replaces the specific lipids contained in the monkey intestinal epithelial cell membranes with the zwitterioninc lipid DPPC and DPPG. The retention factors determined for a set of 50 neutral aromatic solutes using these two LEKC phases are highly correlated (r2=0.99), with a slope near unity (m=0.91) and an intercept near zero (b=0.05). The normalized LSER system coefficients for these lipid phases are also very similar. The LSER system coefficients determined for 15 mM PI10DPPS10DPPC30DPPE30SPM20/9.75 mM cholesterol and 15 mM DPPG20DPPC80/9.75 mM cholesterol were compared with an LSER model generated by Abraham, et al. for human intestinal absorption.
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    The Photophysical and Electrochemical Properties of Rhenium-selenide Dendrimers
    (2003-09-12) Yohannan, Joshua C.; Jim Martin, Committee Member; Dan Feldheim, Committee Member; Chris Gorman, Committee Chair
    Dendritic molecules have demonstrated the ability to encapsulate metal cluster cores and shield them from an external environment. The ability to shield the metal cluster core results in altering of some of the measurable properties of that metal cluster. We propose to obtain photophysical and electrochemical data on an octahedral metal cluster dendrimer. This rhenium-selenide metal cluster was chosen as the dendrimer core because previously characterized rhenium-selenide metal clusters have been demonstrated to luminescence and possess accessible electrochemistry. For these investigations a dendron that has previously exhibited encapsulation and still allowed access to an electroactive will be used. These dendrons will be slightly modified in order to attach them to the rhenium-selenide core. Photophysical and electrochemical investigations will be done on these dendrimers, generations zero through two.