Browsing by Author "Charles Boss, Committee Member"

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • No Thumbnail Available
    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.
  • No Thumbnail Available
    The role of surface chemistry in defining the energetics and kinetics of single electron tunneling through individual gold nanoparticles
    (2003-06-24) McConnell, Wyatt Parks; Orlin Velev, Committee Member; Daniel L. Feldheim, Committee Chair; Christopher Gorman, Committee Member; Edmond Bowden, Committee Member; Charles Boss, Committee Member
    The properties of nanoscale materials are often dominated by their surface chemistry due to their increased surface-to-volume ratio. Metal nanoparticles with diameters smaller than ~12nm show a technologically relevant non-linear current-voltage response known as single electron tunneling. Gold nanoparticles offer an excellent platform for understanding how the surface chemistry of the metal island in a single electron-tunneling device can affect the current response of the structure. This is because the surfaces of these particles can be custom tailored using thiol-based self-assembled monolayer protocols that have been extensively developed for planar gold substrates. This dissertation describes STM measurements of single electron tunneling through individual gold nanoparticles of various sizes and surface chemistries in both air and solvent at room temperature and pressure. The voltage step-width of the resulting coulomb staircase was shown to be dependent on particle size. Solution experiments show that the energetics of single electron tunneling of particles with certain surface chemistries is dependent on the composition of the solution, while other surface chemistries can produce particles that give a stable single electron tunneling response in a wide variety of local chemical environments. Using acid and base terminated surface chemistries, particles were made that showed a defined response to a specific change in the local solution pH. The kinetics of single electron tunneling was also shown to be highly dependent on the chemical bond formed between the capping ligand and the metal particle.
  • No Thumbnail Available
    Synthesis and Characterization of a Dye Sensitizing Molecule for Photoelectrochemical DNA Hybridization Detection
    (2002-10-28) Lowe, Lisa Bizzell; Daniel L. Feldheim, Committee Chair; Stefan Franzen, Committee Member; Charles Boss, Committee Member
    A procedure for detection of DNA hybridization is described for the purpose of application in DNA microarray technology. The approach is based on the attachment of a dye-sensitizing molecule to the target oligonucleotide and detection of hybridization of this target to its complementary, surface-attached probe by photoelectrochemistry. A thiolated ruthenium (II) tris(2,2'-bipyridine) dye was synthesized and characterized. The target oligonucleotide was attached to a 10nm gold colloid before hybridization to the probe oligonucleotide, which was immobilized on a polycrystalline gold substrate. Upon hybridization the gold substrate was exposed to the thiolated [Ru(bpy)₃],²⁺ allowing attachment of the molecule to the gold nanoparticles. The photoelectrochemical response was dependent upon applied potential and target concentration. Attachment of the probe oligonucleotide to the gold substrate was investigated, and the electrolyte solution was tested for optimal performance.