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Adhesion of the opportunistic fungal pathogen, Candida albicans, to host surfaces is mediated through the mannoprotein-rich surface. This thesis examines the role of cell wall mannoproteins in the host-fungus interactions and the mechanism by which these proteins are tethered to the major structural polysaccharides of the wall. The mannosyl modifications of cell surface proteins are involved in host interaction. Periodate oxidation of fungal surface carbohydrates reduced adhesion to epithelial cells confirming that mannan is a component adhesion of C. albicans. Strains of C. albicans disrupted in MNT1, 2 and 3 genes encoding mannosyl transferases, were reduced in adhesion to both epithelial cells and Matrigel. Adhesion was also influenced by the Ura-status of C. albicans strains, which differs as a result of targeted gene disruption by the URA-blaster strategy. Ura-strains were less adhesive but this was not due to altered growth rate and could not be alleviated by adding excess uridine. Therefore current methods for gene deletion have to be questioned when considering adhesion as a virulence factor. Strains defective in glycosylation were altered in covalently associated cell wall proteins (CWPs) in terms of mobility during electrophoresis. The greatest alterations observed were in the CWPs of C. albicans strains with severe glycosylation defects, such as in Dochl/Doch1 and Dpmt1/Dpmt1 mutants, defective in N- and O-linked glycosylation, respectively. These strains also secreted more mannoprotein were altered in morphology or gross cell wall structure, and had elevated cell wall chitin. Therefore glycosylation is required for normal CWP incorporation and cell wall construction. For the first time C. albicans was shown to link a CWP, other than Pir-CWP, to the cell wall network via an alkali-sensitive linkage. The nature of this type of linkage remains unknown, however an O-mannan chain, whose synthesis is not initiated by Pmt1p, may be involved. Pir-CWP incorporation was increased in a Dpmt1/Dpmt1 null mutant and could be partially attributed to increased expression. Pir-CWP expression and incorporation was pH-dependent and may be regulated in response to the different pH at different host niches.

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In this study, a synthetic, water soluble cavitand octa acid (OA) is used as medium for conducting photochemical reactions. The cavitand octa acid is soluble in water in slightly basic conditions. OA forms different types of complexes with variety of organic guest molecules. Remarkably, in presence of a hydrophobic guest, two of these OA molecules self assemble to form a capsular complex (guest@(OA)2). The confined inner phase of the cavitand can be utilized to control both photochemistry and photophysics of organic guest molecules. Stilbene derivatives undergo cis/trans (Z/E) photoisomerization in organic solvents. The results of our studies with stilbenes@(OA)2 suggest that the available free volume for encapsulated guest stilbenes could be manipulated by changing the number and position of the substituent methyl groups which has a significant influence on the photoisomerization process. Further, energy transfer from caged donor ((fluorenone)2@(OA)2) to caged acceptor ((stilbene)@(OA)2) was explored. It is also demonstrated that photoinduced electron transfer (PET) between acceptor (cationic) present outside the OA capsule to donor (a stilbene) present within the capsule is feasible and occurs at a higher than diffusion controlled rate. The PET in the above supramolecular system could be controlled by employing another cavitand, cucurbit[7]uril (CB7) to complex with cationic acceptor. Also, studies with carefully chosen guest molecules suggest that selective photocyclodimerization can be carried out within the inner phase of OA.

Host Defense Peptides (HDPs) are small, cationic and amphipathic molecules with inherent antimicrobial and immunomodular function. However their effects on blood-derived T cells is unknown and is the focus of this investigation. In this thesis, porcine peripheral blood mononuclear cells (PBMCs) were stimulated with bovine myeloid antimicrobial peptide (BMAP)-27, BMAP-28, Indolicidin (Indol), or HH2 in the presence and absence of Concanavalin A (ConA). It was observed that BMAP-27, BMAP-28, and Indol inhibited ConA-stimulated porcine PBMC proliferation. To ensure that the observed effect on cell proliferation was not simply due to a physical interaction between the peptide and ConA, addition of peptide and ConA was staggered. Porcine CD4+/CD8+ T cells were isolated from blood using magnetic activating cell sorting (MACS) and it was determined that BMAP-27 and BMAP-28 inhibited ConA-stimulated T cell proliferation. They did not promote T cell necrosis, but approximately 40 % of the activated T cells undergoes apoptosis in the presence of BMAP-27 and BMAP-28. The remaining 60 % of the T cells consumed very little ATP and showed an increase in expression of cytotoxic T lymphocyte antigen-4 (CTLA-4), indicating the induction of T cell anergy. The addition of exogenous IL-2 decreased the surface expression of CTLA-4 in ConA- activated CD4+ T cells and induced renewed CD4+/CD8+ T cell proliferation, an indicator that these cells underwent activation-induced anergy. Thus, we submit that BMAP-27 and BMAP-28 may play a role in returning the activated T cell population to a homeostatic state through induction of peripheral tolerance mechanisms.

Host Defense Peptides (HDPs) are small, cationic and amphipathic molecules with inherent antimicrobial and immunomodular function. However their effects on blood-derived T cells is unknown and is the focus of this investigation. In this thesis, porcine peripheral blood mononuclear cells (PBMCs) were stimulated with bovine myeloid antimicrobial peptide (BMAP)-27, BMAP-28, Indolicidin (Indol), or HH2 in the presence and absence of Concanavalin A (ConA). It was observed that BMAP-27, BMAP-28, and Indol inhibited ConA-stimulated porcine PBMC proliferation. To ensure that the observed effect on cell proliferation was not simply due to a physical interaction between the peptide and ConA, addition of peptide and ConA was staggered. Porcine CD4+/CD8+ T cells were isolated from blood using magnetic activating cell sorting (MACS) and it was determined that BMAP-27 and BMAP-28 inhibited ConA-stimulated T cell proliferation. They did not promote T cell necrosis, but approximately 40 % of the activated T cells undergoes apoptosis in the presence of BMAP-27 and BMAP-28. The remaining 60 % of the T cells consumed very little ATP and showed an increase in expression of cytotoxic T lymphocyte antigen-4 (CTLA-4), indicating the induction of T cell anergy. The addition of exogenous IL-2 decreased the surface expression of CTLA-4 in ConA- activated CD4+ T cells and induced renewed CD4+/CD8+ T cell proliferation, an indicator that these cells underwent activation-induced anergy. Thus, we submit that BMAP-27 and BMAP-28 may play a role in returning the activated T cell population to a homeostatic state through induction of peripheral tolerance mechanisms.

Solid state lighting industry is booming in recent years because of the green energy requirement. Therefore, phosphorescent OLEDs using phosphorescent emitters doped into charge-transporting hosts as emissive layers (EMLs) have attracted extensive interest due to their highly efficient emission compared to conventional fluorescent OLEDs, through radiative harvesting of both electro-generated singlet and triplet excitons. To achieve better charge balance and device performance, many researchers focus on developing new phosphorescent host materials with bipolar charge transporting property. In this work, we successfully designed and synthesized a host material CzppT containing hole-transporting carbazole and electron-transporting pyridine and investigated the physical properties. With a high triplet energy, CzppT is considered a promising universal host material and has been applied to phosphorescent OLEDs of blue/white colors. Blue/white OLEDs based on CzppT as host and Firpic/Ir(piq)2(acac) as dopant materials show maximum external quantum efficiencies (11.0% for blue, 11.32% for white) and CIE coordinates [(0.18,0.41)for blue, (0.32,0.36) for white)]. The results indicate that the bipolar host CzppT with high triplet energy has potential in manufacturing blue and white OLEDs for display or lighting applications.