In this thesis a series of diphenol phenanthroline (Dpp) peptide conjugates were synthesized and then coupled to ferrocene to give the corresponding organometallic conjugates. The first step of the synthesis was achieved by esterification of peptides with the phenol group of the Dpp. The next step was the removal of the protecting Boc group and the addition of ferrocene acid chloride at high dilutions to give the desired macrocycles of the type Dpp-(peptide)2 Fc. (peptide = Leu-Leu (3), Leu-Leu-Leu (5) ). However, the syntheses proceeded in low yields where only small quantities of the desired products were obtained. A suitable crystal of compound 3 was grown from CHCl3 which shows a number of intra and intermolecular hydrogen bonding interactions between peptides strands.In addition, the system [Dpp-Fc]2 (1) was syntheised by refluxing Dpp and Fc[COCl]2 in dichloromethane. A suitable crystal was grown which has ð-ð interactions between intramolecular Dpp units as well as a number of CH-ð interactions which determine the crystal packing. The electrochemical experiments on compound 1 show a cathodic shift upon addition of Zn2+ to a solution of 1. This observation is believed to occur because of a conformational change in 1. The last area of synthesis that was done was the attempt at â-sheet formation using Fc as a scaffold to align peptide strands. Two systems were studied in this thesis [Fc(n-AA-OMe)(1-AA)]2-1,4butyl diamine. (AA =Ala (8), Gly (9)). Both were studied by 1H NMR to evaluate the presence of hydrogen bonding interactions. The results indicate the presence of intramolecular H-bonding, which is believed to form â-sheet like structures in solution.

Cationic antimicrobial peptides (CAPs) offer a viable alternative to conventional antibiotics as they physically disrupt the bacterial membranes, leading to cell lysis and death. However, colonized bacteria often form “biofilms” – characterized by the overproduction of exopolysaccharides - that restrict the penetration of antibiotics; successful antimicrobial agents must evade this exopolysaccharide ‘matrix’ to reach the bacterial membrane. Since the Pseudomonas aeruginosa biofilm alginate traps CAPs by forming peptide-alginate complexes, the aim of this thesis is to better understand the mechanisms of interaction of CAPs with bacterial membranes and biofilm alginate. Using a series of CAPs designed in our lab derived from the sequence KKKKKK-AAFAAWAAFAA-NH2, we found that hydrophobicity, charge distribution, and amino acid composition of CAPs play important roles in their membrane disruptive power, bioactivities, alginate-binding and alginate-diffusion abilities. These findings suggest routes to an optimal balance of factors in CAP design to allow both biofilm penetration and bacterial membrane destruction.

Cationic antimicrobial peptides (CAPs) offer a viable alternative to conventional antibiotics as they physically disrupt the bacterial membranes, leading to cell lysis and death. However, colonized bacteria often form “biofilms” – characterized by the overproduction of exopolysaccharides - that restrict the penetration of antibiotics; successful antimicrobial agents must evade this exopolysaccharide ‘matrix’ to reach the bacterial membrane. Since the Pseudomonas aeruginosa biofilm alginate traps CAPs by forming peptide-alginate complexes, the aim of this thesis is to better understand the mechanisms of interaction of CAPs with bacterial membranes and biofilm alginate. Using a series of CAPs designed in our lab derived from the sequence KKKKKK-AAFAAWAAFAA-NH2, we found that hydrophobicity, charge distribution, and amino acid composition of CAPs play important roles in their membrane disruptive power, bioactivities, alginate-binding and alginate-diffusion abilities. These findings suggest routes to an optimal balance of factors in CAP design to allow both biofilm penetration and bacterial membrane destruction.

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.

In this thesis a series of diphenol phenanthroline (Dpp) peptide conjugates were synthesized and then coupled to ferrocene to give the corresponding organometallic conjugates. The first step of the synthesis was achieved by esterification of peptides with the phenol group of the Dpp. The next step was the removal of the protecting Boc group and the addition of ferrocene acid chloride at high dilutions to give the desired macrocycles of the type Dpp-(peptide)2 Fc. (peptide = Leu-Leu (3), Leu-Leu-Leu (5) ). However, the syntheses proceeded in low yields where only small quantities of the desired products were obtained. A suitable crystal of compound 3 was grown from CHCl3 which shows a number of intra and intermolecular hydrogen bonding interactions between peptides strands.In addition, the system [Dpp-Fc]2 (1) was syntheised by refluxing Dpp and Fc[COCl]2 in dichloromethane. A suitable crystal was grown which has ð-ð interactions between intramolecular Dpp units as well as a number of CH-ð interactions which determine the crystal packing. The electrochemical experiments on compound 1 show a cathodic shift upon addition of Zn2+ to a solution of 1. This observation is believed to occur because of a conformational change in 1. The last area of synthesis that was done was the attempt at â-sheet formation using Fc as a scaffold to align peptide strands. Two systems were studied in this thesis [Fc(n-AA-OMe)(1-AA)]2-1,4butyl diamine. (AA =Ala (8), Gly (9)). Both were studied by 1H NMR to evaluate the presence of hydrogen bonding interactions. The results indicate the presence of intramolecular H-bonding, which is believed to form â-sheet like structures in solution.

Peptide synthesis and metal doping, combined with mass spectrometric and ion mobility spectrometric techniques, have provided a picture of the fragmentation behavior of a large field of homologous peptide ions, represented as XVGVAZG, where the X amino acid is either arginine, histidine, lysine, aspartic acid or tryptophan and the Z amino acid is proline, glycine, serine, or histidine. These homologous peptide ions have been carefully selected to probe the effects of charge site location and secondary interactions upon the fragmentation chemistry of peptides. Peptides were synthesized on solid support, doped with appropriate metal salts to attach Li+, Na+, K+, Cu+ and Ag+ , and then examined using ion mobility spectrometry, and tandem mass spectrometry, both high energy collision induced dissociation (CID) and photodissociation using 193- nm laser light. Molecular dynamics calculations enabled me to derive candidate structures for these ions that agree with the ion mobility data for the ions. The fragmentation chemistry and structure selection of the first group of peptides, those that contain a proline residue, indicate that the presence of high proton and high metal ion affinity residues at the N-terminal position of the peptide direct the fragmentation of the highly charge-solvated ions according to a charge site directed mechanism. Further examples of charge-solvated structures and charge-directed fragmentation are shown for peptides where the sixth amino acid residue has been replaced with glycine or serine, eliminating the influence of the proline residue in the sixth position. Photodissociation of the peptides indicates that the position of valine residues along the peptide backbone influences the types of abundant fragment ions observed and ai and dai ions are observed exclusively at the site of valine residues. This observation continued, even when the position of the valine residues were altered by synthesis, leading me to the conclusion that the fragmentation of these peptides. The study was expanded to include significantly more complex peptides, those containing second high proton and high metal ion affinity residues, and though the data are complex, the influence of charge solvation in those systems is strong as well, according to my analysis of the candidate structures obtained and the types of fragment ions observed.

Doctoral thesis--organic chemistry--Göteborg university, 2002. / Bibliogr. p. 99-108.

Dissertation--Psychologie--University of Bergen, 1997. / Notes bibliogr.

Thèse doctorat : Chimie : Strasbourg 1 : 2006. / Thèse soutenue sur un ensemble de travaux. Titre provenant de l'écran-titre. Bibliogr. 11 p.