Venoms, toxins and host-defence systems constitute rich sources of biologically active molecules, many of which have enormous therapeutic and biotechnological potential. In particular, peptides are often a significant component of these chemical arsenals, and are fundamentally important as biological effector molecules. The research presented in this thesis is centred on the isolation and investigation of peptides from both frogs and spiders, and endeavours to probe the important structural and mechanistic features of these bioactive compounds. The skin peptide profiles of interspecific hybrids between the green tree frog Litoria caerulea and the magnificent tree frog Litoria splendida have been investigated in a ninemonth survey. Fourteen peptides were characterised primarily using mass spectrometry, of which three had not been identified previously in the skin secretions of either parent. A number of these peptides are antibacterial agents, while others effectively inhibit the formation of nitric oxide by neuronal nitric oxide synthase. Implications for the genetics and expression of amphibian dermal peptides are also discussed. The majority of frogs of the genus Litoria contain at least one peptide in their glandular secretion capable of inhibiting the formation of nitric oxide by the enzyme neuronal nitric oxide synthase. This was proposed to occur by preventing the association of the regulatory cofactor, Ca²⁺ -calmodulin, with its binding site on the enzyme. Non-covalent binding of the amphibian peptides to calmodulin in the presence of Ca²⁺ has been confirmed using electrospray ionisation mass spectrometry, by the observation of complexes in the gas phase with a 1 : 1 : 4 calmodulin / peptide / Ca²⁺ stoichiometry. In addition, the structure and binding interactions of caerin 1.8, a potent nitric oxide synthase inhibitor, have been further probed using mass spectrometry and nuclear magnetic resonance spectroscopy techniques. Recently a number of small, disulfide - containing neuropeptides of the signiferin and riparin families have been characterised from the skin secretion of frogs of the Crinia genus. Of these, signiferin 1 and riparin 1.1 are both ten residue peptides with similar primary sequences, however appear to have a significantly different spectrum of bioactivity. Although both act at cholecystokinin-2 receptors, signiferin 1 is smooth muscle active while riparin 1.1 is not, and instead causes proliferation of lymphocytes. The three-dimensional structures of these peptides were determined using nuclear magnetic resonance spectroscopy and restrained molecular dynamics calculations. Both signiferin 1 and riparin 1.1 adopt β - turn type conformations, however differences in these structures may be responsible for the variation in biological activity noted for these peptides. The dermal secretions of most Australian frogs contain at least one broad-spectrum peptide antibiotic, and often a series of peptides with differing activity to afford greater protection against microbial pathogens. Solid state nuclear magnetic resonance spectroscopy studies were carried out to investigate the interaction of a number of these antibacterial peptides with anionic model membranes, and the results are compared with work previously reported using neutral lipids. It appears the peptides may have a different mode of interaction with the membranes depending upon the charge of the lipid head group. The cupiennin 1 peptides have been identified in the venom of the neotropical wandering spider, Cupiennius salei, and demonstrate potent wide-spectrum antibacterial activity. Primary sequence analysis of these peptides suggests a unique amphipathic structure distinctly different from that of other potentially helical cationic antimicrobial peptides isolated thus far. Using nuclear magnetic resonance spectroscopy and restrained molecular dynamics calculations, cupiennin 1a was found to adopt an α- helical structure with a flexible central hinge region in membrane mimicking solvents. Following this, nuclear magnetic resonance spectroscopy methods were used to further probe the antibacterial and the newly identified neuronal nitric oxide synthase inhibitory activity of this peptide. / Thesis (Ph.D.) -- University of Adelaide, School of Chemistry and Physics, Discipline of Chemistry, 2006

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2009. / Härtill 4 uppsatser.

M. Tech. Pharmaceutical Sciences / Bacteria are present in natural environments and can develop into biofilms. Mucus-like extracellular matrix produced by biofilms provides protection to biofilm formers by inhibiting antimicrobial penetration and de-activating antimicrobial molecules, while allowing strong attachment onto surfaces. Biofilm development is associated with otitis media and cystic fibrosis. In this study, selected biofilm-formers implicated in otitis media and cystic fibrosis, Pseudomonas aeruginosa and Moraxella catarrhalis, were used to evaluate the effect of combinations of mucoactive substances and antibiotics against their biofilms. Microtiter-plate assay and optical density measurements were used to evaluate antimicrobial and antibiofilm activities. Confocal scanning laser microscopy was used to visualise the effect of selected treatments against biofilms.

The search for new antibiotics continues in a rather overlooked hunting ground. In the course of screening for new antibiotic-producing microorganisms, seventy-nine isolates showing antimicrobial activity were isolated from soil samples from various habitats in the KwaZulu-Natal midlands, South Africa. Existing methods of screening for antibiotic producers together with some novel procedures were reviewed. Both modified agar-streak and agar-plug methods were used in the primary screens. The use of selective isolation media, with or without antibiotic incorporation and/or heat pretreatment, enhanced the development of certain actinomycete colonies on the isolation plates. Winogradsky's nitrite medium (Winogradsky, 1949), M3 agar (Rowbotham and Cross, 1977), and Kosmachev's medium (Kosmachev, 1960), were found to be selective for actinomycetes. Statistical analysis showed highly significant interactions between isolates, assay media and the test organisms. The diameters of inhibition zones were found to be larger on Iso-sensitest agar (ISTA)[Oxoid, England] than in nutrient agar plates. Of the 79 isolates that showed antimicrobial activity, 44 isolates were selected for confirmatory screening. Of these, 13 were selected for secondary screening. Criteria for selection were based on significant inhibition of at least two test organisms and/or the inhibition of the specifically targeted organisms, Pseudomonas and Xanthomonas species. Following secondary screening eight isolates were considered for further investigation. The isolates were tentatively identified . on the basis of morphological features, using both light microscopy and scanning electron microscopy(SEM); their ability to utilize various carbon sources; and selected physiological and staining tests. Suspected actinomycetes were further characterized on the basis of selected chemical properties using thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) techniques. High pressure liquid chromatography analysis (Beckman 6300 analyzer) detected the presence of diaminopimelic acid (DAP) in whole-cell hydrolysates of six of the isolates while TLC analysis confirmed the type ofDAP present. The isolates N2, N12, N16, N19 and N35 were tentatively identified as Thermomonospora, Saccharopolyspora, Nocardiodes, Corynebacterium and Promicromonospora, respectively. Isolate N30 was identified as belonging to the coryneform group ofbacteria, possibly an Arthrobacter species. Isolate, N8, tentatively identified as Actinosynnema, was unique among the isolates tested as it showed good antimicrobial activity against all the Gram- positive and Gram-negative bacteria, and yeasts used as test organisms in the present investigation. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Aim: The aim of the study was to explore and describe the perceptions and experiences of rape survivors who were receiving Post Exposure Prophylaxis at a regional hospital. Methodology: A phenomenological approach was used to explore the phenomena, of rape survivors' perception and experiences concerning the Post Exposure Prophylaxis (PEP) they received. The study was conducted in R.K.Khan Hospital, in an Outpatient Department in a gynaecology clinic. This is the regional hospital located in Chatsworth, in the Inner Outer West of Ethekwini District. The sample comprised of ten female rape survivors who were receiving Post Exposure Prophylaxis. Data was collected by means of face-to-face interviews using an interview guide. Interviews were lasting thirty to forty minutes long per participant. The researcher applied the principle of theoretical saturation of data and a total of ten participants were included in the study. All interviews were tape recorded and transcribed verbatim. Data was analysed manually using the Editing Analysis Style. Findings: The results of this study indicated that PEP is the new service to rape survivors and this evoked that when you are being raped you face a risk of range of immediate, medium, and long term health problems; physical, and psychological problems. The rape survivors described a number of emotions and physical reactions that they experienced when they were receiving PEP after rape, which were negative and positive reactions. Most experiences they faced indicated that they benefited from the PEP program, because they gained knowledge, got support from care providers and major diseases and complications were prevented by offering the Post Exposure Prophylaxis A number of recommendations were suggested for the provision of PEP program to the community that is for nursing practice, management and education, the policy makers and for future research in an 'attempt to prevent major complications and health problems that occur in rape survivors. / Thesis (M.A.)-University of KwaZulu-Natal, 2005.

Access to abstract restricted until December 2014. / Review of relevant literature -- Efficiency of constructed wetlands to remove an antimicrobial agent triclosan from wastewater -- The removal of triclosan from laboratory scale constructed wetlands with four species of wetland plants -- Additional research : determination of the hydraulic retention time in an operational subsurface constructed wetland -- Additional research methods : the evaluation of the subsurface constructed wetland for the treatment of iron, phosphorus, ammonia, nitrite, nitrate, dissolved oxygen, pH and E. coli. / Access to thesis restricted until December 2014 / Department of Natural Resources and Environmental Management

Bacteriocin leader pepides are currently receiving much attention due to their possible functions. It is predicted that these leaders prevent cytoplasmic toxicity within the producer organism by rendering the bacteriocin inactive. Leucocin A, a class IIa bacteriocin produced by Leuconostoc gelidum UAL187-22 is synthesized with a 24 amino acid leader pepide which is cleaved during extracellular translocation. The antimicrobial activity of the leucocin A precursor, pre-leucocin A, was determined to gain insight into whether, the presence of a leader peptide has an impact on anti-listerial activity. The leucocin A and pre-leucocin A genes were generated by PCR of L. gelidum UAL187-22 plasmid DNA. Recombinant plasmids, pLcaA and pPreLcaA were isolated by cloning the amplified genes into the Escherichia coli pMAL.c2 vector, and by screening transformant colonies using blue white selection methods. The malE-LcaA and malE-preLcaA fusion genes were expressed, and resulting maltose binding fusion proteins, were purified using amylose affinity chromatography. Fractions collected, contained partially pure forms of MBP-LcaA (46.433 kDa) and MBP-preLcaA (49.088 kDa) fusion proteins. Following Factor Xa digestion, the MBP affinity tag was removed; and recombinant peptides, leucocin A and pre-leucocin A were further purified by reverese phase high performance liquid chromatography. It was determined that leucocin A was eluted with a retention time of 24.893, while pre-leucocin A was eluted with a retention time of 31.447. Fractions of pure leucocin A and pre-leucocin A were thereafter assayed for activity using a deferred antagonism assay, with Listeria monocytogenes being the indicator strain. Pre-leucocin A tested positive for antimicrobial activity. However, when compared to leucocin A it was found that the leucocin A precursor inhibits Listeria to a lesser degree than leucocin A. The relative bactericidal activities of leucocin A and pre-leucocin A was calculated at 6.0 x 10⁵ AU and 4.0 x 10⁵ AU. Taking this into consideration, it was estimated that the leucocin A precursor is ~66.667 % active as mature leucocin A. Hence the presence of a leader peptide does not have an influence on leucocin A antimicrobial activity. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Copies of author's previously published articles inserted. / Includes bibliographical references. / xv, 210 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / A chemical and pharmacological investigation of compounds derived from amphibian skin. Isolates novel amphibian peptides and further investigates the biological activity of some of the peptides discovered. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2000

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 5 uppsatser.

Diss. (sammanfattning) Linköping : Univ., 2002. / Härtill 5 uppsatser.