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Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi
Dissertation (MSc)--University of Pretoria, 2013.
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| Format: | Thesis |
| Language: | English |
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University of Pretoria
2014
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| _version_ | 1867613609275686912 |
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| access_status_str | Open Access |
| author2 | Gaspar, A.R.M. (Anabella Regina Marques) |
| author_browse | Gaspar, A.R.M. (Anabella Regina Marques) |
| author_facet | Gaspar, A.R.M. (Anabella Regina Marques) |
| collection | Thesis |
| dc_rights_str_mv | © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. |
| description | Dissertation (MSc)--University of Pretoria, 2013. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/40349 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:38:52.072Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | University of Pretoria |
| publisherStr | University of Pretoria |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/40349 Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi Gaspar, A.R.M. (Anabella Regina Marques) lezaanp@yahoo.com Neitz, A.W.H. (Albert Walter Herman) Prinsloo, Lezaan Tick Ornithodoros savignyi Carboxy-terminal region UCTD Dissertation (MSc)--University of Pretoria, 2013. In this study the structural characteristics and antibacterial activities of two peptides derived from the carboxy-terminal of a tick defensin were investigated. Two defensin isoforms (OsDef1 and OsDef2) were previously identified in the midgut of the tick, Ornithodoros savignyi. Both OsDef1 and OsDef2 were found to be active against Gram-positive bacteria but showed no antibacterial activity against Gram-negative bacteria. OsDef2 was found to be slightly more active than OsDef1 and was, therefore, used as the template for the design of smaller antimicrobial peptides. Two peptide analogues were synthesised using the carboxy-terminal sequence of OsDef2 and differed in that in the one peptide the cysteine residues were present (Os) and in the other the cysteine residues were omitted (Os-C). Structurally, Os contained more α-helical properties than Os-C, whereas Os-C was more β-sheeted when prepared in 25 mM SDS. Both Os and Os-C showed no antibacterial activity when tested in Luria-Bertani broth or Mueller-Hinton broth indicating that the activities of Os and Os-C were influenced by the presence of broth salts and proteins. When tested in sodium phosphate buffer, both Os and Os-C exhibited Gram-positive and Gram-negative antibacterial activity. Os was slightly more active than Os-C against 3 of the 4 tested strains, with minimum bactericidal concentrations (MBCs) ranging from 0.94 μg/ml to 3.75 μg/ml. Os retained bactericidal activity against both Staphylococcus aureus and Escherichia coli when tested in the presence of 100 mM NaCl or 30% human serum. Os-C retained activity against E. coli in the presence of NaCl but became inactive in 30% human serum against both bacterial strains. At the MBCs, Os exhibited faster killing kinetics than Os-C killing both Bacillus subtilis and E. coli within 5 min, whereas Os-C took up to 120 min and 60 min, respectively. SYTOX Green permeabilization assays showed that both Os and Os-C caused permeabilization of E. coli membranes after 30 min exposure. At high peptide concentrations, both Os and Os-C were shown to interact with plasmid DNA. Both Os and Os-C exhibited no cytotoxic effects against SC-1 and Caco-2 cell lines, even at peptide concentrations 32 times higher than the highest MBC. gm2014 Biochemistry unrestricted 2014-06-24T09:49:43Z 2014-06-24T09:49:43Z 2014-04-09 2013 Dissertation Prinsloo, L 2013, Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi, MSc University of Pretoria, Pretoria, viewed yymmdd <http://hdl.handle.net/2263/40349> E14/4/172/gm http://hdl.handle.net/2263/40349 en © 2013 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. application/pdf University of Pretoria |
| spellingShingle | Tick Ornithodoros savignyi Carboxy-terminal region UCTD Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi |
| title | Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi |
| title_full | Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi |
| title_fullStr | Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi |
| title_full_unstemmed | Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi |
| title_short | Structural and functional characterization of peptides derived from the carboxy-terminal region of a defensin from the tick Ornithodoros savignyi |
| title_sort | structural and functional characterization of peptides derived from the carboxy terminal region of a defensin from the tick ornithodoros savignyi |
| topic | Tick Ornithodoros savignyi Carboxy-terminal region UCTD |
| url | http://hdl.handle.net/2263/40349 |