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dc.contributor.advisorMeiring, S. M.
dc.contributor.authorMotloi, Nthabiseng Cecilia
dc.date.accessioned2017-03-24T07:57:14Z
dc.date.available2017-03-24T07:57:14Z
dc.date.issued2002-11
dc.identifier.urihttp://hdl.handle.net/11660/5991
dc.description.abstractEnglish: The role of factor XI in hemostasis can be seen as a combination of a procoagulant action (the formation of fibrin) and an antifibrinolytic action (the protection of fibrin). High levels of factor XI lead to a prolonged down regulation of fibrinolysis and therefore a risk of thrombosis (Meijers et ai, 2000). Under disease conditions associated with Disseminated Intravascular Coagulation (DIC), the continuous exposure to excess TF typically exhaust the available tissue factor pathway inhibitor (TFPI), leading to rampant thrombin generation by factor XI feedback and therefore also a risk of thrombosis (0sterud and Bjerlid, 2001). I selected possible .inhibitors of factor XI using phage display technology. I started the phage display selection by biopanning in immuno-tubes and eluted the factor XI binding phages non-specifically from the immuno-tube. I did four selection rounds, to enrich the factor XI binding phages. I found only two strong factor XI binding phage clones from a linear 12-mer phage library. Both phage clones bound dose dependently and with a high affinity to factor XI. Both clones also lengthened the partial thromboplastin time (aPTT) dose dependently. The amino acid sequences of the peptides displayed on these two clones indicate that both peptides contain three amino acid sequences of HMWK and thrombin. One clone also contains a three amino acid sequence of factor XII. None of them contains a three amino acid sequence of factor IX. I synthesize a linear peptide with the corresponding sequence as the peptide displayed on the clone that was prevented from binding to factor XI by both factor IX and thrombin. I characterized the peptide by studying its effect on the aPTT. This peptide lengthens the aPTT dose dependently. The lengthening in aPTT of our peptide however indicates that I have selected an inhibitor of the contact system factors of coagulation. In summary, this study shows that the phage display can be used to select novel factor XI inhibitors from random peptide libraries. With further studies, this peptide may be developed as an antithrombotic.en_ZA
dc.description.abstractAfrikaans: Die rol van factor XI in trombose kan beskou word as 'n kombinasie van prostollings- (vorming van trombien) en teen-fibrinolise- (beskerming van die fibrien stolsel teen afbraak) funksies. Verhoogde factor XI-vlakke in plasma lei tot 'n vertraging van fibrinolise en daarom 'n hoë risiko vir trombose (Meijers et al., 2000). Die voortdurende blootstelling van weefselfaktor in siektetoestande soos verspreide intravaskulêre stolling, put die beskikbare weefselfaktorbaaninhibeerder uit. Dit lei dan tot 'n toenemende trombien generasie deur die factor XI terugvoer-baan en daarom ook 'n verhoogde risiko vir trombose (0sterud en Bj0rlid, 2001). In hierdie studie het Ek inhibeerders teen factor XI d.m.v. peptiedblootlegging op fage geselekteer. Herhaalde seleksie van fage vanaf 'n sikliese heptapeptied faag biblioteek asook 'n lineêre 12-aminosuur faag biblioteek het gelei tot die vermeerdering van fage wat spesifiek aan factor XI bind. Ek het immuunbuise in die seleksieproses gebruik en die factor XI-bindende fage nie-spesifiek van die ongebonde fage ge-elueer. Ek het twee klone wat sterk aan factor XI bind geselekteer. Bedie klone het ook die gedeeltelike tromboplastien tyd (PTT) dosis afhanklik verhoog. Die aminosuurvolgorde van die peptiede wat blootgelê is op die fage van hierdie twee klone, bevat 3-aminsuur volgordes van hoë molekulêre gewig kininogeen (HMWK) en van trombien. Die een klone bevat ook 'n 3-aminsuur volgorde van factor XII. Nie een van die peptiede bevat aminosuurvolgordes van factor IX nie. Ek het 'n lineêre peptied met 'n ooreenstemmende aminosuur volgorde as die peptied wat blootgelê is op die klone wat deur factor IX en trombien verhoed is om aan factor IX te bind, laat sintetiseer. Hierdie peptied verleng die PTT dosisafhanklik. Dit dui dus daarop dat Ek 'n inhibeerder van die kontaksisteem suksesvol geselekteer het. Ter opsomming kan ons sê dat die tegnologie van peptied blootlegging op fage gebruik kan word om nuwe factor XI inhibeers vanaf lukraak peptiedbiblioteke te selekteer. Met verdere studies kan hierdie peptied as In antistolmiddel onwikkel word.af
dc.description.sponsorshipMedical Research Councilen_ZA
dc.description.sponsorshipUniversity of the Free Stateen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectBlood coagulation factorsen_ZA
dc.subjectAnticoagulants (Medicine)en_ZA
dc.subjectDissertration (M.Med.Sc. (Haematology and Cell Biology))--University of the Free State, 2002en_ZA
dc.titleSelection and characterization of a novel factor XI inhibiting peptide by using phage display technologyen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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