AbstractsBiology & Animal Science

This thesis addresses the electrochemical and physicochemical characterisation of the interactions between modified phospholipid monolayers and other model membrane components, polysaccharides and proteins. Also, the assembly of metallic nanoparticles (NPs) on their surface at the polarisable liquid/liquid interfaces is studied. The thesis comprises six original publications and an introductory background to the relevant literature. In the literature part, relevant background concerning the structure, composition and properties of biological membranes as well as model membranes is briefly reviewed. Classification of gramicidin (gA) ion-channels, glycosaminoglycans (GAGs), in particular dextran sulfate (DS), and glucose oxidase (GOx), with respect to their structure, properties and interaction with lipids is presented. Monolayers at soft interfaces, such as air/liquid and liquid/liquid interfaces, as well as the theory associated with them are also reviewed. Finally, a brief description of the NPs and their characteristics, and isothermal titration calorimetric properties is given. In the latter part of the thesis, the essential results of the presented publications are summarised and discussed. The thesis introduces an approach to: (i) modify a phospholipid monolayer at a liquid/liquid interface with DS using calcium bridges between DS and the monolayer; (ii) construct polyelectrolyte/gold NP multilayers anchored to a lipid monolayer; (iii) prepare and characterise DS-modified ruthenium NPs, and to study their influence on drug transfer; (iv) study the influence of the peptide gA or enzyme GOx on the lipid layer as well as on the drug permeability; and (v) study the binding mechanism between drug and GAG molecules. Finally, the main conclusions and future perspectives are assessed. All the studies presented in this thesis involved the combination of ac and dc electrochemical techniques, such as ac impedance/voltammetry and cyclic voltammetry, spectroscopic techniques such as FTIR and fluorescence, and surface (TEM) and calorimetric techniques. Furthermore, the capacitance curves were successfully explained and interpreted with theoretical models, in order to get a closer insight on the ion transfer and membrane interactions for each studied system. It is highlighted that electrochemistry can provide useful information on phenomena taking place at the membrane surface. Väitöskirja käsittelee biomembraanimallia, joka muodostettiin fosfolipidiyksikerroksesta ja sitä modifioivista polysakkarideista ja proteiineista. Lipidikerroksen ja muiden membraanikomponenttien välisiä vuorovaikutuksia karakterisoitiin fysikokemiallisin ja erityisesti sähkökemiallisin menetelmin. Myös metallinanopartikkelien vuorovaikutusta membraanimallin kanssa tarkasteltiin käyttäen hyväksi polarisoituvaa neste-neste –rajapintaa membraanimallin rakentamiseksi. Kirjallisuusosassa luodaan katsaus biologisten membraanien ja membraanimallin rakenteeseen, koostumukseen ja ominaisuuksiin. Gramisidiini A -ionikanavat (gA), glykosaminoglykaanit…