Amphiphiles or surfactants are molecules containing both a hydrophilic and a hydrophobic part. The hydrophobic part - also called 'tail(s)' - generally consists of one or two alkyl chains, whereas the hydrophilic part - also called 'head' - is formed by ionic, non-ionic or zwitterionic groups. Upon dispersal in water the surfactants arrange themselves in such a way that the heads become oriented towards the water phase and the tails cluster together leading to the formation of aggregates, viz. micelles, rods, planar bilayers, inverted micelles, bicontinuous structures and vesicles. In this thesis the synthesis and study of the physical properties of amphiphilic protein-polymer hybrids are described. These so-called 'giant amphiphiles' can be seen as a new class of surfactants, next to the low molecular weight amphiphiles and the class of amphiphilic block copolymers, also called 'super amphiphiles'. The biohybrid amphiphiles consist of the protein streptavidin, acting as the polar head group, and one or two biotinylated polymer chains serving as the apolar tails. The affinity between streptavidin and biotin is so high (Ka = 10 15 M-1; 21 kcal mol-1) that the complex formation between the two components can be considered as being irreversible. The remaining free binding sites of the protein can be used to complex other biotinylated molecules to obtain further functionalized protein-polymer hybrids. Apart from being larger than the traditional and polymeric amphiphiles, these biohybrids also have a built-in functionality, namely the protein or enzyme. The biohybrids described in this thesis differ from other protein-polymer systems reported in the literature, in the sense that the protein to polymer ratio is predefined and the position of the conjugation site is precisely known
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