Biological cells, the basic building blocks of all life forms, are surrounded by a lipid membrane. More than half of the membrane is occupied by membrane proteins, which can regulate the cell... Show moreBiological cells, the basic building blocks of all life forms, are surrounded by a lipid membrane. More than half of the membrane is occupied by membrane proteins, which can regulate the cell functionality through specific arrangements. To regulate the arrangements several proteins have to work together. In addition to direct forces, there exists an indirect force between the proteins, which stems from their deformation of the membrane and contributes to their self-organization. Since the actual membrane is very crowded and proteins are too tiny and complex to measure this interaction, in this thesis we used a model system consisting of lipid membranes and solid particles to study the deformation-mediated interaction. We experimentally confirmed for the first time that, unlike many known forces, this deformation-mediated interaction is not additive, i.e. the strength and range of three (or more) deformations cannot be obtained by simple addition of the interactions between pairs of deformations. We found that the interaction weakens with increasing number of membrane-deforming particles and that the particle become less ordered. We investigated deformations in both directions of the membrane and found that the interaction can be both repulsive and attractive, and furthermore depends on the shape of the deformation. This thesis helps to better understand the organization of proteins that deform cellular membranes. Show less
This PhD-thesis presents a study on micron-sized particles, so-called colloids. By controlling the chemical and physical properties of these particles, such as the interparticle interaction... Show moreThis PhD-thesis presents a study on micron-sized particles, so-called colloids. By controlling the chemical and physical properties of these particles, such as the interparticle interaction and the particles’ shape, colloids can act as building blocks that self-assembly into larger structures. This could lead to the development of materials with novel properties such as ‘smart’ materials with the ability to adapt their structure to the environment. In this thesis spherical colloids are used as a starting point to make complex colloidal building blocks and larger microstructures. Anisotropic particles were formed by introducing surface roughness, dents, protrusions and chemical functionalization on the particle surface. Complex structures were obtained by assembling and reconfiguring clusters of spheres. Here, a balance of several phenomena including, the interfacial and potential energy, entropy and geometric constraints, determined the final geometry of the assembled structure. The work also shows how anisotropic elongated particles distorted the hexagonal order in crystals of spheres, either locally or over long distances. These distortions are known to influence the optical, mechanical and electronic properties of colloidal crystals. The complex particles and assemblies made in this study are therefore an important step towards the development of materials with novel and adaptable properties. Show less
