The research done in our group.

Parts of the research described here were or are due to the funding generously provided by the National Research Foundation of South Africa.  Students and research associates have also been funded sometimes by the National Research Foundation, but, amongst others, also by the Organisation for Women in Science for the Developing World, the National Institute for Theoretical Physics, the African Institute for Mathematical Sciences, the Deutsche Akademischer Austauschdienst, the Harry Crossley Foundation, the Claude Leon Foundation.  We are greatly appreciative of the support by all of these organisations.

Filaments in restricted geometries

Filaments or polymers and more complex structures assembled from these can occur in small regions, where the surface causes significant deviation from the bulk properties.  We ask how filaments arrange in these spaces and are currently extending our considerations to networks in these confined regions.  Whereas most of this work is based on analytical theory, we have also performed simulations.

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Networks of polymers and filaments

Networks of filaments are the result of linking together parts of filaments forming a structure that can resist mechanical strains.  The work in the group has a long history of working on networks.  We have now selected this topic as central to our work.  The primary question being on connecting semi-microscopic properties of filaments and cross-linkers to determine bulk and confined network elastic response.  Work on both equilibrium, but also the dynamics (particularly in the light of active cross-links) are being pursued, with several research projects under way.  Outputs will be displayed here.

Above: Growth of tree-like network structure; cartoon of certain types of branching actin networks. (Copyright Kristian Müller-Nedebock)

Membranes, organelles in cells (NanoBio)

This research entails a set of projects in close collaboration with physiologist and super-resolution microscopist, Ben Loos, in the Department of Physiological Sciences.

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When polymer loops or strands that are network are entangled, the strand configurations depend on the topology.  This is quite a challenging problem.  In our group we have been developing alternative ways of dealing with the mathematics topological restrictions place on partition functions.  This research is probably the most abstract and long-term project.

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Active systems

Active systems contain internal sources of directed motion.  We mainly try to understand how molecular machines influence the motion of filaments, particularly when they occur in a network, but have also worked on motility assays.  Yes other elements of future research focus on more collective formalisms.

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Above: Movie of myosin motor exerting force on an actin strand. (Copyright: Kristian Müller-Nedebock)

Diffusion in microporous media

We consider diffusion in highly restricted environments, such as when molecules diffuse in a single file.  Mohau Mateyisi investigated how coupling of pores influences the dynamics of guest particles within these pores.  Many ideas for the project originated in the considerations concerning a publication with colleagues in the Department of Chemistry and Polymer Science at Stellenbosch University.


Funding statement: This work is based on the research supported in part by the
NRFlogoNational Research Foundation of South Africa (Grant Number 99116). National Research Foundation