Dr. Anand Yethiraj - Memorial University


Guest: Dr. Anand Yethiraj
Professor, Memorial University

Title: A tale of two colloidal model systems: gelation and macromolecular crowding

I will describe an experimental colloid science approach to studying two distinct problems in condensed matter and biophysics. Gels are amorphous materials characterized by the presence of an open percolating network. Colloids and polymers (and biopolymers and other macromolecules) in solution will form gels at relatively low volume fraction, provided the interactions are sufficiently attractive. Using a switchable external field, we probe reversibility and irreversibility in gel-forming systems using confocal microscopy.
On the other hand, the innards of living cells are very crowded environments with large/small, charged/uncharged, hydrophobic/hydrophilic macromolecules, and knowing how individual proteins behave in the presence of this crowding is challenging. We use a colloidal model approach with polymer as protein and colloid as crowder. Using a nanoscale polysucrose colloid, Ficoll, as a model crowder, we examine size and diffusion of a model polymer in crowded solution using NMR, in tandem with small-angle neutron scattering and rheology. We compare these results with those in more realistic crowding solutions prepared with a disordered protein, and/or with lysed cells as crowders. 
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