Understanding the sol-gel transition in DSMO/lysozyme/water mixtures

Condensed Matter lunchtime seminar

Understanding the sol-gel transition in DSMO/lysozyme/water mixtures

  • Event time: 1:00pm
  • Event date: 19th July 2010
  • Speaker: Ilja Voets (University of Friburg)
  • Location: Room 2511,

Event details

A remarkably high viscosity has been induced in aqueous solutions of lysozyme by the addition of certain structurally related organic solvents, such as tetramethylurea (TMU), dimethylsulfoxide (DMSO), dimethylformamide (DMF), and hexamethylphosphortriamide. DMSO-induced gelation is observed in samples fulfilling the two following requirements: (1.) lysozyme concentration in excess of 5 mM, and (2.) volume fractions of DMSO exceeding 0.7. When both these critical values are exceeded, a sol-gel transition is found to take place leading to solid-like rheological behaviour instead of Newtonian behaviour. Various spectroscopic and calorimetric experiments performed under dilute conditions have led to a detailed picture of the conformational transitions that lysozyme undergoes upon increasing DMSO volume fraction in the mixtures. However, this is only part of the puzzle. Light scattering experiments indicate that the type of interactions between protein molecules are strongly dependent on both the protein and DMSO concentration. Currently, we are attempting to understand these changes in protein interactions based on our understanding of the conformation of the protein under dilute conditions and how these changes in interaction relate to a sol-gel transition at higher protein volume fractions and define the microstructure of the final gel. In this contribution, we will sketch a detailed physical picture of the conformation of lysozyme in aqueous DMSO mixtures under dilute conditions and discuss its consequences for the sol-gel transition and final gel microstructure at higher protein concentrations.

This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..

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