Measurement of hard-sphere like dynamics in concentrated alpha-crystallin suspensions using X-ray Photon Correlation Spectroscopy

The dynamics of concentrated suspensions of the ocular protein, alpha crystallin have been measured using X-ray Photon Correlation Spectroscopy (XPCS). Measurements were made at wavevectors corresponding to the first peak in the hard-sphere structure factor. The dynamics were measured at volume fractions close to the critical volume fraction for the glass transition, where the intermediate scattering function, f (q, τ ) could be well fit using a double exponential decay. The measured relaxation times were in reasonable agreement with published molecular dynamics simulations for the relaxation times of hard-sphere colloids.
Overall our results lend support to the hard sphere colloid model as a good description of concentrated suspensions of alpha crystallin.