Observation of critical phenomena in a protein-water solution

We report measurements of the intensity of the scattered light and the turbidity of aqueous solutions of the bovine lens protein, ${\gamma }_{\mathrm{II}}$-crystallin, near the critical point for binary liquiid phase separation, in a region of the phase diagram which is metastable with respect to protein-crystal formation. We have determined the magnitudes and critical divergences of the osmotic compressibility, ${\mathrm{\kappa }}_{\mathrm{T}}$, and the static correlation range, ξ. The corresponding critical exponents are γ=1.21±0.05 and ν=0.68±0.1. .AE