ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
We report our measurement of the time average and the temporal autocorrelation function of the intensity of light scattered by the highly monomeric globular protein, bovine γII-crystallin, in aqueous solution as a function of wave number q, protein volume fraction φ, and temperature T. The time average intensity data is used to obtain the q→0 limit of the static structure factor S(φ,T), as a function of φ and T. We show that S(φ,T) may be well characterized by modeling the proteins as interacting through the Baxter adhesive hard sphere pair interaction potential. The temporal autocorrelation function data is used to determine the collective diffusion coefficient D˜(φ,T) of the proteins as a function of φ and T. We then obtain the experimental hydrodynamic factor H˜(φ,T)≡S(φ,T)[D˜(φ,T)/D0(T)], where D0(T) is the diffusion coefficient of the individual proteins in the φ→0 limit. We find that H˜ exhibits a different φ-dependence at low (φ≤0.016) and high (φ(approximately-greater-than)0.02) protein volume fractions. In the low φ domain our data for H˜ are consistent with the theoretical result for the collective diffusion in the q→0, t→0 limit. However, for φ(approximately-greater-than)0.02 we find a deviation from single exponential decay in the autocorrelation functions, and an unexpected, large change in the slope of the H˜ vs φ relation. This crossover at such low φ suggests the existence of a heretofore unappreciated length scale in the dynamics of colloid solutions. Clearly, further theoretical insights are required to understand the origin of this crossover behavior. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.470904
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