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Protein Diffusion Coefficients Determined by Macroscopic-Gradient Rayleigh Interferometry and

Summary: Protein Diffusion Coefficients Determined by
Macroscopic-Gradient Rayleigh Interferometry and
Dynamic Light Scattering
Onofrio Annunziata,* Daniela Buzatu, and John G. Albright
Department of Chemistry, Texas Christian University, Fort Worth, Texas 76129
Received August 5, 2005. In Final Form: October 27, 2005
Dynamic light scattering (DLS) is extensively used for measuring macromolecule diffusion coefficients.
Contrary to classical techniques based on macroscopic concentration gradients, DLS probes microscopic
fluctuations in concentration. DLS accuracy and its concordance with macroscopic-gradient techniques
remains an outstanding important issue. We measured lysozyme diffusion coefficients in aqueous salt
using both DLS and Rayleigh interferometry, a highly accurate macroscopic-gradient technique. The
precision of our results is unprecedented. We find that our DLS values were systematically 2% higher than
interferometry values. We believe that our interferometric mesurements have produced the most accurate
diffusiondata everreportedforaprotein,providinganew standard for quality controlof DLSmeasurements.
Furthermore, by interferometry, we have determined the whole diffusion coefficient matrix required for
rigorously describing lysozyme-salt coupled diffusion. For the first time, we experimentally demonstrate
that DLS does not provide the protein diffusion coefficient but one eigenvalue of the diffusion coefficient
Mutual diffusion coefficients characterize the motion


Source: Annunziata, Onofrio - Department of Chemistry, Texas Christian University


Collections: Chemistry