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Quaternary Diffusion Coefficients in a Protein-Polymer-Salt-Water System Determined by Rayleigh Interferometry
 

Summary: Quaternary Diffusion Coefficients in a Protein-Polymer-Salt-Water System Determined
by Rayleigh Interferometry
Onofrio Annunziata,*,
Alessandro Vergara,
Luigi Paduano,
Roberto Sartorio,
Donald G. Miller,
and John G. Albright
Department of Chemistry, Texas Christian UniVersity, Fort Worth, Texas 76129, Department of Chemistry,
"Federico II" UniVersity of Naples, Naples, 80126, Italy, and Geosciences and EnVironmental Technologies,
Lawrence LiVermore National Laboratory, LiVermore, California 94551
ReceiVed: July 22, 2009; ReVised Manuscript ReceiVed: August 11, 2009
We have experimentally investigated multicomponent diffusion in a protein-polymer-salt-water quaternary
system. Specifically, we have measured the nine multicomponent diffusion coefficients, Dij, for the
lysozyme-poly(ethylene glycol)-NaCl-water system at pH 4.5 and 25 C using precision Rayleigh
interferometry. Lysozyme is a model protein for protein-crystallization and enzymology studies. We find that
the protein diffusion coefficient, D11, decreases as polymer concentration increases at a given salt concentration.
This behavior can be quantitatively related to the corresponding increase in fluid viscosity only at low polymer
concentration. However, at high polymer concentration (250 g/L), protein diffusion is enhanced compared to
the corresponding viscosity prediction. We also find that a protein concentration gradient induces salt diffusion

  

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

 

Collections: Chemistry