To study the effect of charge on protein diffusion in hydrogels, mutual diffusion of a globular protein, myoglobin, has been investigated at various pH and ionic strength levels in two kinds of polysaccharide gels, neutral agarose gel and anionic carrageenan gel, by the recently developed electronic speckle pattern interferometry method. In the uncharged agarose gel, diffusions of myoglobin are not effected by the change in pH and the ionic strength, indicating no electrostatic interaction between the gel and myoglobin. The experimental data in agarose gel agree with the combined model proposed by Clague and Philips for the diffusion of spheres in hydrogels. While in the negatively charged λ-carrageenan gel, the diffusion of myoglobin is accelerated by electrostatic attraction when the pH is lower than the isoelectric point (pI) of the protein, but it is extensively hindered by the electrostatic repulsion when pH > pI. The diffusion of myoglobin in λ-carrageenan gel agrees with the Tsai and Strieder model...

Effect of Charge on Protein Diffusion in Hydrogels

Overview of diffusion measurements by optical techniques

Two methods to measure the diffusion coefficient of a species in a liquid by optical interferometry were compared The methods were tested on a 175 M NaCl aqueous solution diffusing into water at 26 °C Results were D = 1587 × 10−9 m2 s−1 with the first method and D = 1602 × 10−9 m2 s−1 with the second method Monte Carlo simulation was used to assess the possible dispersion of these results The standard uncertainties were found to be of the order of 005 × 10−9 m2 s−1 with both methods We found that the value of the diffusion coefficient obtained by either method is very sensitive to the magnification of the optical system, and that if diffusion is slow the measurement of time does not need to be very accurate

http://iopscience.iop.org/article/10.1088/0022-3727/40/9/015/pdf

Interferometric measurement of a diffusion coefficient: comparison of two methods and uncertainty analysis

Diffusion of lysozyme in gels and liquids. A general approach for the determination of diffusion coefficients using holographic laser interferometry.

The technique of real-time holographic interferometry is used to study free diffusion in a liquid mixture at 25°C. A new mathematical method is derived for determining diffusion coefficients. The results obtained for the KCl-water system from the mathematical method are compared with the results obtained using the mathematical treatment developed by Gabelmann-Gray and Fenichel.

Holographic interferometric study of free diffusion: a new mathematical treatment

A holographic interferometer specially designed for measuring diffusion coefficients in transparent mixtures is described. The diffusion coefficient is simply and directly measured from the interferograms using a finite fringe system intentionally introduced into the interferometer. Preliminary results concerning the KCl-water diffusion system are in reasonable agreement with other methods. The results obtained for diffusion of diphenyl ether in hexadecane are also presented.

B Janowska

Papers

Holographic measurement of diffusion coefficients