CHROMATOGRAPHY, Vol. 22 (2001), No. 2, pp. 91-96

Isoelectric Points Estimation of Proteins by Electroosmotic Flow: pH Relationship Using Physically Adsorbed Proteins on Silica Gel
Chaiyavat Chaiyasut and Takao Tsuda*
Department of Applied Chemistry, Nagoya Institute of Technology
Gokiso, Showa, Nagoya 466-8555, Japan
A surface modification of the silica gel in a mini-packed polypropylene tube had been developed by physically adsorption of proteins. Several proteins (bovine serum albumin, pepsin, globulin, -casein) had been attempted to physically adsorb on the silica gel in a mini-packed cartridge under simple conditions. The proteins were successfully adsorbed on the silica gel, thus, minimizing the effect of the silanol groups. The protein isoelectric point values (pI) might be determined from the pH of which the EOF is zero. The estimated pI values corresponded very well with the literature values. The switchable EOF property of the protein adsorbed phases are fruitful for the manipulation of the magnitude and direction of EOF by selecting pH of buffer solutions and proper adsorbed protein phases. Four replicate different mini-packed cartridges were used to observe the EOF by using a simple homemade apparatus. The technique was easily to handle and did not take too much time consuming.
Keywords: adsorption, proteins, isoelectric points, silica gels, mini-packed cartridge

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