Desalting of proteins

Cheese whey demineralization Desalting of protein hydrolysates (i.e., soy sauce), sugar solutions, molasses, and polysaccharide dispersions Deacidification of fruit juices Tartaric wine stabilization Flavor recover from pickle brines... 

In 1954 Deuel and Neukom briefly pointed out that beds of granulated cross-linked locust bean gum could be used to separate salts from high-molecular weight solutes (this fact was unknown to Dr. Flodin and me until 1961 when Professor Deuel kindly informed us of it). Desalting of proteins was one of the first applications of Sephadex (Porath and Flodin, 1959). Distilled water was first used as a developer for the serum proteins... 

Hashimoto K., Adachi S. and Shirai Y., Continuous Desalting of Proteins with a Simulated Moving-bed Adsorber, Agric. Biol. Chem. 52 (1988) pp. 2161. 

On-line microdialysis desalting of protein solutions [29] or in-between EC and ESI-MS [30-31],... 

Molecular sieves are useftil for the desalting of proteins that have been partially fractionated by salting out with a high concentration of some salt. A gel with a low exclusion hmit, such as Sephadex 25, will allow the proteins to pass right through the column while the salts are retained. The protein dilution is limited to the elution volume of the column (the volume external of the swelled gel to fill the column). 

Wilson, D.J., Konermann, L., Ultrarapid desalting of protein solutions for electrospray mass spectrometry in a microchannel flow device. Ana/. Chem., 11, 6887-6894, 2005. 

Rist,W., Mayer, M.P., Andersen, l.S.,etal. (2005) Rapid desalting of protein samples for on-line microflow electrospray ionization mass spectrometry. Anal Biochem, 342 (1), 160-162. 

Mixed bed cation/anion exchange resins (e.g., Bio-Rad AG 501) are used for desalting nonionic samples in aqueous solutions. Scott (88) has discussed desalting of blood and urine samples prior to carbohydrate TLC by this approach. Desalting of proteins (> 6000 daltons) can be done by gel filtration chromatography on Bio-Rad P-6DG polyacrylamide desalting gel. 

A typical example of dialysis is desalting of proteins. About 500 p,l protein solution is put into a dialysis tube, which is immersed in 500 ml buffer solution (see Fig. 1). The salts diffuse from the sample into the buffer solution, while the buffer (since diffusion can occur in the opposite direction too) diffuses into the sample and maintains the pH. This process not only desalts the protein but also can be used to exchange the buffer. 

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