Electrolytic reduction: modification of proteins occurring in isoelectric focusing electrophoresis and in electrolytic reactions in the presence of high salts.
Artifacts in two-dimensional electrophoresis (2-DE) caused by the presence of salts in isoelectric focusing (IEF) have been previously described as a result of increasing conductivity and inducing electroosmosis. However, electrolysis induced by the presence of salts should not be disregarded. In this study, electrolytic reduction-oxidation reaction (redox) was found to be enhanced in the presence of salts in IEF. The consequence of the electrolytic redox leads to acidification of the low-pH region and alkalization of the high-pH region within the immobilized pH gradient (IPG) strip. As a result, a breakdown of immobilized pH buffer near the high pH region of IPG strips along with reduction of basic proteins resulted in uncharacterized artifacts in 2-DE. Electrolytic reduction in the presence of alkali and alkaline metal ions was demonstrated to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), protein disulfide bonds, and protein carboxylic acids. Importantly, semipreparative electrolytic reduction of proteins can be carried out in the presence of sodium ions in a homemade electrolytic apparatus. These findings give additional explanations to the observed artifacts in 2-DE and reveal the unknown effects of salts in IEF. Moreover, we have provided a method with the potential to convert proteins or peptides to corresponding modified products containing aldehyde groups that can be used for conjugation with amine-containing compounds.
Lee
Der-Yen
DY
Graduate Institute of Biochemical Sciences, College of Life Science, National Taiwan University, P.O. Box 23-106, Taipei 106, Taiwan.
Chang
Geen-Dong
GD
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D015180:Electrophoresis, Gel, Two-Dimensional / Q000379:methods*; D004625:Embryo, Nonmammalian / Q000737:chemistry; D007525:Isoelectric Focusing / Q000379:methods*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011506:Proteins / Q000032:analysis / Q000737:chemistry*; D018892:Proton-Motive Force; D012259:Ribonuclease, Pancreatic / Q000032:analysis; D012492:Salts / Q000737:chemistry*; D013997:Time Factors; D015027:Zebrafish
D011506:Proteins; D012492:Salts; D012259:Ribonuclease, Pancreatic