Precise, fast, and flexible determination of protein interactions by affinity capillary electrophoresis: part 1: performance.

A generic screening approach was performed to investigate the binding of various potential ligands to proteins in order to investigate how proteins interact with ions and the complete surrounding solution. This also allows to study binding behavior and its regulation and protein functionality in general in a native environment. The ACE technique affords an excellent precision by applying appropriate rinsing procedures using a pressure of 2.5 bar and a continuous flow concept. Confidence intervals were estimated to proof significance of the interactions. This enables to investigate smaller yet important interactions, which were not possible with less precise techniques before. The influence of various ions on ovalbumin, β-lactoglobulin, and BSA were screened by comparing the mobility ratios of the free protein and the influenced one. The analysis was performed using the metal ions Ba(2) +, Ca(2) +, Cu(2) +, Mg(2) +, Mn(2) +, Ni(2) +, the pharmaceutical cations ephedrine hydrochloride, ethambutol dihydrochloride, pilocarpine hydrochloride and pirenzepine dihydrochloride, and various anions, in particular phosphate, acetate, succinate, glutamate, and salicylate. For the anion influence study, myoglobin was also included to the screened proteins. The influence of these ions on the proteins was well diversified. The interactions could be distinguished with a fast and precise screening method since 90% of all mobility ratios had a RSD% below 2% and 79% had a RSD% lower than 1%. Hence, for more than 75% of the protein-ligand pairs significant interactions are observed with a very small confidence interval due to the very excellent precision of these used method.