This paper demonstrated simultaneous separation of acidic and basic proteins using cationic gemini surfactants as buffer additives in capillary electrophoresis. We showed that even at a low concentration (0.1 mmol·L-1) of alkanediyl-α,ω-bis(dimethyloctadecylammonium bromide) (18-s-18), the wall adsorption of both acidic and basic proteins could be effectively suppressed under acidic conditions. Smaller micelle size (e.g., s=5-8) is more effective for the separation of acidic proteins than larger micelle size (e.g., s<4 or >10). Varying the spacer length of gemini surfactants can influence the electrophoretic mobility and selectivity of proteins to achieve the desired separation. Under the optimized conditions, RSDs of the migration time were less than 0.8% and 2.2% for run-to-run and day-to-day assays, respectively, and protein recoveries ranged from 79% to 100.4%. Furthermore, we also investigated the use of gemini surfactant-capped gold nanoparticles (gemini@AuNPs) as buffer additives in protein separation. Introduction of AuNPs into the buffer shortened the analysis time and slightly improved the separation efficiencies. Finally, we presented the applications of this method in the analysis of bio-logical samples, including plasma, red blood cells and egg white.
The title compound ethyl 2-（6-（1,3-dioxo-4,5,6,7-tetrahydro-lH-isoindol-2（3H）- yl）-7-fluoro-3-oxo-2H-benzo[b][1,4]oxazin-4（3H）-yl） butanoate 3 was synthesized by the reaction of ethyl 2-（6-amino-7-fluoro-3-oxo-2H-benzo[b][1,4]oxazin-4（3H）-yl） butanoate with 4,5,6,7- tetraydrophthalic anhydride, and its structure was determined by X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group P2 1/n with a = 9.3469（2）, b = 16.7715（5）, c = 13.7153（4） A, β= 104.9680（10）°, μ = 0.107 mm^-1, Mr = 430.42, V= 2077.08（10） ,A3, Z= 4, Dc = 1.376 g/cm3, F（000） = 904, T= 296（2） K, R = 0.0508 and wR = 0.1478.
