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Total protein quantitation using the bicinchoninic acid assay and gradient elution moving boundary electrophoresis
Author(s) -
Kralj Jason G.,
Munson Matthew S.,
Ross David
Publication year - 2014
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.201400025
Subject(s) - chemistry , capillary electrophoresis , chromatography , bicinchoninic acid assay , reagent , electrophoresis , elution , detection limit , analytical chemistry (journal) , tartrate , biochemistry
We investigated the ability of gradient elution moving boundary electrophoresis (GEMBE) with capacitively coupled contactless conductivity detection (C 4 D) to assay total protein concentration using the bicinchoninic acid (BCA) reaction. We chose this format because GEMBE‐C 4 D behaves as a concentration dependent detection system, unlike optical methods that also rely on pathlength (due to Beer's law). This system tolerates proteins well compared with other capillary electrophoretic methods, allowing the capillary to be reused without coatings or additional hydroxide wash steps. The typical reaction protocol was modified by reducing the pH slightly from 11.25 to 9.4, which enabled elimination of tartrate from the reagents. We estimated that copper (I) could be detected at approximately 3.0 μmol/L, which agrees with similar GEMBE and CZE systems utilizing C 4 D. Under conditions similar to the BCA “micro method” assay, we determined the LOD for three common proteins (insulin, BSA, and bovine gamma globulin) and found that they agree well with the existing spectroscopic detection methods. Further, we investigated how long reaction times impact the LOD and found that the conversion was proportional to log(time). This indicated that little sensitivity is gained by extending the reaction past 1 h. Hence, GEMBE provides an alternative platform for total protein assays while maintaining the excellent sensitivity of the optical‐based methods.