Clean up protein for analysis from salt-rich sample using facilitated by copper ion in micro-device

In this study, we made the simple and rapid microfluidic desalting systems. They are 3-phase flow micro-dialysis using simple diffusion and 5-phase flow micro-dialysis based on the coupling of simple diffusion and affinity of urea for the effective removal of urea. The facilitative desalting system is particularly useful for removal of urea and analysis of protein by mass spectroscopy because urea is removed by the mass transfer with the difference of concentration, molecular size and the affinity of urea to copper (II) ion resulting the complex. We also evaluated the activity and MALDI-TOF-MS spectrum of red fluorescent protein (RFP) for protein analysis.