Use of 19 F Differential Labelling for the Simultaneous Detection and Monitoring of Three Individual Proteins in a Serum Environment.

Protein behavior in complex mixtures, such as biological fluids, is often modeled by simplified buffer systems in solution. Here we have used the recently described differential 19 F labelling approach (with NMR detection) to monitor and compare the solution behaviour of three proteins at once: human serum albumin (HSA), transferrin (TrF), and immunoglobulin G (IgG), both in serum and in buffer. We demonstrate that monitoring three proteins simultaneously and independently in biological fluid is possible, and that the presence of other endogenous components greatly changes the association characteristics of these proteins. For example, in the simplified model buffer system, all three proteins diffuse at a similar rate, while in serum HSA diffuses around three times faster than TrF, and four times faster than IgG. This 19 F NMR approach allows characterization of the behaviour of complex multiprotein systems in their native environment, e. g., in biological fluids.