A new method for analysis of components in a mixture without preseparation: evaluation of the concentration ratio and protein-protein interaction.

A new method for evaluating the ratio of two structurally different proteins or other compounds in a mixture that does not require any preseparation steps and is based on using the aqueous two-phase partition technique is described. Mathematical analysis of the partitioning of a mixture of two solutes demonstrates its ability to quantitatively evaluate the ratio of the concentrations of the solutes in the initial mixture. It also provides the means for detecting interactions between the two solutes. Experimental results confirm the analysis to be correct for mixtures of low-molecular-weight compounds as well as for mixtures of structurally different proteins. An example of analysis of a clinically relevant mixture of two proteins-transferrin and carbohydrate-deficient transferrin-is provided. An analysis of interactions between two proteins and/or peptides is also illustrated using two examples. Copyright 2001 Academic Press.