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 protein s or other compounds in a mixture that does not require any preseparation s teps and is based on using the aqueous two-phase partition technique is des cribed. Mathematical analysis of the partitioning of a mixture of two solut es demonstrates its ability to quantitatively evaluate the ratio of the con centrations of the solutes in the initial mixture. It also provides the mea ns for detecting interactions between the two solutes. Experimental results confirm the analysis to be correct for mixtures of low-molecular-weight co mpounds as well as for mixtures of structurally different proteins. An exam ple of analysis of a clinically relevant mixture of two proteins transferri n and carbohydrate-deficient transferrin-is provided. An analysis of intera ctions between two proteins and/or peptides is also illustrated using two e xamples. (C) 2001 Academic Press.