Affinity of the monoclonal antibody M1 directed against the FLAG peptide

The FLAG (Sigma, St. Louis, MO, USA) peptide is a frequently used hydrophilic and immunogenic fusion tag which was specifically designed to facilitate rapid purification by immunoaffinity chromatography. The monoclonal antibody MI recognizes the free N-terminus of the peptide tag in a calcium dependent manner. Dissociation of the complex can be performed by the addition of chelating agents such as EDTA. This effect can be exploited for immunoaffinity purification of FLAG-tagged fusion proteins. Kinetic information obtained from monitoring interactions in real-time measurement (Biacore 2000) using surface plasmon resonance as detection principle did not show any difference for association and dissociation rate constants in the presence (k(a)=3.03(.)10(3) M-1 s(-1) k(d)=1.25(.)10(-3) s(-1)) and in the absence of Ca2+ (k(a)=3.59(.)10(3) M-1 s(-1), k(d)=1.16(.)10(-3) s(-1))(.) These findings corroborate the reports from Mel. Immunol. 33 (1996) 601-608 describing similar binding analyzed by enzyme-linked immunosorbent assay experiments. These investigations are in contrast to the observations in immunoaffinity chromatography with immobilized anti-FLAG antibody M1. (C) 2001 Elsevier Science B.V. All rights reserved.