The CEACAM1 N-terminal Ig domain mediates cis- and trans-binding and is essential for allosteric rearrangements of CEACAM1 microclusters

Klaile, Esther; Vorontsova, Olga; Sigmundsson, Kristmundur; Müller, Mario M.; Singer, Bernhard B.; Öfverstedt, Lars-Göran; Svensson, Stina; Skoglund, Ulf; Öbrink, Björn

In this case, addition of the trimer term does not require additional fit parameters. At equilibrium, it holds that Recalling Eq. 3.1, the total amount of analyte is composed of monomer, dimer, and trimer forms (i.e., A Total in grams/liter). It is beneficial to express these forms with simple functions of the monomer [A] combined with rate constants to provide the minimal amount of variables. We define M W as the molecular mass of the monomer and place it with the proper multiplication terms, i.e., times three for a trimer and times two for the dimers, together with Eqs. , assume a low ligand density and do not account for interactions or bridge formations between ligand units. The models were programmed in IGOR Pro (version 6.03A2) and were applied together with the IGOR Pro Global Fit Procedure based on a nonlinear least-square method using the Levenberg-Marquard algorithm (Press et al., 1999) . For numerical integration, we applied the IGOR Pro algorithm based on a fifth order Runge-Kutta-Fehlberg method (Press et al., 1999) .