Equilibrium and pre-equilibrium fluorescence spectroscopic studies of the binding of a single-immunoglobulin-binding domain derived from protein G to the Fc fragment from human IgG1.

A single-immunoglobulin-binding protein based upon the C2 domain of Protein G from Streptococcus has been shown to bind tightly to the Fc fragment of IgG1. The binding interaction results in a decrease in the fluorescence intensity from the sole Trp residue (Trp-48) in this domain. This spectral change has been used to monitor the binding interactions between the two proteins using equilibrium and pre-equilibrium fluorescence spectroscopy. Comparison of the data from the two techniques suggests that a conformational change occurs after the initial formation of the complex. Mutagenesis studies have shown that the Trp residue is important for binding and that replacement by a Phe residue is important for binding and that replacement by a Phe residue leads to a 300-fold decrease in the affinity for Fc gamma 1. Determination of the rate constants kon and koff at different values of pH between 4.0 and 9.0 suggest that variations in Kd are mediated predominantly by changes in kon. Competition experiments between SpG1 and a single-IgG-binding domain from Protein A from Staphylococcus aureus have been used to determine the affinity of the latter for Fc gamma 1.

Remarriage after divorce: dissolution and reconstruction of family boundaries.

Remarriage is analyzed from the perspective of family boundaries and roles. The nuclear and remarriage family models are compared, and the process that begins with the formation of the first-marriage nuclear family and ends with the formation of a second-marriage family is conceptualized in terms of changing family boundaries and roles. Discussions with remarriage group members provide concrete illustrations of this process and suggest solutions to some of the problems confronting remarriage family members.