Effects of Hofmeister salts on the self-association of glucagon

Publisher Website
Google Scholar
Abstract
The trimerization constants of glucagon at pH 10.6 in 0.76 M K2HPO4 were calculated from circular dichroism data between 5 and 50.degree. C. The free energy, enthalpy and entropy of transfer were evaluated from the current results and published data in 0.20 M phosphate. The free energies of transfer from 0.20 to 0.76 M phosphate were negative at all investigated temperatures. The negative free energies of transfer were derived completely from an increase in the entropy of transfer, since the enthalpy of transfer was less favorable at all temperatures. These parameters were compared with those of various model groups and compounds: CH2, peptide, methane, ethane and the 1-13 N-terminal fragments of ribonuclease. The effects of fluoride and chloride on the self-association of glucagon were compared with that of phosphate at 25.degree. C. These effects were consistent with the binding of approximately 1 molecule of salt to the trimer and a systematic decrease in the number of water molecules bound to the trimer compared to the monomer for the series K2HPO4, KF and KCl.