Thermochemical Characterization of the Interaction of the Zwitterionic Surfactant with Zwitterionic, Cationic, and Anionic Peptides: Binding of Glycyl-Glycine, β-Alanyl- <scp>l</scp> -Histidine, and Glycyl- <scp>l</scp> -Glutamic Acid to Phosphatidylcholine in a Buffered Saline

The enthalpies of dissolution of three peptides, glycyl-glycine (GlyGly), β-alanyl-l-histidine (β-AlaHis), and glycyl-l-glutamic acid (GlyGlu), in buffered saline containing micellar-type aggregates of l-α-phosphatidylcholine (PC) were measured calorimetrically. The thermochemical characteristics of the interaction of peptides with PC micellar-type aggregates in a buffered saline are found from the calorimetric data as the enthalpies of transfer of peptides from a buffer to (buffer + PC) solution. The exothermic effect of interaction with zwitterionic surfactant aggregates was observed to weaken in the series: β-AlaHis cations > GlyGlu anions > GlyGly zwitterions. The effect of peptide charge on the binding characteristics is more pronounced in the case of zwitterionic aggregates than in the case of charged micelles. The observed differences are related to the different binding modes of peptides to micellar-type aggregates and the absence of the effect of counterions in zwitterionic surfactants.