Fluorescence study of some terbium–oligopeptide complexes in methanolic solution

This study concerned the use of lanthanide chelates to detect glycyl-leucyl-phenylalanine (GLF) and its homologues. Spectroscopic analysis of peptides without or with terbium complexation revealed the formation of (LF)3(Tb)2, (GF)3(Tb)2, (GLF)3(Tb)2 and (FL)4Tb, (FG)4Tb complexes with high stability constants in methanolic solutions (pKd>13). Lanthanide chelate emission displayed a large Stokes shift (>270 nm), which allowed Tb chelates of GLF and its derivatives to be used for detection purposes. However, this preliminary study indicated some important limitations associated with lanthanide chelation, such as high methanolic content.