Dithioester complexes formation

Extensive studies of enzyme-substrate complexes by resonance Raman spectroscopy (RR) have prompted the synthesis of new peptide bond modifications such as thionoesters and dithioesters (Scheme l7)t82-83l within simple model substrates. The resulting acyl-enzyme complexes are especially amenable to RR analysis with cysteine proteases such as papain due to formation of the transient dithioester intermediates. 

As stated above, the dithioester-substituted ligand behaved in the same manner as the unsubstituted-trifluoromethyl ligands. The formation of the europium complex and the suspected route of adduct formation is shown in Figures 4 and 5. 

---