How conformation matters: Ionic liquids as reaction media for oxidative folding and native chemical ligation of cysteine-containing peptides

• Applicant: Professorin Dr. Diana Imhof
• Subject Area: Organic Molecular Chemistry - Synthesis and Characterisation
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 187087034

Concerning the increased significance of ionic liquids for applications in protein and peptide chemistry it is as well essential to characterize the ion effects on peptide structures and reactions involving peptides as reactants. This project is focused on studies of two reactions involving cysteine-containing peptides, oxidative folding and native chemical ligation (NCL). In preliminary studies structurally compact multiple disulfide-bridged neurotoxins derived from marine cone snails were shown to efficiently and correctly fold into their biologically active conformation in biocompatible ionic liquids (e.g. [C2mim][OAc], [C2mim][OTs]). Stabilization of pre-formed secondary structures by ILs was suggested to be the cause of this observation. In order to derive a scientific explanation, short and medium-sized model peptides as well as native Cys-rich peptides will be subjected to ionic liquid-mediated oxidative folding. Monitoring by spectroscopic measurements (e.g. CD, and fluorescence spectroscopy) will provide insights into embedment of the peptides in ionic liquids. Reaction conditions will be varied to establish optimization of individual peptide folding processes and to explore whether there are distinct parameter influencing peptide stabilization and disulfide bridge formation. As a second reaction type involving cysteine residues NCL will be investigated in ionic liquids, too. Here, stabilizing and solubilising effects on both, the starting material as well as the reaction products (small proteins, protein domains) is determining the synthetic outcome. The project will therefore provide new methodologies to obtain cysteinecontaining peptides and proteins in a scale enabling biological, biochemical and electrophysiological studies for such complex molecules carrying therapeutic potential.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1191: Ionic Liquids