Synthesis, Characterization, and Secondary Structure Determination of a Silk-Inspired, Self-Assembling Peptide: A Laboratory Exercise for Organic and Biochemistry Courses

This laboratory experiment gives upper-division organic or biochemistry undergraduate students a comprehensive look at the synthesis, chemical characterization, self-assembly, and secondary structure determination of small, N-acylated peptides inspired by the protein structure of silkworm silk. All experiments can be completed in one 4 h lab period, followed by two 3 h lab periods, but can be easily tailored to a particular course curriculum, time restraints, or instrument availability. Students synthesize a peptide using solid-phase techniques and characterize the product using nuclear magnetic resonance spectroscopy, Fourier transform infrared (FTIR) spectroscopy, high-performance liquid chromatography, and mass spectrometry. Unique from other available peptide-based experiments, self-assembly of the peptide is induced in organic solvent, resulting in the formation of a gel. Following solvent evaporation, FTIR spectroscopy is used to evaluate the secondary structure of the peptide before and after assembly. This set of experiments provides students with an opportunity to explore protein structure from the bottom up, starting from the molecular structure of individual amino acids and continuing through the hydrogen bonding interactions that influence protein 3D structure.