Tryptophan Zippers Peptides: Synthesis and Mass Spectrometry Investigation

Tryptophan zippers, also known as tripzips, are a structural motif that can stabilize the beta-hairpin conformation in short peptides. Additionally, they are the smallest peptides that can acquire a unique tertiary fold without requiring metal binding, unusual amino acids, or disulfide crosslinks. These peptides are spanned from twelve to sixteen amino acids in length and have four turn sequences, they would be classified as monomeric and can fold cooperatively in water. In this study, we have synthesized two peptides, tripzip1 and tripzip2, containing 12 amino acids. These peptides were synthesized using the CEM Liberty Blue peptide synthesizer on a solid support of rink amid resin. Compared to liquid phase peptide synthesis, solid phase synthesis requires few steps, easy to separate excess reagents and by-products, and very cost-effective. After completing the peptide synthesis, the cleavage of the resin-peptide complex was achieved using high percentage (95%) of TFA and using water and TIPS as scavengers. By adding cold ether, peptides were precipitated. The synthesis of the peptide was confirmed by liquid chromatography and mass spectrometry. The two peptides, tripzip1 and tripzip2, displayed three strong peaks at m/z 537.00, 805.00, and 1608.75, which correspond to [M+3H]3+, [M+2H]2+, and [M+H] + ions, respectively, which was slightly higher than the than the theoretical mass of 1607.75. Further studies will be conducted to explore the structural features of these tripzip peptides using circular dichroism and hydrogen-deuterium exchange mass spectrometry