Effect of antifreeze activity and lipid interaction of tryptophan scanning of 11-residue lysine homopeptide

Antifreeze peptides and proteins play crucial roles in the survival of organisms that thrive in cold environments, such as polar fish [1].These compounds serve diverse functions, including cryopreservation, which is essential for organisms facing freezing conditions.Peptides exhibit varied primary and secondary structures, offering a range of functionalities in cold adaptation.In our study, we focused on an 11-residue lysine homopeptide, K11, where each position was substituted with Trp using a scanning technique.Peptides were synthesized using the Fmoc/tBu strategy [2], followed by purification and characterization via RP-HPLC and mass spectrometry.Antifreeze activity of peptide was evaluated using differential scanning calorimetry (DSC) and quantifying ice recrystallization inhibition, known as thermal hysteresis (THA).Results showed a slightly increased antifreeze activity with fewer remaining nucleation points across all peptides in the scanning sequence.Substituting internal residues whit Trp, enhanced ice recrystallization inhibition, highlighting the significance of peptide structure.However, Trp substitution disrupted the secondary structure of K11, as obtained by circular dichroism, notably affecting the type II polyproline helix of K11 and resulting in decreased antifreeze activity compared to the K11 homopeptide.This highlights the intricate relationship between peptide structure and functionality in antifreeze mechanisms.