Phage display screen finds short peptides that block ice nucleation, and an alanine swap makes one stronger

Summary. Researchers at Kansai University in Suita, Japan, reported in the Journal of Peptide Science, published online on 22 October, a phage display screen for peptides with anti-ice-nucleation activity. The team used silver iodide, a classic artificial ice-nucleating agent, as the screening target, and found that the phage interacted with silver iodide in a dispersed state rather than in an immobilized state. DNA analysis of the selected phage identified five peptide sequences with high expression levels.

Research context (RUO). The five sequences were synthesized by hand using Fmoc solid-phase peptide synthesis and tested for their ability to suppress ice nucleation. Three showed anti-ice-nucleation activity, and the authors note that two of the peptides were insoluble in water. Among the active peptides, the seven-residue sequence SHIARSV gave the highest activity. To find out which residues mattered, the authors made a series of five alanine-substituted variants of SHIARSV and tested each one. One variant, AHIARSV, in which the first serine is replaced by alanine, showed higher anti-ice-nucleation activity than the original sequence, and it also showed strong ice recrystallization inhibition, a second property that is typical of natural antifreeze proteins. The authors conclude that designing short antifreeze peptides with activity comparable to natural ones is highly feasible. The study is a materials and peptide-chemistry report with no biological or clinical testing. For peptide laboratories, it is an example of how phage display against an inorganic surface, followed by an alanine scan, can turn a screening hit into an improved sequence.