Minimizing ice growth damage is essential to many industries. Cold-adapted organisms have
long solved this issue by producing potent antifreeze proteins (AFPs) that adsorb to the surface
of ice, thus reducing ice growth. While promising, their poor stability, high cost, and lack of
scalability have made AFPs difficult to implement for cryopreservation and food-related
applications. AFPs are widely diverse in structure and sequence motifs, which makes
understanding the key features and interactions that allow them to bind to ice and stop ice growth
challenging. It has been recognized that the position of threonine residues on the ice-binding face
plays a key role in helping certain AFPs bind to ice. We apply less complicated structures of β-
helical AFPs to design our own mimetics via solid-state peptide synthesis. A series of short, β-
stranded peptides with a threonine-any-threonine motif are constrained to fix the position of the
threonine residues to promote ice binding. Linear versions of these peptides were synthesized for
comparison as well. Ice recrystallization inhibition (IRI) and immersion freezing methods are
used to assess the effects of these mimetics on ice recrystallization and thermal hysteresis or
freezing point depression, respectively. Our IRI methodology has been validated by analyzing
the ice growth rate in 17 wt% glycerol solution in addition to 18 and 45 wt% sucrose systems
with and without the presence of a widely known synthetic IRI agent polyvinyl alcohol (PVA).
Ice crystal diameter and growth rate kinetics described by Lifshitz-Slyov-Wagner (LSW) theory
were analyzed to confirm the detection of an IRI agent. We have tested our shortest linear
peptide consisting of 5 amino acid residues with the threonine motif. No sign of IRI was
observed for this linear peptide from concentrations of 1-10 mg mL -1 . Likewise, frozen fraction
curves from immersion freezing experiments showed that our short linear peptide did not induce
freezing point depression at those concentrations either. We will present preliminary results that
show the effect of longer peptide versions having the threonine-any-threonine motif on IRI and
thermal hysteresis activity.

Yinon Rudich

Appearances