Abstract
The biological ice crystal modifiers, antifreeze proteins (AFPs), can bind onto the surface of ice crystals to alter their morphology and arrest their growth. These activities of ordinary AFPs have been evaluated using two concentration-dependent parameters, thermal hysteresis (TH) and ice recrystallization inhibition (IRI). However, it has not been subjected a parameter to correlate TH and IRI, which helps understanding of the icebinding ability of AFPs including defective species that cannot perfectly arrest the ice crystal growth. Here we examined a new parameter named “critical ice shaping concentration (CISC)”, a minimum concentration of an AFP species necessary to alter the shape of the ice crystals. We evaluated the CISC for three different types of fish AFPs including a defective AFP isoform, and examined the correlation between CISC and IRI. The obtained results showed for the first time that effective IRI concentrations of these AFPs are approximately double of their CISCs.
