Isolation, purification and characterization of secondary structure of antifreeze protein fromAmmopiptanthus mongolicus

Antifreeze protein (AFP) fromAmmopiptanthus mongolicus leaves was isolated and purified with DEAE cellulose 52, Sephacryl 300, heat treatment and preparative isotachophoresis. The molecular weight of AFP was 50 ku by SDS-PAGE measurement. The average thermal hysteresis activity (THA) of AFP was 0.35°C at 5 mg/mL using a differential scanning calorimeter (DSC). This AFP showed heated stability. From circular dichroism (CD) of AFP spectral data from 195–240 nm, a well-defined secondary structure of 11% α-helix, 34% antiparallel β-sheet and 55% random coil for the plant AFP was deduced.