Department of Physics and Astronomy, Ohio University, Athens, OH 45701, USA.
Proc Natl Acad Sci U S A. 2010 Mar 23;107(12):5423-8. doi: 10.1073/pnas.0909456107. Epub 2010 Mar 9.
It has been argued that for antifreeze proteins (AFPs) to stop ice crystal growth, they must irreversibly bind to the ice surface. Surface-adsorbed AFPs should also prevent ice from melting, but to date this has been demonstrated only in a qualitative manner. Here we present the first quantitative measurements of superheating of ice in AFP solutions. Superheated ice crystals were stable for hours above their equilibrium melting point, and the maximum superheating obtained was 0.44 degrees C. When melting commenced in this superheated regime, rapid melting of the crystals from a point on the surface was observed. This increase in melting temperature was more appreciable for hyperactive AFPs compared to the AFPs with moderate antifreeze activity. For each of the AFP solutions that exhibited superheating, the enhancement of the melting temperature was far smaller than the depression of the freezing temperature. The present findings clearly show that AFPs adsorb to ice surfaces as part of their mechanism of action, and this absorption leads to protection of ice against melting as well as freezing.
有人认为，为了使抗冻蛋白（AFP）阻止冰晶生长，它们必须不可逆地结合到冰的表面。吸附在表面的 AFP 也应该防止冰融化，但迄今为止，这只是在定性的基础上得到了证明。在这里，我们首次对 AFP 溶液中冰的过热进行了定量测量。过冷的冰晶在其平衡熔点以上稳定数小时，获得的最大过热度为 0.44 摄氏度。当在过冷状态下开始融化时，从表面的一个点观察到冰晶的快速融化。与具有中等抗冻活性的 AFP 相比，超活性 AFP 更能显著提高融点。对于表现出过热的 AFP 溶液，熔融温度的升高远小于凝固温度的降低。目前的研究结果清楚地表明，AFP 作为其作用机制的一部分吸附到冰的表面，这种吸收导致对冰的保护，防止其融化和冻结。
