Li Q Z, Yeh Y, Liu J J, Feeney R E, Krishnan V V
The Theoretical Physics and Biology Laboratory, Department of Physics, College of Sciences and Technology, Inner Mongolia University, Hohhot 010021, China.
J Chem Phys. 2006 May 28;124(20):204702. doi: 10.1063/1.2186309.
Antifreeze proteins (AFPs) and antifreeze glycoproteins (AFGPs), collectively abbreviated as AF(G)Ps, are synthesized by various organisms to enable their cells to survive in subzero environments. Although the AF(G)Ps are markedly diverse in structure, they all function by adsorbing to the surface of embryonic ice crystals to inhibit their growth. This adsorption results in a freezing temperature depression without an appreciable change in the melting temperature. The difference between the melting and freezing temperatures, termed thermal hysteresis (TH), is used to detect and quantify the antifreeze activity. Insights from crystallographic structures of a number of AFPs have led to a good understanding of the ice-protein interaction features. Computational studies have focused either on verifying a specific model of AFP-ice interaction or on understanding the protein-induced changes in the ice crystal morphology. In order to explain the origin of TH, we propose a novel two-dimensional adsorption kinetic model between AFPs and ice crystal surfaces. The validity of the model has been demonstrated by reproducing the TH curve on two different beta-helical AFPs upon increasing the protein concentration. In particular, this model is able to accommodate the change in the TH behavior observed experimentally when the size of the AFPs is increased systematically. Our results suggest that in addition to the specificity of the AFPs for the ice, the coverage of the AFPs on the ice surface is an equally necessary condition for their TH activity.
抗冻蛋白（AFPs）和抗冻糖蛋白（AFGPs），统称为AF(G)Ps，由多种生物体合成，以使它们的细胞能够在零度以下的环境中存活。尽管AF(G)Ps在结构上明显不同，但它们的功能都是通过吸附到胚胎冰晶表面来抑制其生长。这种吸附导致冰点温度降低，而熔点温度没有明显变化。熔点和冰点温度之间的差异，称为热滞（TH），用于检测和量化抗冻活性。对多种抗冻蛋白晶体结构的深入了解，使人们对冰与蛋白的相互作用特征有了很好的认识。计算研究要么集中在验证抗冻蛋白与冰相互作用的特定模型，要么集中在理解蛋白质引起的冰晶形态变化。为了解释热滞的起源，我们提出了一种抗冻蛋白与冰晶表面之间的新型二维吸附动力学模型。通过在增加蛋白质浓度时重现两种不同β-螺旋抗冻蛋白的热滞曲线，证明了该模型的有效性。特别是，当系统地增加抗冻蛋白的大小时，该模型能够适应实验中观察到的热滞行为的变化。我们的结果表明，除了抗冻蛋白对冰的特异性外，抗冻蛋白在冰表面的覆盖率是其热滞活性的同等必要条件。
