Key Laboratory of Green Printing, Beijing National Laboratory for Molecular Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
School of Medicine, Shihezi University, Shihezi, Xinjiang 832000, People's Republic of China.
Biomacromolecules. 2021 Jun 14;22(6):2614-2624. doi: 10.1021/acs.biomac.1c00331. Epub 2021 May 4.
Antifreeze (glyco)proteins (AF(G)Ps) are naturally evolved ice inhibitors incomparable to any man-made materials, thus, they are gaining intensive interest for cryopreservation and beyond. AF(G)Ps depress the freezing temperature () noncolligatively below the melting temperature (), generating a thermal hysteresis (TH) gap, within which the ice growth is arrested. However, the ice crystals have been reported to undergo a retaliatory and explosive growth beyond the TH gap, which is lethal to living organisms. Although intensive research has been carried to inhibit such an explosive ice growth, no satisfactory strategy has been discovered until now. Here, we report that crowded solutions mimicking an extracellular matrix (ECM), in which AF(G)Ps are located, can completely inhibit the explosive ice growth. The crowded solutions are the condensates of liquid-liquid phase separation consisting of polyethylene glycol (PEG) and sodium citrate (SC), which possess a nanoscale network and strong hydrogen bond (HB) forming ability, completely different to crowded solutions made of single components, that is, PEG or SC. Due to these unique features, the dynamics of the water is significantly slowed down, and the energy needed for breaking the HB between water molecules is distinctly increased; consequently, ice growth is inhibited as the rate of water molecules joining the ice is substantially reduced. The present work not only opens a new avenue for cryopreservation, but also suggests that the ECM of cold-hardy organisms, which also exhibit great water confining properties, may have a positive effect in protecting the living organisms from freezing damage.
抗冻（糖）蛋白（AF(G)Ps）是自然进化而来的冰抑制剂，无与伦比的任何人为材料，因此，它们在冷冻保存等方面引起了广泛关注。AF(G)Ps 非共混地降低冰点 () 低于熔点 (), 产生热滞（TH）间隙，在该间隙内，冰的生长被阻止。然而，据报道，冰晶会在 TH 间隙之外经历报复性和爆炸性生长，这对生物体是致命的。尽管已经进行了密集的研究来抑制这种爆炸性的冰生长，但到目前为止，还没有发现令人满意的策略。在这里，我们报告说，模拟细胞外基质（ECM）的拥挤溶液，其中包含 AF(G)Ps，可以完全抑制爆炸性的冰生长。拥挤溶液是由聚乙二醇（PEG）和柠檬酸钠（SC）组成的液-液相分离的凝聚物，具有纳米级网络和强氢键（HB）形成能力，与由单个成分（即 PEG 或 SC）组成的拥挤溶液完全不同。由于这些独特的特征，水的动力学明显减慢，打破水分子之间 HB 所需的能量明显增加；因此，冰的生长受到抑制，因为水分子加入冰的速度大大降低。本工作不仅为冷冻保存开辟了新途径，而且还表明，耐寒生物的细胞外基质也具有很好的水约束特性，可能对保护生物体免受冷冻损伤有积极作用。
