Growth suppression of ice crystal basal face in the presence of a moderate ice-binding protein does not confer hyperactivity
Growth suppression of ice crystal basal face in the presence of a moderate ice-binding protein does not confer hyperactivity
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DOI：
10.1073/pnas.1807461115
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发表时间：
2018-07-17
影响因子：
11.1
通讯作者：
Furukawa, Yoshinori
中科院分区：
文献类型：
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作者：
Bayer-Giraldi, Maddalena;Sazaki, Gen;Furukawa, Yoshinori
冰结合蛋白（IBPs）通过附着在冰晶表面影响冰晶的生长。我们提出了海冰微藻Fragilariopsis us （fcIBP）的冰结合蛋白对冰单晶生长的影响，其特征是未知功能3494 （DUF3494）的广泛结构域，已知会导致中度冰点降低（低于1摄氏度）。通过干涉测量法、明场显微镜和荧光显微镜观察，我们发现fcIBP附着在冰晶的基底面上，从而抑制了冰晶在c方向的生长，并且随着fcIBP浓度的增加，有效过冷度增加。此外，我们观察到fcIBP附着在棱镜表面并抑制其生长。当有效过冷量较小且晶体呈多面时，该过程会导致棱柱面出现，抑制晶体在a方向的生长。当有效过冷较大且冰晶已发育成枝晶形状时，抑制棱柱面生长导致枝晶分支变细，潜热消散增强导致a方向生长加快。我们的观察清楚地表明，fcIBP在IBPs分类中占有一个单独的位置，因为它抑制基底面的生长，尽管它的冰点适度下降。
Ice-binding proteins (IBPs) affect ice crystal growth by attaching to crystal faces. We present the effects on the growth of an ice single crystal caused by an ice-binding protein from the sea ice microalga Fragilariopsis cylindrus (fcIBP) that is characterized by the widespread domain of unknown function 3494 (DUF3494) and known to cause a moderate freezing point depression (below 1 degrees C). By the application of interferometry, bright-field microscopy, and fluorescence microscopy, we observed that the fcIBP attaches to the basal faces of ice crystals, thereby inhibiting their growth in the c direction and resulting in an increase in the effective supercooling with increasing fcIBP concentration. In addition, we observed that the fcIBP attaches to prism faces and inhibits their growth. In the event that the effective supercooling is small and crystals are faceted, this process causes an emergence of prism faces and suppresses crystal growth in the a direction. When the effective supercooling is large and ice crystals have developed into a dendritic shape, the suppression of prism face growth results in thinner dendrite branches, and growth in the a direction is accelerated due to enhanced latent heat dissipation. Our observations clearly indicate that the fcIBP occupies a separate position in the classification of IBPs due to the fact that it suppresses the growth of basal faces, despite its moderate freezing point depression.