冬鲽血清蛋白的抗冷冻机理

在南极和北极的一类鱼的血清中，有一种抗冷冻蛋白（ＡＦＰ）．它们能够保护这类鱼在低于一般鱼的冰点以下生存．这是一种非依数性效应．为了解释观测到的热滞（冰晶生长点和溶点的差），本文提出一个吸附的抗冷冻蛋白能够在冰晶生长方向引起冰晶表面弯曲的模型，在生长动力学的基础上并考虑抗冷冻蛋白在溶液和冰晶中的不同溶解度，计算了冬鲽抗冷冻蛋白溶液的热滞，得出与实验较符合的结论．     

Inhibition of bacterial ice nucleators by fish antifreeze glycoproteins

Certain bacteria promote the formation of ice in super-cooled water by means of ice nucleators which contain a unique protein associated with the cell membrane. Ice nucleators in general are believed to act by mimicking the structure of an ice crystal surface, thus imposing an ice-like arrangement on the water molecules in contact with the nucleating surface and lowering the energy necessary for the initiation of ice formation. Quantitative investigation of the bacterial ice-nucleating process has recently been made possible by the discovery of certain bacteria that shed stable membrane vesicles with ice nucleating activity. The opposite effect, inhibition of ice formation, has been described for a group of glycoproteins found in different fish and insect species. This group of substances, termed antifreeze glycoproteins (AFGPs), promotes the supercooling of water with no appreciable effect on the equilibrium freezing point or melting temperature. Substantial evidence now indicates that AFGPs act by binding to a growing ice crystal and slowing crystal growth. As the ice-nucleating protein surface is believed to have a structure similar to an embryonic ice crystal, AFGPs might be predicted to interact directly with a bacterial ice-nucleating site. We report here that AFGPs from the antarctic fish Dissostichus mawsoni inhibit the ice-nucleating activity of membrane vesicles from the bacterium Erwinia herbicola. The inhibition effect shows saturation at high concentration of AFGP and conforms to a simple binding reaction between the AFGP and the nucleation centre.     

Hyperactive antifreeze protein in a fish

Fish that live in the polar oceans survive at low temperatures by virtue of 'antifreeze' plasma proteins in the blood that bind to ice crystals and prevent these from growing. However, the antifreeze proteins isolated so far from the winter flounder (Pleuronectes americanus), a common fish in the Northern Hemisphere, are not sufficiently active to protect it from freezing in icy sea water. Here we describe a previously undiscovered antifreeze protein from this flounder that is extremely active (as effective as those found in insects) and which explains the resistance of this fish to freezing in polar and subpolar waters.     

鱼抗冻蛋白溶液的热滞与蛋白分子量的关系

分析了鱼抗冻糖蛋白的抗冻机理，根据冰晶生长理论和Ｆｌｏｒｙ的大分子溶液理论，导出了抗冻糖蛋白的热滞（熔点与冰晶生长点之差）与抗冻糖蛋白的分子量的关系，结果与实验数据较好地符合。     

人体脐带血单核细胞与冰晶间相互机械影响的显微研究

利用低温显微镜观察了脐带血单核细胞在降温过程中与冰晶间的相互机械作用,比较了在不同保护剂情况下有无静电场的降温过程中,冰晶形成和生长以及由此引起的机械作用的变化.结果表明,在脐血中的细胞与冰晶间存在一定的机械作用,静电场的引入在一定程度上改变了冰晶的形成和生长特性,使其细化;不同的保护剂,由于其本身的化学机制不同,对冰晶的抑制影响也不同.     

鱼在冻藏中的冰结晶与肌纤维变化的研究

通过冷冻切片,显微摄影,可观察到鱼在冻藏过程中冰晶篚与肌纤维变化。     

Beta-helix structure and ice-binding properties of a hyperactive antifreeze protein from an insect

Insect antifreeze proteins (AFP) are considerably more active at inhibiting ice crystal growth than AFP from fish or plants. Several insect AFPs, also known as thermal hysteresis proteins, have been cloned and expressed. Their maximum activity is 3-4 times that of fish AFPs and they are 10-100 times more effective at micromolar concentrations. Here we report the solution structure of spruce budworm (Choristoneura fumiferana) AFP and characterize its ice-binding properties. The 9-kDa AFP is a beta-helix with a triangular cross-section and rectangular sides that form stacked parallel beta-sheets; a fold which is distinct from the three known fish AFP structures. The ice-binding side contains 9 of the 14 surface-accessible threonines organized in a regular array of TXT motifs that match the ice lattice on both prism and basal planes. In support of this model, ice crystal morphology and ice-etching experiments are consistent with AFP binding to both of these planes and thus may explain the greater activity of the spruce budworm antifreeze.     

超声辅助冷冻对湿面筋蛋白中可冻结水含量及冰晶粒度分布的影响

超声辅助食品冷冻过程是一种新的技术。本文通过对湿面筋蛋白中可冻结水含量及冰晶粒度分布的检测,研究超声辅助食品冷冻过程中冰结晶的热力学机制。用差示扫描量热仪测定了不同冷冻环境下湿面筋蛋白中可冻结水的含量,结果可见：超声辅助冷冻和液氮浸渍冷冻的湿面筋蛋白中可冻结水的含量比传统冷冻过程的高。用扫描电镜间接观察和分析了冷冻的湿面筋蛋白中冰晶的形状和粒度分布,表明适当的功率超声能加速湿面筋蛋白的冷冻过程;超声辅助和液氮浸渍冷冻的湿面筋蛋白中冰晶细小且分布均匀,可减少冷冻时对面筋蛋白网络结构的破坏。显示超声辅助冷冻是改善冷冻食品品质的实用技术。     

过冷水雾相变传播及温度场的实验研究

实验表明在过冷水雾相变传播过程中伴随有脉冲型单峰形式的温度上升,相变传播速率约为1．2cm/s,温度的波形和峰值以及相变的传播速度与过冷水雾的初始温度基本无关,据此对过冷水雾冰晶机制作了探讨。     

抗冻糖蛋白(AFGP1-5)溶液中自由生长条件下冰晶生长激活能的计算

根据冰晶生长速率理论，计算了抗冻糖蛋白（ＡＦＧＰ１－５）溶液中自由生长条件下冰晶生长的激活能．这种定量计算对研究抗冻糖蛋白溶液中冰晶生长习性有重要意义．     

冰蓄冷技术相关固液相变传热现象的研究进展

列举了与常规冰蓄冷技术相关的传热问题，综述了冰－水固液相变导热控制、导热对流耦合控制下圆管外和球内固液相变传热现象的研究进展情况，以及在冰－水固液相交换热实验研究中所采用的实验方法．     

"表面互补"模型--抗冻蛋白通用的分子机理

抗冻蛋白(antifreeze protein,AFPs)是一类能控制冰晶生长和抑制冰晶之间发生重结晶的蛋白质,能在结冰或亚结冰条件下保护生物体不受伤害.AFPs具有两种明显不同的活性--热滞活性和重结晶抑制活性.AFPs虽然在氨基酸序列、物种来源和高级结构等方面具有很大的差异,但都能通过吸附作用与特定的冰晶表面相结合,从而表现出相应的抗冻活性.AFPs与冰晶结合的分子机理主要有"氢键结合"模型和"表面互补"模型,而后者具有更强的优势,已逐渐发展成AFPs通用性的分子机理.目前已测定或建模了三维结构的AFPs都能与冰晶的特定表面形成表面互补,但形成这种表面互补的各种作用力还有待于进一步的研究.     

植物冰结构蛋白的功能机制及其应用

冰结构蛋白是具有热滞效应、冰晶形态效应和重结晶抑制效应的蛋白质.介绍了最近的抗冻蛋白的分类,植物冰结构蛋白作用机制,植物冰结构蛋白与其它病程相关性蛋白或酶的同源性,冰结构蛋白与冰晶间的相互作用,热滞效应和抑制重结晶作用,及其在生产中的应用.     

Ultrafast superheating and melting of bulk ice

The superheating of a solid to a temperature beyond its melting point, without the solid actually melting, is a well-known phenomenon. It occurs with many substances, particularly those that can readily be produced as high-quality crystals. In principle, ice should also be amenable to superheating. But the complex three-dimensional network of hydrogen bonds that holds water molecules together and gives rise to unusual solid and liquid properties strongly affects the melting behaviour of ice; in particular, ice usually contains many defects owing to the directionality of its hydrogen bonds. However, simulations are readily able to 'create' defect-free ice that can be superheated. Here we show that by exciting the OH stretching mode of water, it is possible to superheat ice. When using an ice sample at an initial temperature of 270 K, we observe an average temperature rise of 20 +/- 2 K that persists over the monitored time interval of 250 ps without melting.     

第一类鱼抗冻蛋白分子对冰晶表面平衡结构的影响

根据冰晶生长理论,在一定的生长驱动力作用下,冰晶界面生长机制和动力学规律决定于冰晶界面的微观结构.从大分子溶液热力学性质出发,得到了结合抗冻蛋白后冰晶表面微观平衡结构的变化,并讨论了这种变化对冰晶生长形态的影响.结果显示抗冻蛋白造成冰晶表面微观平衡结构改变,是抗冻蛋白溶液中冰晶生长的形态与纯水中冰晶生长的形态有显著区别的原因之一.     

不连续分凝冰发育规律的研究

提出并推导土体在冻结过程中由于冻结速度和水分移速度的影响,造成不连续分凝冰有单薄冰层、双冰层和厚冰层３种发育模式,采用受控试验的反演分析验证了不连续分凝冰的发育模式,试验结果同时表明：在整个试验期间,分凝暖端的孔隙冰压力变化平稳;当单薄冰层和双冰层发育时,冰分凝温度和孔隙水压力波动较大,尤其是在双冰层生长时,冻结缘发育最充分,分凝暖端的温度和孔隙水压力降低幅度最大;在厚冰层形成后,由于冻结锋面推移     

内融冰式蓄冰桶数学模型的改进

介绍内融冰式蓄冰桶改进的数值计算模型.将盘管分成许多小段进行研究,考虑了蓄冷时冰层和释冷时水层间的连通现象及蓄冷期冰的温度变化和释冷期水温的变化.所得结果可为设计选用提供依据.     

生物组织冻结相变过程的数值模拟

建立了生物组织(含正常生物组织和肿瘤)冻结过程的传热模型.生物组织作为一种多孔介质,其相变发生在一个温度范围内,且存在一个固相与液相共存的糊状过渡区.采用显热容法模拟了生物组织冻结过程中的传热和冰晶增长过程.模拟结果显示,在冻结过程中,冷刀的初始温度越低,冷刀的降温速率越快,生物组织内温度下降和冰晶增长的速率越快.结果还表明组织中液相流动会增加生物组织内传热和冰晶生长的速度.计算结果为冷刀设计和冷冻外科手术提供了理论依据.     

生物组织冻融特性的初步实验研究

以几种典型生物材料为对象，对生物组织冻融过程中的传递现象和界面特性进行可视化实验观测，着重考察冰晶生长及其界面的推进情况，应用微CT技术研究生物组织冻融前后内部结构变化，探讨不同生物材料和冷冻条件下冻融特性的差异．在实验观测的基础上，定性分析了生物组织中水分存在形态对冻融过程特性的影响．     

细粒酒精模型冰的物理性质研究

依据实测数据 ,给出酒精溶液冻结温度和制冰过程中冰池大厅气温、冰表面附近气温、冰温和溶液温度 .介绍模型冰密度、冰内未冻液体含量的实测方法和结果 .得出模型冰物理性质的制约因素和力学性质不受冰温控制的推论