美国科学家发现，阿拉斯加的一种甲虫依赖体内一种特殊的防冻物质在零下60度低温条件下仍能存活，这一发现使人们找到生物防冻物质新的种类。
美国印第安纳州圣母大学的肯特. 沃尔特斯小组描述的新物质名为“beta-Mannopyranosyl”。据该小组在世界上最负盛名的基础科学领域的学术杂志之一《美国国家科学院院刊》上发表的论文写道，它是人们发现的第一种不是由蛋白质，而是由一种相似葡萄糖的化学组合物构成的生物防冻物质。
据报道，沃尔特斯小组用几周时间让阿拉斯加“Upis ceramboides”甲虫适应越来越低的温度，直到零下8度，以激活它的防冻机制，然后再把40克甲虫粉碎，从其液状物中寻找耐受冰冻的基础物质。
报道说，科学家们没有从中找到蛋白质对防冻机能的帮助，代替它的却是一种相似葡萄糖的化学组合物。在一次控制实验中，研究人员摧毁了这种物质，而甲虫的防冻机能也随之崩溃。
报道说，在此之前，最早发现的一种生物防冻物质是从北极的鱼类中找到的，依赖它这些鱼类才能在冰冷的水域中生存。这一情形使很多人感到惊异。
迄今为止，人们只知道蛋白质能承担这项任务。它积聚冰晶，并阻止它们生长。假如越来越多的水分子在小冰晶上积聚使它变得太大，细胞膜就会被穿透，从而造成严重伤害直至死亡。
报道说，新发现的化学组合物据猜测也具有这种机能，它使冰晶尽量保持微小状态。这种物质紧贴在细胞膜上，象薄薄的套子围裹着细胞。
报道说，在动物、植物、细菌和真菌中人们虽然都发现过生物防冻物质，但是大多没有找出各自对其负责的分子。美国科学家用他们的成果提示人们，这类研究不要仅局限于寻找蛋白质类物质。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS November 23, 2009, doi: 10.1073/pnas.0909872106
A nonprotein thermal hysteresis-producing xylomannan antifreeze in the freeze-tolerant Alaskan beetle Upis ceramboides
Kent R. Walters, Jr.a,1, Anthony S. Seriannib, Todd Sformoc, Brian M. Barnesc and John G. Dumana
aDepartment of Biological Sciences and
bDepartment of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556; and
cInstitute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775
Thermal hysteresis (TH), a difference between the melting and freezing points of a solution that is indicative of the presence of large-molecular-mass antifreezes (e.g., antifreeze proteins), has been described in animals, plants, bacteria, and fungi. Although all previously described TH-producing biomolecules are proteins, most thermal hysteresis factors (THFs) have not yet been structurally characterized, and none have been characterized from a freeze-tolerant animal. We isolated a highly active THF from the freeze-tolerant beetle, Upis ceramboides, by means of ice affinity. Amino acid chromatographic analysis, polyacrylamide gel electrophoresis, UV-Vis spectrophotometry, and NMR spectroscopy indicated that the THF contained little or no protein, yet it produced 3.7 ± 0.3 °C of TH at 5 mg/ml, comparable to that of the most active insect antifreeze proteins. Compositional and structural analyses indicated that this antifreeze contains a β-mannopyranosyl-(1→4) β-xylopyranose backbone and a fatty acid component, although the lipid may not be covalently linked to the saccharide. Consistent with the proposed structure, treatment with endo-β-(1→4)xylanase ablated TH activity. This xylomannan is the first TH-producing antifreeze isolated from a freeze-tolerant animal and the first in a new class of highly active THFs that contain little or no protein.
