美國科學(xué)家發(fā)現(xiàn),，阿拉斯加的一種甲蟲依賴體內(nèi)一種特殊的防凍物質(zhì)在零下60度低溫條件下仍能存活，這一發(fā)現(xiàn)使人們找到生物防凍物質(zhì)新的種類,。
美國印第安納州圣母大學(xué)的肯特. 沃爾特斯小組描述的新物質(zhì)名為“beta-Mannopyranosyl”,。據(jù)該小組在世界上最負(fù)盛名的基礎(chǔ)科學(xué)領(lǐng)域的學(xué)術(shù)雜志之一《美國國家科學(xué)院院刊》上發(fā)表的論文寫道，它是人們發(fā)現(xiàn)的第一種不是由蛋白質(zhì),，而是由一種相似葡萄糖的化學(xué)組合物構(gòu)成的生物防凍物質(zhì),。
據(jù)報(bào)道，沃爾特斯小組用幾周時(shí)間讓阿拉斯加“Upis ceramboides”甲蟲適應(yīng)越來越低的溫度,，直到零下8度,，以激活它的防凍機(jī)制，然后再把40克甲蟲粉碎,，從其液狀物中尋找耐受冰凍的基礎(chǔ)物質(zhì),。
報(bào)道說，科學(xué)家們沒有從中找到蛋白質(zhì)對(duì)防凍機(jī)能的幫助,，代替它的卻是一種相似葡萄糖的化學(xué)組合物,。在一次控制實(shí)驗(yàn)中，研究人員摧毀了這種物質(zhì),，而甲蟲的防凍機(jī)能也隨之崩潰,。
報(bào)道說，在此之前,，最早發(fā)現(xiàn)的一種生物防凍物質(zhì)是從北極的魚類中找到的,，依賴它這些魚類才能在冰冷的水域中生存。這一情形使很多人感到驚異,。
迄今為止,，人們只知道蛋白質(zhì)能承擔(dān)這項(xiàng)任務(wù),。它積聚冰晶,，并阻止它們生長。假如越來越多的水分子在小冰晶上積聚使它變得太大,，細(xì)胞膜就會(huì)被穿透,，從而造成嚴(yán)重傷害直至死亡。
報(bào)道說,，新發(fā)現(xiàn)的化學(xué)組合物據(jù)猜測(cè)也具有這種機(jī)能,，它使冰晶盡量保持微小狀態(tài)。這種物質(zhì)緊貼在細(xì)胞膜上,，象薄薄的套子圍裹著細(xì)胞,。
報(bào)道說,，在動(dòng)物、植物,、細(xì)菌和真菌中人們雖然都發(fā)現(xiàn)過生物防凍物質(zhì),，但是大多沒有找出各自對(duì)其負(fù)責(zé)的分子。美國科學(xué)家用他們的成果提示人們,，這類研究不要僅局限于尋找蛋白質(zhì)類物質(zhì),。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
