美國(guó)研究人員最近證實(shí)了２０多年前關(guān)于赤潮海藻產(chǎn)生毒素的理論,。這一發(fā)現(xiàn)或許能為保護(hù)沿海地區(qū)貝類生物,、海洋哺乳動(dòng)物和人類免遭赤潮周期性暴發(fā)的危害提供一些幫助。
美國(guó)麻省理工學(xué)院副教授蒂莫西·賈米森在最新出版的一期《科學(xué)》雜志上發(fā)表論文說,，他和其他研究人員已成功復(fù)制了赤潮海藻產(chǎn)生毒素的一連串化學(xué)反應(yīng),。
哥倫比亞大學(xué)的化學(xué)家中西香爾曾在１９８５年指出，赤潮海藻通過一連串的化學(xué)反應(yīng)制造毒素,。但一直以來,，研究人員都無法在實(shí)驗(yàn)室中復(fù)制這樣的化學(xué)反應(yīng)。賈米森表示,，他和麻省理工學(xué)院的研究生伊萬·維洛蒂耶維奇已經(jīng)能夠在實(shí)驗(yàn)室中啟動(dòng)這樣的化學(xué)反應(yīng),。試驗(yàn)的一個(gè)關(guān)鍵是要在水中進(jìn)行這樣的反應(yīng)。
賈米森猜測(cè),，制造毒素的海洋浮游生物腰鞭毛蟲（一種海洋單細(xì)胞生物,，可引起赤潮）是通過某種酶啟動(dòng)此類化學(xué)反應(yīng)的。通過化學(xué)反應(yīng),，它們能產(chǎn)生一種名叫“Ｂｒｅｖｅｎａｌ”的與赤潮毒素有關(guān)的化學(xué)物質(zhì),。但研究也表明，這種化學(xué)物或許能用來治療囊腫性纖維化,。
赤潮是一種自然現(xiàn)象,，當(dāng)海水溫度和鹽分促使某些海藻和浮游生物過度繁殖的時(shí)候海水就會(huì)變色，產(chǎn)生赤潮,。相當(dāng)一部分赤潮是無害的,，它們會(huì)自生自滅，但也有一些赤潮是有害的,。
美國(guó)東海岸１９７２年曾出現(xiàn)大規(guī)模赤潮,，造成佛羅里達(dá)州的海牛大量死亡。（新華網(wǎng)）
原始出處:
Science 31 August 2007:
Vol. 317. no. 5842, pp. 1189 - 1192
DOI: 10.1126/science.1146421
Epoxide-Opening Cascades Promoted by Water
Ivan Vilotijevic and Timothy F. Jamison*
Selectivity rules in organic chemistry have been inferred largely from nonaqueous environments. In contrast, enzymes operate in water, and the chemical effect of the medium change remains only partially understood. Structural characterization of the "ladder" polyether marine natural products raised a puzzle that persisted for 20 years: Although the stereochemistry of adjacent tetrahydropyran (THP) cycles would seem to arise from a biosynthetic cascade of epoxide-opening reactions, experience in organic solvents argued consistently that such a pathway would be kinetically disfavored. We report that neutral water acts as an optimal promoter for the requisite ring-opening selectivity, once a single templating THP is appended to a chain of epoxides. This strategy offers a high-yielding route to the naturally occurring ladder core and highlights the likely importance of aqueous-medium effects in underpinning certain noteworthy enzymatic selectivities.
Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
* To whom correspondence should be addressed. E-mail: [email protected]
