Science：美国科学家证实20多年前“赤潮海藻产毒”理论
美国研究人员最近证实了２０多年前关于赤潮海藻产生毒素的理论。这一发现或许能为保护沿海地区贝类生物、海洋哺乳动物和人类免遭赤潮周期性暴发的危害提供一些帮助。
美国麻省理工学院副教授蒂莫西·贾米森在最新出版的一期《科学》杂志上发表论文说，他和其他研究人员已成功复制了赤潮海藻产生毒素的一连串化学反应。
哥伦比亚大学的化学家中西香尔曾在１９８５年指出，赤潮海藻通过一连串的化学反应制造毒素。但一直以来，研究人员都无法在实验室中复制这样的化学反应。贾米森表示，他和麻省理工学院的研究生伊万·维洛蒂耶维奇已经能够在实验室中启动这样的化学反应。试验的一个关键是要在水中进行这样的反应。
贾米森猜测，制造毒素的海洋浮游生物腰鞭毛虫（一种海洋单细胞生物，可引起赤潮）是通过某种酶启动此类化学反应的。通过化学反应，它们能产生一种名叫“Ｂｒｅｖｅｎａｌ”的与赤潮毒素有关的化学物质。但研究也表明，这种化学物或许能用来治疗囊肿性纤维化。
赤潮是一种自然现象，当海水温度和盐分促使某些海藻和浮游生物过度繁殖的时候海水就会变色，产生赤潮。相当一部分赤潮是无害的，它们会自生自灭，但也有一些赤潮是有害的。
美国东海岸１９７２年曾出现大规模赤潮，造成佛罗里达州的海牛大量死亡。（新华网）
原始出处:
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: tfj@mit.edu
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