20种不同的有机分子结合起来组成多肽链或蛋白质。这20个氨基酸主结构相同，但每种又分别有各自不同的侧基团。

One of the 20 different organic molecules that are joined together to form a polypeptide chain or a protein the twenty amino acids share a common backbone, but each has a specific side-group.

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那名教练头发浓密，架着一副新闻主播或是知识分子常戴的方框眼镜，皮肤是橄榄色的，身上散发着那种英国教练少有的从容不迫。

The manager has the kind of luxuriant hair, media/intellectual square-rimmed glasses, olive skin and self-control not usually associated with English coaches.

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这样的入侵在2002年春天到达顶点，那时他们包围了主诞堂(the Church of the Nativity)，以色列的狙击手与藏身于这座古建筑里的武装分子对峙了40天。

These incursions culminated in the siege of the Church of the Nativity in spring 2002, a 40-day stand-off between Israeli snipers and armed militants sheltering in the ancient building.

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The backbone's on the outside of the molecule like the upright struts of a ladder on the outside of a ladder.

主链位于DNA分子结构外侧,像梯子两侧上下的支柱,记住是梯子外侧

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