Tryptophan is an essential amino acid that ACTS as a precursor of serotonin - the feel-good chemical - and can be converted to melatonin, eliciting relaxation and pleasure.

色氨酸，一种非常重要的氨基酸，也是血清素(让人感觉良好的化学物质)的前导，会转换成褪黑色素，刺激加强松弛感和愉悦。

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Carbs are also full of tryptophan, the amino acid precursor to the feel-good chemical serotonin produced in the brain.

碳水化合物富含色氨酸，它是大脑中生成的一种能给人带来良好感受的氨基酸—血清素的前身。

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After tweaking the system to adjust the relative amounts of the enzymes, the researchers could feed their yeast a precursor chemical called thebaine, and get pure morphine in return.

在经过对植物体系进行酶相对数量的调整后，研究人员会在这些酵母中加入一种名为二甲基吗啡的混合化学物质，这样就会得到纯净的吗啡。

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For over 30 years, levodopa, the chemical precursor of dopamine, has been the primary medication for PD patients.

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Codexis's technology works with pharmaceutical precision indeed, one of its main commercial products is the enzyme system for making the chemical precursor to Lipitor, a cholesterol-lowering drug that is marketed by Pfizer.

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L-dopa, a chemical precursor to dopamine.

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