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In eighteen ninety-seven, a chemist named Felix Hoffmann at Friedrich Bayer and Company in Germany created acetyl salicylic acid.
VOA: special.2009.10.20
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There are more than 20 amino acids that make up the biological polymers called proteins, so there are 20 choices of each amino acid at a position on a protein.
而那些称为蛋白质的生物活性多聚体,是由二十种不同氨基酸所构成,因此每个蛋白质的,任意位点都有多达二十种氨基酸可供选择
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And then linked to the glycerol instead of a third fatty acid chain is a water soluble molecule, like a salt.
但连到甘油上的第三个基团不是脂肪酸链,而是一种水溶性的分子,像盐一样
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We stopped in the afternoons to fish for a few minutes in little rivers turned black by the acid of cypress trees.
VOA: special.2010.01.30
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And they wanted to use a soluble salt of citric acid, so they could have used sodium, they could have used potassium.
而且他们想用一种柠檬酸的可溶性盐，他们本可以用钠，也可以用钾。
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But it is the first time an amino acid has been discovered on a comet.
VOA: special.2009.09.30
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They're derived from a precursor called triacylglyceride, which is as glycerol molecule with three fatty acid chains dangling off of it.
它们来源于一种叫三酰甘油的前体,由甘油分子上连接了,三个脂肪酸链构成
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High levels of domoic acid in the sardines may have worsened the effects of oxygen loss in the water as the fish crowded into a limited space.
VOA: special.2011.03.15
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Fatty acid chains are fat molecules, they behave, if you have a lot of them in solution like oil.
脂肪酸链就是脂肪分子,它们看上去好像,如果你见过富含脂类的溶液,比如油
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Domoic acid is a powerful neurotoxin produced by one kind of microalgae.
VOA: special.2011.03.15
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So I show that here, so in green, you have what's called a carboxcylic acid group, a c o o h, which gets converted by s o c l 2 to a c double bond o c l or an acid chloride.
我在这里用绿色表示，我们所说的羧酸族化合物，碳，氧，氧，氢，它被亚硫酰氯转化为,一个碳氧双键与碳氯单键组成的酰氯。
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A chromosome contains molecules of deoxyribonucleic acid, better known as DNA.
VOA: special.2009.12.08
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One of them has the right sequence of codons to specify the amino acid sequence of the protein, and the other one has a complimentary sequence.
该段带有正确的密码子序列,能够指导氨基酸序列合成蛋白质,另一段则是它的互补序列
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DNA methylation shows chemical changes in a person's deoxyribonucleic acid,or DNA.
VOA: special.2009.11.24
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And what it's used is to convert one type of group, what's called a carboxylic acid into another type of very reactive intermediate, which is called an acid chloride.
它被用来将一类被称作羧酸的化合物，转化成另外一类活性很高的反应中间体,也就是酰氯。
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Company engineers admit the lead acid battery wasn't technically advanced enough to run a car.
VOA: standard.2010.07.30
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They would naturally hybridize and form a duplex, or a double stranded nucleic acid.
它们会自然杂交并形成双螺旋,或者说双链核酸
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I wrote this son, my father and I wrote this song, for the acid victims of Kandahar City -- a few young girls who were trying to make their way home from school when they got attacked by acid.
VOA: standard.2010.03.08
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They bring into proximity an amino acid so that instead of forming a new polymer of a nucleic acid, a polymer of an amino acids is formed.
同时它所携带氨基酸相互邻接,从而形成了一个氨基酸聚合物,而非核酸聚合物
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That's because every three base pairs describes an amino acid in a protein.
那是因为每三个碱基对,对应一个蛋白质中的一个氨基酸
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So, if you look in the blood of patients that are infected with Hepatitis B you find a lot of Hepatitis B surface subunits, proteins without the nucleic acid circulating in their blood.
因此,如果你观察一下,已经感染乙肝病毒患者的血液,你会发现许多乙肝病毒的表面亚基,以及血液循环中存在没有核酸的蛋白质
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I just wanted to point out that although you see these chlorine atoms in these drugs, in fact, I don't think I've ever seen an acid chloride in a final pharmaceutical product or drug that we take, and the reason is because they're so reactive that you wouldn't want to have that in something you digest.
我只是想指出一点,那就是尽管你在这些药物中看到了氯原子，实际上，我想我从来都没有在一个,成品的药用产品或者药物中见到过酰氯，这原因是因为它们太容易反应了,你不会想让它们出现在你要消化的东西中。
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When you think about a gene or a transcript, the messenger RNA copy of a gene, you know that for every sequence of a nucleic acid there's a complimentary sequence.
当你们考虑一段基因或者一个,转录一段基因的mRNA拷贝,你们知道每个核酸序列,都有互补序列
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