Chemistry Nobel goes to reactions like those that gave life a hand

本文为原文前 6,000 字符的节选翻译，完整内容请查看原文。

Life is remarkably selective. Life relies on many molecules with what is termed “handedness”—they’re chemically identical but are mirror images of each other. Most chemical reactions will make a 50-50 mix of the left- and right-handed forms of a chemical, but life uses only one of them.

生命具有显著的选择性。生命依赖于许多被称为具有“手性”的分子——它们化学性质相同，但互为镜像。大多数化学反应会产生左手型和右手型化学物质的 50-50 混合物，但生命只使用其中一种。

In fact, because of the differences between left- and right-handed chemicals, most of the key enzymes used by organisms will fail to work if they’re presented with chemicals that have the wrong handedness. That poses a bit of a challenge for origin-of-life research, as we’re forced to explain how a world that may have started with an even mix of left- and right-handed chemicals produced organisms that only used one of them.

事实上，由于左手型和右手型化学物质之间的差异，大多数生物体使用的关键酶如果遇到手性错误的化学物质，将无法发挥作用。这对生命起源研究构成了一定的挑战，因为我们必须解释一个可能始于左手型和右手型化学物质均匀混合的世界，是如何产生只使用其中一种的生物体的。

Today’s Nobel Prize in Chemistry goes to two individuals, Henri Kagan and Kenso Soai, who discovered chemical reactions could be biased, producing large excesses of one of the two forms of a chemical.

今年的诺贝尔化学奖授予了亨利·卡甘（Henri Kagan）和曾我恒夫（Kenso Soai）两位研究人员，他们发现化学反应可以产生偏差，从而使两种化学形式中的一种占据绝对优势。

The technical term for molecular handedness is “chirality,” and scientists replace left and right with dextro (D) and levo (L). But the ideas are largely the same. Your hands have all the same components—fingers and thumbs—organized in the same way. Yet if you point your thumb upward, the fingers curl in opposite directions, making one the mirror image of the other.

分子手性的专业术语是“手性”（chirality），科学家用右旋（D）和左旋（L）来代替左和右。但其概念基本相同。你的双手拥有完全相同的组成部分——手指和拇指——且排列方式相同。然而，如果你将拇指向上指，手指弯曲的方向却相反，使得一只手成为另一只手的镜像。

Depending on the arrangements of the chemical bonds, many molecules can form similar mirror-image forms, with all the same parts oriented slightly differently in space. (For the geekier among the readership: carbon atoms have four potential sites that can form bonds, spread evenly across the surface of the atom’s sphere. If each of those sites is linked to a different chemical, then swapping the chemicals located in any two of them can potentially change the way it’s arranged in 3D space.)

根据化学键的排列方式，许多分子可以形成类似的镜像形式，所有相同的部件在空间中的取向略有不同。（对于读者中更专业的人士：碳原子有四个可以形成化学键的潜在位点，均匀分布在原子球体的表面。如果这些位点中的每一个都连接到不同的化学物质上，那么交换其中任意两个位点上的化学物质，就有可能改变其在三维空间中的排列方式。）

This can really matter when it comes to enzymes, which typically latch onto chemicals using binding sites that are sculpted by evolution to fit only that chemical and its close relatives. Try to feed the enzyme the mirror-image version of that same chemical, and it will often fail to fit the binding site. Since life uses nothing but the D form of sugars, all of its enzymes are optimized to latch onto those, and many cannot interact at all with the L form.

当涉及到酶时，这一点至关重要。酶通常利用进化塑造的结合位点来附着在化学物质上，这些位点仅能适配特定的化学物质及其近亲。如果尝试给酶喂食同一化学物质的镜像版本，它通常无法与结合位点匹配。由于生命只使用 D 型糖，其所有的酶都经过优化以附着在这些糖上，许多酶根本无法与 L 型糖发生相互作用。

There are two ways this could have happened. The first life may not have been as picky about the reactions it catalyzed and only evolved chirality preferences slowly. Or life could have evolved in an environment where one chiral form dominated. Or there was some combination of the two. But either of the latter two cases simply pushes the question back a bit: How could chemistry create an environment where one chiral form dominates?

这种情况的发生可能有两种途径。最初的生命可能对它催化的反应并不那么挑剔，只是缓慢地进化出了对手性的偏好。或者，生命可能是在一种某种手性形式占主导地位的环境中进化的。又或者，这两种情况兼而有之。但后两种情况只是将问题推后了一步：化学如何创造出一种某种手性形式占主导地位的环境？

Over the years, there have been a number of ideas about how this might occur. Several of those trace back to a physicist, Frederick Charles Frank, who addressed this issue in a data-free, theory-focused paper. (It’s clear from the Nobel Prize Committee’s writing that, were Frank still alive, he might have shared in this award.)

多年来，关于这种情况如何发生，已经有了许多想法。其中一些可以追溯到物理学家弗雷德里克·查尔斯·弗兰克（Frederick Charles Frank），他在一篇不含数据、专注于理论的论文中探讨了这个问题。（从诺贝尔奖委员会的文稿中可以清楚地看出，如果弗兰克还活着，他可能也会分享这一奖项。）

One option is that a catalyst with only a slight preference for forming a D or L molecule could, over time, produce a large excess of that form. Another is that a chiral reaction product could itself serve as a catalyst for forming more of the same form. Or the chiral reaction product could inhibit the formation of its mirrored form.

一种可能性是，一种对形成 D 型或 L 型分子仅有轻微偏好的催化剂，随着时间的推移，可以产生该形式的大量过剩。另一种可能性是，手性反应产物本身可以作为催化剂，促进更多相同形式的形成。或者，手性反应产物可以抑制其镜像形式的形成。

Many chemical reactions reach an equilibrium, finding a point where forward and reverse reactions occur at similar rates. If the reverse reaction is indifferent to chirality, but the forward one is influenced by one of the factors above, then time would allow this to create a large excess of one chiral form. All of these were hypotheticals, however, until the researchers being honored got to work.

许多化学反应会达到平衡，即正反应和逆反应以相似的速率进行。如果逆反应对手性不敏感，而正反应受到上述因素之一的影响，那么时间将允许这种机制产生某种手性形式的大量过剩。然而，在获奖研究人员开展工作之前，所有这些都只是假设。

Henri Kagan of the University of Paris-Sud also approached his work very theoretically, describing the factors that would be needed to drive reactions that favored a single chirality. But in several cases, he was able to go out and find actual chemical reactions that demonstrated his ideas mattered in the real world.

巴黎南大学的亨利·卡甘也以非常理论化的方式开展工作，描述了驱动偏向单一手性的反应所需的因素。但在几个案例中，他成功地找到了实际的化学反应，证明了他的想法在现实世界中是重要的。

Kagan worked with a catalyst that was itself chiral. He found that, in a mix of L and D versions of his catalyst, one of the forms was much more active than the other. While the forms might be present at the same level, most of the actual catalysis was performed by just one of them. And, if it was used to catalyze a reaction that produced a chiral product, this difference could lead to much higher levels of a single chirality.

卡甘使用了一种本身具有手性的催化剂。他发现，在他的催化剂的 L 型和 D 型混合物中，其中一种形式比另一种活跃得多。虽然这两种形式可能以相同的水平存在，但大部分实际的催化作用仅由其中一种完成。而且，如果它被用来催化产生手性产物的反应，这种差异可能导致单一手性产物的水平大大提高。

By the mid-1960s, Kagan had found three different reactions that could produce an excess of a single chiral form. Other researchers who followed up on his ideas showed that chiral catalysts could also be selectively activated or inhibited by the addition of non-chiral chemicals, allowing a finer degree of control that found its way into the production of pharmaceuticals.

到 20 世纪 60 年代中期，卡甘已经发现了三种可以产生单一手性形式过剩的不同反应。其他后续研究他的想法的研究人员表明，手性催化剂还可以通过添加非手性化学物质来选择性地激活或抑制，从而实现更精细的控制，这种控制方式最终被应用于药物生产中。

About a decade later, Tokyo University’s Kenzo Soai was working on reactions where one of the products of the reaction acted as a catalyst to boost the same reaction. Eventually, he found one that selected for chirality; one form of the reaction product would catalyze the formation of more molecules of the same chirality.

大约十年后，东京大学的曾我恒夫正在研究一种反应，其中反应产物之一充当催化剂来促进同一反应。最终，他发现了一种具有手性选择性的反应；反应产物的一种形式会催化更多相同手性分子的形成。

He started the reaction with a slight excess of one form of catalyst and found that, after a single round of reactions, the excess in the catalyst had risen to 55 percent. Using that as a catalyst for a new round of reactions would enhance the excess further; after several rounds, 90 percent of the products were a single chirality. Eventually, Soai found conditions where one

他以一种形式的催化剂略微过剩的状态开始反应，发现经过一轮反应后，该催化剂的过剩比例上升到了 55%。将此作为新一轮反应的催化剂会进一步提高过剩比例；经过几轮反应后，90% 的产物都是单一手性的。最终，曾我恒夫发现了某种条件，使得一种