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That's one of the beauties of proteins as working molecules is that their structure can be changed by subtle means.
蛋白质作为一种生物活性分子,其优势之一是,能够通过精细的方法改变其结构
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Step three in our Lewis structure rules is to figure out how many electrons we would need in order for every single atom in our molecule to have a full valence shell.
路易斯结构规则的第三步是,找出让分子中每个原子的价壳层,都排满应该需要多少个价电子。
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Now, we know that there's more structure to this molecule.
现在，我们知道关于这个分子更多关于结构的东西。
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So they like to be in the membrane and they're stable there and they won't come out because their structure allows them to exist in these unique spaces.
所以它们在膜里稳定存在,而且也不会脱离膜,因为这些蛋白质的结构使其能存在于,磷脂双分子层这个独特的环境中
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So, how do we figure out first how to draw the skeletal structure of this molecule here?
那么，我们如何来解决它,首先是如何画出这个分子的骨架结构？
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So this means we can actually calculate this for any molecule that we've drawn the Lewis structure for, because we actually do need to draw the Lewis structure before we know, for example, how many of each of these we have, or at least go through the rules.
这意味着我们可以将原来画过,路易斯结构的分子的形式电荷计算出来，因为我们其实在画出,路易斯结构之后才能知道，比如，这些量的值是多少，或者至少我们需要经过前面的那些步骤。
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We'll see why they have to separate that in a minute, but they do that these lipid bi-layers solve that problem for them and they're self-assembled structures from these molecules called phospholipids.
我们马上会讲到为什么要把它们隔离开,脂质双层膜解决了这个问题,而这些自主装结构,就是由磷脂分子组成的
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Now if you read in the book, you read about where this figure is shown in the book, you can understand more about why these structures line up in the right way so that the right molecular elements are together to form hydrogen bonding pairs between them.
如果你预习过课本,课本中有关于这些详细的描述,你可以更深刻的理解,为什么这些结构是采用这种连接方式,以使对应的分子部分靠近,并形成氢键连接
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So, our second step, as we go through our Lewis structure rules, is to figure out how many valence electrons we have in our entire molecule.
那么，我们的第二步，按照路易斯结构的规则，应该是判断在整个分子中,包含多少个价电子。
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A lot of the examples that we're going to give you in terms of trying out your Lewis structures will be molecule that are used in organic synthesis, or maybe they're molecules that react in interesting ways with biomolecules in your body or proteins in your body.
很多我们将要用来,训练路易斯结构的例子,都是在有机合成中用到的分子，也有可能是那些在你体内的生物分子,或者蛋白质中发生有趣反应的分子。
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But you need to be able to predict what kind of properties a certain atom's going to have within a molecule, whether you're talking about something, for example, that's very electronegative, or something that is not electronegative at all, it is going to make a difference in terms of thinking about how molecules are structured and also how they interact with other molecules.
但是你需要能够预言，什么性质,某个原子在分子中能够具有，无论你讨论的是哪一种情况，比如，它有很高的电负性，还是它根本没有电负性，都将会产生影响,对这个分子的结构,以及与其它分子相互作用的情况。
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So that means that we don't have to worry about things like wave functions when we're talking about Lewis structures, but because they're so simple to use and because they so often predict the electron configuration of molecules accurately, we end up using them all the time in chemistry, so it's very valuable to know how to draw them correctly and to know how to work with them.
因此这也就意味着我们在讨论路易斯结构的时候,不需要担心波函数之类的东西，但是由于路易斯结构不仅简单易用,而且用它来预测分子的电子排布,经常可以得到非常精确的结果，结果我们在化学中一直都在用它，因此知道如何正确地画出并运用,路易斯结构是非常有价值的。
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Now the bases, and you don't need to memorize the structures of these I'm going - I'm describing the whole molecule to you in its molecular detail and then we're going to simplify it down to a version that we can talk about more easily.
现在讲碱基,你不需要记住这些结构,我将给你们详述整个分子,的结构细节,然后我们把它简化为一个模板,使我们更容易讨论
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But they're not accurate all the time in predicting bonding within molecules, and the reason for this is because Lewis structures are not, in fact, based on quantum mechanics.
但它们在预测分子内,成键时不总是正确的，这是因为Lewis结构，实际上不是基于量子力学的。
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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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We talked about the structure of DNA, how it works in terms of a physical chemical model of the DNA molecules.
上节课我们讲了DNA的结构,从理化模型的角度讲了,DNA分子是如何工作的
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This was something we could not predict using Lewis structures, but we can predict using MO theory that we have a radical species here.
这是我们从Lewis结构里不能预测的，但我们可以用分子轨道理论,预测自由基。
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So far we've exclusively been using Lewis structures any time we've tried to describe bonding within molecules.
目前为止任何时候我们尝试要,描述分子内的成键,我们都是利用Lewis结构。
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When these nucleotides get polymerized to form a long DNA molecule they all get polymerized in exactly the same way, the chemistry is the same.
当这些核苷酸多聚化,形成一条长链DNA分子时,它们的聚合方式和,化学结构都完全相同
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In class on Monday, we did go over the geometries, and the geometries themselves are very straightforward, once you know what the Lewis structure is, but remember, you can't just always look at a molecule and automatically know the Lewis structure.
在周一的课上，我们讲过了几何形状，一旦你们知道了Lewis结构，这些几何形状是十分直接的，但记住，你不能总是仅仅看一眼,分子就知道它的Lewis结构。
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We don't need to really talk about all the molecular detail in order to completely describe a DNA or an RNA molecule because these structures repeat themselves.
我们在完整的描述一个DNA或RNA时,不需要说明,分子上的每一个细节,因为它们的结构都是重复的
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It has to do with the nature of this complementary binding between double stranded DNA and the fidelity of this base pair matching in forming stable DNA molecules.
这些特性能从根本上解释,为何DNA双链的碱基能互补配对,以及在形成稳定的DNA分子结构时,碱基互补配对为何具有一致性
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It's really remarkable how far--how fast we have come from just knowing the structure of this molecule to be able to manipulate it and study it in great detail.
我们在短时间内取得了非凡的成就,从最初仅仅知道DNA分子的结构,发展到能够深入研究并加以操控它
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The whole structure of a DNA molecule looks like this, going back to a more cartoon version like I showed you before but adding some detail onto it now.
NA分子的全部结构都和,刚才的卡通模型上差不多,但细节更为丰富
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So my goal today is to talk about sort of the basics of the molecules, their chemistry, the function of DNA in cells, sort of basic - the basic side of that.
所以我今天的任务是告诉你们,DNA分子的各种基团,它们的化学结构,细胞内DNA分子的功能
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This is a feature of DNA shown in this cartoon form, so if you can keep that sort of schematic in mind, it makes it a lot easier to understand the detailed structure.
这是卡通模型所表现的DNA的特点之一,如果你能把这个模型记住,你会很容易理解DNA分子的详细结构
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And resonance is the idea that sometimes one single Lewis structure does not adequately describe the electron configuration around a given molecule, so instead you need to draw two different Lewis structures to describe that more appropriately.
而所谓共振态,就是有时候一个路易斯结构不足以,完整描述一个给定分子的电子排布，因此这时你需要同时画出两个,不同的路易斯结构来描述它,这样会更恰当。
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We'll talk about some chemistry today, what DNA molecules are like, why they have the behavior that they do, and you need to understand this in order to understand how you manipulate DNA.
今天我们会谈到一些化学结构,比如DNA分子的形态,它们为什么会以这种形态存在,你必须先掌握这些,才能理解如何操控DNA
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That's what I want to do for the first few minutes of the lecture here is tell you a little bit about the details of the structure and how molecules fit into this image of DNA that's already very familiar to you.
这是我想要,在这节课最初几分钟告诉你们的,有关DNA结构的一些细节,DNA分子结构与这个卡通模型如此一致,对你们来说很熟悉
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That RNA is made into proteins, and proteins are the working molecules of the cell, they're enzymes, they're structural molecules, they're are proteins that exist in the membrane that allow things to go in and out of the cell, so really the working molecules are the cell in every sense.
这些RNA指导合成蛋白质,蛋白质是细胞生命活动的承担者,它们可以是酶,或是结构性分子,也可以存在于细胞膜上的膜蛋白,能够让一些物质通过它们进出于细胞,所以蛋白质才是真正意义上,细胞生命活动的承担者
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