Lecture 32: Lipids

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OK. Let's get started. A couple of announcements. First of all, I draw attention to the special lecture this afternoon by Bill Chernikoff. And I will have more to say about that later in today's lecture.

Reminder, two weeks from today -- Only two weeks from today will be the festival of festivals, the grand celebration of learning called "the final exam." I draw your attention to the fact that we will not have a weekly quiz next week, so much of the material we are learning now is, in fact, going to be untested until the final exam.

And I know for many of you the opportunity to express yourselves on a weekly basis is both an opportunity for showing what you have learned, but also a stimulus to induce you to do the learning. And so I urge you not to put off learning this material until the night of the 14th because, as I have mentioned before, you have other exams.

You are going to be tired, so I urge you to prepare over an extended period of time. That way the sticking coefficient will be much higher. Last day we talked about protein synthesis which is affected by condensation polymerization of amino acids.

We further looked at protein structure. We saw there was a primary structure that involves the instant amino acid sequence, secondary structure which was indicated up on the screen with this one here with the alpha helix, beta sheet and random coil.

I thought I would draw attention to this. The next time you look at a telephone cord, you can think of this as having primary, secondary and tertiary structure. The primary structure is the instant sequence down the chain.

The secondary structure, this is an alpha helix. And the tertiary structure is however the thing lies after you have made the telephone call. We have the same elements here, primary, secondary and tertiary structure in the telephone cord.

You will never look at a telephone cord the same way again. There is tertiary structure. What I want to do today is finish up proteins and then move onto some other biomolecules. We have been talking about proteins in their natural state.

I want to talk about how things can change. And that is under the title of denaturing of proteins. And denaturing of proteins is nothing more than the disturbance of the natural state. What we are really doing is disrupting the secondary and tertiary structures.

Let's document that as disturbing the natural state which means disrupting secondary and tertiary structures. We do not disrupt the primary structure. That is the instant amino acid sequence. We are not going to have impact on that.

Disrupt secondary and tertiary structures. And what are the devices at our disposal? I am going to list four. First of all is temperature. By raising temperature we can disrupt the tertiary structure.

An increase in temperature breaks bonds. And here we are talking about the weaker bonds, these secondary bonds, things such as hydrogen bonding or Van der Waals bonding. You see this when you fry or poach an egg.

The egg white is 90% water and 10% protein. It is an ovalbumin and has a molecular weight of about 43,000. It is a decent size. We also know that the egg white, in its natural state, is transparent to visible light because the protein, the tertiary structure is folded up into a ball.

And, when you heat, you break some of those bonds and the ball unfolds. Then two things happen. First of all, the chain length becomes large in comparison with visible light. The egg white turns white from transparent.

Secondly, those chains entangle which gives you that rubbery texture of egg white. This is a vivid example of use of temperature in changing the structure. Second example, you can also use this on egg.

Everything I am talking about here could be used in cooking. What is another thing we can change? We can change pH. When we change pH, this has an impact on hydrogen bonds. We saw this last day with the example of hair.

By introducing water, we end up with interrupting the hydrogen bonds. A change in pH will do this. And also electrostatic interactions can be affected by flooding of protons or loss of protons. If you look up on the graphic on the screen right now, you could imagine, for example, here we have a hydrogen bond at site number two.

If all of a sudden this is, say, in the wall of the stomach and somebody has a drink of lemonade or a cola beverage and the pH drops, now there is a flood of proton in here. The proton can get into the midst of this hydrogen bond and break it.

If that breaks then there is no obligation for the chain to make this sharp turn, and it may start to change its bend there. That is a second example of how we can denature protein. A third example is oxidizing, reducing agents.

Again, we saw this example last day with reference to a permanent wave. And these can either create or destroy. And I have matched these up. Oxidizing agents will create. Reducing agents will destroy disulfide linkages.

You see, at position number one, disulfide linkage. If this protein is exposed to intense reducing conditions those sulfurs will get capped each with a hydrogen, break this bond, and now the chain is free to move in a way that it was not when that bond was in place.

And the fourth one is through the action of detergents. These can solvate nonpolar entities, and what that will do is destabilize the clusters. Destabilize these hydrophobic clusters, which is shown at position number four.

We have not talked about detergents so I better do so for two reasons. One is you will understand what I just said. Secondly, you will know how to do your laundry properly next time effectively. Here is how a detergent works.

A detergent is a long molecule. The zigzag, shown here, is a carbon chain. This is a long carbon chain. It is not soluble in water. It can solvate nonpolar entities but has a hydrophilic head. Carboxylic acid here can bond to the water.

There are different types of ways we soil our clothing, but one of the most common ways is to have some inorganic matter trapped against the clothing under a layer of grease and oil. The grease and oil is not water-soluble.

That is why when you get grease on a garment and you take water and you rub it, you don't remove the grease stain. What you need is to solvate it. What happens here is we filled a washing machine with molecules that looked like this.

The hydrophobic tails are able to solvate the grease and oil, they hydrophilic heads can bond to the water, and then you take the whole thing and agitate. And, as you agitate, eventually you pull this grease and oil off.

That way you can liberate the soil, and the soil will just fall free. That is the principle of detergency. You can imagine now, if you expose this to detergent-like molecules, they will stab the inside of this loop, break it apart and, thereby, cause the unfolding of the chain.

Those are four good examples of how we can denature proteins. I think that is a good place to stop. There is lots more to be said, but we need to move on. I want to talk about the second of the three types of biomolecules that we are going to cover in 3.091, and that is lipids.

Lipids are unique because normally we classify types of chemicals on the basis of their composition. In this case, we classify lipids more on the basis of how they behave. They are classified based upon their properties rather than their composition, so not composition.

There are many ways to devise something that would be called a lipid. The main property that we are looking at is something that is soluble in nonpolar solvents, nonpolar media. Low polarity. That means it is insoluble in water.

May be oily to the touch. This would be fats, oils, cholesterol and hormones. What I would like to do is show you a couple of examples, and I have put them up on the screen. We are going to look at triglycerides here.

Again, I don't expect you to be able to write these from memory. I would give the chemical formula, chemical structure, and then we would talk about what their properties are. Here is the origin of the triglyceride.

We start with glycerol which is this triple alcohol shown here. We break off those hydrogens. And now we have an oxygen acting as an ester linkage. Then we put these long molecules here on the end, long chains.

There is C 1, 2, 14, 15. They are very, very long chains. And so you end up with this triglyceride. This is a fat, and this one here is an oil. Both cases, look, these are all aliphatic. These will not dissolve in water.

It is all hydrocarbon here. There is the odd little oxygen in here as an ester, but it is not enough to cause solubility in water. That fits the bill here. Soluble nonpolar solvents. But, look, one other thing that is very interesting.

This one here is a fat, so it is a solid. This one here is an oil. It is a liquid. Why is this one a solid and this one a liquid? What is the only thing operative? Well, you ask, how does one fat molecule bond to another fat molecule? There are only Van der Waals forces here.

This thing is 16, 17 units long. And this one here is shorter, therefore, it is weaker. And so, therefore, at room temperature this shorter chain triglyceride is a liquid, the longer chain triglyceride is a fat.

All this stuff comes back. This is called palmitic acid because you can see there is a proton attachment site there. There is the oxygen bridge. We have seen oxygen bridges over and over again. In silicates we saw them.

And we see them here. Well, we can do something else. What we can do is replace one of the fatty acids on that glycerol. See here, this is where the glycerol was. There is one, two. And, instead of three fatty acids, we are going to put a phosphate group here.

And that phosphate now makes this a phospholipid. What do we see now? Now we are seeing something that looks more like the detergent because these long tails do not want to dissolve in water. These are hydrophobic tails.

But look at this thing. This thing will dissolve in water. I have a hydrophilic head and twin hydrophobic tails. Now let's do one more thing. We can replace this and cause this oxygen to act as a bridge.

There is one ester right there. We can make another ester. And here is one that is shown in your text where you bond this to an ethanol amine. C2H5OH. We throw off the OH and put the amine in here.

Now what do we have? This thing is called a phosphotide. It is a phospholipid. Again, hydrophobic tails, hydrophilic head. There are the twin fatty acids. There is the glycerol. Phosphates acting as a bridge.

And this ethanol amine. Twin hydrophobic tails. Hydrophilic head. And, to boot, look at that, minus here, plus here. It is zwitterionic. This is phospholipids. And you might say there is a lot of chemistry.

What does it all mean? Self-assembly. I am going to show you how you take molecules like this and build cellular structure. How do you build cellular structure? Remember when we had a whole bunch of hydrophobic side groups, how the chain coiled around and made that hydrophobic pocket? I want to represent this molecule as the hydrophilic head.

And then we have twin hydrophobic tails. This is the carbon chain. This is hydrophobic here and this is hydrophilic here. Normally, if you had something that was hydrophilic and something that was hydrophobic, they would want to separate.

The want to phase separate like oil and water. But this cannot because it is covalently bonded right here. That phosphate bridge bonds the hydrophobic tails to the hydrophilic head. The best thing it can do is run from itself.

And the hydrophobic tails go in one direction and the hydrophilic head just goes "ew." But now watch. I am going to take a whole bunch of these and throw them in the water. If I take a whole bunch of these and throw them into water, these things feel very uncomfortable in water.

What are they going to do? Just for ease, if you would allow me, instead of drawing twin tails, I am just going to draw a single tail. If one is here, it is just going nuts. Actually, if I put one, it would probably throw its tail up in the air at the free surface.

I am going to put a whole bunch of them in here. Does it stand to reason that all of the hydrophobic tails are going to cluster? And this will keep going on and on and on. Then they are going to say, well, wait a minute, what about here? I have naked exposure on this side.

What am I doing? I am encapsulating this pocket in here with a bilayer. This is a lipid bilayer. Really, it is a phospholipid bilayer. I could schematically represent this as follows. This is a wall or a membrane.

This is how nature builds walls. What is the key here? The key here is we start with a molecule like this, which we call amphipathic. That is to say it is a mix of hydrophobic and hydrophilic elements.

Amphipathic molecules. And you put lots of them together. And we have self-assembly. Cell structure, and here I am talking about a cell wall, comes from what? It comes from the combination of amphipathy plus self-assembly.

It is just simple physical chemistry. The oily stuff wants to get as far removed from the water, and so it builds a hydrophilic shell around it. There we go. There is a cartoon in your reading that looks like this.

This one. What do we have here? You see the hydrophilic heads are shown in dark, and then you have the twin hydrophobic tails, so they made this bilayer. And then, every once in a while, there is what is called an integral protein.

That integral protein has some other shape. Look at this protein carefully. Train your eye right up here. By the way, look at the heads. These heads are essentially spherical. And what is the pattern you see on the top here? It is a crystalline array.

I have a crystalline array with twin tails dropping down. A raft of hydrophilic heads. All of a sudden there is this integral protein sticking out. Well, why isn't the protein expelled? It must have something to do with the instant R sequence in this vicinity.

What must be the R groups in this vicinity? They must be, at the very least, net neutral. At most, they are hydrophilic as well. Maybe they have charged species sticking out. They certainly are not nonpolar R groups because, if they were polar R groups, this thing would get pushed down further.

And what must be going on in here in the protein? I must have a dominance of nonpolar R groups. Then we drink the cola. We drink some cola beverage and the pH changes. And, if the pH changes, maybe the conformation changes right here.

All of a sudden this opens up. And this can become a valve or a gate. And it can be specific to only certain molecules, because only certain molecules have the same mix of complimentary R groups that can open this thing up.

I told you, secondary bonding is the key to understanding animation. There it is right there. You understand primary, secondary, tertiary structure, throw in some temperature, throw in some intervention with new chemistry, the next thing you know you are doing this, moving.

Changing conformation is all I am doing. Secondary structure. Tertiary structure. It is directed. I am directing it. It is that simple. Now you know the origin of life. Now let's move on and talk about nucleic acids.

This will be our last of the three. These carry information that directs metabolic processes. Carry information directing metabolic activity. This is metabolic activity in biomolecules, of course.

This includes replication. That is why this is so important, because it includes replication. And so nucleic acids are polymers of a sort. I am using the term loosely here because we allow for a variation of R groups.

And the mer unit is called a nucleotide. And the nucleotide has three building blocks. It has a sugar, it has an amine and it has a phosphate. Those are the three building blocks in a nucleic acid.

There are two types of sugars that we will find. One is ribose. And we did not study carbohydrates. The only reason people study carbohydrates is so that they can give you this. I will just show you the structure.

There is ribose and deoxyribose, and they look like this. These are carbons. Where you don't see anything there are carbons. This is ribose. It is a five-fold sugar. And this is deoxyribose. You see there is any oxygen here.

It is missing in this position. That is the only difference. There is ribose. Take off the OH here and there is the deoxyribose. The amines are a slightly larger library. There are five of these.

And we can document them, as shown here. Amines are shown on this one. And this is all out of your reading. The amines we have for DNA are four, and RNA have four. They have three in common. All three of them have the three on the left.

The adenine, the guanine and the cytosine, A, G and C, are found in both DNA and RNA. Whereas, the fourth one is different. In this case, the DNA is thymine and in RNA it is uracil. Again, I don't expect you to know these by heart.

I want you to recognize those names. If I wanted you to do anything with them, I would give you the formula and the structure. And then the phosphate is the third element. It turns out that the backbone of this polymer is not just one.

There are actually two of these species in the backbone alternating. And the backbone consists of the sugar and the phosphate. That makes sense that the phosphate would be in the backbone because we have seen phosphate already acting as a bridge.

In fact, it acts as an incredible bridge because it is bridging something that is hydrophilic with something that is hydrophobic. It has very good negotiating skills. And then the amines, these are side groups off the backbone, or what we have been calling substituents.

That looks like this. This is out of your book. They break them into purines and pyrimidines. Again, I don't expect you to know this stuff. I would give you the formula if you needed it. This is taken from another text.

There are the two sugars, the pentose sugars. These are called bases. Biologists call them bases because, as you know, these compounds are Bronsted bases. They are proton acceptors. As I will tell you later in the lecture, a lot of this chemistry was unfurled by wet chemical analysis.

And so people used acid-base equilibria in order to determine the structures. And so they refer to these things as bases. Here is the basic structure of DNA. This is the primary structure. You see sugars bonded together by phosphates and bases hanging off the side of the sugar.

Here is what it looks like. There is a sugar. In this case, this is the deoxyribose. And there is a phosphate, so it has ester linkages on both sides. Sugar, ester linkage and so on. And then you have a choice of, in the case of DNA, one of these four to hang off the side.

There is another. This is out of your text. There is the acid end and the basic end. One more. I couldn't resist. I found all these pictures, and they just go on and on and on. You see it now.

This is the sugar phosphate backbone. And you get your choice of four different side groups to hang off. That is primary structure. Now, let's talk about secondary structure. How do we get secondary structure? How do we get to this? We get to this by maximizing hydrogen bonds or by maximizing packing.

Well, here is what happens if you put two of these together. Here is what happens. If you put an adenine opposite a thymine, you end up with perfect matching for hydrogen bonding between the nitrogens here and on the other side.

And, if you put a guanine opposite a cytosine, you end with the possibility of three hydrogen bonds forming. That opportunity to form hydrogen bonds is going to dictate what the secondary structure of this nucleic acid is going to be.

We have seen that already in proteins. And, just to make the point, every time I see this, I am just blown away. If you look at the distance across the double hydrogen bond between thymine and adenine, it is 1.085 nanometers.

If you look at the triple hydrogen bond between cytosine and guanine, 1.085 nanometers. Four significant figures identical. That means these things are not only going to link up, it prevents misregistry.

There is no way you can put a thymine opposite a guanine because thymine wants two and guanine wants three, and they won't fit. Spell-checker. Here is what it looks like now. It is going to form a helix.

We already know about the alpha-helix but, in this case, it is going to form a double-helix. This is DNA, double-helix. You have a sugar phosphate chain here. This is taken from your book. And you see cystosine, guanine, triple, triple, thymine, adenine, double, double.

Here are more pictures. Here is the sugar phosphate backbone. And these are the pairs of amino groups which the biologists call the base pairs. They are the pairs of the amino groups, hydrogen bonding.

And there is the close packed model. This is DNA. There is another one. Again, sugar phosphate. And these are the amine linkages across your hydrogen bonds. Now I want to say what is the language? I said this bears information.

How do we encode information here? Well, let's say we want to direct protein synthesis. Here is how you direct protein synthesis. Some authority has to come in and say there is a library of 20 amino acids here, I have my condensation polymerization apparatus here, and I want to have a certain amino acid sequence.

Somebody has to say give me some alanine, click, give me some glycine, click. Somebody has to be able to call out, in direct order, the amino acid sequence. You have to call the amino acids. I need an alphabet and I need a language that has at least 20 words.

I need at least 20 words. How do I figure that out? Right now I have shown you I have four letters. A, T, G and C. If I had only one-letter words, that would not do it because I cannot call 20 amino acids.

If you look at number of words I can build in an alphabet. It would then be number of letters. And I am assuming all the words are the same length here. It would be the number of letters raised to the power of number of letters per word.

If I have four one-letter words, that gives me a maximum of four. And four is less than 20, so that won't help me do protein synthesis. Suppose I said that the way information is encoded here is not A, T, C or G.

But I go down the chain and take groups of two. The word consists of two letters. It is two adjacent amine groups taken together that give me the words. That would give me four two-letter words. I have four letters, two letters per word, which would give me 16, which is less than 20.

That won't do it. Let's suppose, as I go down the chain, I count every three amine groups. Every three base pairs and call that a word. Every three base pairs is a word. If I did that, I would have four raised to the power of three is 64, which is greater than 20.

That is OK. And, indeed, what we know today is that 61 combinations of three base pairs, and I am talking three base pairs adjacent, address 20 amino acids. Now, some amino acids have more than one label.

In fact, one of the amino acids is known by six different labels. There is a lot of redundancy in the system. What are the other three combinations of three base pairs used for? Punctuation. Mother Nature has punctuation.

If I give you something that is one meter long written in this strange language, how do I know where to begin? How do you know where to begin this sentence? Well, we put a capital letter here. Sometimes we use dashes and spaces.

That is how you know. Mother Nature does the same thing. There are three of the three base pair combinations. One says start, one says stop and one says spacebar all down the DNA. And to whom do we owe this? We owe this to Oswald Avery.

Oswald Avery worked at the Rochester Institute in New York. And it was in 1944 that Avery proposed that it is nucleic acids that carry the information. At that time, people thought that genes were composed of proteins.

Do you know why? They did not like to think about nucleic acids as bearers of information because their structure is too complex. They said anything that complex is impossible to unravel information.

All it meant was that it was impossible for them. That is the arrogance of the scientist, you see. But Avery said no, this was it. Now, how do we get to this point? I mean, what I have given you is pretty potent information.

What I am showing you here on the graphic is here is the double-helix, so there is a sugar phosphate chain going up one side, sugar phosphate chain going up the other side. If you look in here, and I apologize the graphic here is rather weak, you look at three of these in sequence.

One, two, three. This is an A, a C and a T. And then, of course, it has its mate across the way. But, if you just count these three, that is one word. And these three-letter words are called, by the way, codons, because that is where the information is encoded.

These are the three-letter words. Now I want to go back and show you how we got to where we are. We start with Erwin Chargaff also in New York. This was at Rochester Institute in New York. And Chargaff was working at one of the hospitals affiliated with Columbia University also, New York City.

And he worked right after the war, 1945-1949, fastidiously doing chemical analysis of nucleic acids taken from various animal sources and plant sources. And, in 1950, he publishes a paper that summarizes all this.

What he observed was the following. First of all, remember, they don't know the structure yet. It is 1949. All he knows is that when he analyzes these things, the ratio of the adenine is 1:1 to thymine.

Whatever he looks at. The absolute magnitudes are different, but they are always found identical. Secondly, the guanine and the cytosine are one-to-one. Lastly, if you sum G plus A, you get the same as C plus T.

And these are known as Chargaff's Rules. These are the rules for base pairing. And some interesting slides here. There is Chargaff. Look at this. Here is in humans, 31:31, 19:18, roughly 1:1. If you go to the fly, the fruit fly has different numbers in absolute, but ratios 1:1.

Mold, bacteria, corn 1:1. This language is used throughout nature. Plant world, animal world, same language, same codons. Point number one. I am trying to teach you how we get to the structure. Point number two, what was the second major thing that gave us the clue to the double-helix structure was -- How do we really determine structure? If we really want to know structure, what have we used in 3.091? X-ray diffraction.

But how are you going to do x-ray diffraction on something that is a million units long and fluid. Well, there was a woman by the name of Rosalind Franklin at King's College in London. And that was her specialty, x-ray diffraction of biomolecules.

She developed a technique to do x-ray diffraction on DNA. And what she would do is solvate it, use a needle and draw it out. It is now a strand extended. But now, if she just lets it dry, it will embrittle, so she has to keep it under certain conditions of humidity while conducting the x-ray diffraction.

In those days, you had to run for hours, for days to get an x-ray pattern of any value. This work was painstaking, fastidious. And this is one of the most famous images of the 20th century. This is Rosalind Franklin's Pattern No.

51. It is sodium deoxyribose from a calf thymus. That is a beta structure. And here is what I want you to see here. This is a Laue pattern so it shows the symmetry of the crystal lattice. And so what you have here are five stripes, one, two, three, four, five.

The fourth one is missing. It is in a Saint Andrew's cross configuration. And this has the clue that tells you that you have first of all a double-helix structure. You have a double-helix on the basis of this.

And, furthermore, you can analyze it. And you get 3.4 angstroms per spacing between nucleotides on the basis of that spectrum. And the last thing, which was extremely important. Even if you know you have a sugar and you have a phosphate and you have an amine, what is their order? She was able to look at that and say -- Remember, they didn't have computers in those days.

You have to do the Fourier transform to go K space back into Cartesian space. You have to do this with a paper and pencil. It is very difficult work. You need a lot of intuition. You have to really understand math, instead of memorizing some formulas and shoving it into software that you bought on the Internet.

You have to know what you are doing, in other words. And she did. And what did she realize? She realized that if you take sugar, phosphate and amine, the phosphorus is the heaviest nucleus, the heaviest atom.

On the basis of that, she was able to infer that the heaviest elements, the phosphate groups must lie on the outside of this helix, which means then that the amines or the bases lie inside. I am going to read to you what happens in this quest to unravel the DNA structure.

I am going to read from this book. It is "The Eight Day of Creation" by Freeland Judson. She was at King's College. Watson and Crick were up at Cambridge. And Watson had come to London in January of 1953.

This was taken in May of 1952. She worked for a fellow by the name of Morris Wilkins. And on that day in January of 1953, Watson visited the lab at King's. And he and Rosalind Franklin did not get along.

One version says they got into a little bit of an argument and then Watson left. He goes down and talks to Watson. And Wilkins told Watson that Franklin had found the DNA fibers, when kept wet, yielded a different x-ray pattern suggesting a second structure.

14 months after the King's colloquium, despite repeated correspondence, conversations, visits, meals together between Wilkins, Watson and Crick, the possibility of a second structure was news to Watson.

He wrote, when I asked what the pattern was like, Morris, this is Wilkins, this is her boss, went into the adjacent room to pick up a print of the new form they called the B structure. That is the image I just showed you.

The pattern was unbelievably simpler than those previously obtained, the A form. Moreover, the black cross of reflections, which dominated the picture, could arise only from a helical structure. Remember, Pauling had already said, in 1951, that protein has an alpha helical structure.

With the A form, the argument for a helix was never straightforward with the B form. However, mere inspection of its x-ray picture gave several of the vital helical parameters. I want you to remember this because I am going to read to you from their paper.

The picture that Wilkins showed Watson was Rosalind Franklin's. It was one of the two good pictures of the B form she had taken during the first week in May the year before. Watson goes back to Cambridge, and within a few days they had built this structure on the strength of what they had seen in London.

This is the young James Watson and this is Francis Crick. He is holding a slide rule here which he was invited to do by the photographer. Here is the paper in Nature on April 25, 1953. It talks about, "We wish to suggest a structure for the salts of deoxyribose nucleic acid (D.N.A.)." There it is.

And they talk about what kind of information they had, referring to other work as being incomplete and not knowing what they had to know on the basis of x-ray diffraction patterns to have unraveled this structure.

And towards the end --- Well, this is a letter to Nature, so who are the authors? It is Watson and Crick. And there is some acknowledgment here. "We are indebted to Dr. Jerry Donahue," etc. "We have been stimulated by a knowledge of the general nature of the unpublished experimental results and ideas of Dr.

M.H.F. Wilkins and Dr. R.E. Franklin and their coworkers." There is no mention of it. This is in stark contrast to the Human Genome Project when it was published last year. It goes on for several pages with all the authors on it.

Everybody and his pet dog are on this one. I want to draw your attention to this one little phrase here. You need to know this when you talk to your friends in biology. "It has not escaped our notice that the specific pairing we have postulated suggests a possible copying mechanism for genetic material." This is about structure, but they speculate that maybe this is where the copying mechanism is.

When this paper was published 50 years later, at one point in the paper somebody said let's use that phrase, it has not escaped our notice. That is the key. If you want to give the goat to one of your colleagues in biology say, it has not escaped our notice.

They know this phrase. Here is the Nobel ceremony. This is 1962. Here is the King of Sweden. There is Crick. There is Watson. There is Wilkins. These two guys are getting some other Nobel. There is no Rosalind Franklin.

No Rosalind Franklin. If you want to read more about this, this is far better than this. This is Watson's account of things, and it does not square with some of the other things that people have said.

What was the problem? The problem was that Rosalind Franklin was marginalized because she was a woman. In 1950, in England, women at the university were not allowed into the common room. And, as you know, the country stops at 4:00 PM and people collect to drink tea.

A lot of conversation goes on there. She was denied access to that. She was marginalized by her coworkers. And, after this happened, she was so broken by the mistreatment when the paper was published, she stayed on at King's for a year or two and eventually left and took a job at Berkbeck College.

Her terms of severance were that she not work on DNA again. She had to abandon her work. I mean, these are unthinkable. I am not talking about Dickens' England. I am talking about England after World War II.

This is unbelievably low. These people plumbed new depths of bad behavior. Every one of us is here because we had help of others. When you work with others, you acknowledge your coworkers. This was absolutely disgraceful.

You might say, well, what happened to her? Why isn't she in the picture? It was 1962. She contracted ovarian cancer and died in 1958. You might say, well, that is terrible that they have Wilkins there.

But I think that is good news. I think what it says is that the Nobel Committee knew that it was not Watson and Crick alone that unraveled this. That, in fact, he is standing in there for Rosalind Franklin.

Let's learn from this that there is a proper way to conduct one's self in the quest of fame. I think it is important that we know this story, that we recognize how the people that enjoy all the fame for unraveling the structure of this, how they went about their business.

And it is despicable. Crick just passed away this year. Watson is still around with his Nobel Prize. There is a picture of Rosalind Franklin. She loved to hike, so she was obviously in France at the time.

I think this is a good place to stop. And what I thought I might do is give you a few minutes with our speaker this afternoon. I am going to introduce Bill Chernikoff who will give us a couple of comments about what he is going to say this afternoon.

But I would ask not to make so much noise with your books and papers. B. CHERNIKOFF: Thank you, Professor. It has actually been about 11 years since I was sitting exactly where you guys are today, and about seven since I have TA'ed the course.

And, while a lot has happened, really, what I would like to talk about later today in the hydrogen economy, which a lot of you have been hearing about in the news, certainly a topical issue, it is going to affect a lot of us over the course of our lives, really relates back to what I learned here 11 years ago.

Issues like diffusion, structure, materials, properties, large manufacturing all relates back to what has been covered here today. I will talk a little bit about that. I will talk about how this fits in with society, the role that you as young engineers will play.

We will discuss. We answer a lot of the questions. There is certainly a lot of controversy around this. And I look forward to having some interaction with the next generation of engineers. I believe we are in Room 3-270.

I look forward to seeing everyone at 4:00. Thank you. [APPLAUSE] D. SADOWAY: You never applaud at the end of my lecture. [APPLAUSE] No, that doesn't count. It looks as though I was trolling for compliments.

You cannot do that. No love tests. OK. I will see you at 4:00.

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