3.091 Introduction to Solid State Chemistry, Fall 2004 Transcript

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3.091 Introduction to Solid State Chemistry, Fall 2004




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3.091 Introduction to Solid State Chemistry, Fall 2004
Transcript – Lecture 32



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.