00:00:50 It won't bother me if you talk, you know.

00:09:29 When I started in research as a graduate student,

00:09:36 x-ray crystallography was just really getting going.

00:09:41 Only a few places in the world were determining the structure of crystals with x-rays.

00:09:48 I was interested in metals and alloys and inorganic substances,

00:09:55 and the first substance whose structure I determined,

00:10:00 together with the man who was teaching me the business,

00:10:04 Roscoe Dickinson, professor in California Institute of Technology,

00:10:09 or later he became professor,

00:10:13 we determined the structure of a mineral, molybdenite, molybdenum disulfide.

00:10:20 It looked something like graphite, black shiny plates.

00:10:24 You could even make lead pencils out of it.

00:10:27 It's used as a lubricant too.

00:10:30 And that structure determination explained why it could be used as a lubricant.

00:10:37 And also it gave new insight into the chemistry of molybdenum

00:10:45 in showing how the sulfur atoms were arranged around the molybdenum atom.

00:10:51 The next crystal that I worked on was an intermetallic compound,

00:10:56 the first intermetallic compound to have its structure determined

00:11:01 by the x-ray diffraction method or in any other way.

00:11:05 And it was a magnesium tin compound that I made by melting magnesium and tin together.

00:11:13 In a furnace that I had made, I took an aluminum crucible

00:11:18 and wound it with nichrome wire and passed an electric current through.

00:11:23 I lagged it with asbestos, of course,

00:11:26 and passed an electric current through to heat the crucible

00:11:30 enough to melt the magnesium and tin together.

00:11:34 We used to do those things 60 years ago.

00:11:40 This was 66 years ago, 1922, when I made this furnace to melt up my metals.

00:11:48 Now you buy a furnace, of course, with fancy controls,

00:11:53 and you can even press the buttons to tell the furnace what temperature you want it to reach

00:12:00 and how fast it should reach that temperature.

00:12:03 In some ways, doing science isn't so much fun now, I think,

00:12:09 as it used to be when you built your own apparatus.

00:12:13 I even built an experimental piece of apparatus to make x-ray photographs.

00:12:20 We had in the laboratory one apparatus for that purpose,

00:12:27 but we needed a somewhat different one, so I made it.

00:12:31 And I lined the box that the x-ray tube was in with lead, sheet lead,

00:12:38 and I fastened the layers of lead together, the sheets at the corners,

00:12:44 by melting the lead and letting it run together.

00:12:48 You had to be very careful about having the soldering iron

00:12:53 to melt the lead at the right temperature.

00:12:57 Every month or so, I learned, well, more rapidly than that,

00:13:03 I learned more about the nature of chemical substances.

00:13:07 First, inorganic substances.

00:13:10 Then, 1930-31, I became interested in organic compounds

00:13:18 and used a new method of investigation to determine their structure,

00:13:23 electron diffraction by a beam of gas molecules.

00:13:29 A very powerful method and very useful method at that time

00:13:35 when x-ray diffraction had not become powerful enough

00:13:39 to permit one to determine the structure of most organic compounds.

00:13:45 It's a much more powerful technique now,

00:13:48 but in those days, it wasn't quite good enough for organic chemistry.

00:13:55 By 1935, I had learned enough about the structure of molecules

00:14:02 so that I felt I might be able to make some progress

00:14:07 in attacking the problem of the structure of the large molecules

00:14:13 that make up the human body.

00:14:15 I had become interested in them in 1929.

00:14:21 In 1929, Thomas Hunt Morgan came to the California Institute of Technology

00:14:28 from Columbia University,

00:14:31 and he brought with him the other people, students of his,

00:14:37 who had been with him and helped him in discovering the gene.

00:14:43 He didn't know, of course, at that time, in 1929, nor did I,

00:14:49 that the gene consists of molecules of DNA, a nucleic acid, DNA.

00:14:59 It wasn't until about 20 years later that that information became available.

00:15:07 But he knew what the genes do.

00:15:10 The genes are large.

00:15:12 We assumed were large molecules, probably protein molecules, I thought,

00:15:17 and perhaps Morgan did too, that carry information.

00:15:23 The amount of this material that one inherits from his father or her father and mother

00:15:31 carries all of the information in a very small volume,

00:15:36 far smaller than a pinhead,

00:15:38 to construct that particular human being,

00:15:44 to program the construction of that human being.

00:15:47 Well, the main thing that I knew in 1929

00:15:52 was that human beings contain a lot of large molecules called protein molecules.

00:16:00 In 1927, the molecular weight of hemoglobin had been determined.

00:16:06 It hadn't been known up to that time.

00:16:10 Earlier, chemists had taken hemoglobin, the red molecules inside the red cells of the blood,

00:16:18 and had analyzed it for carbon and nitrogen and oxygen and hydrogen and iron.

00:16:25 There are iron atoms in hemoglobin.

00:16:29 One could be pretty sure that the hemoglobin molecule contained at least one iron atom.

00:16:37 It might contain one or two or three or four or five or six,

00:16:42 any integral number of iron atoms.

00:16:45 The amount of iron in a crystal of hemoglobin—

00:16:49 you can crystallize hemoglobin very nicely and purify it in that way—

00:16:54 the amount of iron is such that the molecular weight had to be at least 16,000.

00:17:01 That is, there had to be at least 2,500 atoms of carbon and hydrogen, oxygen, and nitrogen

00:17:11 in this molecule plus the one iron atom.

00:17:15 If there were two iron atoms, it would have a molecular weight of 32,000,

00:17:20 about 5,000 atoms of carbon, nitrogen, and so on.

00:17:24 And if there were three iron atoms, it would be 48,000.

00:17:28 If there were four, it would be 64,000.

00:17:33 I guess my arithmetic has been all right there.

00:17:39 In 1927, an investigator in England discovered,

00:17:46 by measuring the molecular weight of hemoglobin,

00:17:49 by measuring the osmotic pressure of a solution of hemoglobin in water,

00:17:55 that the molecular weight is 68,000,

00:17:59 and the molecule contains four iron atoms

00:18:03 and about 10,000 other atoms which constitute the protein globin,

00:18:09 which, when it attaches itself to the iron atom plus a few other atoms,

00:18:16 becomes hemoglobin.

00:18:19 So here we have this beautiful red material that you can work with in the laboratory.

00:18:27 You get blood and break open the red cells to get the insides out,

00:18:33 and then you can crystallize the hemoglobin and separate the crystals from everything else,

00:18:39 dissolve the crystals back, and get a solution of pure hemoglobin that you can work with.

00:18:46 If you add oxygen to it, if it's oxygenated, it has a beautiful red color.

00:18:53 If you pump off the oxygen or put in some vitamin C, say,

00:18:58 which is a reducing agent that will take away the oxygen,

00:19:02 then the hemoglobin becomes blue, changes its color in a remarkable way.

00:19:08 That's why the veins look blue and arteries look red.

00:19:15 When oxygen is added to the hemoglobin in the lungs,

00:19:19 the hemoglobin becomes oxyhemoglobin and changes color.

00:19:24 And this hemoglobin molecule, with its four iron atoms,

00:19:28 picks up four molecules of oxygen, O2, each of them having two oxygen atoms.

00:19:36 I became interested in the question, about 1934,

00:19:42 how does the hemoglobin bind the oxygen molecules?

00:19:50 I shan't go into the matter, but my first papers, first papers on proteins,

00:19:57 were about what the iron atoms are doing inside the hemoglobin molecule,

00:20:03 how the oxygen molecules hook on to the iron atoms,

00:20:07 how the iron atoms are related to the other neighboring atoms in the hemoglobin molecule,

00:20:14 and where the four iron atoms are in this pretty concise molecule relative to one another.

00:20:23 So I became interested in the structure of proteins.

00:20:30 A man came, an older investigator who had been working on hemoglobin,

00:20:37 came from the Rockefeller Institute for Medical Research to work with me for two years,

00:20:44 Dr. Mursky, Alfred Mursky.

00:20:47 He had been interested in proteins for quite a while, and hemoglobin in particular.

00:20:53 If you take a solution of hemoglobin in water and heat it to the boiling point,

00:21:01 or somewhat less than the boiling point, it precipitates out.

00:21:07 It changes color to sort of brown color and forms an insoluble coagulum that precipitates out.

00:21:17 Alfred Mursky and I published a paper, the first paper on a theory of this coagulation,

00:21:27 of denaturation of proteins in general.

00:21:31 Egg white is mainly a single protein called ovalbumin,

00:21:40 with molecular weight 34,000 and about 5,000 atoms in the molecule.

00:21:46 If you take an egg white, you can stir it up in water and it dissolves.

00:21:53 It's sort of in solution already in the egg white, but there's some other material.

00:21:58 The whole thing will dissolve.

00:22:00 If you now heat that solution, it forms an insoluble coagulum that precipitates.

00:22:07 You don't need to dissolve it in water.

00:22:09 You just take an egg, boil it, and the ovalbumin, that protein, is no longer soluble in water.

00:22:18 It's been denatured.

00:22:20 So Alfred Mursky and I said,

00:22:23 we think we understand this phenomenon of denaturation of proteins,

00:22:30 the difference between a native protein and a denatured protein.

00:22:35 We think, and most scientists then thought the same thing about proteins,

00:22:41 we think that they consist of very long chains.

00:22:45 Each protein molecule consists of a long chain of residues of amino acids.

00:22:54 The amino acids are simple molecules, 15, 10, 15, 20 atoms in the molecule,

00:23:02 that have the property of combining with loss of water, H2O,

00:23:10 combining with one another into these long chains.

00:23:14 It was about 1900 that a German chemist, Emil Fischer,

00:23:20 formed this theory about protein structure.

00:23:25 He began taking amino acids, which you can get by decomposing proteins

00:23:34 and separating them into the amino acids.

00:23:37 He began combining amino acids one after another into chains.

00:23:43 He got up to 18 amino acids in a chain.

00:23:47 Well, that's still ten times smaller than most protein chains.

00:23:54 Some of them are 20 or 30 times 18 residues in a long chain.

00:24:00 Many of them are around 8 or 10 of these times 18,

00:24:08 that is, with 140 or 150 or 105 residues in the polypeptide chain.

00:24:17 It's very interesting that not every chemist agreed

00:24:22 that these proteins consist of chains, even in my lifetime.

00:24:28 In 1938, when I was lecturing at Cornell University for one semester,

00:24:36 a young woman came to see me, an English mathematician,

00:24:43 brought to me by the Rockefeller Foundation

00:24:46 so that I could talk with her about her ideas on proteins.

00:24:50 She didn't believe that proteins consist of polypeptide chains.

00:24:55 She thought they had a different sort of chemical structure.

00:24:59 This was called the cyclotheory.

00:25:02 It's remarkable that a great chemist of that time, Irving Langmuir,

00:25:09 who received the Nobel Prize for his work on thin films on surfaces

00:25:16 and other work that he did,

00:25:19 believed with Dorothy Rensch that proteins didn't have this chain structure.

00:25:27 One of my associates, Carl Nieman, and I—

00:25:31 Carl Nieman was a biochemist in our institute in Pasadena—

00:25:36 wrote a paper.

00:25:38 He and I wrote a paper in which we marshaled the arguments

00:25:43 to support the belief, the hypothesis,

00:25:48 that proteins consist of these long polypeptide chains.

00:25:52 That was published in 1938 or 1939

00:25:56 in the Journal of the American Chemical Society.

00:26:00 So there came some questions even earlier.

00:26:06 Dr. Murski and I said that if you take an ovalbumin molecule

00:26:11 or a hemoglobin molecule twice as large,

00:26:15 you have these polypeptide chains.

00:26:18 But we know that these molecules are nearly round.

00:26:22 Irving Langmuir had developed a method of spreading films on the surface of water.

00:26:29 He could measure what the area was

00:26:34 covered by a certain number of molecules.

00:26:37 In that way, we could determine the diameter of the hemoglobin molecule.

00:26:43 It was about what you would get if you folded

00:26:47 the 660 or 670 residues back and forth into a sphere.

00:26:59 So we asked,

00:27:02 how is the polypeptide chain folded?

00:27:06 We couldn't answer the question,

00:27:08 but we said it's probably held together by hydrogen bonds.

00:27:14 Because you're heading into it,

00:27:16 and you have to change tapes in order to get your answer.

00:27:18 Yes.

00:27:19 You're heading into an area that we...