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I am pleased to see so many of you here this morning after the lovely evening yesterday. I would like to take the opportunity to express my thanks to the Lindau Group for inviting me and my wife to this event. Fortunately, the invitation fit in well with the schedule of our trip to Europe, which we are going on with our three daughters. They are also happy about this gesture of hospitality. All I can say is that I am very reminded of an earlier enjoyable experience in Stockholm that my wife and I enjoyed very much. Lindau, it seems to me, is just a little bit of Sweden. But now to the actual topic, the viruses. I find it extremely difficult to define the character of my presentation today, as the audience consists of experts from a wide range of subjects, including, as I understand, students in their first semester. That makes things a bit problematic. So I'll try to show you a cross-section of virus research in our laboratory at the University of California at Berkeley. First, if you agree, I would like to try briefly to explain the philosophical background. Then we turn to chemistry and current work on the poliomyelitis virus and vaccine. I hope that one or the other area has something interesting to offer you. Well, viruses are a comparatively new area of ​​research because they weren't discovered until the turn of the century. The first virus to be found was tobacco mosaic virus, a plant virus. This was followed by the virus that causes foot-and-mouth disease in cattle. The third virus, yellow fever virus, was discovered in 1901 by Reed et al. discovered. For about 30 years, virus research revolved mainly around medical aspects, i.e. the disease-causing properties of viruses. Very little was known about the true nature of these infectious pathogens. Well, maybe I should start by defining what viruses are. They are small, extremely small, self-replicating mechanisms that only multiply or reproduce within living cells of a particular host. During their multiplication or their growth in these living cells, they occasionally change or mutate, so that a new form of disease arises. The viruses thus represent an unusually successful path that leads to exactly the topic that Professor Muller will talk about later. Because of their ability to multiply, grow, mutate or change, viruses have been considered a form of life for years. In order to understand what it is about when we speak of a living being, we have to deal a little with philosophy in relation to the essence of life. You have no problem perceiving the people sitting around you as living beings. The metal of the microphone, however, everyone will concede, is an example of a non-living structure. But in between lies a boundary, a line of the unknown, so to speak, a boundary between the living and the non-living. It is interesting that the ancient philosopher Aristotle pondered this boundary and pointed out about 2000 years ago that this line between the living and the inanimate is dubious and possibly nonexistent. You may now ask “How do the viruses fit into the dimension of the structures in our world?” I have prepared a slide that I hope will give you a better idea of ​​this border area. By 1930 chemists had worked their way up to the large molecules. Professor Staudinger explained some of them to you yesterday: the large macromolecules of proteins, which on this scale range up to this point. In other words, chemists were researching ever larger molecules through to protein molecules, e.g. the hemocyanin molecule. Beyond that lay uncharted territory. The biologists, in turn, who had worked their way down from the very large animals, reached the second row from the top, e.g. the Bacillus prodigiosus. Bacteria have a size of approx. 450 nanometers on this scale. This unknown zone lay between the bacteria or the smallest living organisms of the biologists and the largest chemical molecules of the chemists. This, in my opinion, is the area that Aristotle spoke of, and the boundary of which he considered dubious and possibly nonexistent. Before the virus was discovered, this area was uncharted territory. But as you can see, this gap has now been filled by numerous structures. If you look at the size of these structures, from the smallest here to the largest there, there is practically a continuum. In truth, there is no borderline between the recognized living organisms of biologists such as Bacillus prodigiosus and the molecules of chemists on this level. It was the viruses, these infectious pathogens, that finally filled this gap that had existed for many years. Well, I mentioned earlier that from the discovery of viruses around the turn of the century until about 1935, the underlying nature of the structures in this area was unknown. No one knew whether a virus was a normal, small, living organism like Bacillus prodigiosus, a new type of chemical molecule, or simply a specialized group attached to a chemical molecule. Determining the exact nature of any of these viruses was of very great importance. It is for this reason that this virus in the middle, the tobacco mosaic virus, was selected for a chemical study. In short, the virus was isolated in the form of a crystallizable nucleoprotein. After a long series of tests to find out whether the biological activity is an integral part of the nucleoprotein molecule, it was concluded that there is no reasonable doubt that virus activity is a specific property of the nucleoprotein. Then of course you had to check whether the tobacco mosaic virus is a representative virus or atypical. A number of viruses have therefore been examined. For example, you got another virus in the form of the beautiful dodecahedron crystals that you see here. This is another plant virus, tomato dwarf bush virus. It can be isolated in the form of the crystals you see here. These crystals consist of the tiniest macromolecules with a diameter of approx. 30 nanometers. So that you get a cross-section through the variety of structures isolated so far in the form of purified viruses, I would like to show you this slide, which in fact covers the entire size range of the viruses that I showed you on the first size diagram. Starting at the very top left, we have cowpox, elementary bodies of cowpox, the smallpox vaccine - you probably all had this little scratch on your arm and didn't realize that you had those large rod-shaped structures that you see in the top right corner rubbed into your cut. At the top right we have an example of a smaller virus, the flu virus. An extremely interesting virus that you could give your own talk about. In the winter of 1918, 150 million people were infected with the flu, 50 million of whom died. In our own country, the United States, more than 400,000 people died in four months. You can see the activities of the virus here at the top right. A similar virus in pigs was discovered in our laboratory by Richard Erwin Shope. Here is an example of a group of viruses called bacterial viruses, which are viruses that attack bacteria. This is a T2 bacterial virus with an unusual structure, as you can see, with a head and a sperm-shaped tail. Here, on the right, is an extremely interesting virus - it caused cancer in rabbits in the United States. The virus is of particular interest because it could show us a way to solve the cancer problem. This is another example of a bacterial virus. It has a very short stub tail. This tail area is of great importance as it is believed to provide a mechanism by which the infectious process occurs. For a long time it was not recognized that this particular bacterial virus had a tail. This is an example of the tiny macromolecules that make up the tomato dwarf shrub virus that make the beautiful crystals you just saw. Here we have the well-known tobacco mosaic virus, which I'll say a little more about in a moment. Here are some molecules, macromolecules is perhaps the better word, a virus that affects orchids. The ladies among you may not know that the flowers on your evening dresses - orchids - are also infected with viruses. If you isolate the virus that leads to an orchid disease, you get what you see here on the right. If we now move from the small, spherical virus through the various orders of magnitude that you see here, almost the entire spectrum from around 20 to 300 nanometers is covered. Here you can see the real structures existing at the border between living beings and inanimate matter from a bird's eye view. Well, that was a bit of chemistry, because my background and training means I'm naturally based in chemistry. So after isolating some of these materials, such as the tobacco mosaic virus, it was only natural to subject purified specimens of these viruses to normal procedures for characterization, analysis, and so on. In the next slide you can see the building blocks that make up the tobacco mosaic virus. For those of you non-chemists, don't worry, I'll give you the broad outline of what this slide means. But first of all, these rows or columns indicate the amounts of the various amino acids that make up the tobacco mosaic virus. You can see it here. These quantities are quite characteristic. It does not matter whether you isolate the tobacco mosaic virus in Sweden, the United States or Australia, nor whether you isolate it from Turkish tobacco plants, tomato plants or spinach plants. In other words, the composition is characteristic all over the world and regardless of the host in which the material is grown. Well, I suggested at the beginning of this talk that one property of viruses is that they can mutate. Of course, as chemists, we asked ourselves what would happen if a virus mutated and caused a slightly different form of the disease. So we isolated the material and purified different strains of the tobacco mosaic virus. You can also see the results of these analyzes on this slide. We have the masked virus strain, the JD141 strain, the green aukube, the yellow aukube, the ribwort virus, and two cucumber viruses. These were thought to be strains of the tobacco mosaic virus for a while. Whenever there was a difference in composition compared to the tobacco mosaic virus, the relevant number was noted in the block accordingly. As I indicated, the non-chemists of you need only figure the number of small numbers on a gravity line to get an idea of ​​the nature and extent of the changes. For example, the JD141 trunk is only changed in two places, here and here. On the other hand, in the case of the Holmes ribwort virus, there are many changes in the amino acids. As you can see, this is an example of the introduction of a new amino acid into the stem. In other words, the amino acid or, if you will, the component histidine does not exist in the tobacco mosaic virus. However, when this strain mutated and formed the Holmes ribwort strain, this was accompanied by the introduction of a new amino acid, namely histidine. These data therefore provided the first information about the nature of mutation in viruses. I hope they also provide clues about the nature of the changes that occur when genes mutate in higher organisms. If so, this is an experimental approach to the nature of change that Professor Muller has been interested in for many years. Well, we have recently become interested in the exact structure of the tobacco mosaic virus. This virus can be examined using a wide variety of studies; An approach that is expedient from the standpoint of technology is the spray-drop technique, newly developed by Professor Williams in our laboratory, in which a virus solution is mixed in known proportions with a polystyrene-latex solution. The polystyrene latex particles are shown here, the tobacco mosaic virus particles here. On the right you can see a small section that has been enlarged so that you can see the particles on the surface. By mixing the two solutions, a relationship can be established between the number of polystyrene latex particles you know because you made the solution and the number of tobacco mosaic viruses. Using a spray technique, you will receive a microdroplet using an atomizer and thus a representative sample of this mixture. The spray drop has a fairly clear outline here. The microdroplet thus represents a representative sample and enables you to establish a relationship between the number of tobacco mosaic virus particles and the number of polystyrene latex particles. So you are deeply concerned with the relationship between biological activity and the tiny rods that make up the virus. Well, our latest work on the detailed structure of these rods has produced some relatively unusual results. We were mainly motivated by the results obtained in our laboratory and other laboratories on bacteriophages. Researchers here in Germany are working, for example, on a protein building block that is created when the tobacco mosaic virus breaks down. The next slide shows an overview of some of the electron microscope images obtained from such mixtures. At the top left you can see the intact tobacco mosaic virus particle, greatly enlarged. If you smash this particle, for example using high frequency treatment, you can cut it open like a piece of sausage. In that case, you get the two particles, or you get particles like the one in the top right corner. Since it was shown to be hexagons, the cross-section of this rod appears to be a hexagon. In the last few months we have succeeded in developing a technique that can be used to partially denature a single macromolecule. When a tobacco mosaic virus solution is subjected to a gentle, low-heat treatment, one end often curls up. If a treatment with a detergent such as sodium dodecyl sulphate is carried out, that part of the protein that has curled up disappears, leaving this thin thread that you see here. We believe today that this was the first evidence for the location of the nucleic acid segment of the nucleoprotein. In other words, proof that the nucleic acid is in the middle of the virus rod. Other information suggests a similar conclusion: if you take a so-called X-protein, which can be obtained from diseased plants, or a decomposition product, as Dr. Klauser showed in Germany, and lets it aggregate again, you get the material with the hexagonal cross-section again. But as you can see here, the tube has an opening in the middle. Well, of course, the re-aggregation or re-partial synthesis of this unusual virus is a very big challenge for the chemist. In theory, it should be possible to combine the protein building blocks that make up this biologically active material with the nucleic acid components. Hopefully the biologically active particle could then be re-synthesized from this. I am sure that we are currently working very actively on this in Germany, and I know that intensive research in this direction is also being carried out in our laboratory. This is the origin of the detailed structure of a biologically active mechanism, i.e. the biological activity that consists in the ability to multiply under very specific conditions. I believe that, in time, chemists should be able to synthesize the building blocks of a virus, such as the tobacco mosaic virus, the ultimate building blocks of which are protein units with a molecular weight of only 17,000. Synthesis approaches related to insulin and some other hormones are already being initiated. I think that in the next few years biochemists will be able to synthesize these small building blocks, the structural units of viruses, and use a special technique to arrange them around the nucleic acid components so that they regain their activity. That may be a bit utopian, but I think it will be a real possibility in the next few years. If we look a little further outside the box, we see that one day, because of the genetic nature of viruses, chemists should ultimately be able to explain the bioism of all pathogens in the world. That would of course give them a power that only nuclear physicists seem to hold in their hands at the moment.Now that I've come this far with the structure of the tobacco mosaic virus, I realize that I don't dare to stop here, especially since Professor Butenandt is in the audience, or at least I think I discovered him there. I would like, at least in his favor, to present what may be our latest ideas on the ultimate structure of the tobacco mosaic virus. I have to say that the next structure is not based solely on the work of our own laboratory, but also on research in Germany and England and many other laboratories. It is simply a kind of experimental balloon with regard to the exact structure of this highly interesting nucleoprotein rod. We think, maybe I should say we know or it is a fact, that this rod is 150 Å in diameter and 1500 Å in length, and consists of a series of spirals with probably 12 1/3 small subunits per turn. Looking at the cross-section, the nucleic acid, which consists entirely of ribonucleic acid, is in the central area of ​​the nucleoprotein molecule. Of course, today we have quite specific experimental procedures. There is reason to believe, based largely on X-ray tests in England, that the protein is made up of small, bifurcated subunits of 17,000 molecular weight, the protein chain is likely in that direction, and the center of the structure is most likely an opening, a completely empty hole having. Why should nature choose such a structure for this unusual biological activity of viruses? I really don't know, but I believe that this virus structure could be characteristic because something very similar seems to be occurring with the bacterial viruses. Since a similar pattern appears in three or four viruses that we know better, it could be an unusual structure that leads to this type of genetic material. It is assumed that the infectious process represents the entry point for the virus particle and that the protein shell then dissolves or disappears. The nucleic acid segment is then reproduced and then the individual particles are given a protein shell. Obviously, this protein shell represents the means by which nature will give this important genetic material the ability to withstand the hardships of the world. This is also the reason why the viruses can exist as infectious pathogens. Could I have the light, please? I want to change the subject and talk briefly about work on the poliomyelitis virus. The person operating the slide projector has kindly shown you a slide preview of the purified poliomyelitis virus. Maybe we'll come back to that. We worked as chemists for the National Foundation for Polio, studying the biochemical properties of the poliomyelitis virus. In the beginning we used material from the spinal cord and brain wrapped in cotton wool as the starting material. Recently, as a result of the extremely important discovery by Dr. Enders of Harvard University that the poliomyelitis virus can also be grown in tissue other than nerve tissue for tissue culture generation of the poliomyelitis virus. As you know, monkey kidneys serve as tissue for tissue cultures. This gave us an unusually good starting material and, to the best of our knowledge, was able to obtain completely pure poliomyelitis virus. In short, this virus is a small, spherical particle 28 nanometers in diameter that unexpectedly contains about 30% ribonucleic acid. I have to say we assumed it contained deoxyribonucleic acid. However, that was not the case. As far as we can tell, it consists entirely of ribonucleic acid. Remember, if that 30% - a very large amount of nucleic acid, compared to tobacco mosaic virus only has 6% - so if the nucleic acid is in the middle, then trying to make a vaccine by treatment with formaldehyde, which is mainly acts on the peripheral protein component may be wrong, as the antigenic properties of the virus are likely to be located in the outer area. The reproductive function probably lies in the nucleic acid, inside. The approach pursued by researchers in Chicago, for example, namely to deactivate the virus with ultraviolet light, appears to be more promising. We have developed a process for purifying the poliomyelitis virus on an industrial scale over the years. Unfortunately, this has not yet been used in the United States, although there is reason to believe that this may change following what our newspapers commonly refer to as the fiasco. It may be of general scientific interest that we in the United States made some extremely serious mistakes in our poliomyelitis vaccine program. This program has been controlled solely by the National Polio Foundation, a voluntary organization run by a layperson, Mr. Basil O’Connor. Decisions regarding the program were made almost exclusively by closed bodies consisting of a few individuals. As a result, the progress of the program has not been subjected to normal scientific procedures. I do not need to explain to this audience that advances in science are based on the simple and step-by-step process of discovery, publication This was not possible in the context of the polio program because publication was a long time coming. Important decisions were made by small, closed groups that did not face criticism from their colleagues. Following the original recommendation of Dr. Salk introduced the commission, which consisted of highly respected virologists, for example, the so-called Mahoney strain into the vaccine - amid massive protests by numerous scientists, because this strain often leads to paralysis. As you may have read from the newspapers, in the United States, in some cases, the disease has developed as a result of vaccination. Serological tests show that this was due to the Mahoney strain. The day before I went to Europe, a group of experts including Dr. Salk unanimously agreed at a congressional hearing to remove the Mahoney strain and replace it with a less virulent strain. If this point had been critically discussed by the professional world, I believe that the Mahoney strain would not have made it into the vaccine in the first place. Another example: the use of formaldehyde as a means of deactivating the virus. The tissue culture fluid consists of approximately one 10,000th of a milligram of virus per cm3. In a medium that contains about 1,000 to 10,000 times more foreign protein than virus, the interaction between formaldehyde and the virus is mainly determined by this large amount of impurities. The chemists among you know very well that all chemical reactions are subject to equilibrium constants and that these can fluctuate. The assumption that the interactions between formaldehyde and the poliomyelitis virus would run to the end and a completely inactive material was created was de facto wrong and violated the best-known chemical principles. But even this was not put up for discussion in a critical manner. If this had happened, I believe it would have resulted in a different or possibly more stringent testing procedure, which would have avoided this particular bug. It is not widely known, but I happen to know, and it is no secret, that the six manufacturers in our country have massive problems obtaining absolutely inactive vaccine. Most of them gain around 30% vaccine that contains the fully active virus. Testing procedures have gradually improved so the material now released is relatively safe. But is that really it? Information that has recently become known shows that strains from this virus strain pool, which are completely inactive in all known tests, are activated when mixed with the valid test pool. In other words, this vaccine consists of mixtures of three different poliomyelitis strains of equal size. You can take completely inactive single strains according to every conceivable test, mix them together and test again, you will always find active material. That was a big surprise for Dr. Salk and the manufacturers. But again: If it had been recognized that the ratio between the biologically active virus and the inert monkey kidney protein was 1: 1000 to 1: 10,000, the renewed activation could have been explained if the formaldehyde had been redistributed. As a result of this, of course, another 30% of the vaccine produced by the manufacturers was discarded. So I can assure you that the United States' experience with manufacturers has not been very profitable. Finally, I indicated that we had developed an industrial-scale virus purification process. No one knows what happens with repeated injections of a vaccine that contains so much organ protein - monkey kidney protein. Some respected immunologists believe that repeated vaccination with a vaccine containing large amounts of organ protein will ultimately sensitize a significant number of people to that organ protein, with catastrophic results. Again, I think it is quite likely that now that everything has come to light, a purification process will be used in vaccine manufacture. I just want to note that if this happens, the safety of the vaccine can be immeasurably increased, perhaps 100 to 1000 fold, by working with concentrated material in concentrated form and then doing a back dilution. There is a good chance that ultraviolet light, as I mentioned earlier, will find its way into the vaccine program. I think this is an example of rush with a while, considering the great pressure to produce a vaccine that causes Mr. O’Connor to urge his scientists so relentlessly. I'm sure he did it with the best of intentions, but he's not familiar with science, he doesn't know how it actually works. I think we scientists made a mistake because we didn't prevent him from deviating from the usual path, because we may have had a pretty serious setback, if not a fiasco, in United States medicine as a result, hopefully that will soon be cleared up. Fortunately, this mistake has not been repeated in too many countries. England, for example, has called off its entire program and, as far as I know, it has not even started in Germany. Please allow me to close my lecture with a few remarks on the place of viruses in our world. I have indicated that they are in the border region between the living and the non-living and that certain viruses can cause cancer in plants and animals. We believe viruses offer a very fruitful approach to the human cancer problem. Just last month in our laboratory we isolated a normal human cell that can be grown in large quantities and that is actually readily available anywhere in the world because it is made up of the human amnion, the small membrane that the baby is born with enveloped, originates. Just like in the United States, you have many babies in Germany, and whenever a baby is born, in the case of the amnion, the chorionic membrane, you have an amount of cells that corresponds, for example, to that of a monkey kidney. We also recently discovered that this human amniotic cell can be used to support the growth of the poliomyelitis virus. Again, polio vaccine production will most likely be switched from the monkey kidney, which, as those of you in medical research know is extremely difficult to obtain, to the human amniotic cell. You just have to rule out the likelihood or possibility of carrier viruses, which shouldn't be too difficult, however. This human amnion cell therefore offers great possibilities not only for poliomyelitis, which we did not even have in mind when we made this discovery, but also for the cancer problem, because here there is the possibility of producing extracts from various tumors and determining the effect of such extracts on normal ones human cells. In my opinion, the viruses represent an excellent approach to the problem of cancer in humans. They will of course always be of interest to us simply because of the nature of life itself, because we have here in the structures that you see on the canvas have seen examples of living, reproductive mechanisms that are certainly the most elementary form of life. Today, as we worry so much about what might happen to the world, I believe that viruses, despite the fact that they are pathogens, probably hold many important secrets. As we gain knowledge of the structure of the virus, we should be able to conquer infectious diseases and possibly cancer as well. I think cancer is one of the most devastating diseases we have to deal with. However, the viruses give us this approach, with the help of which the health of the world's population could be improved. I am sure that even if we master the difficulties associated with our militant attributes and achieve a peaceful world, we cannot enjoy life if we have infectious diseases, organic diseases, or cancer. In a peaceful world, however, mankind has the opportunity to enjoy life if they can make good use of the knowledge that, in my opinion, viruses can be extracted from these small microscopic structures. Many Thanks.