by Andrew Brown
Sage was delighted by their accolades and does not seem to have been troubled by the slightest prick of envy. Perutz wrote to him:
Dear Sage,
I was touched by your good wishes, and not only because it was you who started me off, but because of the many occasions when your visits filled me with fresh enthusiasms and determination to carry on. I wish that you who opened up the field could also have had the thrill of solving the first structure, and I always regard with great admiration your gracious and genuine pleasure in seeing John and me doing the job, and now getting this tremendous reward for it.39
The remainder of the letter was taken up with a novel observation made by his PhD student, Hilary Muirhead, of a subtle change in the configuration of human haemoglobin when it combined with oxygen – news which Perutz found as exciting as the Nobel Prize itself.
Kendrew wrote an equally affectionate letter to Sage.
… I’m always grateful that it was you, during the war, who more than anyone awoke biological interests in a chemist tired of chemistry: and as to the bomb in the jungle, I’ve been dining out ever since on the story… Anyway, after being a renegade chemist all these years I now seem to be a respectable one once more and as to you, it seems to me that you’ve fathered five Nobel Prizes this year alone. Yours ever, John Kendrew40
Crick, only fifteen years younger than Sage, revealed his awe of Bernal’s stature by telling him that ‘Watson and I have always thought of you as our scientific “grandfather”, fortunately perennially young.’41
The revolutionary discoveries that emerged from the MRC Unit for Molecular Biology were the fruits of creative individuals and small groups toiling in cramped and shabby conditions. When a young South African physicist wishing to study biomolecules by X-ray crystallography came to Cambridge in 1949 on an 1851 Exhibition Scholarship, Bragg told him that there was no room in the Unit. To this day, Aaron Klug does not know whether the Unit was really full, or whether Bragg was just disappointed by the previous research student from South Africa. Instead Klug ‘finished up doing a PhD in a very dull subject – phase transitions in steel – a problem left over from the war’.42 While the subject was not what Klug would have chosen, it proved to be invaluable experience for his future. He developed mathematical techniques and physical models for the kinetics of phase changes in solids. This work led his supervisor to recommend Klug to F.J.W. Roughton, the Professor of Colloid Science, who was interested in the diffusion of oxygen into red blood cells and its reaction with haemoglobin. Klug saw this simultaneous diffusion–chemical reaction in terms of a phase change in haemoglobin, and he developed the mathematical equations to describe its kinetics. After about a year working with Roughton, Klug successfully applied for a Nuffield research fellowship, which brought him to Birkbeck College and Bernal at the end of 1953.
Klug and his Nuffield research assistant joined Carlisle’s team working on the enzyme, ribonuclease. This was proving to be an endlessly challenging task, made more difficult by the fact that Carlisle was labouring under two misapprehensions. One, due largely to Bernal, was that the phase problem might be avoided by placing more reliance on the strong X-ray reflections (which Bernal called constellations) that resulted from the most salient and regular features of a protein molecule. Bernal had aired this approach at the 1952 Royal Society meeting, suggesting that it could provide a shortcut to seeing the essential features of a protein structure. In the middle of a mathematical paper, he threw in a couplet from Donne’s elegy on an ugly woman to illustrate his point:43
Though all her parts be not in their usual place
She hath yet an Anagram of a good face
Carlisle’s second error was to assume that ribonuclease was predominantly an α-helix. Klug, fresh from Cambridge, had no doubt that isomorphous replacement was the only remedy to the phase problem and that no mathematical gimmick would solve the complex structures of proteins, with their thousands of atoms. On the question of α-helical features, Klug devised a mathematical search programme to analyse Carlisle’s photographs of ribonuclease and concluded that the molecule did not contain any significant amounts of α-helix. Klug’s quiet, unassuming manner cloaks a formidable intellect, which in his youth was accompanied by a precocious self-confidence. Carlisle refused to believe that this young upstart knew what he was talking about and so they parted company.
Klug was ‘banished upstairs to the attic at 21 Torrington Square’,44 while Carlisle kept his research assistant. He found himself in the next room to Rosalind Franklin, who had moved to Birkbeck from King’s College in March 1953. Her first task had been to write up her crucially important crystallographic work on DNA, but Bernal’s intention was that she should switch to virus research, starting with Tobacco Mosaic Virus (TMV).45 She had been deeply unhappy at King’s and even though she was pleased to escape to Birkbeck, she still felt isolated. In a letter written in December 1953, she reflected on her move:
For myself, Birkbeck is an improvement on King’s, as it couldn’t fail to be. But the disadvantages of Bernal’s group are obvious – a lot of narrow-mindedness, and obstruction directed especially at those who are not Party members. It’s been very slow starting up… I’m starting X-ray work on the viruses (the old TMV to begin with).46
The appearance of Klug, who was pleasant and scientifically alert, transformed Rosalind’s Birkbeck career – she now had someone she liked and trusted, working alongside her. Like Margot Heinemann, Rosalind was the product of a famous British girl’s school and Newnham College. Both women were Jewish and similar in physique, but where Margot was self-confident and radical, Rosalind was shy and withdrawn. She was also immune to Bernal’s predatory charm and disapproved of his promiscuous behaviour. Although Sage was now living with Margot and their baby daughter, Jane, he still used his flat at Torrington Square for quick liaisons. Sometimes his wife, Eileen, came to see Sage and there might be audible crying and swearing. From her room, Rosalind could not fail to see various women come down the stairs from the flat and indicated her disgust to Klug.47 But she and Sage soon developed a mutual respect for each other as scientists.
Rosalind Franklin impressed Klug as a brilliant experimenter. This did not just mean that she was deft with her fingers, but that she first planned methodically how she was going to proceed and then carried out her work with patience and dedication. In his Nobel lecture many years later, Klug stated: ‘It was Rosalind Franklin who set me the example of tackling large and difficult problems.’48 Both Franklin and Klug were new to virus work and the natural starting point for them was the earlier series of papers written by Sage and Fan. There was the earliest Cambridge paper, co-authored by Bawden and Pirie, that had first identified the nucleic acid component (RNA) of TMV and the ‘quasi-regular’ assembly of protein sub-units that constituted the virus particles. In their second paper, Bernal and Fankuchen described more fully a technique for orientating the virus particles and mounting them for X-ray exposures (which were as long as 400 hours).49 These practical details would form the basis of Franklin’s experiments, although she now had better X-ray tubes and cameras than Bernal and Fan used, and was able to obtain finer photographs with shorter exposure times.
The key difficulty remained the interpretation of the numerous spots obtained on the photographs. In 1937, Bernal struggled to fit the patterns he and Fan saw into a traditional crystal model. He wrote that ‘normally, crystallinity presupposes an indefinite repetition of identical units in three-dimensional space. These [TMV] proteins appear not to possess this degree of regularity.’50 In late 1952, an important breakthrough was made by Jim Watson in Cambridge. He was trying his hand at X-ray crystallography for the first time, after he and Crick had built a model of DNA that was so bad, Bragg ordered them to do something else. Again starting from the pre-war experiments of Bernal and Fankuchen and having ‘pilfered’51 their 1941 paper from the library, Watson took X-ray photographs of TMV and proposed that it was a helical structure.52 He was able to reach this co
nclusion only because Crick and others had derived the mathematical theory of helical diffraction that predicted that a helical molecule would give rise to an X-shaped diffraction pattern. When Watson took his results to Birkbeck, Sage looked at the photographs and said, ‘It [TMV] looks like a pineapple.’53
Klug applied himself to the helical nature of TMV and to the key question of the shape of the protein sub-units and how they were arranged together. Bernal showed a great interest in this: Watson’s pictures were quite similar to those that he and Fan had obtained. In his photographs, Bernal had concentrated on a series of smeared lines, in which every third line appeared especially strong. He had wondered whether this resulted from a rotational pattern that repeated every 120 degrees. Now he would come up to Klug every few days and say: ‘Tell me again, why isn’t it a simple screw axis?’54 Klug would explain the X-ray diffraction theory of helices to him in a physical way. ‘He would grasp it physically, Bernal could do mathematics if he wanted to, he was just too busy. He took an interest and would come running up the stairs, every now and again, and say: “What’s new?” I would never answer him, but under my breath say that “We’re still struggling with what’s old”.’55
Looking back, Klug thinks that Bernal ‘had all the right ideas about biomolecular research’, but that as a chief he did not pay enough attention to details. This was probably inevitable given the multiplicity of his talents and his ubiquity. Anita Rimel would get very angry if anyone took Sage his mail; she once attacked Alan Mackay for doing this, saying, ‘Don’t you know he is not allowed to have his own letters, he only makes a mess of it and loses them.’56 Lenton assumed the role of departmental accountant in addition to being the head technician. He collected about fifty invoices per month, for which Sage just signed the cheques without question. Lenton understood the Customs procedures for importing equipment. In July 1950, Bernal visited Berlin as an invited guest at the 250th anniversary celebrations of the German Academy of Science. He visited Katie Dornberger-Schiff in East Berlin and she agreed to send one of her goniometers to Birkbeck. Lenton normally took charge of importing equipment and was asked to step in by Anita, when the goniometer was impounded by Customs. He went to the airport office and found that Sage had filled out the Customs form: instead of writing ‘No commercial value’ he had entered the word ‘Priceless’.
Sage was once asked whether he ran his lab on communist lines. He said he had advanced socially only as far as the state of feudalism so that people had to plough the Lord’s land for half the time and for the other half, they could plough their own.57 The dilapidated buildings in Torrington Square, crammed with workers from different departments, caused their own problems. Rosalind Franklin frequently wrote notes to Bernal58 complaining about the pharmacy department pouring large quantities of ether down the sink, oblivious to the fire risk, and on another occasion flooding her laboratory on the first floor. Safety was not a priority – in one lab there were beakers used for brucine (a poisonous alkaloid like strychnine). There was a handwritten notice next to them: DO NOT USE FOR COFFEE.59
During the early 1950s, Sage carried out virtually no original work himself, but would occasionally show glimpses of his mastery of crystallography. One day he asked Klug for a microscope and mounted an inky blue crystal of azulene; Klug was amazed by the amount of information Sage extracted in this simple way. The crystals are diamond-shaped with one acute corner truncated: Sage thought that many crystallographers had misinterpreted the axis of symmetry, and he wrote a brief note to Nature pointing out their error.60 Mackay, who was by now an assistant lecturer in the department and studying iron oxides, had a similar experience of Sage’s astounding ability with a light microscope. ‘He could look at the interference pattern from a crystal in polarized light, and it might look pinkish in one place and he would say “I can see the molecules lined up in a particular direction” – he inferred directly from the asymmetry of the optical scattering that’s how molecules must be aligned.’61
Although his personal finances remained haphazard, Sage was adept at attracting grant money to his department. Franklin’s original Turner and Newall Fellowship ended at the end of 1954, and Sage managed to secure funding from the Agricultural Research Council to pay her salary, purchase equipment and to provide salaries for two research workers. The first to arrive was John Finch, a shy young physicist from King’s College, London, who wanted to make the transition to research with potential application to medicine. He was joined in July 1955 by Kenneth Holmes, freshly graduated from Cambridge, who wrote to Bernal for a research job because he did not think he would get a good enough degree to be taken on at the Cavendish. Rosalind took them both on as doctoral students, but as she had no official University of London status, Bernal was their nominal supervisor.
The money from the ARC could not change the rabbit warren layout of Torrington Square. Franklin wrote a note of despair to Sage reminding him that ‘my desk and lab are on the fourth floor, my X-ray tube in the basement, and I am responsible for the work of four people distributed over the basement, first and second floors on two different staircases’.62 To her, one obvious improvement would be to move Jim Jeffery and his cement group, but when she put this to him with her typical brusqueness, Jeffery instantly declined her offer. She could not understand why he was so unreasonable, and it was left to Klug to explain to her gently that Jeffery ‘was here before you came along’ and was not going to give up his territory.63 Her group continued to expand steadily and grabbed small workspaces where they could. Close international ties were forged with two other centres working on TMV: Tübingen in Germany and Berkeley in California. Both labs provided Franklin with TMV material that she used to establish further fundamental details about the virus, but a problem arose with her British supplier, Bill Pirie.
Pirie, whom Klug came to regard as a professional sceptic, took exception to a paper by Franklin in which she, correctly, pointed out that infective TMV particles were all the same length and consisted of identical protein sub-units. Pirie could not accept such simple regularity and wrote a scalding letter to her.64 He also refused to send any more TMV to Birkbeck. Franklin and Klug did not ask Bernal to intercede on their behalf with his querulous friend, but decided to grow their own TMV through the University’s Botanical Unit. In the meantime, they were working with a TMV preparation from Berkeley in which mercury atoms were incorporated into the viral protein to make it more amenable to X-ray analysis. The Berkeley group using electron microscopy had shown that TMV could re-assemble itself, in vitro, from its component protein and RNA into biologically active virus particles (an experiment hailed in the press as creating life in a test tube).
Franklin acquired some new X-ray tubes from France, which enabled her to focus the beam down to very small dimensions while maintaining high spatial resolution. The Beaudouin tubes, which were difficult to use, were again housed in the basement, where condensation dripping from the pipes often caused Franklin to operate under an umbrella.65 Despite working in these slum conditions, Franklin’s Birkbeck group provided the most detailed picture yet of the ultrastructure of the rod-shaped virus: it was a hollow, knobbly, protein helix with a thread of RNA deeply embedded within it, probably following the line of the helix throughout the length of the virus particle.66 These findings were presented at a landmark meeting in March 1956, one of a series sponsored by the Ciba Foundation, in London. It was a select international gathering of the world’s leading virus researchers. Bernal did not attend, but Birkbeck was well represented by Franklin and Klug. At the meeting, Crick and Watson teamed up again to explore, with their trademark brilliance, the assumption that the amino acid sequence in the protein of progeny viruses is determined by the genetic specificity of the infecting virus, and not to any significant extent by the genetic machinery of the infected host cell. They asserted that there was no direct means of copying the protein subunits from one generation of virus to the next: the amino acid sequence was controlled by the molecular structure
of the RNA of the infecting virus, expressed through a relatively simple code (they estimated that three consecutive bases in the RNA molecule would specify one amino acid in the viral protein coat).
Two weeks before the Ciba meeting, Crick and Watson had just published a paper in Nature attempting to answer the question ‘Why are all viruses either rods or spheres?’67 Starting with TMV, the most studied virus, they were struck by the regularity and symmetry of the protein sub-units bound together in a helix: ‘This feature is the clue to the general principle which we can apply whenever, on the molecular level, a structure of a definite size and shape has to be built up from smaller units; namely, that the packing arrangements are likely to be repeated again and again – and hence the sub-units are likely to be related by symmetry elements’.68 Were there corresponding sub-units that locked together in a regular way to form the protein shell of spherical viruses? Two early papers from Bernal suggested that there might be repeated symmetries for both tomato bushy stunt virus (TBSV) and turnip yellow mosaic virus (TYMV). Now there was evidence from Donald Caspar, an American friend of Watson’s working in the MRC laboratory at the Cavendish, that TBSV showed icosahedral symmetry (a high degree of symmetry that approximates to a sphere), and that each spherical shell probably comprised sixty (or a multiple of sixty) sub-units. Crick and Watson pointed out that this was one of three symmetrical arrangements that would automatically form a spherical shell. The question now became ‘how are the sub-units arranged?’ Crick and Watson’s analogy was to find identical shapes that could be fitted together to cover the surface of a tennis ball.