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The physicist of biology

Francis Crick, one of the discoverers of the structure of DNA and of the genetic code, explored to the maximum the freedom for doing science

Irony or not, the author of some of the most important contributions to biology in the last century was not originally a biologist. Francis Harry Compton Crick was born on June 8, 1916 in Northampton, in the central region of England, and graduated in physics at University College, in London, in 1937. In the following years, Crick carried out researches into hydrodynamics, and during the Second World War, designed acoustic and magnetic mines in the Research Laboratories of the Admiralty, of the British Royal Navy. But the same deep interest for the mysteries of nature led Crick to study physics and to make a change of direction in his scientific career, en route to biology.

In the course of his life, Crick proved to be a very unorthodox researcher as far as the way of choosing the investigations to which he would dedicate himself is concerned. After the war, the British physicist began to question himself about which path to follow, and concluded that he ought to dedicate himself to biology. The justification for the change was only to come later, when he confessed: “What really interests us is what we like to chat about”. At the end of the 1940’s, the interest for physics began to cool down. Crick was getting more interested in the recent advances in biology, an area that, he believed, could become just as important in the following years as physics had been at the beginning of the 20th century.

“Convinced that the chat test had led him to his true vocation, he became one of those rare post-war adventurer physicists to cross the frontier and to go into biology”, explain David Brody and Arnold Brody in their book The Seven Greatest Scientific Discoveries in History and The People Who Made Them. Orthodox or not, his methods put him on the way to the discovery that was to make him known all over the world: the identification of the structure of the molecule of DNA (deoxyribonucleic acid), the genetic material of cells. Right from the start, Crick decided to dedicate himself to the frontier between the living and the non-living, so as to reveal how lifeless atoms and molecules were capable of originating a living being, and also what the mechanism was for transmitting hereditary information.

Crick started investigating the physical characteristics of cytoplasm, the gelatinous portion that covers the nucleus of the cell, and in a short time he realized that he was looking in the wrong direction. In the 1940’s, experiments like those carried out by Oswald Avery in the United States with the pathogenicity of bacteria, besides works popularizing science, like the series of talks by Austrian physicist Erwin Schroedinger, brought together in the book What is life?, were reinforcing the idea that DNA could be the molecule responsible for the transmission of the hereditary characteristics in living beings.

It did not take long for Crick to understand that it was necessary first to reveal the molecular structure of genes, whose function he imagined – correctly, as he was to discover later on – to be to control the synthesis of proteins by means of an intermediary molecule, RNA (ribonucleic acid). Crick was to start investigating the structure of this molecule in earnest after getting to know the young American biologist James Watson, in 1951. Two years before, Crick had swapped the Strangeways Research Laboratories, at Cambridge University, for the recently inaugurated Cavendish Laboratories, at the same institution, where he dedicated himself to studying the structure of proteins by means of a technique called X-ray diffraction – when they hit a molecule, the X-rays scatter in a characteristic manner, indicating the position of the atoms that form them.

At this same time, another physicist who had migrated to biology, the New-Zealander Maurice Wilkins, a colleague of Crick, was already using X-rays to study DNA in a laboratory of King’s College, in London. After listening to a talk by Wilkins, Watson, who was studying biochemistry in Copenhagen, Denmark, realized that that technique really could reveal the structure of the molecule of deoxyribonucleic acid. Interested in studying X-ray diffraction, Watson set off for the Cavendish Laboratories, in Cambridge, even before the approval of the American institution that was financing his studies in Europe.

Watson arrived in Cambridge without knowing anything about X-ray diffraction, but he found in Crick the ideal partner. United by their interest in the shape of DNA, both worked in harmony over almost 18 months, often hidden, because neither of them was officially carrying out research with the DNA molecule – in England, it was not good form for Crick to investigate DNA by X-ray diffraction, work being carried out by Wilkins and his laboratory colleague, Rosalind Franklin. Much effort and a good stroke of luck – Watson found an essential clue about the structure of DNA in X-ray images made by Rosalind and Wilkins during a visit to King’s College – made it possible for Watson and Crick to unveil the three-dimensional form of the DNA molecule. Made up of two long parallel filaments, which are twisted around the axis, the DNA molecule had the appearance of a spiral staircase, as the researchers described in the study published in Nature on April 25, 1953 – the first of a series of four articles.

Separation
With this discovery, which earned Watson, Crick and Wilkins the Nobel Prize in Physiology or Medicine for 1962 – Rosalind died before, in 1958, and did not get the recognition she deserved -, the abstract idea of a gene took on a concrete form. More than this, the identification of the structure of DNA made it possible to understand how genes are duplicated: normally in a spiral, the molecule unrolls, and each filament acts as a model for the other, which complements it. In spite of the success, the collaboration Watson and Crick did not last. While Watson returned to the United States, Crick remained in England, working in the field that he had helped to create, molecular biology.

In the following years, the boy from Northampton started a collaboration with South African researcher Sydney Brenner, which led to the discovery that each sequence of three of the four bases that form DNA (adenine, thymine, cytosine and guanine) corresponds to an amino acid, a fundamental unit of proteins. Crick’s work also assisted with the elucidation of how the information contained in the DNA is transformed into protein, with the assistance of RNA. In the mid-1970’s, Crick believed that he was no longer capable of contributing towards molecular biology. And, as had already occurred before, he once again gave a new direction to his career, this time to neurobiology.

In 1976, Crick moved to the Salk Institute, in the United States, where he investigated the neurological bases of human consciousness – a challenge just as great as those that he pursued the whole of his life. Curiosity over the great mysteries of nature guided Crick’s life to the end. On July 28 this year, Crick was till working on a scientific article on his bed, in Thornton Hospital, in San Diego, hours before dying, 88 years old, as a consequence of colon cancer.

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