Tuesday, July 29, 2014

Dorothy Hodgkin and the Structure of Penicilin

Dorothy Hodgkin
(1910 – 1994)
On July 29, 1994, British chemist and Nobel Laureate Dorothy Mary Hodgkin passed away. She advanced the technique of X-ray crystallography, a method used to determine the three-dimensional structures of biomolecules. Among her most influential discoveries are the confirmation of the structure of penicillin.

Dorothy Crowfoot's (late Hodgkin's) interest in chemistry started around the age of only 10. Her parents were involved in education projects in Egypt and Sudan and during a visit, their daughter was allowed to study and analyze some chemicals with a friend of the family. Also, when she was attending the Sir John Leman School, she was allowed to join the boys as they studied chemistry. By the end of her early schooling, she had already decided that chemistry was something she wanted to pursue. Also, it is assumed that her time in Sudan played a big role in her future career. She was able to help with excavations and studied pebbles with a portable mineral analysis kit, which pushed her fascination and interest in crystals and minerals. This experience almost made her give up chemistry and replace it with archaeology instead. Then she was given a copy of “Concerning the Nature of Things” by Sir William Henry Bragg when she was 15, and she was intrigued at the thought of being able to study the properties of atoms and molecules using x-rays. She began studying chemistry at Somerville College, Oxford University and continued at the University of Cambridge to earn her PhD with John Desmond Bernal, who had worked for five years with the senior Bragg [1]. Hodgkin and Bernal used X-ray crystallography to determine the three-dimensional structure of several complex organic molecules important to the functioning of living organisms [2].

To Hodgkin's most important contributions to the science of chemistry belongs presumably the determination of the structures of penicillin, insulin, and vitamin B12. She determined the exact structure of penicillin in 1945. The results contradicted general scientific thought at the time and therefore put researchers on the right path to developing further and more sophisticated uses for penicillin-based antibiotics, including the development of semisynthetic versions. In the 1950s, the scientist and her colleagues published an analysis of vitamin B12 which expanded the understanding of how this vital nutritional component functions and how it is utilized by the human body. Hodgkin spent years honing and improving the available methods to penetrate the mysteries of ever-more complicated structures. After 35 years of work, the internal structure of insulin was solved [3]. She received the Nobel Prize in chemistry "for her determinations by X-ray techniques of the structures of important biochemical substances". Also, she was the third woman ever to win the prize in chemistry, after Marie Curie and Irène Joliot-Curie [2].

Next to her research studies, Dorothy Hodgkin was highly involved in humanitarian projects including the welfare of scientists and people living in nations defined as adversaries by the United States and the United Kingdom in the 1960s and 1970s, for example, the Soviet Union, China, and North Vietnam. She was also the chair of the Pugwash movement, which dealt with potential dangers raised by scientific research [2].

At yovisto, you may be interested in a video lecture by Georgina Ferry, Dorothy Hodgkin's biographer. She explains the story of the structure of penicillin and the personal and professional challenges, Hodgkin faced during her years of research.



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Monday, July 28, 2014

Karl Popper and the Philosophy of Science

Karl Raimund Popper (1902-1994)
On July 28, 1902, Austrian-British philosopher Sir Karl Raimund Popper was born. He is generally regarded as one of the greatest philosophers of science of the 20th century. Popper is known for his rejection of the classical inductivist views on the scientific method, in favour of empirical falsification: A theory in the empirical sciences can never be proven, but it can be falsified, meaning that it can and should be scrutinized by decisive experiments.

Karl Raimund Popper was born in Vienna to Simon Siegmund Carl Popper, a lawyer from Bohemia and Jenny Schiff Popper, who was of Silesian and Hungarian descent. All of Karl Popper's grandparents were Jewish, but the Popper family converted to Lutheranism before Karl was born. They understood this as part of their cultural assimilation, not as an expression of devout belief. Carl's father was a bibliophile who had 12,000–14,000 volumes in his personal library. By the time, Vienna claimed to be the cultural epicentre of the western world.

Karl attended the local Realgymnasium, where he was unhappy with the standards of the teaching, and, after an illness which kept him at home for a number of months, he left to attend the University of Vienna in 1918. However, he did not formally enrol at the University by taking the matriculation examination for another four years. In 1919 he became heavily involved in left-wing politics, joined the Association of Socialist School Students, and became for a time a Marxist. However, he was quickly disillusioned with the doctrinaire character of the latter, and soon abandoned it entirely. He also discovered the psychoanalytic theories of Siegmund Freud and Alfred Adler, and listened entranced to a lecture which Albert Einstein gave in Vienna on relativity theory. The dominance of the critical spirit in Einstein, and its total absence in Marx, Freud and Adler, struck Popper as being of fundamental importance: the pioneers of psychoanalysis, he came to think, couched their theories in terms which made them amenable only to confirmation, while Einstein's theory, crucially, had testable implications which, if false, would have falsified the theory itself [1].

Popper had a rather melancholic personality and took some time to settle on a career; he obtained a primary school teaching diploma in 1925, took a Ph.D. in philosophy in 1928 and qualified to teach mathematics and physics in secondary school in 1929. The dominant philosophical group in Vienna at the time was the Wiener Kreis, a circle of ‘scientifically-minded’ intellectuals including Rudolf Carnap, Otto Neurath, Viktor Kraft, and Hans Hahn with the principal objective to unify the sciences. For his part, Popper became increasingly critical of the main tenets of logical positivism. He articulated his own view of science, and his criticisms of the positivists in "Logik der Forschung" in 1934 (translated by Popper himself twenty-five years later under the title The Logic of Scientific Discovery), which gained him an enormous reputation and had a tremendous impact on the scientific community.
"In point of fact, no conclusive disproof of a theory can ever be produced; for it is always possible to say that the experimental results are not reliable or that the discrepancies which are asserted to exist between the experimental results and the theory are only apparent and that they will disappear with the advance of our understanding. If you insist on strict proof (or strict disproof) in the empirical sciences, you will never benefit from experience, and never learn from it how wrong you are." (Karl Popper)
Due to the rise of fascism in Austria as well as in Germany and the steady growth of anti-Semitism, Popper was forced to leave Austria. In 1937, he went to New Zealand and taught philosophy as a senior lecturer at the University of Canterbury. After the Second World War, he went to London, first as reader in logic and scientific method, then in 1949 became a professor of logic and scientific method at the London School of Economics, a post which he held until 1969. Many visits as a guest professor in the United States followed, amongst them the William James Lectures at Harvard in 1950.[2]

Popper's relations with many of his most devoted students were now often stormy and, with the exception of one or two cases, tended to end in open hostility. Popper had become intolerant of dissent and also inclined to misunderstand the nature of his own contribution to the philosophy of science. He believed that he had solved the problem of how scientific knowledge is generated and established. In reality he had merely moved the problem one step forward and so opened an entirely new problem. In demonstrating that all scientific knowledge is only provisional and hypothetical, he had invited doubts as to the degree to which it genuinely corresponded to reality. These doubts were pursued by Thomas Kuhn and led him to a relativism which never gained Popper’s approval.[3]

He had public debates with Ernst Bloch and Theodor Adorno, two of the most popular luminaries of Continental philosophy in the 1950s and 1960s, and in 1972 he published his third major book, Objective knowledge, in which he established a close link between his philosophy of science and the development of neo-Darwinism. He was knighted in 1965. Popper continued to think and write until the very last years of his life. He died on 17 September 1994 in Croydon, Surrey.

At yovisto, you can listen to an excerpt of Sir Karl Popper's 'Science as Falsification' from his 1963 book 'Conjectures and Refutation'.


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Sunday, July 27, 2014

Rosalind Franklin and the Beauty of the DNA Structure

Rosalind Franklin (1920-1958)
On July 25, 1920, British biophysicist and X-ray crystallographer Rosalind Elsie Franklin was born. She made the first clear X-ray images of DNA’s structure. Her work was described as the most beautiful X-ray photographs ever taken. Franklin’s ‘Photo 51’ informed Crick and Watson of DNA’s double helix structure for which they were awarded a Nobel Prize.

Rosalind Franklin was born in Notting Hill, London, as the second of five children into an affluent and influential British Jewish family. From early childhood, Franklin showed exceptional scholastic abilities. She was educated at St Paul's Girls' School where she excelled in science, Latin and sports. From the age of 15 on, she knew already that she wanted to become a scientist. Rosalind Franklin enrolled at Newnham College, Cambridge, in 1938 and studied chemistry. In 1941, she was awarded Second Class Honors in her finals, which, at that time, was accepted as a bachelor's degree in the qualifications for employment. When she graduated, Franklin was awarded a research scholarship to do graduate work. She spent a year in R.G.W. Norrish's lab without great success. Norrish recognized Franklin's potential but he was not very encouraging or supportive toward his female student. She went on to work as an assistant research officer at the British Coal Utilisation Research Association, where she studied the porosity of coal—work that was the basis of her 1945 Ph.D. thesis "The physical chemistry of solid organic colloids with special reference to coal." [1] CURA was a young organization and there was less formality on the way research had to be done. Franklin worked fairly independently, a situation that suited her. Franklin worked for CURA until 1947 and published a number of papers on the physical structure of coal.

Franklin's next career move took her to Paris from 1947 to 1950. An old friend introduced her to Marcel Mathieu who directed most of the research in France. He was impressed with Franklin's work and offered her a job as a "chercheur" in the Laboratoire Central des Services Chimiques de l'Etat. Here she learned X-ray diffraction techniques from Jacques Mering. In 1951, Franklin was offered a 3-year research scholarship at King's College in London. With her knowledge, Franklin was to set up and improve the X-ray crystallography unit at King's College. Maurice Wilkins was already using X-ray crystallography to try to solve the DNA problem at King's College. Franklin arrived while Wilkins was away and on his return, Wilkins assumed that she was hired to be his assistant. It was a bad start to a relationship that never got any better. [2]

Wilkins' mistake, acknowledged but never overcome, was not surprising given the climate for women at the university then. Only males were allowed in the university dining rooms, and after hours Franklin's colleagues went to men-only pubs. But Franklin persisted on the DNA project. J. D. Bernal called her X-ray photographs of DNA, "the most beautiful X-ray photographs of any substance ever taken." Between 1951 and 1953 Rosalind Franklin came very close to solving the DNA structure. She was beaten to publication by Crick and Watson in part because of the friction between Wilkins and herself. At one point, Wilkins showed Watson one of Franklin's crystallographic portraits of DNA. When he saw the picture, the solution became apparent to him, and the results went into an article in Nature almost immediately. Franklin's work did appear as a supporting article in the same issue of the journal.[3]

A debate about the amount of credit due to Franklin continues. What is clear is that she did have a meaningful role in learning the structure of DNA and that she was a scientist of the first rank. Franklin moved to J. D. Bernal's lab at Birkbeck College, where she did very fruitful work on the tobacco mosaic virus. She also began work on the polio virus. In the summer of 1956, Rosalind Franklin became ill with cancer. She died less than two years later.

Franklin was never nominated for a Nobel Prize. She had died in 1958 and was therefore ineligible for nomination to the Nobel Prize in 1962 which was subsequently awarded to Crick, Watson, and Wilkins in that year. The award was for their body of work on nucleic acids and not exclusively for the discovery of the structure of DNA. Watson has suggested that ideally Wilkins and Franklin would have been awarded the Nobel Prize in Chemistry.

At yovisto you may enjoy the video lecture 'You say you want a revolution: DNA analysis methods' by Prof. Dr. Qiang Zhou from Berkeley University.



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If you like the daily blog posts of yovisto about the history of science, please support us by clicking on the amazon links and making your next amazon purchase via our offered links. Nevertheless, please do also support your local (real world) bookstore at the corner of the street.