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Wednesday, October 3, 2012

Frederick Gowland Hopkins

 

Frederick Gowland Hopkins is considered the founder of British biochemistry. A pioneer in the study and application of what he called accessory food factors and what we call vitamins, he made important contributions to the study of uric acid , isolated tryptophan (a necessary component in nutrition), and developed the concept of essential amino acids. He also did pioneering work on cell metabolism, elucidating the role of enzymatic activity in oxidation processes. With the assistance of physiologist Walter M. Fletcher , he explained the relationship between lactic acid and muscle contraction. He became a member of the Royal Society in 1905, serving as its president in 1931. He was knighted in 1925 and received the Copley Medal of the Royal Society in 1926. For his contributions in the field of nutrition, he was awarded the 1929 Nobel Prize in physiology or medicine, sharing the award with the Dutch chemist Christiaan Eijkman. He was presented with the highest distinction of civil service, the Order of Merit, in 1935. In addition, many honorary degrees were bestowed on him by universities worldwide.
Hopkins was born in Eastbourne, Sussex, England, on June 20, 1861, to Frederick Hopkins and Elizabeth Gowland Hopkins. The poet Gerard Manley Hopkins was his second cousin. His father died soon after his birth and he was taken by his mother to live with her family in London. He was a solitary and scholarly boy, given to reading Charles Dickens and writing poetry, although he showed no particular aptitude for any subject in school except chemistry. According to the Dictionary of Scientific Biography, he was captivated by what he saw through the microscope, saying that "the powers of the microscope thus revealed to me were something very important --the most important thing I had as yet come up against." But his scientific education was delayed when his uncle secured a position for him in the insurance business. The seventeen-year-old Hopkins stuck it out for six months before leaving. He did publish his first paper while working for the insurance company, on the vapor ejected by the bombardier beetle. Although entomology remained an interest throughout his life, Hopkins said that his work on the beetle had made him realize that his true vocation was biochemistry. A small inheritance enabled him to study chemistry at the Royal School of Mines and London's University College, where he received a B.Sc. in 1890. An exemplary performance on his final chemistry examination led to a position as an assistant to Thomas Stevenson, an expert in forensic medicine at Guy's Hospital, who also served as medical jurist to the Home Office. As assistant to Stevenson, Hopkins used his analytical skills to help secure the convictions of several notorious murderers.
Despite these achievements, Hopkins was aware that he needed more education. He entered Guy's Hospital to study medicine in 1890, earning his M.B. in 1894. He remained at Guy's to teach for four years after receiving his degree. In 1898, at the age of thirty-seven, he was invited to Cambridge to undertake the triple duties of teacher, tutor, and developer of the chemical physiology department. The demands of that heavy workload caused Hopkins to suffer a temporary breakdown in 1910. Even with that workload and his subsequent ill health, Hopkins managed to publish more than thirty papers. Trinity College made him a fellow and elected him to a praelectorship in biochemistry. His appointment at Trinity, when he was nearly fifty years old, allowed him to give full attention to research and the advancement of biochemistry within the university.
Hopkins became the first professor of biochemistry at Cambridge in 1914. He established an open admissions policy for his department and attracted biochemists from many nations, including some who had escaped from dire political situations. A great teacher as well as a brilliant and unassuming researcher, Hopkins was known for encouraging his students to pursue their own line of work and often handed over to them promising new research in which he had made a breakthrough. Any credit or distinction resulting from pursuit of that new work went to his students, not Hopkins. This generosity, coupled with his faith that biochemistry could provide important answers to biological questions, was largely responsible for the widespread development of biochemical thought and experimentation. At the time of his death, approximately seventy-five of his former students held professorial positions in universities throughout the world.
One of his earliest contributions to biochemistry, made while he was still at Guy's Hospital and used for many years, was the method he developed to detect the presence of uric acid in urine. His work on uric acid led him to the study of proteins, the presence of which in the diet affects uric acid excretion. Hopkins first developed methods to isolate and crystallize proteins. He isolated the amino acid tryptophan and determined its structure. He also studied the effect of bacteria on tryptophan, laying the foundation of bacterial biochemistry. Hopkins showed that tryptophan is essential in the diet, since proteins lacking the substance are nutritionally inadequate. He also studied the role of the amino acids arginine and histidine in nutrition, which led to the theory that the presence of different amino acids determines the nutritional quality of proteins.
Hopkins, however, was not satisfied that an adequate diet depended upon the presence of essential amino acids alone. He suspected that additional substances, which he called accessory food factors, also played an essential role in nutrition. Experiments with rats that were fed a synthetic diet of milk proteins, carbohydrates, fats and salts showed that such a diet caused a decline in growth in the animals. When milk was added to the diet, even in small quantities, the rats once again underwent normal growth. This preliminary work enabled Hopkins to isolate what are now called vitamins A and D. His observations led him to conclude that such diseases as rachitis (popularly called rickets, and caused by a vitamin D deficiency) and scurvy occurred when food lacked certain vitamins. Although it had been known for a long time that scurvy, a common shipboard ailment, could be prevented or cured by supplementing one's diet with lemons, Hopkins' work on isolating vitamin C was the first to explain this experiential finding scientifically.
In 1912 Hopkins published the work for which he is probably best known, "Feeding Experiments Illustrating the Importance of Accessory Food Factors in Normal Dietaries." During World War I, Hopkins continued his work on the nutritional value of vitamins. His efforts were especially valuable in a time of food shortages and rationing. He agreed to study the nutritional value of margarine and found that it was, as suspected, inferior to butter because it lacked the vitamins A and D . As a result of his work, vitamin-enriched margarine was introduced in 1926. Hopkins' nutritional theories were contested by colleagues until about 1920 but have been considered indisputable since then.
Although Hopkins won the 1929 Nobel Prize in medicine and physiology (shared with Christiaan Eijkman ) for his work in nutrition, he was primarily interested in the biochemistry of the cell. The originality and vision of his research in this area set the standard for those who followed him. His study with Fletcher of the connection between lactic acid and muscle contraction was one of the central achievements of his work on the biochemistry of the cell. Hopkins had long studied how cells obtain energy from a complex metabolic process of oxidation and reduction reactions. He showed that oxygen depletion causes an accumulation of lactic acid in the muscle. The research techniques developed by Hopkins and Fletcher to study muscle stimulation were later used by others to study other aspects of muscle metabolism. Their work paved the way for the later discovery by Archibald Vivian Hill and Otto Meyerhof that a carbohydrate metabolic cycle supplies the energy used for muscle contraction. The discovery that alcohol fermentation under the influence of yeast is a process analogous to the formation of lactic acid in the muscle is also due to Hopkins's ground-breaking work. Hopkins' work on muscle metabolism led to an understanding of the importance of enzymes as catalysts to oxidation . He isolated glutathione, which plays an important role as an oxygen carrier in cells, and several oxidizing enzymes. Hopkins and his assistant, E. J. Morgan, made further contributions to this field in the late thirties.
Hopkins married Jessie Ann Stevens in 1898. They had three children. A gentle eccentric who struggled with feelings of insecurity about his worth as a scientist throughout his life, he considered himself an "intellectual amateur," despite his achievements and the honors bestowed on him by his peers. Hopkins died at Cambridge on May 16, 1947.


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