Arthur Harden's groundbreaking work in the field of alcoholic fermentation has led to a greater understanding of metabolic processes, including the formation of lactic acid in muscles and the ossification of tissue. Apart from his discoveries in biochemistry, he distinguished himself as a Nobel laureate, professor, and contributor of scholarship to the field.
Born on October 12, 1865, Harden was the third of nine children--and the only son--of Manchester businessman Albert Tyas Harden and Eliza MacAlister Harden. His family's puritanical leanings and nonconformist attitude toward social conventions, such as the celebration of Christmas and interest in the theatre, remained an influence throughout Harden's life. Despite his austere upbringing, however, he was an accomplished skater and avid gardener, as well as a great fan of Charles Dickens and Victorian literature in general. He attended private school beginning at age seven, and then studied at Tattersall College between 1876 and 1881 in Staffordshire, reaching the age of sixteen at the time that he left there. His undergraduate studies at Owen College of the University of Manchester under the instruction of Henry Roscoe culminated in a degree with first class honors in chemistry in 1885. A year later he was awarded the Dalton scholarship and started graduate studies at the University of Erlangen under the tutelage of Ernst Otto Fischer. After completing his Ph.D. in 1888 by writing his dissertation on properties and purification of -nitroso-a-naphthylamine, he returned to Owens where he served as junior and then senior lecturer under Roscoe's successor, H. B. Dixon.
Harden was more interested in teaching and writing than research. He was intrigued with the history of chemistry, and taught an honors class in that subject. Among the most prodigious writings he had done up until 1896 were several papers that had resulted from studying John Dalton 's notebooks with Roscoe in a joint research project. Their 1896 book, A New View of the Origin of Dalton's Atomic Theory, represented an area of interest which fascinated Harden for many years. (Dalton theorized his atomic principles by observing the diffusion of gases.) Harden then collaborated with F. C. Garrett on Practical Organic Chemistry, published in 1897, and revised and edited Roscoe's Treatise on Inorganic Chemistry, admirably supplementing his teaching salary of 200 or less a year.
After unsuccessfully applying for jobs as a private school principal and as an inspector, Harden was appointed professor of biochemistry in 1897 at the British Institute of Preventative Medicine (renamed a year later to the Jenner Institute and, in 1903, the Lister Institute), where Roscoe was treasurer. While the institute staff taught students pursuing careers as public health officers, testing water for city officials and otherwise doing little scientific research, Harden was hired at Roscoe's suggestion to teach chemistry and bacteriology. As medical schools began to offer the same subjects, Harden's classes were phased out and the head of the bacteriology department, recommended he consider research. Fermentation , or the breakdown of sugar by bacteria, became Harden's objective as he set upon discovering a chemical means of distinguishing various fermentation patterns in the bacteria Escherichia coli. Harden was able to show that the ratio of alcohol to acetic acid, two of the compounds formed during bacterial fermentation, was a useful guide in determining which variety of the bacterium was involved in a given fermentation process.
The year Harden arrived at the institute, Eduard Buchner had released his revolutionary research on fermentation. Buchner had discovered that fermentation could take place in the absence of living yeast cells, yielding an enzyme he named zymase. Although the reaction took longer than it would have had live cells been present, it produced the familiar end products of fermentation, carbon dioxide and alcohol. Buchner's experiment was the first evidence of the existence of enzymes. Like many others in the scientific community, Harden began to build on Buchner's work. He showed that fermentation could occur because zymase acted on glycogen (a sugar) that had been within the cells themselves. Assisted by William Young, Harden made significant discoveries about the role of phosphate in fermentation over the next decade.
In 1904, Harden put a semipermeable membrane bag full of yeast extract into pure water. Harden knew that the molecules, densely packed inside the bag, would move through the membrane into the water because of the lower density of yeast outside of the bag. He also knew that the membrane would allow only molecules of a given size to pass through--a process called dialysis. Zymase stopped breaking down the sugar inside the bag while reintroducing water from outside the bag which contained the small molecules that had diffused out through the membrane. When Harden boiled the yeast extract, it failed to cause fermentation at all, indicating that zymase actually consisted of two parts. Because zymase lost its activity after dialysis, he decided that the larger part remained trapped inside the bag; this, together with its loss of effectiveness led Harden to conclude that the larger part was probably a protein, the smaller part (having not perished during boiling), a nonprotein.
Pursuing the matter further, Harden and Young added boiled yeast juice to an ongoing fermentation and measured the amount of carbon dioxide released. Although all active agents should have been destroyed by the boiling, the addition sped up the process. They discovered the boiled juice contained a phosphate substance called cozymase. Harden's work showed that three factors are necessary for fermentation to occur: the ferment, the enzyme, and a coenzyme. By attending to the entire fermentation process--not only the end products as had been the previous practice--he laid the important groundwork for further understanding of metabolic processes, such as ossification.
In 1911, Harden was among the founders of the Biochemical Society, and the following year named coeditor of the Biochemical Journal. Although Harden left the institute in 1912 for a professorship in biochemistry at the University of London, his association with the institute was not over. He became acting director when the head of the institute went off to war in 1914. For the duration, his research focused on nutrition, particularly on the diseases beriberi and scurvy , while much of his free time was spent digging trenches with the Volunteer Reserve.
Harden married Georgina Sydney Bridge, of Christchurch, New Zealand, in 1900; they had no children. She died in 1928, a year before Harden and Hans Euler-Chelpin received the Nobel Prize in chemistry for work in fermentation. In 1909 he was named a fellow of the Royal Society, being awarded its Davy Medal in 1935, and the following year he was knighted. He received honorary degrees from the universities of Manchester, Liverpool, and Athens, and was named an honorary member of the Institute of Brewing and a member of the Kasierlich Leopold Deutsche Akademie der Naturforsche, Halle.
A year after winning the Nobel Prize Harden retired from teaching, although he stayed on as editor of the Biochemical Journal until 1937. His garden at Bourne End remained one of his great joys until he died at home on June 17, 1940, of a progressive disease.
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