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Levene, Phoebus (Aaron)

nucleic dna acid chemistry

[luh veen ] (1869–1940) Russian–US biochemist, who showed that ‘nucleic acid’ is of two kinds (RNA and DNA) and defined the difference between them.

Levene’s father was a prosperous Jewish shirt-maker in St Petersburg, and the boy was able to become a student in the Imperial Medical Academy there taught physiology, and chemistry, in the Academy; the latter apparently influenced Levene the most, because he afterwards inclined more towards chemistry than medicine. In 1891 the family emigrated to the USA and after completing his MD degree in St Petersburg Levene began his medical practice in the Russian-Jewish colony on New York’s East Side. He and a brother-in-law shared a small office; the brother-in-law, a socialist lawyer, was very similar in appearance to Levene and, as neither of them could afford to lose a client, it was their custom to ‘bluff it out’ for one another when alone in the office.

Levene continued to spend much time studying chemistry and in about 1900 decided to abandon medical practice for medicinal chemistry. He worked for a year with in Berlin; by 1905 he had a reputation in biochemical research and was appointed to the new Rockefeller Institute for Medical Research in New York, where he spent the rest of his life. He was small, energetic, artistic and multilingual, prone to toss his heavy shock of hair about and devoted to his own experimentation despite having a team of co-workers. His work ranged over a large area of tissue constituents and was notably productive in sugar chemistry.

His best-known work concerns nucleic acids, which had first been isolated in laboratory, in 1869. It is now known that nucleic acids are long, chain-like molecules, constructed from repeating units: in which the bases are of four different kinds.

Levene’s important contribution was to show that the sugar component came in two kinds, both of them unknown until he isolated them by breaking down nucleic acids. The first sugar, isolated in 1909, was soon shown to be ribose. The second sugar, 2-deoxyribose, was not discovered for another 20 years. This was because 2-deoxyribose is destroyed by acid used to break up the chain, and a non-destructive enzyme for the purpose could not be found. Success was eventually achieved by passing a solution of this nucleic acid through a gastrointestinal segment of a dog, by introducing it through a gastric fistula and withdrawing it through an intestinal fistula, a difficult procedure. With Levene’s identification of 2-deoxyribose, it was clear that the nucleic acid found in cells is of two kinds, ribonucleic acid and deoxyribonucleic acid, and their abbreviations (RNA and DNA) became familiar.

The more detailed structure of the nucleic acids (notably the precise mode of linkage of base and phosphate groups to the sugar) was elucidated especially by the work of A R Todd (1907– ); and then in 1953 virtually created molecular biology by showing that the sequence of the four bases (in groups of three) along the DNA chains form a code of genetic information which directs the synthesis of RNA, which in turn directs the synthesis of proteins. They also showed that DNA exists in cells in the form of a double helix of two entwined strands of DNA, whose uncoiling provides templates for their own replication. With their work genetics and heredity had found its basis at the molecular level, with Levene’s work (from a quarter of a century earlier) forming a key part of these later developments.

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