History of DNA Discovery (3): Albrecht Kossel, Nucleic Acid, Purine, Pyrimidine

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Brief biography of Albrecht Kossel

Albrecht Kossel was born in 1853 into a merchant family in Rostock, Germany. His father was a merchant, bank director and Prussian Consul in this Baltic seaport. He showed a keen interest in chemistry and botany in his young age. He began medical studies at the University of Strassburg in 1872 and obtained a medical license in 1877. The following year, he earned his doctorate in medicine. After serving on university faculties in Berlin and Marburg, he became head of the physiology department at the University of Heidelberg in 1901. He lived in there with his family until his death from heart disease in 1927.

Albrecht Kossel was fortunate to meet the renowned biochemist Hoppe Seyler and served as his assistant in his laboratory from 1877 to 1881. It was there that his interest shifted from medicine to biochemistry. When the research on "nuclein" was introduced to him, Kossel decided to continue along the path Miescher had pioneered.

Albrecht Kossel Discovers Phosphate, Sugar and Five Nitrogenous Bases in Nucleic Acids

In 1878, Kossel confirmed that "nuclein" would decompose in boiling water to release phosphorus, and a large amount of hypoxanthine existed in incompletely cleaved "nuclein". The next year, he isolated another nitrogenous base, guanine, from the "nuclein" of yeast.

He discovered that "nuclein" was actually a combination of protein and another substance in 1884 (today, we know it is nucleic acid). He isolated a basic, salt-like protein that binds with nucleic acids from bird red blood cells, which looked different from protamine. Kossel named it histone.

In 1885, Kossel extracted a new basic precipitate, adenine, from hydrolysis of yeast and pancreas "nuclein". Then he delivered a paper to discuss how these adenine was converted to guanine during the hydrolysis of "nuclein", thus guanine was not a component of “nuclein”. He also found that "nuclein" isolated from egg yolk did not yield guanine upon hydrolysis.

Richard Altmann claimed to have obtained a "nuclein" completely devoid of protein in 1888, which he called nucleic acid. When isolating phosphoric acid from the hydrolysis of nucleic acid in 1891, Albrecht Kossel claimed to have detected large amounts of guanine, adenine and a substance resembling carbohydrates. He mistakenly thought these carbohydrate molecules contained six carbon atoms, whereas they actually have five. Two years later, he and his student Neumann isolated thymine and cytosine from bovine thymus and predicted their structure.

Although Kossel's interests gradually shifted towards amino acids and proteins, he still guided students in studying the composition and properties of nucleic acids. In 1901, one of his students, Ascoli, published a paper on uracil. Ascoli attributed this discovery to his mentor who had advised him to study yeast.

Kossel was awarded the Nobel Prize

For his outstanding contributions to the field of nucleic acids and protein, Albrecht Kossel was awarded the Nobel Prize in Medicine in 1910. Although some scientists in that era had begun to realize that nucleic acids might store genetic information and play a significant role in regulating hereditary traits, the prevailing view was still that proteins were the carriers of genetic information, as the structure of nucleic acids was not yet understood, and the rich structure of proteins was thought to support the myriad of genetic traits. Albrecht Kossel also believed that it was proteins, not nucleic acids, that determined the function of chromosomes.

Frequently Asked Questions

What components did Albrecht Kossel discover in nucleic acids?

Albrecht Kossel and his research team found that nucleic acids were present not only in the cell nucleus but also in the cytoplasm. They discovered that nuclear material was composed of nucleic acids and histones. From the hydrolysis of nuclear material, they isolated phosphoric acid, carbohydrates and nitrogenous bases—adenine, guanine, thymine, cytosine, and uracil.

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