Kristian Anfinsen

Kristian Anfinsen

American biochemist
Date of Birth: 26.03.1916
Country: USA

Biography of Christian Anfinsen

Christian B. Anfinsen was an American biochemist born in Monessen, Pennsylvania, a small industrial town near Pittsburgh. His father, who he was named after, immigrated to the US from Norway, and his mother, Sofia Anfinsen (maiden name Rasmussen), was also of Norwegian descent. After completing high school, Anfinsen attended Swarthmore College, where he received his bachelor's degree in 1937. He then studied organic chemistry at the University of Pennsylvania, while also serving as a teaching assistant. In 1939, he earned a Master of Science degree, and the following year, he moved to the Carlsberg Laboratory in Copenhagen, Denmark, as a fellow of the American-Scandinavian Foundation. Upon returning to the US in 1940, Anfinsen received a scholarship at Harvard University. Three years later, he obtained his Ph.D. in biochemistry and became a faculty member at the Department of Biological Chemistry at Harvard Medical School in Boston. From 1944 to 1946, he served in a civilian position at the United States Office of Scientific Research and Development. During the academic year of 1947/48, he worked as a junior investigator at the American Cancer Society, under the biochemical division of the Nobel Institute in Sweden, where he was mentored by A. Hugo Theorell. After returning to the US, Anfinsen became an adjunct professor at Harvard, but at the end of the year, he left that position and became the head of the Laboratory of Cellular Physiology at the National Heart Institute, part of the National Institutes of Health (NIH), in Bethesda, Maryland. In his doctoral dissertation, Anfinsen described his research on the development of methods for measuring the activity of enzymes found in the retina of the eye. Enzymes are chains of amino acids that control chemical reactions in living organisms. As enzymes are predominantly catalytic rather than structural proteins (similar to muscle proteins), they regulate reactions without being directly involved. When Anfinsen began this work, it was known that amino acid chains were folded into three-dimensional spherical shapes. It was believed that each type of protein was folded in a specific way, although the mechanism was unknown, and this unique shape was associated with its function. However, at that time, no one had determined the complete amino acid sequence of any enzyme and little was known about how enzymes control the vast array of known biochemical reactions. Anfinsen believed that to understand the relationship between the structure and function of enzymes, it was necessary to study the process of their assembly in living organisms. In the mid-1940s, he and his colleague David Steinberg began investigating the incorporation of isotopically labeled amino acids into proteins. Previously, Frederick Sanger at the University of Cambridge in England had determined the sequence of the 51st amino acid of insulin protein. Applying Sanger's methods in his own research, Anfinsen hypothesized that if he synthesized a chain of amino acids by sequentially adding them and measured its activity after each stage, he could accurately determine the relationship between the enzyme's properties and its amino acid sequence. He chose bovine pancreatic ribonuclease, an enzyme composed of 124 amino acids and synthesized in the pancreas, for his research. By partially unraveling ribonuclease, denaturing it, and chemically breaking the four disulfide bonds contained within, Anfinsen obtained a single randomly coiled (and therefore inactive) chain of amino acids. He then discovered that when this disordered structure was placed in a chemical environment resembling the one in which ribonuclease exists in the body, the original active tertiary structure gradually reformed. By 1962, Anfinsen completed the thermodynamic studies that demonstrated his "thermodynamic hypothesis". According to his viewpoint, the active tertiary structure of ribonuclease is formed by the rearrangement of amino acids under physiological conditions, and this configuration has the lowest energy and is therefore the most stable. Only one amino acid sequence determines both the tertiary structure of the enzyme and its functional activity. In 1962, Anfinsen left the NIH and became a professor of biochemistry at Harvard Medical School, but the following year, he returned to the NIH to head the Laboratory of Chemical Biology at the National Institute of Arthritis, Metabolism, and Digestive Diseases. Here, during the 1960s, he studied the structural-functional relationships of many proteins. Realizing that he could simplify his work by using an enzyme that did not contain disulfide bonds, Anfinsen investigated the molecule of nuclease from Staphylococcus aureus bacteria. By 1970, the enzyme was fully synthesized by researchers at Rockefeller University. For his research on ribonuclease, especially the relationship between amino acid sequence and its biologically active conformation, Anfinsen was awarded half of the 1972 Nobel Prize in Chemistry. Moore and Stein shared the other half of the prize for similar work. In his presentation speech, Bo G. Malmström, a member of the Royal Swedish Academy of Sciences, congratulated the three laureates, who armed other researchers "with an approach to solve problems of enzymatic activity at the molecular level." Malmström noted that Anfinsen's particular interest was focused on the mechanism responsible for the configuration of the peptide chain. "In a series of elegant experiments, he showed that the necessary information resides in the linear sequence of amino acids of the peptide chain, that no extra genetic information beyond what is contained in the DNA is required." After receiving the Nobel Prize, Anfinsen became interested in interferon, a protein that plays a key role in the body's defense against viruses and cancer. After isolating this substance, he conducted a series of studies to investigate its structure and properties. In 1982, he was appointed professor of biology at Johns Hopkins University. In 1941, Anfinsen married Florence Bernice Kenenger, with whom he had three children - two daughters and a son. They divorced in 1978. The following year, Anfinsen married Libby Esther Schulman-Ely. In his spare time, he enjoys sailing and listening to music. Anfinsen is a member of the board of the Weizmann Institute of Science in Rehovot, Israel, and a member of the American Society of Biochemists, the National Academy of Sciences, and the Danish Royal Academy. In 1954, he received the Civil Service Award from the Rockefeller Foundation. He has been awarded honorary degrees from Swarthmore College, Providence College, New York Medical College, as well as the University of Pennsylvania and Brandeis University.

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