Erwin Chargaff

Erwin Chargaff (11 August 1905 – 20 June 2002) was an Austro-Hungarian-born American biochemist, writer, Bucovinian Jew who emigrated to the United States during the Nazi era, and professor of biochemistry at Columbia University medical school. He wrote a well-reviewed autobiography, Heraclitean Fire: Sketches from a Life Before Nature. Chargaff was born on 11 August 1905 to a Jewish family in Czernowitz, Duchy of Bukovina, Austria-Hungary, which is now Chernivtsi, Ukraine.

At the outbreak of World War I, his family moved to Vienna, where he attended the Maximiliansgymnasium (now the Gymnasium Wasagasse). He then went to the Vienna College of Technology (Technische Hochschule Wien), where he met his future wife, Vera Broido. From 1924 to 1928, Chargaff studied chemistry in Vienna and earned a doctorate working under the direction of Fritz Feigl.

He married Vera Broido in 1928. Chargaff had one son, Thomas Chargaff. From 1925 to 1930, Chargaff served as the Milton Campbell Research Fellow in organic chemistry at Yale University. Still, he did not like New Haven, Connecticut. Chargaff returned to Europe, where he lived from 1930 to 1934, serving first as the assistant in charge of chemistry for the department of bacteriology and public health at the University of Berlin (1930–1933) and then, being forced to resign his position in Germany as a result of the Nazi policies against Jews, as a research associate at the Pasteur Institute in Paris (1933–1934).

Chargaff immigrated to Manhattan, New York City, in 1935, taking a position as a research associate in the department of biochemistry at Columbia University, where he spent most of his professional career. Chargaff became an assistant professor in 1938 and a professor in 1952. After serving as department chair from 1970 to 1974, Chargaff retired as professor emeritus. After his retirement as professor emeritus, Chargaff moved his lab to Roosevelt Hospital, where he continued to work until his retirement in 1992.

He became an American citizen in 1940. During his time at Columbia, Chargaff published numerous scientific papers primarily studying nucleic acids such as DNA using chromatographic techniques. He became interested in DNA in 1944 after Oswald Avery identified the molecule as the basis of heredity. Cohen says, "Almost alone among the scientists of this time, Chargaff accepted the unusual Avery paper and concluded that genetic differences among DNAs must be reflected in chemical differences among these substances. 

He was actually the first biochemist to reorganize his laboratory to test this hypothesis, which he went on to prove by 1949." Chargaff said of the Avery discovery: "I saw before me (in 1944), in dark contours, the beginning of a grammar of biology", and in 1950, he published a paper with the conclusion that the amounts of adenine and thymine in DNA were roughly the same, as were the amounts of cytosine and guanine. This later became known as the first of Chargaff's rules. Instrumental in his DNA discoveries were the innovation of paper chromatography and the commercially-available ultraviolet spectrophotometer tool.

Chargaff lectured about his results at Cambridge University in 1952, with Watson and Crick in attendance. Key conclusions from Erwin Chargaff's work are now known as Chargaff's rules. The first and best-known achievement was to show that in natural DNA, the number of guanine units equals the number of cytosine units, and the number of adenine units equals the number of thymine units. 

In human DNA, for example, the four bases are present in these percentages: A=30.9% and T=29.4%; G=19.9% and C=19.8%. This strongly hinted towards the base pair makeup of the DNA, although Chargaff did not explicitly state this connection himself. For this research, Chargaff is credited with disproving the tetranucleotide hypothesis (Phoebus Levene's widely accepted hypothesis that DNA was composed of many repeats of GACT). 

Most researchers had previously assumed that deviations from equimolar base ratios (G = A = C = T) were due to experimental error. Still, Chargaff documented that the variation was real, with [C + G] typically being slightly less abundant. He did his experiments with the newly developed paper chromatography and ultraviolet spectrophotometer. Chargaff met Francis Crick and James D. Watson at Cambridge in 1952, and, despite not getting along with them personally, he explained his findings to them. 

Chargaff's research would later help the Watson and Crick laboratory team to deduce the double helical structure of DNA. The second of Chargaff's rules is that the composition of DNA varies from one species to another, particularly in the relative amounts of A, G, T, and C bases. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein.