Jerome Karle (1918–2013) Chemist Who Pioneered Mathematical Methods to Solve Crystal Structures
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COMMENT OBITUARY Jerome Karle (1918–2013) Chemist who pioneered mathematical methods to solve crystal structures. hortly after the German physicist Max Crystallographica, which laid out step by step von Laue discovered in 1912 that crys- how to determine crystal structures. Others tals diffract X-rays, the British physi- joined the venture with computer programs, cist Lawrence Bragg realized that he could and ever increasing numbers of ever more S LAB. RES. NAVAL use the pattern of X-rays diffracted from a complex structures came to be determined crystal to pinpoint the precise positions of through direct methods. its constituent atoms. Yet as increasingly By the time Karle and Hauptman received complex materials began to be studied, ever the Nobel prize, Karle had become prominent more clever methods were needed to ‘solve’ in crystallography circles, having served as the crystal structures. Jerome Karle, Jerry to President of the International Union of Crys- those who knew him, established new ways tallographers in the early 1980s. to convert an observed diffraction pattern As I discovered during my postdoctoral into a set of atomic positions. He did so in time with Karle in the early 1970s, the power principle by deriving mathematical formu- of the statistical methods underlying his and lae together with Herbert Hauptman, and he Hauptman’s approach is not unbounded (I did so in practice by inventing procedures tried with little success to apply his methods for applying the formulae to real crystals to protein crystals). Nevertheless, Karle’s together with his wife, Isabella Karle. influence extends to macromolecules. He The mathematical approaches that Karle was fascinated by resonance in diffraction and Hauptman established, known as direct electron-diffraction experiments. In par- (whereby certain atoms behave anomalously methods, have helped researchers to eluci- allel, Karle made a theoretical analysis when the energy of incident X-rays matches date the structure of key molecules such as predicting what diffraction patterns to the energy of an electronic orbital), and he vitamins and hormones, and to gain insight expect from oriented hydrocarbons, and this made seminal contributions to the theory into biochemical mechanisms. Karle and got him wondering about applying his theo- underlying an approach now called multi- Hauptman shared the 1985 Nobel Prize in ries to the analysis of crystal structures. It wavelength anomalous diffraction (MAD). Chemistry for their work. was around this point that Karle was joined MAD and SAD, MAD’s single-wavelength Karle, who died on 6 June, was born in by Hauptman. counterpart, are now commonly used to Brooklyn in New York city. A precocious The problem they faced was that although determine macromolecular structures, such product of New York public schools, he com- X-rays diffracted from crystals carry infor- as membrane proteins. Both require that the pleted high school at just 15 years old and mation that can produce a picture of the resonant atoms be located as a first step, and went on to the City College of New York. He atomic structure, only part of that informa- the Karle–Hauptman direct methods are now graduated in 1937 along with Hauptman and tion is accessible experimentally. Only the the approach of choice for finding them. Arthur Kornberg, another of City College’s amplitudes of the electromagnetic waves Karle’s interests were broad, as suggested many Nobel laureates. He then went to Har- bouncing off the atoms can be observed by by the name he gave his unit at the NRL — vard University in Cambridge, Massachusetts, photon detectors; the phase offset of each the Laboratory for the Structure of Matter. where he gained a master’s degree in biology. periodic wave relative to the others cannot The work there ranged from electron diffrac- After spending about a year at the New York be measured. Fortunately, for typical crystals tion of gases to quantum chemistry of excited State Health Department in Albany, Karle there are many more X-ray reflections than states, to the study of glasses and amorphous pursued further graduate studies, this time there are atoms, which implies that the reflec- materials, and of course, crystals. Although in chemistry at the University of Michigan tions must be mathematically interrelated. these activities engaged several group mem- in Ann Arbor. At Michigan, Karle studied Starting in 1950, Karle and Hauptman drew bers and were largely experimental, the Jerry the diffraction patterns resulting from firing on fundamental knowledge about the nature I knew was a lone theoretician; he authored electrons at gases. It was also here that he met of matter (specifically, that one cannot have many papers alone and his main working Isabella Lugoski, a fellow graduate student, negative electron density) to find mathemati- interaction was with a computer program- whom he married in 1942 and with whom he cal relationships among the diffracted waves. mer who tested his theories. had three daughters. Soon after, they established a probability Ultimately, Karle’s major contribution After completing his dissertation in 1943, theory, which they brashly announced in was to allow researchers to shift their focus Karle moved to the University of Chicago to 1953 in an abstruse monograph entitled from the intricacies and challenges of crystal work on the Manhattan Project. He returned ‘Solution of the Phase Problem’. lography to molecules and biochemical to Michigan in 1944 to take on a research Early reception of the Karle–Hauptman mechanisms. He turned chemical crystal- project for the US Navy, which involved work was at best muted. Quoting Karle lographers into crystallographic chemists. ■ studying the structure of hydrocarbon lubri- himself, “during the early 1950s … a large cants. In 1946, he and his wife moved to the number of fellow-scientists did not believe Wayne A. Hendrickson is at Columbia US Naval Research Laboratory (NRL) in a word we said.” The tide was turned by University, New York, USA. He was a Washington DC, where they remained until Isabella applying the work to challenging postdoctoral fellow and then a research their retirement in 2009. structures such as peptides. In 1966, she and biophysicist with Karle from 1969 to 1984. Initially, they continued to focus on Karle published a landmark paper in Acta e-mail: [email protected] 410 | NATURE | VOL 499 | 25 JULY 2013 © 2013 Macmillan Publishers Limited. All rights reserved.