U. W. Arndt

Designer of scientific instruments

Ulrich Wolfgang Arndt, science-instrument developer: born Berlin 23 April 1924; staff, Metallurgy Department, Birmingham University 1948-49; staff, Davy-Faraday Laboratory, Royal Institution 1950-63, Dewar Fellow 1957-61; staff, University of Wisconsin, Madison 1956; staff, Medical Research Council Laboratory of Molecular Biology, Cambridge 1963-89; staff, Institut Laue-Langevin, Grenoble 1972-73; FRS 1982; married 1958 Valerie Hilton-Sergeant (three daughters); died Cambridge 24 March 2006.

U. W. Arndt played an important part in the development of a broad range of instrumentation for X-ray diffraction from protein crystals. Over the last 50 years information about protein structure has been one of the cornerstones underpinning the progress of molecular biology. Without advanced instrumentation, the now routine determination of tens of thousands of protein structures would have been impossible.

Ulrich Wolfgang Arndt was born in Berlin in 1924. His father and mother had respectively German-Russian and Dutch-German origins, a combination that left Uli with strongly pan-European leanings for the rest of his life. In 1930 the family moved to Darmstadt and Uli made good progress with his schooling, despite growing political unrest. He transferred to the Gymnasium in 1933 but found much of the teaching amounted to National-Socialist indoctrination, a process that was counteracted on long weekend walks with his parents in the Odenwald, away from unfriendly ears.

Uli was already learning Latin at school and began private lessons in French and English, giving him a facility with languages. Reading poetry with his mother created an enduring love of literature. Uli Arndt found himself one of the few children in his class who chose not to be a member of the Hitler Youth but avoided the worst of the harassment by allowing his notebooks to be cribbed by the less talented students.

His parents' position, as half-foreigners with suspected left-wing sympathies, was becoming increasingly untenable. His father was by now commercial director of a company that made weighing, testing and dynamic balancing machines. In 1936 he succeeded in appointing himself head of a British subsidiary of the company and the family moved to London, where after some coaching Uli passed the entrance examination to Dulwich College.

Although starting on the classical side and obtaining credits at School Certificate in all subjects except Greek, Uli decided, under the influence of a family friend, to switch from Classics to science. Schooling was disrupted by the Munich crisis and in 1939 his father's company was taken over, as his father had hoped, by a British company, entailing a move to Birmingham and enrolment for Uli at King Edward VI High School. The family lived in a semi-detached house the other half of which was occupied by Professor (later Sir) Rudolf Peierls, whose lodgers included Otto Frisch and Klaus Fuchs. In later years Uli Arndt realised that the first studies on the feasibility of an atomic bomb had perhaps been drafted next door.

Arndt passed Higher School Certificate sufficiently well to win a Birmingham University Entrance Scholarship and spent a year there, before gaining a place at Emmanuel College, Cambridge, to read Physics and Electronics. He took the Part II physics tripos in two years, the maximum time allowed during the Second World War, embarking on his final practical examination set by the Professor, Sir Lawrence Bragg, on D-Day 1944.

It was the practical aspects of the university courses that had most interested him and an outstanding performance in the final practical encouraged him to approach Bragg about the possibility of a research position. A metallurgical project in the Crystallography Department, then run by Henry Lipson, was forthcoming. It was at this point that Arndt started to design and construct equipment for X-ray crystallography, an endeavour that he was to pursue for the rest of his life.

A powerful way to determine the atomic structure of matter, whether metallic or biological, is to shine a beam of X-rays at a crystal of the material and to measure the strengths of the resulting scattered beams, which make up the so-called diffraction pattern. For a metal there might be hundreds of beams but for a large protein molecule there would be tens of thousands of such measurements, from which an atomic picture of the structure can be computed. This was clearly a process crying out for advanced instrumentation and automation. In the post-war years, little in the way of laboratory equipment was available commercially and the instruments needed for basic research had to be designed and constructed in the laboratory.

After completion of his PhD and a brief spell back in Birmingham, Arndt was invited in 1949 to join the Royal Institution in London, where the group of Dennis Riley was working on solution X-ray scattering of proteins. Arndt designed a compact X-ray source and a number of diffractometers with various kinds of X-ray detectors. The appointment of Sir Lawrence Bragg as new director in 1954 signalled a switch in interests to protein crystallography.

This was bolstered by the arrival of David Phillips in 1955 and together Arndt and Phillips designed the famous linear diffractometer, which employed for the first time an analogue computer to make the complicated settings required to move the crystal and detector and measure the intensity of the X-ray beams. This was used by John Kendrew to collect some of the data for his historic map of myoglobin, the first protein structure to be determined.

In 1963, at the invitation of Max Perutz, Arndt joined the newly formed MRC Laboratory of Molecular Biology in Cambridge. This was a time of great excitement in X-ray work, since in 1962 Nobel Prizes had been awarded to Kendrew and Perutz for solving the first protein crystal structures and to Francis Crick and James Watson for their double helical structure of DNA, a model based in part on the X-ray data of Rosalind Franklin and Maurice Wilkins.

By this time, digital computers were becoming available to drive more sophisticated diffractometers and they also opened the possibility of more general methods of collection of X-ray data on photographic film, as computer-controlled film scanners were designed to measure the intensities of the spots. Arndt played a leading role in all of these developments and the Arndt-Wonacott rotation camera, which established the rotation method as the mainstay of protein crystallography worldwide, was particularly important. He also developed a fast television-camera-based detector for X-rays and co-authored two influential monographs, Single Crystal Diffractometry (1966) and The Rotation Method in Crystallography (1977).

Arndt's wide-ranging contributions to the field were recognised by his election to Fellowship of the Royal Society in 1982. After his "official" retirement in 1989, he continued work until shortly before his death on a miniature microfocus X-ray source and its associated optics. Many of his inventions went into commercial production. Arndt often described himself as more of a tinkerer than a scientist or engineer and his continually evolving designs sometimes made things difficult for his workshop collaborators.

Uli Arndt was a strong family person, delighting in skiing abroad and in walking in the Lake District, especially around Buttermere, accompanied by his wife, Valerie, and their three daughters. He enjoyed travelling to conferences around the world but, on returning from an exotic location, he would explain how much he loved the wonderful British rain. A born raconteur, he read avidly and was a fount of knowledge about history and biography, and enjoyed going to the theatre. Latterly he gained great satisfaction from sketching and watercolour painting, as he said it helped him keep his eyes open.

Last year he completed his forthcoming autobiography, Personal X-Ray Reflections, which describes a rich and rewarding life.

R. A. Crowther