Alfred Guillou Redfield, 1929-2019

It is with great sadness that we report the death of our friend, colleague and mentor Alfred (Al) Redfield on July 24th, 2019 in Alameda, California.   Al moved to California from Lexington, Massachusetts several years ago, as his beloved wife Sarah’s health deteriorated, to be close to their eldest daughter, Rebecca, and to escape the East Coast winters. His two other children, Samuel and Wendy reside in Massachusetts.  

Al was born in Milton, Massachusetts and grew up in Cambridge and Woods Hole, where his father, Alfred C. Redfield, worked at the Oceanographic Institute.   He graduated from Harvard in 1950 with a B.A., then received his M.S. and Ph.D. degrees in physics from the University of Illinois in 1952 and 1953.   His Ph.D. thesis focused on the Hall effect on electron mobilities in photoconductors.    Al's thesis acknowledges "Professor C.P. Slichter and his associates … for their friendliness and cooperation while I was occupying their magnet and laboratory".  Al and Charlie Slichter remained good friends throughout their lives.

After returning to Harvard for a postdoc, he published a 1955 Physical Review paper "Nuclear Magnetic Resonance Saturation and Rotary Saturation in Solids" in which he established the concept of spin temperature in the rotating frame, including spin-locking, T1r relaxation, and dipolar order that were essential to many subsequent developments.  In his Principles of Magnetic Resonance, Slichter called this paper "one of the most important papers ever written on magnetic resonance".  A more general treatment, "Nuclear Spin Thermodynamics in the Rotating Frame", was published in Science in 1969.

Al then took a position at IBM Watson Laboratories at Columbia University, where he remained until 1970.  There he pursued applications of NMR in solids, as well as fundamental aspects of magnetic resonance.   His work included measurements of spin-lattice relaxation in metals at very low temperatures (Anderson and Redfield, Phys. Rev. 1959), analysis of spin relaxation in solids driven by translational diffusion (Eisenstadt and Redfield, Phys. Rev. 1963), investigations of the properties of impurities in copper using field cycling (Redfield, Phys. Rev. 1963), the first demonstration of NMR for characterizing the vortex lattice in a type II superconductor (Redfield, Phys. Rev. 1967), and experiments and theory to show that spin diffusion in a magnetic field gradient generates dipolar order (Genack and Redfield, Phys. Rev. Lett. 1973). He also developed an indirect detection method for rare spins, observing natural abundance 43Ca in CaF2 using 19F (Bleich and Redfield, J. Chem. Phys. 1971), the intellectual ancestor of contemporary indirect detection methods.

In 1957, Al published his theory of spin relaxation, the eponymous Redfield Theory, in the IBM Journal of Research and Development.  Years later, John Waugh, the editor of the nascent Advances in Magnetic Resonance, convinced Al to publish the theory "for real". His article became the centerpiece of the premier issue of that monograph series (Adv. Magn. Reson. 1, 1 (1965)). Redfield Theory as applied to statistical mechanical and spectroscopic systems has found applications throughout the physical sciences. Even so, Al would say of his theory when asked, "Well, it was just a better way of writing down what everybody already knew". In 1970, Al received the IBM Outstanding Contribution Award for his development of a high-resolution pulsed NMR spectrometer, which included one of the earliest implementations of quadrature detection in time-domain NMR (Redfield and Gupta, Adv. Magn. Reson. 1971).  He also received a faculty appointment at Columbia.  In 1969, he began using NMR to investigate biological materials during a sabbatical with Dan Koshland at U.C. Berkeley. In 1972, he joined the faculty at Brandeis University, with a joint appointment in physics and biochemistry, where he remained for the rest of his career.   He became a National Academy of Sciences member in 1979 and an American Academy of Arts and Sciences Fellow in 1983.  Al received the Max Delbruck Prize from the American Physical Society in 2006.

Al's many pioneering contributions to biological NMR include early studies of electron transfer in cytochrome c using saturation transfer (Gupta and Redfield, Science 1970), solvent suppression via composite pulse excitation (Redfield, Kunz, and Ralph, J. Magn. Reson. 1975), measurements of hydrogen exchange rates in tRNA and proteins (e.g., Johnston, Figueroa, and Redfield, PNAS 1979; Stoesz, Redfield, and Malinowski, FEBS Lett 1978), and an early 1H-detected 2D 15N-1H correlation experiment that he referred to as the “forbidden echo” (Redfield, Chem. Phys. Lett. 1983).  

Al would have been as comfortable in an engineering department as he was in physics. His home-built NMR spectrometer at Brandeis was the first instrument designed to specifically target biological systems.  He optimized selective pulses for water suppression years before pulse trains such as WATERGATE and flip-backs came into common usage.  Al’s first superconducting magnet, a 6.4 T magnet acquired in the early 1980s, was brought to field at Bruker in Billerica, MA and shipped cold and charged to Brandeis on a flatbed, a 20-mile trip.   FIDs on his earlier instrument were digitized as they were acquired and stored on a 2048-bit ring memory before being passed to an IBM PC for Fourier transformation and analysis.  All processing software was written by Al, as were the pulse sequences. 

By 1989, his NMR spectrometer had evolved into a surprisingly user-friendly instrument, with a commercial 11.7 T magnet and a probe optimized for multinuclear experiments.  He used his spectrometer primarily for studies of 15N-labeled proteins, particularly the Ras oncoprotein. As some users needed access to homonuclear experiments, particularly TOCSY and NOESY, Al obliged by “burning” EPROMs with those sequences.  The appropriate sequence could be selected by a switch, and pulse lengths adjusted with an analog pot to get the best S/N and “jump-return” selective pulse water suppression.   A z-shim pulse (homospoil) was used to prevent radiation damping.  Al also implemented data transfer protocols that allowed data to be processed and plotted in contours.  (Al consistently used stacked plots for looking at 2D data, something most users could not get used to).   Along with his long-time engineering associate Sara Kunz and technician Mary Papastravos, we at Brandeis knew that we could always count on Al’s advice, help with grant proposals, and clarification of points of physics.

After his retirement in 1999, Al focused on combining high-resolution NMR with field cycling for characterization of intrinsic relaxation phenomena at low field.  He built a portable sample shuttle that could be wheeled up the magnet.  His original shuttle was pneumatic, using a vacuum to suck a sample up to an adjustable stop rod for field selection, with a Helmholz coil at the top of the magnet for near-zero field.   After relaxation at low field, the vacuum was released and a gas cushion used to return the sample to the probe for measurement. He later upgraded to a computer-controlled mechanical shuttle, with transit times less than a second.  He used this system for characterizing the relaxation of 31P, 13C, 15N or 1H over a field range of 0.003 to 11.7 T.  The shuttle apparatus allowed him to investigate local dynamics of membrane proteins and lipids in detail not previously possible.  Much of this work was done in collaboration with Mary Roberts (Boston College) and Liz Hedstrom (Brandeis).  

Al did not often crack jokes or banter.  But once he got to know you, his subtle sense of humor would show up.  When our first commercial 500 MHz NMR arrived at Brandeis, Al knew he could get me (Tom) nervous just by waving a soldering iron at the machine and threatening to "make it work better".           

Al Redfield’s presence was probably the single most important reason that I (Tom) chose to come to Brandeis, and he was my mentor and friend for many years. His unassuming nature (and admittedly odd wardrobe choices) belied his formidable intelligence. Ideas that he tossed off almost as an aside became the bases of complete careers for others.   He would often complain, when seeing what he considered to be a trivial publication, “I thought of that years ago!”  I would ask, “Well, Al, did you publish it?”, he would invariably answer: “No, I didn’t think it was important”.

Tom Pochapsky, Brandeis University

Mary Roberts, Boston College

(with contributions from Robert Griffin of MIT and Robert Tycko of NIH)