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All of us at CERM are very sorry for the loss of Seymour Koenig.

Seymour, awarded with a honoris causa degree in Chemistry at the University of Florence, pioneered field-cycling relaxation as a technique to obtain information on both molecular structure and dynamics. Together with Rodney D. Brown III, he developed a field-cycling relaxometer, also installed in four other research centers in the world, among which CERM, our research infrastructure in Florence, thus allowing many other scientists to benefit from this technique. The presence of a field-cycling relaxometer in Florence stimulated Stelar (www.stelar.it) to develop the first commercial field-cycling relaxometer. The Koenig-Brown relaxometer permitted the measurement of the nuclear relaxation rates as a function of the magnetic field from 0.01 to 50 MHz proton Larmor frequency. This technique, that he named “relaxometry”, is nowadays used by a wide community spread all around the world. The relaxometry profiles contain in fact information on molecular hydration and on the mobility of the investigated molecules over a very wide range of timescales, not achievable through high field NMR, and on the electronic structure of paramagnetic systems. - Using relaxometry, Seymour achieved outstanding results in the characterization of proteins and tissues for understanding the source of the contrast and for the optimization of Magnetic Resonance Imaging (MRI) (see, for instance, Koenig and Brown, Progress NMR Spectr. 1990, 23, 487). He also applied relaxometry to the study of paramagnetic complexes, and of contrast agents for MRI in particular (see, for instance, Koenig and Brown, Magn. Reson. Med. 1984, 1, 478). We remember with pleasure the many exciting discussions we had with him in many occasions, among which the Chianti Workshops on Magnetic Resonance, where he was often invited for his brilliant contributions. The scientific collaborations that several of the senior CERMians had with Seymour resulted in the characterization of the hydration and of the nuclear and electron relaxation properties of paramagnetic proteins, among which cobalt-substituted carbonic anhydrase (Koenig, Brown, Bertini, Luchinat, Biophys. J. 1983, 41, 179), copper- and vanadyl-substituted transferrin (Bertini, Briganti, Koenig, Luchinat, Biochemistry 1985, 24, 6287), copper-zinc and copper-copper superoxide dismutase (Bertini, Banci, Brown, Koenig, Luchinat, Inorg. Chem. 1988, 27, 951), dicopper transferrin (Bertini, Luchinat, Brown, Koenig, J. Am. Chem. Soc. 1989, 111, 3536), copper and manganese alkaline phosphatase (Bertini, Luchinat, Viezzoli, Banci, Koenig, Leung, Coleman, Inorg. Chem. 1989, 28, 352, and Schulz, Bertini, Viezzoli, Brown, Koenig, Coleman, Inorg. Chem. 1989, 28, 1490).