A leading 20th-century physical and biophysical chemist known for incisive contributions in both theory and experiment, Harden Marsden McConnell is also remembered as a kind colleague and dedicated mentor. Over his career, he significantly advanced understanding of magnetic resonance, cell membrane biophysics and immunology. His early work elucidated how the electronic structure of molecules contributes to electron spin and nuclear magnetic resonance (ESR and NMR) spectra. He developed the spin labeling technique, using free-radical labels with ESR spectroscopy to reveal protein and lipid membrane structure and kinetics. Leveraging this and related work, Professor McConnel and colleagues founded Molecular Devices, Inc. in 1983, to develop tools to study cellular response. His later career focused on biophysical studies of membranes, antibodies and molecules of the major histocompatibility complex.
Born in Richmond, Virginia in 1927, Professor McConnell completed his undergraduate studies at George Washington University (BS 1947). His doctoral research in chemistry guided by Norman Davidson at the California Institute of Technology (PhD 1951) focused on optical interaction absorption, a phenomenon of higher-than-predicted light absorption by two ion species in solution. After graduation, he studied charge transfer processes during postdoctoral research under physicist and chemist Robert Mulliken at the University of Chicago. He returned to the West Coast to pursue studies of nuclear magnetic resonance spectral characteristics at the Shell Development Company in Emeryville, California, before joining the Caltech faculty in 1956. Starting as assistant professor, he rose to associate professor in 1959 and full professor in 1959. He was recruited to Stanford in 1964. Here, he continued explorations into stable free-radicals that led to the spin labeling technique, and conducted research into membrane dynamics and proteins of the immune system, which he continued even after his official retirement to emeritus status.