R. Linn Belford
Emeritus Professor of Chemistry and Medical Information Sciences
Professor Belford was awarded the B.S. in chemistry by the University of Illinois in 1953 and the Ph.D. in chemistry by the University of California (Berkeley) in 1955. Since then, he has been on the faculty at Illinois, where he has exploited special electronic and EPR spectroscopic techniques to characterize transition metal ions, radicals, and catalytic surfaces, and shock-tube methods to study high-temperature fast reactions. He is currently Director of the Illinois EPR Research Center. His research interests are in physical, biophysical, and inorganic chemistry, including anisotropies in solid-state structure and spectra; EPR spectra of coordination compounds including contrast agents for MRI; nuclear quadrupole and spin-spin interactions; EPR theory; ENDOR and ESE spectroscopy of disordered materials; fast motion studied by low-to-high frequency EPR; catalysis.
We use electron paramagnetic resonance (EPR) to focus on structures in disordered solids, solutions and crystals, and biomolecular systems. In the Illinois EPR Research Center, we have developed the world's first S-band (2 to 4 GHz) pulsed EPR, which is used to study very weak interactions between a free radical or transition metal ion and a remote atom. We have also developed high-sensitivity, very-high-frequency EPR spectrometers with wide sweep and cryostatic capability that provide exquisite resolution of nearly identical radical species and of anisotropies, and that permit detailed characterization of species. These spectrometers also allow measurement of fast (picosecond) motion and other dynamic processes in membranes and materials.
Current applications of EPR and related spectroscopies in our group include: (1) systematic studies of relationships between dynamics and structure in paramagnetic relaxation agents used for NMR imaging; (2) protein folding; (3) use of unpaired electrons native to carbonaceous materials as probes of their complex molecular structures; (4) use of unpaired electrons to probe catalytic surfaces and internal interfaces in materials; (5) fast (picosecond) dynamics in condensed phases; (6) metalloprotein structures; (7) paramagnetic sensors for oxygen and nitric oxide.
Throughout our EPR work, we use special techniques. Much attention has been given to full computer simulation analyses of complex spectra. New theories and improvements on traditional computational methods are developed to make some of the more difficult analyses tractable. We employ a wide range of spectroscopic frequencies and magnetic fields, with very low frequencies (~0.03 cm-1 or less) and fields (~100 G) favoring non-Zeeman effects, and very high frequencies (> 3 cm-1), and fields (up to 70,000 G, with sweeping superconducting magnets) accentuating Zeeman splittings and high-transition probabilities. Electron spin echo (ESE) spectroscopy is a rapid-pulsed EPR technique we use to study very small hyperfine couplings and local structure in disordered materials. Electron-nuclear double resonance (ENDOR) is a method used to probe intermediate hyperfine couplings and, in effect, do NMR studies on paramagnetic centers. In both techniques, we use magnetic field position to select specific molecular orientations. Dynamic nuclear polarization (DNP) enables us to study chemical and physical interactions at the solid-liquid interface.
"Ligand-Induced Changes in Estrogen Receptor Conformation as Measured by Site-Directed Spin Labeling," K. M. Hurth, M. J. Nilges, K. E. Carlson, A. Tamrazi, R. L. Belford, and J. A. Katzenellenbogen, Biochemistry, 43, 1891-1907, (2004).
"Observation of Single-Crystal-Type Epr Spectra from Monolayers of Copper-Exchanged Zeolite Na-a Crystals Assembled on Glass Plates," H. So, K. Ha, Y. J. Lee, K. B. Yoon, and R. L. Belford, J of Phys. Chem. B, 107, 8281-8284, (2003).
"LODEPR Measurements and Models for Electron Spin Relaxation T-1e in Four Gd3+ Chelates," A. Borel, L. Helm, A. E. Merbach, V. A. Atsarkin, W. Demidov, B M. Odintsov, R. L. Belford, R. B. Clarkson RB., J of Phys. Chem., 106, 6229-6231 (2002).
"Multifrequency EPR of High-Spin S-State Ions: Examples from Gd3+ Chelates," R. B. Clarkson, A. I. Smirnov, T. I. Smirnova, and R. L. Belford, in The Chemistry of Contrast Agents in Medical Magnetic Resonance Imaging, A. E. Merbach & E. Tóth, eds., Ch. 9, pp. 383-415; Wiley, New York (2001).
"Electron Paramagnetic Resonance W-Band Spectrometer with a Low Noise Amplifier," M. J. Nilges, A. I. Smirnov, R. B. Clarkson, and R. L. Belford, Appl. Magn. Reson., 16, 167 (1999).
"Solid-Liquid Electron Density Transfer in Aqueous Char Suspensions by 1H-Pulsed Dynamic Nuclear Polarization at Low Magnetic Field.", B. M. Odintsov, R. L. Belford, P. J. Ceroke, and R. B. Clarkson, J. Am. Chem. Soc., 120, 1076 (1998).
"Comparative Spin Label Spectra at X-Band (9.5 TGHz) and W-Band (95 GHz)," A. I. Smirnov, R. L. Belford and R. B. Clarkson, in Spin Labeling: The Next Millennium (Ed., L. J. Berliner), Biol. Magn. Reson., 14, 83 (1998).
"Electron Paramagnetic Resonance and Dynamic Nuclear Polarization of Char Suspensions - Surface Science and Oximetry," R. B. Clarkson, B. M. Odintsov, P. J. Ceroke, J. H. Ardenkjaerlarsen, M. Fruianu and R. L. Belford, Phys. Med. Biol., 34(7): 1907 (1998).
"Lipid-MRI Contrast Agent Interactions: a Spin Labeling and a Multifrequency EPR Study," T. I. Smirnova, A. I. Smirnov, R. L. Belford and R. B. Clarkson, J. Am. Chem. Soc., 120, 5060 (1998).
"Multi-Frequency EPR Determination of Zero Field Splitting of High Spin Species in Liquids: Gd(III) Chelates in Water," R. B. Clarkson, A. I. Smirnov, T. I. Smirnova, H. Kang, R. L. Belford, K. A. Earle and J. H. Freed, Mol. Phys, 95, 1325 (1998).