Ian Carmichael

Ian Carmichael

Director - Notre Dame Radiation Laboratory

University of Glasgow, Scotland, B.Sc.Hons (1971) Ph.D. (1974)

Phone: (574) 631-4502
Email: carmichael.1@nd.edu
Office: 321 Radiation Research Building

Theoretical Studies of Reactive Intermediates

Scientific Interests

Quantum Chemistry of Reactive Intermediates

Structure and properties of radicals, radical ions, and excited states in solution and on surfaces.

Magnetic Interactions in Molecular Species

EPR splittings; NMR spin-coupling constants and chemical shifts; nuclear quadroplar couplings.  

Theory of Radiation and Photochemical Transformations

Photophysical processes; transient absorption spectroscopy.

Radiation Damage in Macromolecular Crystallography

Specific damage mechanisms and mitigation strategies.

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Recent Accomplishments

New Graphic

Radiation Damage in MX

Quantitative comparison of X-ray induced radiation damage to both protein and DNA constituents of a nucleoprotein complex, C.Esp1396I, shows that the protein component is much more radiation sensitive. Typical specific damage patterns were observed for both the protein on particular amino acid residues and for the DNA in the cleavage of base-sugar N1-C and sugar-phosphate C-O bonds. Strikingly however, the DNA component was seen to be far more resistant to specific damage than the protein over the investigated dose range. Whether the protein is inherently more fragile or is merely acting as a scavenger of the damage agents remains an open question.

Intramolecular H-atom Transfer in Dyads

Chiral discrimination in the intramolecular abstraction of phenolic hydrogems by benzophenone triplets was observed in suitably constructed molecular dyads. Extensive density functional theory (DFT) calculations provided a clear understanding of the geometrical requirements underpinning these observed differences. In related transfers, a comparison of the dyads' experimental3J(Hα-Hβ(a/b)) spin-spin coupling constants with theoretical values obtained by weighting DFT-computed spin-spin coupling constants with MD-computed probability distributions for the dyads' configuration offered independent confirmation of the validity of such calculations.

NMR Spin Couplings in Biomolecules

Methyl α- and β-d-glucopyranuronides singly labeled with 13C at C1-C6 were prepared from the corresponding 13C-labeled methyl d-glucopyranosides, and multiple NMR J-couplings (JHHJCH, and JCC) were measured in their protonated and ionized forms in aqueous (D2O) solution. Solvated density functional theory (DFT) calculations on J-couplings in structurally related model compounds were performed to determined how well the calculated J-couplings matched the experimental values in saccharides bearing an ionizable subsituent. These calculations suggest that substituents proximal to the exocyclic COOH group (i.e., the C4-O4 bond) influence the activation barrier to C5-C6 bond rotation due to transient intramolecular H-bonding. A comparison of J-couplings in the glucopyranuronides to corresponding J-couplings in the glucopyranosides showed that more pervasive changes occur upon conversion from a COOH to a CH2OH substituent at C6 than from COOH ionization within the uronides.

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Selected Publications

Dawley, M.M., K. Tanzer, I. Carmichael, S. Denifl, and S. Ptasinska. "Dissociative Electron Attachment to the Gas-Phase Nucleobase Hypoxanthine." J. Chem. Phys 142 (2015): 21501. link

Bury, C., E.F. Garman, H.M. Ginn, R.B.G. Ravelli, I. Carmichael, G. Kneale, and J.E. McGeehan. "Radiation Damage to Nucleoprotein Complexes in Macromolecular Crystallography." J. Synchrotron Radiat 22 (2015): 213-24link

Klepach, T., H. Zhao, X. Hu, W. Zhang, R. Stenutz, M.J. Hadad, I. Carmichael, and A.S. Serianni. "Informing Saccharide Structural NMR Studies with Density Functional Theory Calculations" in Methods in Molecular Biology: Glycoinformatics, ed. T. Lutteke and M. Frank (New York, Humana Press, 2015), 289-331.

Allan, E.G., M.C. Kander, I. Carmichael, and E.F. Garman. "To scavenge or not to scavenge, that is STILL the question." Journal of Synchrotron Radiation 20 (2013): 23-36. link

De la Mora, E., I. Carmichael, and E.F. Garman. "Effective Scavenging at Cryotemperatures: Further Increasing the Dose Toleranace of Protein Crystals." Journal of Synchrotron Radiation 18 (2011): 346-57. link

Lewandowska, A., I. Carmichael, G. Horner, G.L. Hug, and B. Marciniak. "Steric effects on intramolecular reactivity in cyclic dipeptides: Conformational analysis validated by a combined MD/DFT approach." Chemical Physics Letters 512 (2011): 123-28. link

Full List of Publications

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