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

Li, Z., A.R. Milosavljevic, I. Carmichael, and S. Ptasińska. "Characterization of Neutral Radicals from a Dissociative Electron Attachment Process."  Phys. Rev. Lett. 119 (2017) 053402. link.

Bury, C.S.,  I. Carmichael, and E.F. Garman. "OH Cleavage from Tyrosine: Debunking a Myth." J. Synchrotron Rad 24 (2017): 7-18. link

Turney, T., Q. Pan, L. Sernau, I. Carmichael, W. Zhang, X. Wang, R. Woods, and A.S. Serianni. "O-Acetyl Side-Chains in Saccharides: Redundant NMR Spin-Couplings and Statistical Models for Acetate Ester Conformational Analysis." J. Phys. Chem. B 121 (2017):66-77. link

Li, Z., M.M. Dawley, I. Carmichael, and S. Ptasińska. "Electron Induced Fragmentation of Methylated Formamides." Int. J. Mass Spectrom 410 (2016): 36-46. link

Bury, C.S., I. Carmichael, J.E. McGeehan, and E.F. Garman. "Radiation Damage with Nucleoprotein Complexes Studied by Macromolecular X-ray Crystallography."  Radiat. Phys. Chem. 128 (2016): 118-25. link

Bury, C.S., J.E. McGeehan, A. Antson, I. Carmichael, M. Gerstel, M. Shevtsov, and E.F. Garman. "RNA Protects a Nucleoprotein Complex against Radiation Damage." Acta Crystallogr. D 72 (2016): 648-57. link

 

Full List of Publications

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