Professor Douglas P. Ridge

Physical Chemistry

Current Research

Exploration of the frontiers of our knowledge of chemical structure and reactivity and the latest developments in the technology of mass spectrometry, in particular Fourier transform mass spectrometry (FTMS) come together in a complementary way in Ridge's research. FTMS involves trapping ions formed by electron impact, laser desorption or electrospray ionization and measuring the frequency of the cyclotron motion of the trapped ions. This facilitates very accurate high resolution mass measurements. In addition the trapped ions can be photoactivated or activated by chemical reaction or high energy collisions with pulses of neutrals introduced into the ion trap. Studies of peptides and proteins provide not only accurate mass information but sequence and secondary structure information.

Recent work has shown that linkage isomers of peptides can be distinguished using collision induced decomposition. Ion molecule reactions studies have demonstrated the persistence of helical secondary structure of selected peptides on electrospray ionization, provided information on the energetics of intramolecular hydrogen bonding in amino acids, and elucidated details of the mechanisms of metabolic processes relevant to the toxicity of halogenated industrial wastes.

Investigation of the potential of electron attachment as a means of activating multiply charged peptide ions is under way. FTMS examination of protein-RNA non-covalent complexes promises to characterize bonding between the protein and RNA. Studies of metals and metal ions have led to measurement of the binding energy of NO to several metalloporphyrins including heme, and a demonstration of the application of organometallic ion-molecule reactions to the determination of the molecular weight distributions of polyolefins. Another problem of environmental interest studied recently is the complexation of potentially toxic metals with sulfides in river water. Particularly exciting is the recent demonstration that IR multiphoton dissociation, IRMPD, vibrational spectra of trapped metal clusters not otherwise observable can be obtained using FTMS and a tunable free electron laser, opening the door to structural investigations of a rich variety of reactive and interesting species.

Representative Publications

D. T. Moore, J. Oomens, J. R. Eyler, G. von Helden, G. Meijer and D. P. Ridge "Determining Structures for Small, Anionic Iron Carbonyl Clusters by Gas-Phase Infrared Spectroscopy," J. Amer. Chem. Soc., (2004) 126, 14726 – 14727.
N. C. Luu, S. Robinson, R. Zhao, R. McKean and D. P. Ridge "Mass spectrometric differentiation of α and β aspartic acid in a pseudo-tetrapeptide thrombosis inhibitor," Eur. J. Mass Spectrom., (2004) 10, 279 – 288.
M. H. C. Byrd, C. M. Guttman and D. P. Ridge "Molecular Mass Determination of Saturated Hydrocarbons: Reactivity of η5- cyclopentadienylcobalt ion (CpCo+) with Linear Alkanes up to C-30,"
J. Amer. Soc. for Mass Spec., (2003) 14, 51 – 57.
R. D. Kinser, G. Nicol and D. P. Ridge "The Proton Affinity and Entropy of Protonation of Lysinamide. The Effects of Intramolecular Proton Solvation," J. Phys. Chem. A, (2002) 106, 9925 – 9929.
T. F. Rozan, M. E. Lassman, D. P. Ridge and G. W. Luther III "Evidence for Iron, Copper and Zinc Complexation as Multinuclear Sulfide Clusters in Oxic Rivers," Nature, (2000) 406, 879 – 882.
N. C. Luu, R. A. Iyer, M. W. Anders and D.P. Ridge "Bioactivation Mechanisms of Haloalkene Cysteine
S-Conjugates Modeled by Gas- Phase, Ion-Molecule Reactions," Chemical Research Toxicology, (2000) 13, 610 – 615.
O. Chen, S. Groh, A. Liechty and D. P. Ridge "Binding of Nitric Oxide to Iron(II) Porphyrins: Radiative Association, Blackbody Infrared Radiative Dissociation and Gas-Phase Association Equilibrium," J. Amer. Chem. Soc., (1999) 121, 11910 – 11911.