@article{franzen_bailey_dyer_woodruff_hu_thomas_boxer_2001, title={A photolysis-triggered heme ligand switch in H93G myoglobin}, volume={40}, ISSN={["0006-2960"]}, DOI={10.1021/bi0023403}, abstractNote={Resonance Raman spectroscopy and step-scan Fourier transform infrared (FTIR) spectroscopy have been used to identify the ligation state of ferrous heme iron for the H93G proximal cavity mutant of myoglobin in the absence of exogenous ligand on the proximal side. Preparation of the H93G mutant of myoglobin has been previously reported for a variety of axial ligands to the heme iron (e.g., substituted pyridines and imidazoles) [DePillis, G., Decatur, S. M., Barrick, D., and Boxer, S. G. (1994) J. Am. Chem. Soc. 116, 6981-6982]. The present study examines the ligation states of heme in preparations of the H93G myoglobin with no exogenous ligand. In the deoxy form of H93G, resonance Raman spectroscopic evidence shows water to be the axial (fifth) ligand to the deoxy heme iron. Analysis of the infrared C-O and Raman Fe-C stretching frequencies for the CO adduct indicates that it is six-coordinate with a histidine trans ligand. Following photolysis of CO, a time-dependent change in ligation is evident in both step-scan FTIR and saturation resonance Raman spectra, leading to the conclusion that a conformationally driven ligand switch exists in the H93G protein. In the absence of exogenous nitrogenous ligands, the CO trans effect stabilizes endogenous histidine ligation, while conformational strain favors the dissociation of histidine following photolysis of CO. The replacement of histidine by water in the five-coordinate complex is estimated to occur in < 5 micros. The results demonstrate that the H93G myoglobin cavity mutant has potential utility as a model system for studying the conformational energetics of ligand switching in heme proteins such as those observed in nitrite reductase, guanylyl cyclase, and possibly cytochrome c oxidase.}, number={17}, journal={BIOCHEMISTRY}, author={Franzen, S and Bailey, J and Dyer, RB and Woodruff, WH and Hu, RB and Thomas, MR and Boxer, SG}, year={2001}, month={May}, pages={5299–5305} }
 @article{franzen_miskowski_shreve_wallace-williams_woodruff_ondrias_barr_moore_boxer_2001, title={Electrostatic and conformational effects on the electronic structures of distortional isomers of a mixed-valence binuclear Cu complex}, volume={40}, ISSN={["0020-1669"]}, DOI={10.1021/ic010494g}, abstractNote={The electronic structure of the binuclear copper complex [Cu(2)(L)](3+) [L = N(CH(2)CH(2)N(H)CH(2)CH(2)N(H)CH(2)CH(2))(3)N] has been investigated by resonance Raman and electroabsorption spectroscopy. Crystallographic Cu(2) distances of 2.364(1) and 2.415(1) A determined for the nitrate and acetate salts, respectively, are consistent with a substantial metal-metal interaction. The Cu-Cu bonding interaction in the binuclear complex is modulated both in the solid state and in solution by the ligand environment through coupling to ligand torsional modes that are, in turn, stabilized by hydrogen bonding. Electroabsorption data on the three major visible and near-infrared electronic transitions of Cu(2)L, lambda(max) (epsilon(max)) = 1000 nm ( approximately 1200 M(-1) cm(-1)), 748 nm (5600 M(-1) cm(-1)), and 622 nm (3350 M(-1) cm(-1)), reveal a difference dipole moment between the ground and excited states (Deltamu(A)) because of symmetry breaking. The difference polarizability for all three of the transitions is negative, indicating that the ground state is more polarizable than the excited state. A general model to explain this behavior in terms of the proximity of accessible transitions involving copper d electrons is proposed to explain the larger polarizability of the ground state. Raman excitation profiles (REPs) provide evidence for multiple conformational states of [Cu(2)(L)](3+). Separate REPs were obtained for each of the components of the two major Raman bands for nu(1) (a Cu-Cu stretching mode) and nu(2) (a Cu-Cu-N(eq) bending mode). The Raman data along with quantum chemical ZINDO/S CI calculations provide evidence for isomeric forms of Cu(2)L with strong coupling between the conformation of L and the Cu-Cu bond length.}, number={25}, journal={INORGANIC CHEMISTRY}, author={Franzen, S and Miskowski, VM and Shreve, AP and Wallace-Williams, SE and Woodruff, WH and Ondrias, MR and Barr, ME and Moore, L and Boxer, SG}, year={2001}, month={Dec}, pages={6375–6382} }
 @article{franzen_boxer_dyer_woodruff_2000, title={Resonance Raman studies of heme axial ligation in H93G myoglobin}, volume={104}, number={44}, journal={Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces & Biophysical}, author={Franzen, S. and Boxer, S. G. and Dyer, R. B. and Woodruff, W. H.}, year={2000}, pages={10359–10367} }
 @article{miskowski_franzen_shreve_ondrias_wallace-williams_barr_woodruff_1999, title={Distortional isomers of a mixed-valence binuclear Cu complex}, volume={38}, ISSN={["0020-1669"]}, DOI={10.1021/ic981415c}, abstractNote={The resonance Raman spectra of a mixed-valence copper dimer [Cu2(L)]3+ encapsulated by the ligand L = N(CH2CH2N(H)CH2CH2N(H)CH2CH2)3N are reported. Copper isotope data (63/65Cu) of solution spectra of [Cu2(L)]3+ allow identification of vibrational bands at 289 and 172 cm-1 as predominately Cu−Cu stretching and Cu−Cu−Neq bending modes. The results indicate that the Cu−Cu bond is sufficiently weak that ligand conformations, influenced by hydrogen bonding, can give rise to distortional isomers of the Cu−Cu bond.}, number={11}, journal={INORGANIC CHEMISTRY}, author={Miskowski, VM and Franzen, S and Shreve, AP and Ondrias, MR and Wallace-Williams, SE and Barr, ME and Woodruff, WH}, year={1999}, month={May}, pages={2546–2547} }