@article{el kasmi_leopold_galligan_robertson_saavedra_el kacemi_bowden_2002, title={Adsorptive immobilization of cytochrome c on indium/tin oxide (ITO): electrochemical evidence for electron transfer-induced conformational changes}, volume={4}, ISSN={["1388-2481"]}, DOI={10.1016/S1388-2481(01)00299-5}, abstractNote={The adsorptive immobilization and electrochemistry of horse and yeast cytochrome c on indium/tin oxide (ITO) electrodes is reported. Near-monolayer coverage was achieved in pH 7 phosphate buffers of ionic strength equal to 10 and 50 mM, respectively, for the horse and yeast species. The layers exhibit very well-behaved voltammetry and are stable on the timescale of hours to days. Cyclic voltammetry revealed quasireversible behavior that is a product of both electron transfer (ET) kinetics and ET-induced conformational changes. A square scheme mechanism linking the redox states and the conformational states is proposed. Using a simple ET kinetic model that adequately describes the voltammetry at higher scan rates, a standard ET rate constant of 18s−1 was determined for adsorbed horse cytochrome c. With decreasing scan rate, we observed a limiting peak separation of approximately 10 mV, an example of unusual quasireversibility (UQR) that we attribute to the effect of conformational changes. Finally we note that the intrinsic cytochrome c ET rate on ITO is some 6 orders of magnitude less than for gold.}, number={2}, journal={ELECTROCHEMISTRY COMMUNICATIONS}, author={El Kasmi, A and Leopold, MC and Galligan, R and Robertson, RT and Saavedra, SS and El Kacemi, K and Bowden, EF}, year={2002}, month={Feb}, pages={177–181} }
 @article{leopold_bowden_2002, title={Influence of gold substrate topography on the voltammetry of cytochrome c adsorbed on carboxylic acid terminated self-assembled monolayers}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la011456c}, abstractNote={Interfacial investigations of a protein monolayer electrochemical system, equine cytochrome c (cyt c) adsorbed to carboxylic acid terminated self-assembled monolayer (COOH SAM) modified gold electrodes, were performed. Electrochemical, spectroscopic, and scanning probe microscopy techniques were utilized to explore the influence of gold topography in the cyt c/COOH SAM/gold system. COOH SAMs were prepared from 14-mercaptotetradecanoic acid and 11-mercaptoundecanoic acid on a variety of substrates including evaporated, bulk, single crystal, and epitaxially grown gold on mica. These substrates encompassed a wide range of surface roughness. As the topography of the gold became smoother, SAMs exhibited an increased ability to block a solution probe molecule, indicative of a lower level of defectiveness. At the same time, after exposure to equine cyt c deposition solutions, the extent of adsorption and the magnitude of the electrochemical response of the adsorbed cyt c decreased significantly with increasingly...}, number={6}, journal={LANGMUIR}, author={Leopold, MC and Bowden, EF}, year={2002}, month={Mar}, pages={2239–2245} }
 @article{leopold_black_bowden_2002, title={Influence of gold topography on carboxylic acid terminated self-assembled monolayers}, volume={18}, ISSN={["0743-7463"]}, DOI={10.1021/la011683e}, abstractNote={Film permeability and double layer capacitance (Cdl) results are reported for mercaptotetradecanoic acid self-assembled monolayers (C13COOH SAMs) on gold substrates spanning a range of topography. Whereas film permeability was observed to decrease with increasing substrate smoothness, indicative of lower defect density in the SAMs, the capacitance, unexpectedly, was observed to increase as the topography became smoother. To explain these results, a simple structural model is proposed in which the extent of hydrogen bonding (H-bonding) among carboxylic acid endgroups is related to the underlying gold substrate topography. The model predicts that more extensive H-bonding will occur as substrates become smoother which, in turn, impacts the dielectric properties of the film. The model also provides an explanation for the discordant pKa results that have heretofore been reported for COOH SAMs. Altered surface acidity of up to 3 pKa units appears to be attributable to substrate topography.}, number={4}, journal={LANGMUIR}, author={Leopold, MC and Black, JA and Bowden, EF}, year={2002}, month={Feb}, pages={978–980} }
 @article{goldstein_leopold_huang_atwood_saunders_hartshorn_lim_faget_muffat_scarpa_et al._2000, title={3-Hydroxykynurenine and 3-hydroxyanthranilic acid generate hydrogen peroxide and promote alpha-crystallin cross-linking by metal ion reduction}, volume={39}, ISSN={["0006-2960"]}, DOI={10.1021/bi992997s}, abstractNote={The kynurenine pathway catabolite 3-hydroxykynurenine (3HK) and redox-active metals such as copper and iron are implicated in cataractogenesis. Here we investigate the reaction of kynurenine pathway catabolites with copper and iron, as well as interactions with the major lenticular structural proteins, the alpha-crystallins. The o-aminophenol kynurenine catabolites 3HK and 3-hydroxyanthranilic acid (3HAA) reduced Cu(II)>Fe(III) to Cu(I) and Fe(II), respectively, whereas quinolinic acid and the nonphenolic kynurenine catabolites kynurenine and anthranilic acid did not reduce either metal. Both 3HK and 3HAA generated superoxide and hydrogen peroxide in a copper-dependent manner. In addition, 3HK and 3HAA fostered copper-dependent alpha-crystallin cross-linking. 3HK- or 3HAA-modifed alpha-crystallin showed enhanced redox activity in comparison to unmodified alpha-crystallin or ascorbate-modified alpha-crystallin. These data support the possibility that 3HK and 3HAA may be cofactors in the oxidative damage of proteins, such as alpha-crystallin, through interactions with redox-active metals and especially copper. These findings may have relevance for understanding cataractogenesis and other degenerative conditions in which the kynurenine pathway is activated.}, number={24}, journal={BIOCHEMISTRY}, author={Goldstein, LE and Leopold, MC and Huang, XD and Atwood, CS and Saunders, AJ and Hartshorn, M and Lim, JT and Faget, KY and Muffat, JA and Scarpa, RC and et al.}, year={2000}, month={Jun}, pages={7266–7275} }
 @article{huang_cuajungco_atwood_hartshorn_tyndall_hanson_stokes_leopold_multhaup_goldstein_et al._1999, title={Cu(II) potentiation of Alzheimer A beta neurotoxicity - Correlation with cell-free hydrogen peroxide production and metal reduction}, volume={274}, ISSN={["0021-9258"]}, DOI={10.1074/jbc.274.52.37111}, abstractNote={Oxidative stress markers as well as high concentrations of copper are found in the vicinity of Aβ amyloid deposits in Alzheimer's disease. The neurotoxicity of Aβ in cell culture has been linked to H2O2generation by an unknown mechanism. We now report that Cu(II) markedly potentiates the neurotoxicity exhibited by Aβ in cell culture. The potentiation of toxicity is greatest for Aβ1–42 > Aβ1–40 ≫ mouse/rat Aβ1–40, corresponding to their relative capacities to reduce Cu(II) to Cu(I), form H2O2 in cell-free assays and to exhibit amyloid pathology. The copper complex of Aβ1–42 has a highly positive formal reduction potential (≈+500–550 mV versus Ag/AgCl) characteristic of strongly reducing cuproproteins. These findings suggest that certain redox active metal ions may be important in exacerbating and perhaps facilitating Aβ-mediated oxidative damage in Alzheimer's disease.}, number={52}, journal={JOURNAL OF BIOLOGICAL CHEMISTRY}, author={Huang, XD and Cuajungco, MP and Atwood, CS and Hartshorn, MA and Tyndall, JDA and Hanson, GR and Stokes, KC and Leopold, M and Multhaup, G and Goldstein, LE and et al.}, year={1999}, month={Dec}, pages={37111–37116} }