| AUTHOR |
TITLE |
Baldwin, M. J.,
Law, N. A.,
Stemmler, T. L.,
Kampf, J. W.,
Penner-Hahn, J. E.,
Pecoraro, V. L. |
Reactivity of [{MnIV(salpn)}2(µ-O,µ-OCH3)]+ and [{MnIV(salpn)}2(µ-O,µ-OH)]+: Effects of Proton Lability and Hydrogen Bonding
Inorganic Chemistry; 1999; 38(21); 4801-4809. |
| Experimental Section Methods.
Spectra of unstable solutions (such as 4 and [{MnIV(salpn)}2(µ-OH,µ-OCH3)](CF3SO3)2, 5) were collected by mixing reactants with an OLIS stopped-flow apparatus and collecting spectra of the initial mixture within 10 ms, prior to decomposition, using an OLIS rapid-scanning monochromator. This same system was used for collecting rapid kinetic data for the reactions of 3 with various bases. Typical experiments mixed a 0.1 mM solution of 3 in CH3CN with a 5 mM solution of base in CH3CN. In experiments with added H2O or D2O, 0.1% (55 mM) water was added to the solution of 3 prior to introduction of the samples to the stopped-flow apparatus. Comparison of the relative overall reaction rates was accomplished by fitting the data to a simple single-exponential decay. |
Gelasco, A.,
Bensiek, S.,
Pecoraro, V. L. |
The [Mn2(2-OHsalpn)2]2-,1-,0 System: An Efficient Functional Model for the Reactivity and Inactivation of the Manganese Catalases
Inorganic Chemistry; 1998; 37(13); 3301-3309. (Article) |
Experimental Section<
Initial Rate Measurements.
UV-visible spectra were measured on a Perkin-Elmer lambda 9 dual beam scanning spectrophotometer, with scan rates from 240 to 960 nm/min. Additional spectroscopic data were acquired on an OLIS-RSM stopped-flow spectrometer at a scan rate of 1-10 full spectrum scans/s. |
Hamstra, B. J.,
Colpas, G. J.,
Pecoraro, V. L. |
Reactivity of Dioxovanadium(V) Complexes with Hydrogen Peroxide: Implications for Vanadium Haloperoxidase
Inorganic Chemistry; 1998; 37(5); 949-955. (Article) |
Experimental Section
All reactions were performed on an OLIS RSM-SF rapid-scan stopped-flow spectrophotometer at a temperature of 25.0 ± 0.1 °C, and the resulting data were fit using the software package provided with the OLIS RSM-SF. Initial rate data (< 20% of reaction) were fit to a line using the general equation y = mx + b, and reaction curves were obtained under pseudo-first-order conditions for the general equation y = a exp(bx) + c. Rates obtained by these methods were compared to each other and to the results of global fitting routines also found in the software package provided with the OLIS RSM-SF, and all were consistent within experimental error. Kinetic parameters and equilibrium constants were obtained from plots of observed rates vs concentrations and fit using the curve-fitting routines in the program Kaleidagraph. |
Caudle, M. T.,
Riggs-Gelasco, P.,
Gelasco, A. K.,
Penner-Hahn, J. E.,
Pecoraro, V. L. |
Mechanism for the Homolytic Cleavage of Alkyl Hydroperoxides by the Manganese(III) Dimer MnIII2(2-OHsalpn)2
Inorganic Chemistry; 1996; 35(12); 3577-3584. (Article) |
Experimental Section
Materials and Equipment.
UV-visible kinetic studies were performed at 25 °C on an OLIS RSM-1000 rapid-scanning stopped-flow device. |
Demadis, K. D.,
Meyer, T. J.
, White, P. S. |
Reactivity of Osmium(VI) Nitrides with the Azide Ion. A New Synthetic Route to Osmium(II) Polypyridyl Complexes
Inorganic Chemistry; 1998; 37(14); 3610-3619. (Article) |
Experimental Section
Physical Measurements and Instrumentation. Electronic absorption spectra were recorded on Beckman 2000, OLIS-modified Cary 14, or Hewlett-Packard 8452A diode array UV-visible spectrophotometers in quartz cuvettes. Electrochemical measurements were carried out in CH3CN solutions with 0.1 M TBAH as the supporting electrolyte or in aqueous solutions of varying ionic compositions. |
Brian T. Farrer,
H. Holden Thorp |
Redox Pathways in DNA Oxidation: Kinetic Studies of Guanine and Sugar Oxidation by Para-Substituted Derivatives of Oxoruthenium(IV)
Inorganic Chemistry; 1999; ASAP Article |
| Kinetics. The reaction of the ruthenium oxo species with guanine 5'-monophosphate was monitored using an OLIS-RSM stopped-flow spectrophotometer scanning at 32 scans/s for 10 s. The reactions were carried out in 50 mM phosphate buffer (pH 7). The reactions were observed to be first order with respect to [5'-GMP], and rate constants were obtained from plotting the initial rate vs [5'-GMP] and taking the slope to be k[RuO2+]. Initial rates were obtained by using the kinetic trace at the Ru(II)/Ru(III) isosbestic point around 410 nm, allowing the loss of RuO2+ to be observed directly. d[RuO2+]/dt was obtained from dA/dt using the relation d[RuO2+]/dt = -{1/[(εII - εIV)b]} dA/dt. Here εII and εIV are the extinction coefficients of Ru(II)OH22+ and Ru(IV)O2+, respectively, and b is the path length of the cell (1.8 cm). The kinetics of 2'-deoxycytidine 5'-monophosphate oxidation were also followed using an Olis-RSM spectrophotometer. Data were collected over 30 min taking 1 scan/s in 50 mM phosphate buffer (pH 7). |
Farrer, B. T.,
Thorp, H. H. |
Driving Force and Isotope Dependence of the Kinetics of Proton-Coupled Electron Transfer in Oxoruthenium(IV) Polypyridyl Complexes
Inorganic Chemistry; 1999; 38(10); 2497-2502. |
| Measurements. Stopped-flow experiments were carried out at 298 ± 1 K on an OLIS-RSM stopped-flow apparatus. Scans were taken at the rate of 1000 scans/s, obtaining data from 350 to 550 nm for 1-5 s. Solutions of the metal-oxo complexes were prepared by dissolving a small amount of RuO2+ solid in 50 mM sodium phosphate buffer (pH 7.8). Half of this solution was held at a potential of +0.85 V (vs Ag/AgCl, Pt wire counter, vitreous carbon working) to ensure the absence of lower oxidation state Ru. The remaining half was reduced to RuOH22+ via bulk electrolysis by holding at a potential of 0.0 V (vs Ag/AgCl, Pt wire counter, vitreous carbon working) to ensure absence of higher oxidation state complexes. Both solutions were diluted using buffer to obtain final concentrations. The solutions were then frozen in liquid nitrogen until just prior to use to preserve the integrity of the oxidation state. Freezing the solutions is more important for the RuO2+ because it is less stable than RuOH22+. |
Macatangay, A. V.,
Mazzetto, S. E.,
Endicott, J. F. |
Ground-State, Mode-Dependent Vibronic Coupling in Some Simple, Cyanide-Bridged Transition-Metal Donor-Acceptor Complexes
Inorganic Chemistry; 1999; 38(22); 5091-5101. |
Experimental Procedures
B. Spectroscopic Measurements. Most of the experimental procedures have been described in detail previously.1-3,33 Ultraviolet, visible, and near-infrared spectra of the ruthenated complexes were obtained in distilled water on an OLIS-modified Cary-14 spectrophotometer controlled by a Gateway 486/33 PC. |
Arzberger, S.,
Soper, J.,
Anderson, O. P.,
la Cour, A.,
Wicholas, M. |
Synthesis and Structure of an Air-Stable, Free-Radical Cobalt(III) Semiquinone Complex
Inorganic Chemistry; 1999; 38(4); 757-761. |
Experimental Section
Instrumentation. Infrared spectra were recorded from 4000 to 400 cm-1 with a Mattson Galaxy 5000 FTIR spectrometer. Electronic spectra were obtained from 220 to 2500 nm using an HP 8452 diode array spectrometer and an Olis-modified Cary 14 spectrophotometer. Magnetic susceptibility was measured with a Johnson Matthey Magnetic Susceptibility balance. The EPR spectrum was obtained with a Bruker ECS spectrometer at 9.5 GHz at the University of British Columbia. Elemental analyses were performed by Quantitative Technologies, Inc. |
He, Q.-Y.,
Mason, A. B.,
Pakdaman, R.,
Chasteen, N. D.,
Dixon, B. K.,
Tam, B. M.,
Nguyen, V.,
MacGillivray, R. T. A.,
Woodworth, R. C. |
Mutations at the Histidine 249 Ligand Profoundly Alter the Spectral and Iron-Binding Properties of Human Serum Transferrin N-Lobe
Biochemistry; 2000; ASAP Article |
Materials and Methods
Absorption Spectra. UV-vis spectra were recorded on a Cary 219 spectrophotometer under the control of the computer program Olis-219s (On-line Instrument Systems, Inc., Bogart, GA). The appropriate buffer served as the reference for full-range spectra from 250 to 600 nm. Difference spectra were generated by storing the spectrum of the apo-protein as the baseline and subtracting it from the sample spectra.
Anion-Exchange and Iron-Uptake Kinetics. Anion-exchange and iron-uptake experiments were also performed with the Olis-RSM 1000 stopped-flow spectrophotometer in 50 mM Hepes, pH 7.4. For anion exchange, the reaction was monitored by scanning full-scale spectra (460 ± 115 nm) over time and the resulting 3D data were processed using a global-fitting function (Olis) to determine the kinetic changes of all species. |
