| AUTHOR |
TITLE |
Bruice, T.C.,
Tsubouchi, A.,
Dempcy, R. O.,
Olson, L. P. |
One- and Two-Metal Ion Catalysis of the Hydrolysis of Adenosine 3'-Alkyl Phosphate Esters. Models for One- and Two-Metal Ion Catalysis of RNA Hydrolysis
Journal of the American Chemical Society; 1996; 118(41); 9867-9875. (Article) |
Experimental Section.
Kinetic Measurements.
The rates of the hydrolysis of 1a in the presence of La3+ were measured by the stopped-flow method using an OLIS RSM-1000 rapid-scanning stopped-flow system thermostated at 30 °C. One driving syringe contained LaCl3 in buffer solution (0.1 M), and the other driving syringe contained the substrate (20 μM) in the same buffer solution (0.1 M). Ionic strength was held constant at 1.0 with KCl. The reactions were followed by monitoring the change of the absorbance at 260 nm. The collected data points were fit to theoretical curves by software written for OLIS RSM (rapid-scanning monochromator) to give the pseudo-first-order rate constants. |
Bourassa, J.,
DeGraff, W.,
Kudo, S.,
Wink, D. A.,
Mitchell, J. B.,
Ford, P. C.
|
Photochemistry of Roussin's Red Salt, Na2[Fe2S2(NO)4], and of Roussin's Black Salt, NH4[Fe4S3(NO)7]. In Situ Nitric Oxide Generation To Sensitize -Radiation Induced Cell Death1
Journal of the American Chemical Society; 1997; 119(12); 2853-2860. (Article) |
Experimental Section.
Instruments. UV-vis absorption spectra were obtained with either a HP8572 diode array or a Cary 118 spectrophotometer modernized by OLIS. |
Bernasconi, C.F.,
Leyes, A.E. |
Physical Organic Chemistry of Transition Metal Carbene Complexes. 9.1 Thermodynamic and Kinetic Acidity of (2-Oxacyclopentylidene)pentacarbonylchromium(0) in Aqueous Acetonitrile
Journal of the American Chemical Society; 1997; 119(22); 5169-5175. (Article) |
Experimental Section.
Kinetics and Spectra.
The time-dependent spectra shown in Figure 1 were taken on a Durrum-Gibson stopped-flow apparatus equipped with an OLIS RSM 1000 rapid scan spectrophotometer.
Figure 1 text: Time-dependent absorption spectra for the deprotonation of 7.5 x 10-5 M 3 by 0.14 M Me4NOH in 50% MeCN-50% water. Spectra taken at 16-ms intervals. |
Mustafi, D.,
Knock, M. M.,
Shaw, R. W.,
Makinen, M. W. |
Conformational Changes in Spin-Labeled Cephalosporin and Penicillin upon Hydrolysis Revealed by Electron Nuclear Double Resonance Spectroscopy
Journal of the American Chemical Society; 1997; 119(51); 12619-12628. (Article) |
Experimental Procedures
Enzyme Kinetics
The change in absorbance at 264 nm for CEP-C (Δ = 7344 M-1 cm-1) or for SLCEP ( Δ= 3589 M-1 cm-1) due to hydrolysis of the  -lactam group was followed with a Cary 15 spectrophotometer modified by On-Line Instrument Systems, Inc. (Jefferson, GA 30549) for microprocessor controlled data acquisition. |
Hoober, K. L.,
Thorpe, C. |
Egg White Sulfhydryl Oxidase: Kinetic Mechanism of the Catalysis of Disulfide Bond Formation
Biochemistry; 1999; 38(10); 3211-3217. |
Materials and Methods
>Stopped-Flow Spectrophotometry. Reactions were followed at 4 °C in a kinetic instruments stopped-flow spectrophotometer equipped with a 2 cm path length cell using peripherals and software from On-line Instruments Systems. |
DuPlessis, E. R.,
Pellett, J.,
Stankovich, M. T.,
Thorpe, C. |
Oxidase Activity of the Acyl-CoA Dehydrogenases
Biochemistry; 1998; 37(29); 10469-10477. (Article) |
Materials and Methods
Stopped-Flow Spectrophotometry. A Kinetics Instruments stopped-flow instrument equipped with a 2-cm path length cell was prepared for anaerobiosis as described previously (41). Data acquisition and analysis software was from On-Line Instuments Systems, Inc. Standard buffers were bubbled for 2 h at 25 ºC with nitrogen, air, or oxygen as needed. Intermediate oxygen concentrations were prepared immediately before use by mixing volumes of these solutions containing the appropriate ligand concentrations, taking care to avoid gas bubbles and exposure to the atmosphere. Sodium dithionite or photoreduced enzyme was prepared anaerobically in tonometers and loaded onto the stopped-flow as before (41). All concentrations are quoted after mixing. |
Rudik, I.,
Ghisla, S.,
Thorpe, C. |
Protonic Equilibria in the Reductive Half-Reaction of the Medium-Chain Acyl-CoA Dehydrogenase
Biochemistry; 1998; 37(23); 8437-8445. (Article) |
Materials and Methods
General Methods.
Rapid reaction experiments were performed using a Kinetic Instruments stopped-flow spectrophotometer with peripherals and software for data acquisition and fitting from On-line Instruments Systems. All experiments were performed at 4 °C. |
Sloan, M. J.,
Phillips, R.S. |
Effects of -Deuteration and of Aza and Thia Analogs of l-Tryptophan on Formation of Intermediates in the Reaction of Escherichia coli Tryptophan Indole-lyase
Biochemistry; 1996; 35(50); 16165-16173. (Article) |
Experimental Procedures
Pre-Steady-State Kinetic Measurements. Single-wavelength stopped-flow kinetic measurements and rapid-scanning experiments were performed using an RSM spectrophotometer and a stopped-flow compartment with a 18-mm path length observation cell from Olis, Inc. This instrument has a mixing dead time of about 2 ms; thus, a reaction with a rate constant of 350 s-1 will lose about half its amplitude during mixing.
Some of the single-wavelength measurements were performed on a Kinetics Instruments stopped-flow mixer with a modified Cary 14 UV/Vis spectrophotometer (Olis), and preliminary rapid-scanning experiments were performed with a diode array detector from EG&G Princeton Applied Research, as previously described (Phillips, 1991).
Time courses at selected wavelengths were analyzed by fitting with the SIFIT or LMFIT programs (Olis, Inc.), which can fit up to three exponentials with amplitudes and an offset, where At is the absorbance at time t, ai is the amplitude of each phase, ki is the rate constant for each phase, and c is the final absorbance, if non-zero (eq 3).
Robust global analysis of the spectra was performed with the Global Fit program of I. B. C. Matheson, provided by Olis, Inc. (Matheson, 1990; Maeder & Zuberbuhler, 1990). Both single-wavelength fits at several wavelengths and global fits were performed on all sets of data, and the results were judged to be valid when identical values of rate constants were obtained. |
Subramanian, M.,
Jutila, A.,
Kinnunen, P. K. J. |
Binding and Dissociation of Cytochrome c to and from Membranes Containing Acidic Phospholipi
Biochemistry; 1998; 37(5); 1394-1402. (Article) |
Experimental Procedures
Stopped-Flow Fluorescence Measurements. Membrane association and detachment of cyt c were measured in the millisecond to second time range using stopped-flow spectrofluorimeter equipped with a rapid-scanning emission monochromator (On-line Instrument Systems Inc., Bogart, GA) to monitor resonance energy transfer from a pyrene-fatty acid containing phospholipid derivative (fluorescence donor) to the heme (acceptor) of cyt c. Fluorescence excitation was provided by a water-cooled 450 W Xe arc lamp. The 20 mm path length and 1.5 mm diameter quartz glass fluorescence observation chamber was connected to a sample mixing jet having a dead time of 2 ms. Two syringes mounted in parallel were driven pneumatically at a gas pressure of 7 bar to inject the reactants into the rapid-mixing chamber. Temperature of the stopped-flow solution barrels and the flow cell was maintained by a circulating waterbath. |
Zaslavsky, D.,
Sadoski, R.C.,
Wang, K.,
Durham, B.,
Gennis, R. B.,
Millett, F. |
Single Electron Reduction of Cytochrome c Oxidase Compound F: Resolution of Partial Steps by Transient Spectroscopy
Biochemistry; 1998; 37(42); 14910-14916. |
Experimental Section
Flash Photolysis.
All absorbance transients were analyzed using a KINFIT kinetics program obtained from On-line Instruments Systems Inc. |
