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Stopped flow studies

Figure 4-12. Stopped-flow study of the pyridine-catalyzed hydrolysis of acetic anhydride, showing the formation and decay of the acetylpyridinium ion intermediate. Initial concentrations were 0.087 M pyridine, 2.1 x im M acetic anhydride the pH was 5.5 ionic strength, 1.0 M temperature, 25 C. Five hundred data points tabsorbance at 280 nm) were measured in I s. The smooth curve is a ht to Eq. (3-27). Source Data of D. Khossravi and S.-F. Hsu, University of Wisconsin. Figure 4-12. Stopped-flow study of the pyridine-catalyzed hydrolysis of acetic anhydride, showing the formation and decay of the acetylpyridinium ion intermediate. Initial concentrations were 0.087 M pyridine, 2.1 x im M acetic anhydride the pH was 5.5 ionic strength, 1.0 M temperature, 25 C. Five hundred data points tabsorbance at 280 nm) were measured in I s. The smooth curve is a ht to Eq. (3-27). Source Data of D. Khossravi and S.-F. Hsu, University of Wisconsin.
Figure 4-12 shows a stopped-flow study of the pyridine-catalyzed hydrolysis of acetic anhydride. The absorbance-time curve reveals tbe formation and decay of the reactive intermediate acetylpyridinium ion. [Pg.180]

A stopped-flow study of the formation of CrOs yielded the following rate law for acidities of 0.01 to 0.05 M... [Pg.284]

Mn(III) perchlorate in HCIO4 oxidises H2O2 with a stoichiometry of 2 Mn(III) 1 H202 . Stopped-flow studies show the reaction to be approximately first-order in both reactants but that the second-order rate coefficient k2 varies as follows... [Pg.369]

A second recent stopped-flow study indicated some enhancement of the initial absorption of Mn(III) at 470 nm on mixing with H2O2, and a complex of formula MnH02 is incorporated into the reaction scheme. The decomposition of this constitutes the rate-determining step (Atj = 80 sec at 25 °C with p. = 4.0 M). k is independent of initial [Mn(riI)]/[H202], of acidity (between 0.5 and 3.7 M) and of temperature. No dependence on [Mn(II)] was looked for. [Pg.369]

A stopped-flow study of the Ce(IV) sulphate oxidations of several of these substances to the corresponding disulphide produced a general rate law... [Pg.394]

A recent stopped-flow study of the autoxidation of the complexes Cu(NH3)2 and Cu(imidazole)2 in aqueous acetonitrile indicates a common rate law ... [Pg.448]

The kinetics of the reaction between metMb and peroxides has attracted attention in studies that have focused on the role of the distal H64 ligand and other amino acid residues present in the distal heme pocket. Brittain et al. reported stopped-flow studies of the reaction of hydrogen peroxide with seven variants in which the distal H64 residue was replaced with a series of residues of var5fing polarity (194). Although the H64Y variant was unreactive toward peroxide, the other... [Pg.25]

In a stopped-flow study on cytochrome cdi from P. aeruginosa, the ferrous d heme-NO species was formed despite electron transfer from the c to the d heme being relatively slow, rate constant approximately 1 s , for the relatively short distance between the two hemes (32). Such a distance would normally predict much faster electron transfer. The relatively slow interheme electron transfer rate has been observed on a number of occasions, and before the structure of the protein was known was thought to reflect the relatively large interheme separation distance and/or relative orientation of the two hemes (30). The crystal structures provide no evidence for either of these proposals there is nothing unusual about the relative orientation of the c and di heme groups. [Pg.181]

Optical Spectroscopy General principles and overview, 246, 13 absorption and circular dichroism spectroscopy of nucleic acid duplexes and triplexes, 246, 19 circular dichroism, 246, 34 bioinorganic spectroscopy, 246, 71 magnetic circular dichroism, 246, 110 low-temperature spectroscopy, 246, 131 rapid-scanning ultraviolet/visible spectroscopy applied in stopped-flow studies, 246, 168 transient absorption spectroscopy in the study of processes and dynamics in biology, 246, 201 hole burning spectroscopy and physics of proteins, 246, 226 ultraviolet/visible spectroelectrochemistry of redox proteins, 246, 701 diode array detection in liquid chromatography, 246, 749. [Pg.6]

Rudolph, R., Holler, E. and Jaenicke, R. 1975. Fluorescence and stop-flow studies on N-F transition of serum albumin. Biophys. Chem. 3, 226-233. [Pg.165]

A wide variety of esters is hydrolyzed with the same Vmax (Table 7.8),37 constant product ratios are found (Table 7.9) stopped-flow studies using p-nitrophenyl phosphate find a burst of 1 mol of p-nitrophenolate ion released per enzyme subunit and the enzyme is covalently labeled by diisopropyl fluorophosphate.38... [Pg.454]

The improvement in the instrumental SNR afforded by the use of polarization modulation has permitted CD detection to be applied to stopped-flow studies of biological reactions. The important information which can be obtained from such an approach has served as an impetus for the development of new instrumental approaches for the measurement of CD. These new approaches have allowed CD measurements to be extended to the time domain below that available with stopped-flow techniques. Presently, nanosecond, and even picosecond CD techniques have been developed, and it seems clear that extension to the sub-picosecond regime will follow. [Pg.50]

LC-NMR data may be acquired in either onflow or stopped-flow modes. In the onflow mode, effluent flows directly from the column through the probe, where spectra are collected at fixed time intervals. Figure 4 shows a typical onflow LC-NMR spectrum.6 In the stopped-flow mode, several fractions are collected and analysed individually at a later time. Although mass spectrometry continues to be the favoured technique for the analysis of combinatorial libraries, the value of LC-NMR was demonstrated in a study by Chin et al.A1 in a stopped-flow study of four positional isomers of dimethoxybenzoylglycine. Iso-molecular-weight mixtures such as this can be problematic to analyse using mass spectrometry however, in this case assignment of the compounds was readily accomplished from the LC-NMR data (Fig. 5). [Pg.122]

Jantschko W, Furtmuller PG, Zederbauer M et al (2005) Reaction of ferrous lactoperoxidase with hydrogen peroxide and dioxygen an anaerobic stopped-flow study. Arch Biochem Biophys 434 51-59... [Pg.310]

Shinosaki and Yonetani (1989), Shinosaki et al. (1994) performed stop-flow studies on tubular transport of uric... [Pg.104]

Shinosaki T, Yonetani Y (1989) Stop-flow studies on tubular transport of uric acid in rats. Adv Exp Med Biol 253A 293-300... [Pg.104]

Robinson and Jencks118,119,165,228 have made detailed kinetic studies of the hydrolysis of several imidazolinium cation derivatives. With the aid of stopped-flow studies, all rate and equilibrium constants shown have been evaluated118,119,228 at 25° for the ring opening of the 1,3-diphenylimid-azolinium cation (63) in aqueous base to N-(2-anilinoethyl) formanilide (64). Kinetic studies165 of the hydrolysis of the N5,10-methenyltetrahydrofolate... [Pg.44]

Interfacial protonation of tetraphenylporphin (TPP) was investigated by means of a two-phase stopped-flow method [7] and a CLM method [10]. The protonation of TPP at the interface, which can be detected from a definite shift in its absorption maximum from 416 to 438 nm, is very fast. The rate of interfacial protonation was spectrophoto-metrically determined from the rate of formation of the protonated TPP at the interface of dodecane/aqueous trichloroacetic acid. The rate of protonation was so fast that the observed rate was governed by the TPP diffusion rate in the organic phase. In the two-phase stopped-flow study, the rate of protonation was observed less than 200 milliseconds after two-phase mixing. The observed first-order rate constant of 19 s , which was independent of both acid and TPP concentrations, was analysed on the basis of the simple diffusion layer model [3] ... [Pg.207]

The most important conclusion from stopped-flow studies is that the rate constants of propagation of several styrene derivatives are approximately kp 105-1 mol, L sec I at 0° C, which is relatively high compared with those of radical and anionic systems (average kp == 102 mol 1L-sec 1 at 0° C). Solvent effects are noticeable, with propagation slower in more nucleophilic 1,2-dichloroethane [17] than in CH2Cl2 [18] under comparable conditions. That is, the carbenium ion reactivity is apparently reduced by interaction with more nucleophilic solvents. However, such interactions do not result in formation of chloronium ions, whose spectra would be very different compared to those of the corresponding carbenium ions. [Pg.196]


See other pages where Stopped flow studies is mentioned: [Pg.2964]    [Pg.323]    [Pg.368]    [Pg.201]    [Pg.207]    [Pg.360]    [Pg.364]    [Pg.573]    [Pg.400]    [Pg.85]    [Pg.106]    [Pg.106]    [Pg.257]    [Pg.423]    [Pg.426]    [Pg.18]    [Pg.565]    [Pg.252]    [Pg.1238]    [Pg.570]    [Pg.198]    [Pg.435]    [Pg.49]    [Pg.85]    [Pg.106]    [Pg.106]    [Pg.14]    [Pg.1092]    [Pg.194]    [Pg.194]    [Pg.212]   


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