Stopped-flow rapid scan spectra

Similarly, the spectrum of a mixture of Fe(tpps)H20 and Fe(tpps)(OH) can be measured by rapid scan/stopped-flow at various pH s within a few milliseconds after generation (Fig. 3.9). In this short time, dimerization is unimportant so that the spectrum of Fe(tpps)OH can be measured and the pAi of Fe(tpps)H20 estimated. 

Fig. 1. Rapid-scanning stoppcd-flow (RSSF) study of the reaction ofN-furylacryloylr-tryptophan methyl ester (FATME) with a-chymotrypsin (a-Ct) at pH 5.0 in the absence and presence of proflavin. (A) RSSF difference spectra for the reaction of 19 pM a-Ctwith 7.5 pM FATME in 0.1 M pH 5.0 sodium acetate buffer at 25°. Spectrum 0 is 7.5 pM free FATME, spectra 1 -5 are difference spectra measured during reaction wherein the spectrum of a-Ct has been subtracted from the set. Spectrum 6 is the spectrum of the hydrolysis product furylacryloyl i-tryptophan with the spectrum of a-Ct removed by subtraction. Spectra were measured at the following time intervals after flow had stopped (1) 8.54, (2) 162.3, (3) 341.6 (4) 1409.1 and (5) 3074.4 ms. Spectrum 6, t = oo.

Fig. 11. Rapid-scanning, stopped-flow data comparing the accumulation of transient intermediates during the reaction of 8 mM z>i-[a- H]-serine (A) and 8 mM o/.-[a-2H]-serine (B) with 13.3 M a232 from E. coli. The trace designated 0 is the reconstructed spectrum of the reactants before mixing. The insets to both (A) and (B) are 460-nm reaction time courses reconstructed from the RSSF data. Each experiment was conducted using 0.1 M potassium phosphate and 1 mM EDTA buffer at pH 7.80 and25°C. All conditions refer to concentrations immediately after mixing. The initiation of scanning in both (A) and (B) occurred 2 ms after flow stopped. Scans 2 through 19 were collected at 4.7, 9.3, 14.0, 18.7,23.4,28.0,32.7,42.0,51.4,60.7,70.1,107, 154,247,387, 761, 1135, and 1980 ms after the first scan, respectively, with a repetitive scan rate of 4.7 ms/scan. [Taken from Drewe and Dunn (85) with permission.]...

Fig. 16. Rapid-scanning data for the reactions of 5 mM indole (A) and 5 mM benzimidazole (B) with 17.2 iM tryptophan indole-lyase (tryptophanase) that has been preequilibrated with 0.25mM t-alanine. i-Alanine was premixed in both syringes to prevent unwanted concentration changes. In panel A, scans were collected at 15,92.5,170,247.5, 325,402.5,480,557.5, 635, 712.5, 790,867.5, and 945 ms after flow stopped. Spectrum 0 represents the spectrum of the enzyme-alanine complex before mixing with indole. In panel B, scans were collected at 15, 390, 765, 1140, 1515, 1890, 2265,2640, 3015,3390, 3765, and 4140 ms after mixing. Spectrum 0 represents the enzyme-alanine complex before mixing with benzimidazole. [Taken from Phillips (104) with permission.]...

Fig. 17. Rapid-scanning data for the reaction of 20.9 pM tryptophanase with 20 mM S-ethyl-i-cysteine in the absence (A) and presence (B) of 5 mM benzimidazole. Spectra shown in both(A) and (B)were collected atlO, 31,52,73,94,115,136,157,178,199,220, 241, and 262 ms after flow stopped. Curve 0 is the spectrum of the native enzyme in the absence of substrates. [Taken from Phillips (104) with permission.]...

Fig. 20. Rapid-scanning, stopped-flow spectra (A), difference spectra (B), and singlewavelength, stopped-flow time courses at 300, 422, and 485 nm (C, D, E) for the y-elimination reaction of CGS with OSH S. Data were obtained as described in Figure 19. All concentrations refer to conditions immediately after mixing [OSHS] = lOmM, [CGS] = 6.25 pM, 0.1 M potassium phosphate, 1 mM EDTA, pH 7.2 at 25°C. (A) RSSF spectra, Trace 0 is the spectrum of the enzyme in the absence of substrates. The initiation of scanning occurred 1.3 ms after flow stopped. Spectra shown were collected at 1.3,10.2, 19.1, 28.0, 36.9, 72.5, 117.0, 161.5, 250.5, 392.9, and 695.5 ms after flow stopped. (B) Difference spectra were computed as (scan)t-(scan)0 from the data presented in (A). Singlewavelength time courses (C-E) were collected in SWSF experiments under conditions identical with those described for (A). [Taken from Brzovic et al. (107) with permission.]...

In Fig. 8, the UV-Vis spectral changes that occurred upon mixing aqueous solutions of 1 and H2O2 in the chamber of the stopped-flow instrument equipped with a rapid scan spectroscopic attachment are reported as a ftmction of time. The final spectrum of the reaction solution is in good agreement with the spectrum of [Ru (edta)0)] Umax=391nm, emax=8000M cm )... 

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