Figure 2. Anaerobic reduction of ZmCKX1 with cytokinins.

Using a stopped-flow instrument equipped with a photodiode array detector, spectral data were obtained upon anaerobic mixing of ZmCKX1 with cytokinin substrates. The spectral species shown were derived from global analysis of the data obtained. The data could be fitted using a model in which species A decays in an exponential fashion to form B (A→B). If needed, more exponential decay steps were included in the model. Typically, 23 μM ZmCKX1 was mixed with 0.5 mM of a cytokinin substrate (except for N-methyl-isopentenyladenine and kinetin where 0.25 mM was used) under anaerobic conditions in 75 mM imidazole/HCl (pH 6.5) at 25 °C. The deconvoluted spectra are shown for: (a) isopentenyladenine, (b) trans-zeatin, (c) N-methyl-isopentenyladenine, (d) kinetin, and (e) p-topolin. For p-topolin (e), spectra of species B obtained with 75 mM Tris/HCl (pH 7.5; broken line) and (pH 8.5; dotted line) are shown. Time courses obtained by global analyses for the respective species are shown in the insets. For experimental details see the Materials and methods section.