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![[Figure 5]](ms5002fig5mag.jpg)
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Figure 5
Alexa radiolysis and determination of X-ray dose. (a) Dose response plot of 1.0 µM Alexa 488 in 10 mM sodium cacodylate pH 7.0 buffer containing 0.1 mM EDTA irradiated with synchrotron X-rays at 190–220 mA beam current. After exposure the Alexa is diluted (1:500) prior to fluorescence analysis. A Turner Biosystems TBS-380 fluorometer is used to determine the emission intensity at 516 nm with an excitation wavelength of 496 nm. The solid line represents the fitting of data to a first-order reaction kinetics. The insets in the top right and the bottom left corners show the dye structure and the decrease in fluorescent emission caused by irradiation at different times, respectively. (b) Rate constant of 1.0 µM Alexa 488 in 10 mM sodium cacodylate pH 7.0 buffer without EDTA as a function of the beam current. The solid line represents the linear fit with a slope of 0.41 ± 0.03 s−1 mA−1. (c) Dose response plots of 1.0 µM Alexa 488 in 10 mM of different buffers. (d) Rate constant of radiolytic degradation of 1.0 µM Alexa 488 in 10 mM sodium cacodylate pH 7.0 buffer with addition of MgCl2, ATP, glycerol and EDTA at different concentrations. The connections between the points are represented by respective spline-lines. |
![[Figure 5]](ms5002fig5.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
