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# Quantification of Radiation-Induced Hydroxyl Radicals within Nucleohistones Using a Molecular Fluorescent Probe

G. M. Makrigiorgos, M. Folkard, C. Huang, E. Bump, J. Baranowska-Kortylewicz, S. K. Sahu, B. D. Michael and A. I. Kassis
Vol. 138, No. 2 (May, 1994), pp. 177-185
DOI: 10.2307/3578587
Stable URL: http://www.jstor.org/stable/3578587
Page Count: 9
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## Abstract

We present a method that specifically records ${}^{\bullet}{\rm OH}$ formation within histones and possibly at other sites in irradiated nucleohistone. The approach uses the radiation-induced fluorescence emissions from a chromatin-conjugated ${}^{\bullet}{\rm OH}$ detector, SECCA (a succinylated derivative of coumarin), that is converted to a fluorescent derivative, 7-hydroxy-SECCA (7-OH-SECCA), after interaction with ${}^{\bullet}{\rm OH}$ in neutral aqueous solutions. It is shown that (a) the fluorescent product 7-OH-SECCA cannot be generated by direct radiation effects after γ or neutron irradiation of SECCA; (b) when SECCA-labeled histone is complexed with DNA to form nucleohistone, the physical properties of the modified nucleohistone are similar to those of unlabeled nucleoprotein; and (c) after irradiation of SECCA-labeled nucleohistone, a linear induction of the fluorescence signal is observed within the radiation doses examined (0.3-30 Gy). Since the sample remains available for further studies after registration of the optical signal, the current approach should permit the investigator to correlate in a single sample the localization and frequency of ${}^{\bullet}{\rm OH}$ formation with the results of other assays.

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