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Chemiluminescence concomitant with 1,10-phenanthroline-copper/ascorbate/hydrogen peroxide-induced DNA damage Wenjian Ma En-Hua Cao* (Institute of Biophysics, Academia Sinica, Beijing 100101,P.R.China) *Correspondence should be addressed to: En-Hua Cao Institute of Biophysics Academia Sinica 15 Datun Road, Chaoyang District Beijing 100101, P.R.China Fax: +86-10-62027837 E-mail: caoeh@sun5.ibp.ac.cn Key Words: DNA damage; phenthroline-Cu2+ complex ; oxidative stress; reactive oxygen species; chemiluminescence. Abstract The chemiluminescence(CL) concomitant with Phen-Cu2+/ascorbate/H2O2-induced DNA damage was studied. The emission intensity increases linearly with increasing DNA concentration. An emission spectrum with maximal wavelength at about 410 nm was obtained. The luminescence was inhibited by histone in a histone concentration dependent manner. The CL is characteristic of guanine. Of five common bases only guanine can give rise to luminescence. Investigation of various guanine derivatives show that emission intensity weakens when N7 and O6 guanine methyl derivatives replace guanine, whereas it is enhanced when the N9 site is linked with ribose or ribose phosphate and further enhanced with increasing of phosphate number. Compared with guanine riboside or guanine nucleotide, guanine deoxyriboside or guanine nucleotide was more powerful in producing CL. The luminescence was inhibited by all three classes of reactive oxygen species’ ( •OH, , 1O2) scavengers with 1O2 scavenger being the most powerful. By comparing the effect of scavengers on the luminescence of DNA with dGMP, we propose that •OH may not be the principle species responsible for DNA damage of above system.