ELSEVIER Journal of Chromatography B, 683 (1996) 85-89 JOURNAL OF CHROMATOGRAPHY B: BIOMEDICAL APPLICATIONS Short communication Measurement of 6°Co-'y ray-induced DNA damage by capillary electrophoresis Zeena Nackerdien*, Donald Atha Biotechnology Division, Bldg. 2221A353, National Institute (?f Standards and Technology. Gaithersburg, MD 20899, USA Abstract Capillary electrophoresis was employed in this study to monitor ""Co-y ray-induced damage to a I kb DNA ladder which consists of restriction fragments ranging from 75 to 12 000 bp. DNA samples (0.5 mg/ml) were exposed to 0-60 Gy of y-radiation in the presence and absence of 110 /zmol/1 ethidium bromide (EB). The analysis showed peak broadening without significant changes in the size distribution of irradiated fragments. Radiation-induced conformational changes may account for this peak broadening. EB addition caused small increases in the retention times of DNA fragments without affecting the overall DNA damage. This indicates that the presence of intercalated EB during radiation will not stabilize the DNA against ~'°Co-y ray-induced damage. Kevwords: DNA; ~Cobalt 1. Introduction Ionizing radiation produces a spectrum of DNA damage ranging from base lesions to strand breaks and cross-links [1,7]. Few analytical tools exist to monitor the chemical nature of DNA damage at either low or high doses of radiation. Strand break assays are the most popular, with alkaline centrifuga- tion and unwinding assays as prominent examples [2,8,9]. Radiation-induced DNA conformational changes are frequently monitored with the nucleoid or "comet assays" [2,3]. These assays are extremely sensitive at low doses of radiation, provided lysis conditions and other experimental variables are stringently controlled. High-performance liquid chro- matography (HPLC) and gas chromatography-iso- tope dilution mass spectrometry (GC-MS) provide *Corresponding author. powerful analytical alternatives to these tools 1101. Novel tools that can augment these analytical meth- ods are crucial in understanding the chemical nature of radiation-induced DNA damage. Capillary electrophoresis (CE) is a relatively new tool which has been used with success in the fields of analytical chemistry, pharmacy, forensic sciences and molecular biology [6]. Its enhanced resolution, speed, sensitivity and reproducibility over slab gel electrophoresis have been used to great advantage in applications such as the study of human diseases [1 1,15-17], DNA sequencing and the sizing of DNA fragments [4,6]. DNA damage studies using CE include the determination of point mutations in DNA [11] and the measurement of oxidative damage to fluorescein-labelled deoxyadenylic acid [141. In the present study high resolution CE with a UV detector was used to monitor radiation-induced dam- age to a commercial preparation of a l-kb DNA 0378-4347/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved PII S0378-4347(96)00127-2