Nucleic Acids Research, 1975, Vol. 2, No. 2 143-148
© 1975
Articles |
Detection by electron microscopy of photo-induced denaturation in
DNA
Biology Division, Oak Ridge National Laboratory Oak Ridge, Tennessee 37830, USA
Received November 22, 1974.
We have used an electron microscope to study localized denatured regions in ultraviolet-irradiated DNA. DNA from bacteriophage
was UV-irradiated and then prepared for electron microscopy after fixing in buffered (pH 9.5) formaldehyde solutions at 25°C. The denatured regions observed corresponded to those described by Inman and Schnös (1) who used alkaline denaturation to preferentially destroy thymine-adenine base pairing. In UV-irradiated DNA, pairs of neighboring thymine residues are converted into photodimers; hence, loss of hydrogen bonding most likely occurs in thymine-rich regions and denaturation results. Conceivably, photo-induced denaturation may under some circumstances represent a more convenient method than alkaline denaturation for mapping thymine-rich regions in DNA.