title: Detection by electron microscopy of photo-induced denaturation in lambda DNA.
abstract: We have used an electron microscope to study localized denatured regions in ultraviolet-irradiated DNA. DNA from bacteriophage lambda was UV-irradiated and then prepared for electron microscopy after fixing in buffered (pH 9.5) formaldehyde solutions at 25 degrees 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.
mesh_terms: D003090:Coliphages; D004267:DNA Viruses; D004279:DNA, Viral / Q000528:radiation effects*; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D012834:Silver; D013941:Thymine / Q000032:analysis; D014466:Ultraviolet Rays
chemical_list: D004279:DNA, Viral; D012834:Silver; D013941:Thymine