1,981 research outputs found

    Drosophila nuclear proteins bind to regions of alternating C and T residues in gene promoters

    Get PDF
    Proteins from Drosophila nuclei that bind to regions of alternating C and T residues present in the promoters of the heat shock genes hsp70 and hsp26 and the histone genes his3 and his4 have been purified. These proteins bind to isolated linear DNA, and genomic footprinting analyses indicate that they are bound to DNA in nuclei. In supercoiled plasmids at low pH, some of these DNA sequences adopt triple-helical structures which, if they form in vivo, could significantly affect chromatin structure. The nuclear proteins described here, and not necessarily the deformed conformation of the DNA, may be responsible for maintaining a potentially inducible promoter structure before transcriptional activation

    Oxygen isotopes implanted in the LDEF spacecraft

    Get PDF
    Secondary ion mass spectrometry was used to study oxygen implanted in the surface of copper from the Long Duration Exposure Facility (LDEF). Oxidation that occurred in orbit shows a characteristic oxygen isotope composition, depleted in O-18. The measured depletion is comparable to the predicted depletion (45 percent) based on a model of the gravitational separation of the oxygen isotopes. The anomalous oxygen was contained within 10nm of the surface. Tray E10 was calculated to have received 5.14 x 10(exp 21) atoms of oxygen cm(sup -2) during the LDEF mission and so there is sufficient anomalous implanted oxygen present in the surface to obtain a reliable isotopic profile
    corecore