Showing papers by "Université Paris-Saclay published in 1986"
TL;DR: Variation of nonexchangeable proton resonance chemical shifts for deoxycytidine and deoxy-adenosine as a function of protonation and imino tautomer formation has been determined and may be utilized in the elucidation of the nature of hydrogen bonding between mismatched base pairs in DNA oligomers containing cytosine or adenine residues.
Abstract: Variation of nonexchangeable proton resonance chemical shifts for deoxycytidine and deoxy-adenosine as a function of protonation and imino tautomer formation has been determined. Protonation induces downfield shifts of proton resonances whereas formation of the rare imino tautomer induces upfield shifts. Titration curves are constructed on the basis of spectrophotometrically determined pK values. Excellent fit is obtained between theoretical titration curves and experimental data, which indicates that chemical shifts of base protons may be used to quantitatively determine the relative concentrations of either rare imino tautomeric conformations or protonated base forms. These data may be utilized as an aid in the elucidation of the nature of hydrogen bonding between mismatched base pairs in DNA oligomers containing cytosine or adenine residues. These data, in conjunction with the oligonucleotide study of Patel et al. [Patel, D. J., Kozlowski, S.A., Ikuta, S., & Itakura, K. (1984) Biochemistry 23, 3218-3226], have been used to rigorously argue the existence of a "protonated" adenine residue in the A-C mismatch. This structure allows reconciliation of the NMR solution data with crystallographic data [Hunter, W.N., Brown, T., Anand, N.N., & Kennard, O. (1986) Nature (London) 320, 552-555], which support the protonated base pair.
53 citations
TL;DR: The W(001) and Mo(110) surfaces are investigated by inverse photoemission and the implications of the data on the driving mechanism for the surface reconstruction are discussed using all-electron self-consistent local-density calculations.
Abstract: The W(001) and Mo(110) surfaces are investigated by inverse photoemission. At Gamma-bar we observe an unoccupied surface state just above the Fermi level. The angular dependence and chemisorption behavior identify it as a d/sub z//sub =/ surface state similar to one observed and calculated just below E/sub F/. For W(001) a second state is seen near M-bar at 1.4 eV above E/sub F/ and assigned to a Sigma-bar/sub 2/ back-bonding state. The implications of our data on the driving mechanism for the surface reconstruction are discussed using all-electron self-consistent local-density calculations.
25 citations
TL;DR: In this paper, the authors analyzed muons and multimuons detected in the Frejus underground nucleon decay detector between February 1984 and June 1986, and found that no excess events were observed in the direction of Cygnus X-3, which yields a 90 % confidence level upper flux limit of 0.7 10-12 cm-2 s-1, for an average rock overburden of 5000 hg cm2 corresponding to energies > 3 TeV.
21 citations