title: Thermodynamic parameters of cooperative helix-to-coil transitions from synthetic A-U-rich oligoribonucleotides up to fourteen basepairs.
abstract: Heat induced helix-to-coil transitions are studied in the form of ultraviolet-hypochromicity profiles by absorbance spectroscopy, and delta Cp-curves by differential scanning calorimetry of self-complementary ribonucleotides. The results are analyzed and compared. Van 't Hoff transition enthalpies derived by UV-experiments incorporating concentration variations are found to differ from six-parameter and two-parameter Marquardt-fits on the melting profiles. A measure for the maximum number of nucleotides in intermediate states is obtained from a statistical deconvolution. It yields a range from 12.5% for the shortest nucleotide up to 31.5% for r(UA)7. Model independent calorimetric data are reported. A limit for intra-molecular loop-formation preference is reached by rG(UA)6C within this sequence.
authors.affiliation: Institut für Physikalische Chemie, Universität Freiburg, FRG.
authors.forename: N
authors.initials: N
authors.lastname: Windhab
authors.forename: J
authors.initials: J
authors.lastname: Ohms
authors.forename: T
authors.initials: T
authors.lastname: Ackermann
mesh_terms: D000225:Adenine / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D018257:Helix-Loop-Helix Motifs; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D009843:Oligoribonucleotides / Q000737:chemistry*; D013816:Thermodynamics; D014529:Uridine / Q000737:chemistry*
chemical_list: D009843:Oligoribonucleotides; D000225:Adenine; D014529:Uridine