title: Thermodynamic and spectroscopic characterization of the berenil and pentamidine complexes with the dodecanucleotide d(CGCGATATCGCG)2.
abstract: The dodecanucleotide d(CGCGATATCGCG)2 was characterized by thermodynamic and UV-spectrophotometric measurements. A van't Hoff enthalpy of delta H(uv)v.H. approximately -190 kJ/mol was determined for the thermal transition using UV spectroscopy. This value was confirmed by differential scanning calorimetry (DSC). In addition we obtained the thermodynamic data delta HDSC = -405.1 kJ/mol, delta SDSC = -1290 J/mol.K and delta GDSC = -53.2 kJ/mol for the helix to coil transition of the dodecanucleotide. The association of berenil and the oligonucleotide was accompanied with a stabilization of the host duplex (increase in Tm) and an increase in the van't Hoff enthalpy. The berenil binding parameters (delta delta HDSC = -32.6 kJ/mol, delta delta SDSC = -72 J/mol.K and delta delta GDSC = -11.1 kJ/mol) revealed significant differences compared to those of the pentamidine aggregation (delta delta HDSC = -23.7 kJ/mol, delta delta SDSC = -53 J/mol.K and delta delta GDSC = -7.8 kJ/mol). The transition of the pure oligonucleotide was characterized by a substantial amount of intermediate states (sigma DSC = 0.43) which decreased significantly upon binding of the drugs (sigma DSC approximately 0.80). The structural features of the complexes were analyzed by FT-IR spectroscopy. From these experiments we conclude that the configurations in the berenil and pentamidine complexes are different.
authors.affiliation: Abteilung Physikalische Chemie, Universität Freiburg i.Br., Albertstraße 23 a, D-79104 Freiburg i.Br., Bundesrepublik Deutschland.
authors.forename: Hans-Uwe
authors.initials: HU
authors.lastname: Schmitz
authors.affiliation: Abteilung Physikalische Chemie, Universität Freiburg i.Br., Albertstraße 23 a, D-79104 Freiburg i.Br., Bundesrepublik Deutschland.
authors.forename: Wigand
authors.initials: W
authors.lastname: Hübner
authors.affiliation: Abteilung Physikalische Chemie, Universität Freiburg i.Br., Albertstraße 23 a, D-79104 Freiburg i.Br., Bundesrepublik Deutschland.
authors.forename: Theodor
authors.initials: T
authors.lastname: Ackermann
mesh_terms: D000981:Antiprotozoal Agents; D001483:Base Sequence; D002152:Calorimetry, Differential Scanning; D004133:Diminazene / Q000031:analogs & derivatives* / Q000737:chemistry; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000737:chemistry*; D010419:Pentamidine / Q000737:chemistry*; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014344:Trypanocidal Agents
chemical_list: D000981:Antiprotozoal Agents; D009838:Oligodeoxyribonucleotides; D014344:Trypanocidal Agents; D010419:Pentamidine; C003915:diminazene aceturate; D004133:Diminazene