title: Prediction of pH-dependent properties of DNA triple helices.
abstract: The thermodynamic properties of two triple helices were investigated by uv thermal denaturation, differential scanning calorimetry, and pH titrations. Starting from the grand partition function and using matrix methods we present a formalism that describes pH effects on the thermal stability of triple helices. The formalism can be used over a wide pH range and is not restricted to the limiting case where the pH is larger or smaller than the pK alpha of cytosine. Furthermore, it covers nearest neighbor electrostatic effects of closely spaced cytosines in the Hoogsteen strand which can shift the pK alpha of cytosine to lower pH values. A procedure is employed to predict enthalpy and entropy changes for triplex formation. These values are in accordance with the results obtained by differential scanning calorimetry.
authors.affiliation: Department of Biochemistry, University of Cape Town, Rondebosch, Republic of South Africa.
authors.forename: P L
authors.initials: PL
authors.lastname: Hüsler
authors.forename: H H
authors.initials: HH
authors.lastname: Klump
mesh_terms: D001483:Base Sequence; D002152:Calorimetry, Differential Scanning; D004247:DNA / Q000737:chemistry*; D015342:DNA Probes; D006863:Hydrogen-Ion Concentration; D008956:Models, Chemical; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009691:Nucleic Acid Denaturation; D011237:Predictive Value of Tests; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: D015342:DNA Probes; D004247:DNA