Thermodynamics of the melting of PNA(2)/DNA triple helices.
Equilibrium melting curves were obtained for triplexes, formed by single stranded DNA containing an A10 target with bis-PNA consisting of two T10 decamers. Thermodynamic parameters of melting were determined for Na(+) concentrations 50, 200 and 600mM by two methods. The melting enthalpy Delta H degrees was evaluated from the width of the differential melting curves and from the concentration dependence of the melting temperature. The latter method allowed also evaluating the melting entropy Delta S degrees. The following results were obtained: Delta H degrees = - 137 kcal/M, Delta S degrees = - 368 cal/M.K, Delta G degrees (298)= - 27 kcal/M. No dependence of Delta H degrees, Delta S degrees and Delta G degrees (298) was observed upon ionic strength within the accuracy of the experiment (+/- 10%). The absolute values of Delta H degrees, Delta S degrees and Delta G degrees(298) are 2 to 3 times higher than the published values of corresponding melting parameters for decameric PNA/DNA duplexes of various nucleic base sequences. The origin of the extremely high stability of the triplexes is discussed.
Krupnik
O V
OV
Institute of Molecular Genetics, Russian Academy of Sciences, Kurchatov sq. 2, Moscow 123182, Russia.
Guscho
Y
Y
Sluchanko
K
K
Nielsen
P
P
Lazurkin
Y
Y
D001482:Base Composition; D001483:Base Sequence; D055592:Biophysical Phenomena; D001703:Biophysics; D004247:DNA / Q000737:chemistry*; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009841:Oligonucleotides / Q000737:chemistry; D020135:Peptide Nucleic Acids / Q000737:chemistry*; D012016:Reference Values; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D013816:Thermodynamics
D009841:Oligonucleotides; D020135:Peptide Nucleic Acids; C051802:triplex DNA; D004247:DNA