title: Thermal stability and energetics of 15-mer DNA duplex interstrand crosslinked by trans-diamminedichloroplatinum(II).
abstract: The effect of the location of the interstrand cross-link formed by trans-diamminedichloroplatinum(II) (transplatin) on the thermal stability and energetics of 15-mer DNA duplex has been investigated. The duplex containing single, site-specific cross-link, thermodynamically equivalent model structures (hairpins) and nonmodified duplexes were characterized by differential scanning calorimetry, temperature-dependent uv absorption, and circular dichroism. The results demonstrate that the formation of the interstrand cross-link of transplatin does not affect pronouncedly thermodynamic stability of DNA: the cross-link induces no marked changes not only in enthalpy, but also in "reduced" (concentration independent) monomolecular transition entropy. These results are consistent with the previous observations that interstrand cross-links of transplatin structurally perturb DNA only to a relatively small extent. On the other hand, constraining the duplex with the interstrand cross-link of transplatin results in a significant increase in thermal stability that is primarily due to entropic effects: the cross-link reduces the molecularity of the oligomer system from bimolecular to monomolecular. Importantly, the position of the interstrand cross-link within the duplex modulates cooperativity of the melting transition of the duplex and consequently its thermal stability.
authors.affiliation: Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, CZ-61265 Brno, Czech Republic.
authors.forename: Ctirad
authors.initials: C
authors.lastname: Hofr
authors.forename: Viktor
authors.initials: V
authors.lastname: Brabec
mesh_terms: D001704:Biopolymers / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D002945:Cisplatin / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D006358:Hot Temperature; D015394:Molecular Structure; D009841:Oligonucleotides / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D001704:Biopolymers; D003432:Cross-Linking Reagents; D009841:Oligonucleotides; C034697:transplatin; D004247:DNA; D002945:Cisplatin