title: Structural features of two distinct molecular complexes of copper(II) cationic porphyrin and deoxyribonucleotides.
abstract: The associations of the water-soluble cationic copper(II)-5,10,15,20-meso-tetrakis(4-N-methylpyridyl) porphyrin (CuP) with d(pT)9 oligothymidylate and its building blocks deoxythymidine (dT) and deoxythymidine 5'-monophosphate (dTMP) were investigated by spectrophotometric titration [absorption, nanosecond transient resonance Raman (ns-RR) and picosecond time-resolved resonance Raman (ps-TR3) spectroscopies] to elucidate the structural requirements for the CuP exciplex formation in molecular complexes with unchained mononucleotides. In the d(pT)9 a factor analysis and global fit of the CuP absorption spectra revealed the formation of a single spectral species attributable to a 1 : 1 CuP. d(pT)9 complex throughout a wide range of d(pT)9/CuP ratios (0-10). Using ps-TR3 spectroscopy, the CuP. d(pT)9 complex was shown to be fully responsible for exciplex formation. In contrast, CuP mixed with dTMP ([dTMP]/[CuP] < 3000) yielded two spectroscopically distinct types of molecular complexes with 1 : 1 (CuP. dTMP) and 1 : 2 (CuP. (dTMP)2) (or even higher for [dTMP]/[CuP] > 3000) stoichiometry, the latter being spectroscopically identical to the CuP. d(pT)9 and providing a microenvironment favorable for exciplex formation to the same extent as the oligothymidylate. On the other hand, the 1 : 1 CuP. dTMP complex (prevailing for [dTMP]/[CuP] < 100) yielded no exciplex features. Similar behavior was observed for the CuP complexed with dT. To explain the difference in the ability of the CuP. dTMP and CuP. (dTMP)2 species to form the exciplex, two types of molecular complexes were suggested and discussed, differing in the orientation of the thymine planes with respect to the porphyrin macrocycle.
authors.affiliation: Institute of Physics, Charles University, Ke Karlovu 5, Prague 2, CZ-12116, Czech Republic. mojzes@karlov.mff.cuni.cz
authors.forename: Peter
authors.initials: P
authors.lastname: Mojzes
authors.forename: Petr
authors.initials: P
authors.lastname: Praus
authors.forename: Vladimir
authors.initials: V
authors.lastname: Baumruk
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Turpin
authors.forename: Pavel
authors.initials: P
authors.lastname: Matousek
authors.forename: Michael
authors.initials: M
authors.lastname: Towrie
mesh_terms: D002412:Cations; D003300:Copper / Q000737:chemistry*; D003854:Deoxyribonucleotides / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D007700:Kinetics; D008956:Models, Chemical; D011166:Porphyrins / Q000737:chemistry*; D011485:Protein Binding; D013053:Spectrophotometry / Q000379:methods*; D013941:Thymine / Q000737:chemistry
chemical_list: D002412:Cations; D003854:Deoxyribonucleotides; D011166:Porphyrins; D003300:Copper; D013941:Thymine