title: Selective time-resolved binding of copper(II) by pyropheophorbide-a methyl ester.
abstract: The complexation behavior of pyropheophorbide-a methyl ester (PPME) with transition metal ions as well as other biologically relevant metal ions has been investigated in water-DMF (2 : 1 v/v) solution. PPME was found to selectively complex Cu(2+) ions, which leads to a distinct change in its absorption spectrum as well as efficient fluorescence quenching. The degree of fluorescence quenching by Cu(2+) depended on concentration and time. Upon addition of Cu(2+), the fluorescence showed a time-resolved decay on the time scale of minutes to hours, with the decay rate being dependent on the cation concentration. Fitting according to a bimolecular reaction rate law provided a rate constant of 650 +/- 90 M(-1) s(-1) at 298 K for metallochlorin formation. The potential implications of Cu(2+) binding for the use of PPME in photodynamic therapy are discussed, along with its use as a fluorescent sensor for detection of micromolar concentrations of Cu(2+).
authors.affiliation: School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, D-28759, Bremen, Germany.
authors.forename: Indrajit
authors.initials: I
authors.lastname: Ghosh
authors.forename: Na'il
authors.initials: N
authors.lastname: Saleh
authors.forename: Werner M
authors.initials: WM
authors.lastname: Nau
mesh_terms: D003300:Copper / Q000737:chemistry* / Q000378:metabolism; D004126:Dimethylformamide / Q000737:chemistry; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry* / Q000378:metabolism; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D011166:Porphyrins; C452939:pyropheophorbide-a methylester; D014867:Water; D003300:Copper; D004126:Dimethylformamide