title: PDN-1: a spin-labeled analog of cis-diamminedichloroplatinum(II). Biophysical studies in aqueous, lipophilic, and biological media.
abstract: Biophysical and biochemical studies on a biradical-labeled analog of Cisplatin, PDN-1, in aqueous, biological, and lipophilic media are presented. The ESR spectra from PDN-1 in aqueous meida show five-line spectra typical of biradicals in which intramolecular spin exchange occurs. The spectrum of PDN-1 in 1-octanol is characterized by three broad lines overlying a fourth line that is approximately three times as wide as the others. Although the characteristics of the aqueous spectra differ substantially from those of the octanol spectra, both the midfield peak height and the integral of the absorption spectrum can be used as a linear measure of PDN-1 concentration in either media. The smallest concentration used in these linear calibrations was equivalent to the detection of 60 femptomoles of PDN-1 at a signal-to-noise ratio of 30. PDN-1 is shown to "decay" in tissue culture medium which involves either the reduction of a nitroxyl moiety, the labilization of an amino bond, or a combination of both. Spectra of intracellular PDN-1 show that both a mobile ("free") fraction and slowly tumbling ("bound") fraction of the compound can be detected within CHO cells. The spin-labeled cisplatin method is at least as sensitive as conventional chromatographic and spectroscopic methods, yet has the added advantage of offering information about the molecular environment of the complex.
mesh_terms: D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002945:Cisplatin / Q000031:analogs & derivatives*; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005260:Female; D007700:Kinetics; D000442:Octanols; D010053:Ovary; D013113:Spin Labels; D014867:Water
chemical_list: D003470:Culture Media; D000442:Octanols; D013113:Spin Labels; D014867:Water; C048391:PDN-1; D002945:Cisplatin