title: Spectroscopic studies on the anticancer antibiotic Altromycin H and the interaction with copper(II) ions.
abstract: The antitumor antibiotic Altromycin H was studied using electronic absorption (UV-Vis.) and circular dichroism (CD) spectroscopy. The dissociation constants of the phenolic groups on C(5) and C(11) were estimated as pK(1)=6.7 and pK(2)=11.8 at 25 degrees C, respectively, and a complete assignment of the CD and UV-Vis. bands is proposed. The interaction of Cu(II) ions with the Altromycin H has been also investigated by UV-Vis., CD and electron paramagnetic resonance (EPR) spectroscopy. A pH depended stepwise complex formation was observed. At pH<4 no copper-Altromycin H interactions were detected. At the 4<pH<8 the Cu(II) ions coordinate to Altromycin H via the C(4)O and C(5)OH groups atoms of the chromophore ring and the [Cu(AltroH)(2)] complex (formation constant, K(f), 4.00+/-0.9 x 10(11) M(-2) at 25 degrees C) is the predominant species. In alkaline solution the hydroxo-bridged complex, [Cu(OH)(AltroH)](2), is proposed to be as the unique present species.
authors.affiliation: Inorganic Chemistry Laboratory, Department of Chemistry, University of Athens, 15771 Panepistimiopolis, Athens, Greece.
authors.forename: Constantinos
authors.initials: C
authors.lastname: Menidiatis
authors.forename: Constantinos
authors.initials: C
authors.lastname: Methenitis
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Nikolis
authors.forename: George
authors.initials: G
authors.lastname: Pneumatikakis
mesh_terms: D000617:Aminoglycosides / Q000737:chemistry*; D000903:Antibiotics, Antineoplastic / Q000737:chemistry*; D002942:Circular Dichroism; D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009285:Naphthoquinones / Q000737:chemistry*; D013053:Spectrophotometry
chemical_list: D000617:Aminoglycosides; D000903:Antibiotics, Antineoplastic; D009285:Naphthoquinones; C090483:altromycin H; D003300:Copper