title: The Synthesis and Characterization of Aromatic Hybrid Anderson-Evans POMs and their Serum Albumin Interactions: The Shift from Polar to Hydrophobic Interactions.
abstract: Four aromatic hybrid Anderson polyoxomolybdates with Fe(3+) or Mn(3+) as the central heteroatom have been synthesized by using a pre-functionalization protocol and characterized by using single-crystal X-ray diffraction, FTIR, ESI-MS, (1) H NMR spectroscopy, and elemental analysis. Structural analysis revealed the formation of (TBA)3 [FeMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ]⋅3.5 ACN (TBA-FeMo6 -bzn; TBA=tetrabutylammonium, ACN=acetonitrile, bzn=TRIS-benzoic acid alkanolamide, TRISR=(HOCH2 )3 CR)), (TBA)3 [FeMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ]⋅2.5 ACN (TBA-FeMo6 -cin; cin=TRIS-cinnamic acid alkanolamide), (TBA)3 [MnMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ]⋅3.5 ACN (TBA-MnMo6 -bzn), and (TBA)3 [MnMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ]⋅2.5 ACN (TBA-MnMo6 -cin). To make these four compounds applicable in biological systems, an ion exchange was performed that gave the water-soluble (up to 80 mM) sodium salts Na3 [FeMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ] (Na-FeMo6 -bzn), Na3 [FeMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ] (Na-FeMo6 -cin), Na3 [MnMo6 O18 {(OCH2 )3 CNHCOC6 H5 }2 ] (Na-MnMo6 -bzn), and Na3 [MnMo6 O18 {(OCH2 )3 CNHCOC8 H7 }2 ] (Na-MnMo6 -cin). The hydrolytic stability of the sodium salts was examined by applying ESI-MS in the pH range of 4 to 9. Sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that human and bovine serum albumin (HSA and BSA) remain intact in solutions that contain up to 100 equivalents of the sodium salts over more than 4 d at 20 °C. Tryptophan (Trp) fluorescence quenching was applied to study the interactions between the sodium salts and HSA and BSA at pH 5.5 and 7.4. The quenching constants were extracted by using Stern-Volmer analysis, which suggested the formation of a 1:1 POM-protein complex in all samples. It is suggested that the aromatic hybrid POM approaches subdomain IIA of HSA and exhibits hydrophobic interactions with its hydrophobic tails, whereas the Anderson core is stabilized through electrostatic interactions with polar amino acid side chains from, for example, subdomain IB.
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at.
authors.forename: Emir
authors.initials: E
authors.lastname: Al-Sayed
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at.
authors.forename: Amir
authors.initials: A
authors.lastname: Blazevic
authors.affiliation: Institut für Anorganische Chemie, Fakultät für Chemie, Universität Wien, Währinger Straße 42, 1090 Wien (Austria).
authors.forename: Alexander
authors.initials: A
authors.lastname: Roller
authors.affiliation: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstraße 14, 1090 Wien (Austria) http://www.bpc.univie.ac.at. annette.rompel@univie.ac.at.
authors.forename: Annette
authors.initials: A
authors.lastname: Rompel
mesh_terms: D000097:Acetonitriles / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D004591:Electrophoresis, Polyacrylamide Gel / Q000379:methods*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012709:Serum Albumin / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D014961:X-Ray Diffraction
chemical_list: D000097:Acetonitriles; D000644:Quaternary Ammonium Compounds; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; C009405:tetrabutylammonium; C032159:acetonitrile
keywords: X-ray crystallography; characterization; hydrophobic effect; polyoxometalates; synthesis