title: Tris-functionalized hybrid Anderson polyoxometalates: synthesis, characterization, hydrolytic stability and inversion of protein surface charge.
abstract: Single- and double-sided functionalized hybrid organic-inorganic Anderson polyoxomolybdates with Ga(III) and Fe(III) positioned as central heteroatoms have been synthesized in a mild, two-step synthesis in an aqueous medium. Compounds 1-4 were isolated as hydrated salts, [TBA]3[GaMo6O18(OH)3{(OCH2)3CCH2OH}]×12 H2O (1) (TBA = tetrabutylammonium), Na3[FeMo6O18{(OCH2)3CCH2OH}2]×11 H2O (2), [TMA]2[GaMo6O18(OH)3{(OCH2)3CNH3}]×7 H2O (3) (TMA = tetramethylammonium), and Na[TMA]2[FeMo6O18(OH)3{(OCH2)3CNH3}](OH)×6 H2O (4). All the compounds were characterized based on single-crystal X-ray diffraction (SXRD), FTIR, UV/Vis, thermogravimetric, ESI-MS, NMR, and elemental analyses. Compound 1 was also crystallized with two smaller organic cations, giving [TMA]3[GaMo6O18(OH)3{(OCH2)3CCH2OH}]×n H2O (5) and [GDM]3[GaMo6O18(OH)3{(OCH2)3CCH2OH}]×n H2O (6) (GDM = guanidinium) and were characterized based on UV/Vis, NMR, FTIR, and elemental analyses. The use of these compounds as additives in macromolecular crystallography was investigated by examining their hydrolytic stability by using ESI-MS in a pH range of 4 to 9. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that BSA remains intact in a solution containing up to 100 equivalents of 1 or 4 over more than four days at 20 °C. Zeta potential measurements demonstrate that 1-4 induce charge inversions on the positively charged surface of BSA (1 mg mL(-1)) with concentrations starting as low as 1.29 mM for compounds 1 and 2, which have the highest negative surface charge.
authors: Institut für Biophysikalische Chemie, Fakultät für Chemie, Universität Wien, Althanstrasse 14, 1090 Wien (Austria).
authors: Amir
authors: A
authors: Blazevic
authors: Emir
authors: E
authors: Al-Sayed
authors: Alexander
authors: A
authors: Roller
authors: Gerald
authors: G
authors: Giester
authors: Annette
authors: A
authors: Rompel
mesh_terms: D000818:Animals; D002417:Cattle; D018360:Crystallography, X-Ray; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013818:Thermogravimetry; D017973:Tungsten Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy; D000099294:Polyoxometalates
chemical_list: D012710:Serum Albumin, Bovine; D017973:Tungsten Compounds; C102296:polyoxometalate I; D000099294:Polyoxometalates
keywords: POM-protein interactions; crystal growth; organic-inorganic hybrid composites; polyoxometalates