title: Protein Immobilization Capabilities of Sucrose and Trehalose Glasses: The Effect of Protein/Sugar Concentration Unraveled by High-Field EPR.
abstract: Disaccharide glasses are increasingly used to immobilize proteins at room temperature for structural/functional studies and long-term preservation. To unravel the molecular basis of protein immobilization, we studied the effect of sugar/protein concentration ratios in trehalose or sucrose matrixes, in which the bacterial photosynthetic reaction center (RC) was embedded as a model protein. The structural, dynamical, and H-bonding characteristics of the sugar-protein systems were probed by high-field W-band EPR of a matrix-dissolved nitroxide radical. We discovered that RC immobilization and thermal stabilization, being independent of the protein concentration in trehalose, occur in sucrose only at sufficiently low sugar/protein ratios. EPR reveals that only under such conditions does sucrose form a microscopically homogeneous matrix that immobilizes, via H-bonds, the nitroxide probe. We conclude that the protein immobilization capability depends critically on the propensity of the glass-forming sugar to create intermolecular H-bond networks, thus establishing long-range, homogeneous connectivity within the matrix.
authors.affiliation: Laboratorio di Biochimica e Biofisica Molecolare, Dipartimento di Farmacia e Biotecnologie, FaBiT, Università di Bologna , I-40126 Bologna, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Malferrari
authors.affiliation: Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim (Ruhr), Germany.
authors.forename: Anton
authors.initials: A
authors.lastname: Savitsky
authors.affiliation: Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim (Ruhr), Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lubitz
authors.affiliation: Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim (Ruhr), Germany.|Fachbereich Physik, Freie Universität Berlin , D-14195 Berlin, Germany.
authors.forename: Klaus
authors.initials: K
authors.lastname: Möbius
authors.affiliation: Laboratorio di Biochimica e Biofisica Molecolare, Dipartimento di Farmacia e Biotecnologie, FaBiT, Università di Bologna , I-40126 Bologna, Italy.|Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM) , c/o Dipartimento di Fisica e Astronomia (DIFA), I-40126 Bologna, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Venturoli
mesh_terms: D011506:Proteins / Q000737:chemistry*; D013395:Sucrose / Q000737:chemistry*; D000073893:Sugars / Q000737:chemistry*; D014199:Trehalose / Q000737:chemistry*
chemical_list: D011506:Proteins; D000073893:Sugars; D013395:Sucrose; D014199:Trehalose