title: In Vitro Characterization of the Two-Stage Non-Classical Reassembly Pathway of S-Layers.
abstract: The recombinant bacterial surface layer (S-layer) protein rSbpA ofLysinibacillus sphaericusCCM 2177 is an ideal model system to study non-classical nucleation and growth of protein crystals at surfaces since the recrystallization process may be separated into two distinct steps: (i) adsorption of S-layer protein monomers on silicon surfaces is completed within 5 min and the amount of bound S-layer protein sufficient for the subsequent formation of a closed crystalline monolayer; (ii) the recrystallization process is triggered-after washing away the unbound S-layer protein-by the addition of a CaCl₂ containing buffer solution, and completed after approximately 2 h. The entire self-assembly process including the formation of amorphous clusters, the subsequent transformation into crystalline monomolecular arrays, and finally crystal growth into extended lattices was investigated by quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM). Moreover, contact angle measurements showed that the surface properties of S-layers change from hydrophilic to hydrophobic as the crystallization proceeds. This two-step approach is new in basic and application driven S-layer research and, most likely, will have advantages for functionalizing surfaces (e.g., by spray-coating) with tailor-made biological sensing layers.
authors.affiliation: Department of Nanobiotechnology, Institute for Biophysics, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, Vienna 1190, Austria. andreas.breitwieser@boku.ac.at.
authors.forename: Andreas
authors.initials: A
authors.lastname: Breitwieser
authors.affiliation: Department of Nanobiotechnology, Institute for Biophysics, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, Vienna 1190, Austria. jagoba.iturri@boku.ac.at.
authors.forename: Jagoba
authors.initials: J
authors.lastname: Iturri
authors.affiliation: Department of Nanobiotechnology, Institute for Biophysics, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, Vienna 1190, Austria. jose.toca-herrera@boku.ac.at.
authors.forename: Jose-Luis
authors.initials: JL
authors.lastname: Toca-Herrera
authors.affiliation: Department of Nanobiotechnology, Institute for Biophysics, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, Vienna 1190, Austria. uwe.sleytr@boku.ac.at.
authors.forename: Uwe B
authors.initials: UB
authors.lastname: Sleytr
authors.affiliation: Department of Nanobiotechnology, Institute for Biophysics, University of Natural Resources and Life Sciences Vienna, Muthgasse 11, Vienna 1190, Austria. dietmar.pum@boku.ac.at.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Pum
mesh_terms: D000327:Adsorption; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D003460:Crystallization; D057927:Hydrophobic and Hydrophilic Interactions; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D009004:Monosaccharide Transport Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D011994:Recombinant Proteins; D013499:Surface Properties
chemical_list: D001426:Bacterial Proteins; D008562:Membrane Glycoproteins; D009004:Monosaccharide Transport Proteins; D011994:Recombinant Proteins; C055764:S-layer proteins; C120455:SbpA protein, bacteria
keywords: Ca2+ binding; S-layer proteins; non-classical crystal growth; self-assembly kinetics; two-step crystallization