Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca(2+)) ions, with an optimal concentration of 10 mM. Further increase of the Ca(2+) concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 µm compared to 2.69 µm at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

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Based on experimental studies on tube formation during self-assembly of bacterial surface (S)-layers, a mechanistic model for describing the underlying basic mechanisms is proposed and the effect of process parameters on growth velocity and tube radius is investigated. The S-layer is modeled as a curved sheet with discrete binding sites for the association of monomers distributed along the S-layer edges. Reported changes of the tube radius owing to genetic protein modifications are explained within the framework of continuum mechanics. S-layer growth velocity and shape development are analyzed by Monte Carlo simulation in their dependence on the attachment and detachment frequencies of monomers at the S-layer. For curved S-layer patches, a criterion for the formation of S-layer tubes is derived. Accordingly, tubes can form only within a certain range of the initial monomer concentration. Furthermore, the effect of calcium ion concentration on tube formation is discussed, including recent experimental findings on the calcium effect.

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SS phages are genetically enginnered by replacing 2 N-terminal amino acids of the p8 coat protein of the fd phage. AGE and zeta potential measurements show that SS phages carry at least 1/4 less net negative surface charge than fd phages. Morphology and thickness of phages are studied at different counterion concentrations (10(-3) , 10(-2) and 10(-1)  M) by AFM, SEM and immunofluorescence analyses. Bundles induced by CoCl2 and CaCl2 are either metallized by chemical reduction or biomineralized for apatite-like material formation. EDX spectroscopy confirms the presence of Co, P and Ca peaks in mineralized samples. Such bottom-up manufactured phage scaffolds might be applied in bioengineering studies.

Objectives To determine of antioxidant, cytotoxic and tyrosinase inhibitory (TI) activities, and phenolic profiles with a new high performance liquid chromatography (HPLC) method of green, white and black teas. Methods Antioxidant activities of the teas were examined by means of scavenging of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), and cupric reducing antioxidant capacity (CUPRAC). The phenolic contents were investigated by means of HPLC. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to evaluate the cytotoxic potential of tea extracts in cancer and normal cell lines. TI activity was investigated against diphenolase (DOPA), using kojic acid as a positive control. Results The green tea extract exhibited stronger antioxidant than white and black tea extracts. The green tea contained syringaldehyde, p-coumaric acid, benzoic acid, and quercetin. The white tea extract had the highest tyrosinase inhibitor activity. The extracts exhibited higher cytotoxic potential toward cancer cells than normal cells. The methanol extract of green tea had the highest cytotoxic potential, while the water extracts were less toxic. Conclusion The green, white, and black teas can be regarded as an important in terms of rich antioxidant, tyrosinase inhibitor, and cytotoxic activities in both the pharmaceutical and food industries.

Surface layer (SL) proteins are self-assembling nanosized arrays which can be recrystallized in solution or on surfaces. In this paper, we investigate the metallization, contact potential difference and conductivity of in vitro recrystallized mSbsC-eGFP tube-like assemblies for possible applications in nanobiotechnology. Treatment of mSbsC-eGFP tube-like structures with 150 mM Pt salt solution resulted in the formation of metallized SL assemblies decorated with Pt nanoparticles (∅ > 3 nm) which were closely packed and aggregated into metal clusters. Kelvin probe force microscopy (KPFM) measurements revealed that metallized and unmetallized SL templates showed different surface potential behaviours, demonstrating that the metal coating changes the electrostatic surface characteristics of SL assemblies. In situ conductivity measurements showed that unmetallized SL assemblies were not conductive. Metallized samples showed linear I-V dependence between - 1 and + 1 V with a conductivity of ∼ 10(3) S m( - 1).

Most bacterial surface layers (SLs) are formed by self-assembly of a single type of protein. Native and recombinant surface layer monomers are capable to self-assemble on solid substrates and in solution to highly regular nanosized arrays which make them attractive for nanobiotechnological applications. In this study, we expressed the surface layer protein SbsC of Bacillus stearothermophilus ATTC 12980, tagged with Enhanced Green Fluorescent Protein, in the yeast Saccharomyces cerevisiae. We observed a network of tubular structures in the cytosol of the transformed yeast cells that did not colocalize with microtubules or the actin cytoskeleton. Time-resolved analysis of the formation of these structures during vegetative growth and sporulation was investigated by live fluorescence microscopy. While in meiosis ascospores seemed to receive assembled structures from the diploid cells, during mitosis, SL structures were formed de novo in the buds. SL assembly always started with the appearance of a dot-like structure in the cytoplasm, suggesting a single nucleation point.