Numerical Investagation of a Castle-like Contour Plasmonic Nanoantenna with Operating Wavelengths Ranging in Ultraviolet–Visible, Visible Light, and Infrared Light

We propose a new design of a plasmonic nanoantenna and numerically study its optical properties by means of the 3D finite element method. The nanoantenna is composed of two identical castle-like contour nanometal-filled dielectric media inside the hollows. We examine the influence of the contour thickness, gap width, and dielectric media filled inside the hollows on the antenna resonance conditions. Through these simulations, we show that it is possible to tune an antenna with a constant length over a broad spectral range (ranging in ultraviolet–visible, visible light, and infrared light).     

Biophysical Characterization of a Recombinant α-Amylase from Thermophilic <Emphasis Type="Italic">Bacillus</Emphasis> sp. strain TS-23

Environmental variables can significantly influence the folding and stability of a protein molecule. In the present study, the biophysical properties of a truncated Bacillus sp. TS-23 α-amylase (BACΔNC) were characterized in detail by glutaraldehyde cross-linking, analytical ultracentrifugation, and various spectroscopic techniques. With cross-linking experiment and analytical ultracentrifuge, we demonstrated that the oligomeric state of BACΔNC in solution is monomeric. Far-UV circular dichroism analysis revealed that the secondary structures of BACΔNC were significantly altered in the presence of various metal ions and SDS, whereas acetone and ethanol had no detrimental effect on folding of the enzyme. BACΔNC was inactive and unstable at extreme pH conditions. Thermal unfolding of the enzyme was found to be highly irreversible. The native enzyme started to unfold beyond ~0.2 M guanidine hydrochloride (GdnHCl) and reached an unfolded intermediate, [GdnHCl]_{0.5, N–U}, at 1.14 M. BACΔNC was active at the concentrations of urea below 6 M, but it experienced an irreversible unfolding by >8 M denaturant. Taken together, this work lays a foundation for the future structural studies with Bacillus sp. TS-23 α-amylase, a typical member of glycoside hydrolases family 13.     

Adsorption-elution purification of chimeric <Emphasis Type="Italic">Bacillus stearothermophilus</Emphasis> leucine aminopeptidase II with raw-starch-binding activity

Summary A chimericBacillus stearothermophilus leucine aminopeptidase II (LAPsbd) has been constructed by introducing the raw-starch-binding domain of Bacillus sp. strain TS-23 α-amylase into the enzyme. LAPsbd was adsorbed onto raw starch and the adsorbed enzyme could be eluted from the adsorbent by soluble starch in 20 mM Tris–HCl buffer (pH 8.0). The adsorption of LAPsbd onto raw starch was affected by raw starch concentration, pH, and temperature, while the temperature and incubation time had no obvious effects on the elution of adsorbed enzyme. The molecular weight of purified enzyme was estimated to be 61 kDa. About 84% of LAPsbd in the cell free extract was recovered through one adsorption–elution cycle with a purification of 20-fold. The high quantity and purity of the recovered enzyme coupled with the easy performance make the adsorption–elution procedure suitable for industrial applications.     

Functional Contribution of Ca2+ and Mg2+ to the Intermolecular Interaction of Visinin-like Proteins

The interaction of human visinin-like protein 1 (VILIP1) and visinin-like protein 3 (VILIP3) with divalent cations (Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺) was explored using circular dichroism and fluorescence measurement. These results showed that the four cations each induced a different subtle change in the conformation of VILIPs. Moreover, VILIP1 and VILIP3 bound with Ca²⁺ or Mg²⁺ in a cooperative manner. Studies on the truncated mutants showed that the intact EF-3 and EF-4 were essential for the binding of VILIP1 with Ca²⁺ and Mg²⁺. Pull-down assay revealed that Ca²⁺ and Mg²⁺ enhanced the intermolecular interaction of VILIPs, and led to the formation of homo- and hetero-oligomer of VILIPs. Together with previous findings that Ca²⁺-dependent localization of VILIPs may be involved in the regulation of distinct cascades and deprivation of Ca²⁺-binding capacity of VILIPs did not completely eliminate their activity, it is likely to reflect that Mg²⁺-bound VILIPs may play a role in regulating the biological function of VILIPs in response to a concentration fluctuation of Ca²⁺ in cells.     

Recombinant dioscorins of the yam storage protein expressed in Escherichia coli exhibit antioxidant and immunomodulatory activities

Dioscorins, the major storage proteins in yam tubers, exhibit biochemical and immunomodulatroy activities. To investigate the potential application of dioscorins in biomedical research, we expressed the dioscorin genes Dj-dioA3 and Dp-dioA2 from Dioscorea japonica and Dioscorea pseudojaponica, respectively, in E. coli and routinely obtained approximately 15mg proteins per liter Escherichia coli culture (mg/L) to 30mg/L of rDj-dioscorinA3 and 4 to 8mg/L of rDp-dioscorinA2. Western blot analyses revealed that both recombinant dioscorins contained epitopes with similar antigenicities to those of the native dioscorins. Results from dithiothreitol (DTT) treatment followed by monobromobimane (mBBr) staining showed that both recombinant dioscorins, like the native dioscorins, contain an intramolecular disulfide bond between Cys(28) and Cys(187) residues. Circular dichroism spectroscopy findings indicated that the secondary structural contents of the recombinant dioscorins showed high similarity to those of their corresponding native dioscorins. Both recombinant dioscorins, like the native dioscorins, exhibited 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and Toll-like receptor 4 signaling activities, and stimulated the phagocytosis of E. coli by macrophage. Overall, our results indicated that substantial amounts of recombinant dioscorins can be purified easily from E. coli and that these recombinant dioscorins are appropriate for application in future investigations of the biomedical functions of dioscorins.     

Influencing effect of intra-granule mass transfer in expanded granular sludge-bed reactors treating an inhibitory substrate

Two expanded granular sludge-bed (EGSB) reactors (superficial velocity u s=6.0 and 9.0m/h) were used to treat an inhibitory substrate phenol. The granule diameter (dp) increased with increasing organic loading rate (OLR) and u(s). At the OLRs of 1.67-4.44 kg phenol/m3 d, the accumulation of volatile fatty acids (VFAs) was insignificant; whereas at the OLR of 5.11 kg phenol/m3 d, both the accumulation of VFAs and the washout of large hollow granules (average dp=2.90-3.12 mm) occurred. The comparative experimental and simulated results showed that the proposed kinetic model is suitable for design and predicting purposes. The calculation results of mass transfer parameters (Thiele modulus, Biot number, diffusion layer thickness, and overall effectiveness factor) and parametric sensitivity analysis results (half-saturation constant Ks and dp) showed that the intra-granule mass transfer would lead to a more influencing effect than the external mass transfer on the overall substrate removal rate in EGSB reactors.     

Role of the Conserved Thr399 and Thr417 Residues of <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> γ-Glutamyltranspeptidase as Evaluated by Mutational Analysis

Role of the conserved Thr399 and Thr417 residues of Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) was investigated by site-directed mutagenesis. Substitutions of Thr399 and Thr417 of BlGGT with Ser resulted in a dramatic reduction in enzymatic activity. A complete loss of the GGT activity was observed in T399A, T399C, T417A, and T417K mutant enzymes. Furthermore, mutations on these two residues impaired the capability of autocatalytic processing of the enzyme. In vitro maturation experiments showed that BlGGT mutant precursors, pro-T399S, pro-T417S, and pro-T417A, could precede a time-dependent autocatalytic process to generate the 44.9- and 21.7-kDa subunits; however, the processed T417A had no enzymatic activity. Measurement of intrinsic tryptophan fluorescence revealed alteration of the microenvironment of aromatic amino acid residues, while Far-UV circular dichroism spectra were nearly identical for wild-type and mutant enzymes. These results suggest that residues Thr399 and Thr417 are important for BlGGT in the enzymatic maturation and reaction. An erratum to this article can be found at