Characterization of a Tryptophan 6-Halogenase from Streptomyces albus and Its Regioselectivity Determinants

Tryptophan halogenases are found in diverse organisms and catalyze regiospecific halogenation. They play an important role in the biosynthesis of halogenated indole alkaloids, which are biologically active and of therapeutic importance. Here, a tryptophan 6-halogenase (SatH) from Streptomyces albus was characterized by using a whole-cell reaction system in Escherichia coli. SatH showed substrate specificity for chloride and bromide ions, leading to regiospecific halogenation at the C6-position of l -tryptophan. In addition, SatH exhibited higher performance in bromination than that of previously reported tryptophan halogenases in the whole-cell reaction system. Through structure-based protein mutagenesis, it has been revealed that two consecutive residues, A78/V79 in SatH and G77/I78 in PyrH, are key determinants in the regioselectivity difference between tryptophan 6- and 5-halogenases. Substituting the AV with GI residues switched the regioselectivity of SatH by moving the orientation of tryptophan. These data contribute to an understanding of the key residues that determine the regioselectivity of tryptophan halogenases.     

A fast and fully automatic registration approach based on point features for multi-source remote-sensing images

Automatic registration of multi-source remote-sensing images is a difficult task as it must deal with the varying illuminations and resolutions of the images, different perspectives and the local deformations within the images. This paper proposes a fully automatic and fast non-rigid image registration technique that addresses those issues. The proposed technique performs a pre-registration process that coarsely aligns the input image to the reference image by automatically detecting their matching points by using the scale invariant feature transform (SIFT) method and an affine transformation model. Once the coarse registration is completed, it performs a fine-scale registration process based on a piecewise linear transformation technique using feature points that are detected by the Harris corner detector. The registration process firstly finds in succession, tie point pairs between the input and the reference image by detecting Harris corners and applying a cross-matching strategy based on a wavelet pyramid for a fast search speed. Tie point pairs with large errors are pruned by an error-checking step. The input image is then rectified by using triangulated irregular networks (TINs) to deal with irregular local deformations caused by the fluctuation of the terrain. For each triangular facet of the TIN, affine transformations are estimated and applied for rectification. Experiments with Quickbird, SPOT5, SPOT4, TM remote-sensing images of the Hangzhou area in China demonstrate the efficiency and the accuracy of the proposed technique for multi-source remote-sensing image registration.     

Bone morphogenic protein-2 (BMP-2) loaded hybrid coating on porous hydroxyapatite scaffolds for bone tissue engineering

In this study, a silica xerogel-chitosan hybrid is utilized as a coating material to incorporate bone morphogenic protein-2 (BMP-2) on a porous hydroxyapatite (HA) scaffold for bone tissue engineering. BMP-2 is known as a therapeutic agent for improving bone regeneration and repair. Silica xerogel-chitosan hybrids have been used for the delivery of a growth factor as well as osteoconductive coatings. The biological properties of the hybrid coating incorporated with BMP-2 were evaluated in terms of the BMP-2 release behavior, osteoblastic cellular responses and in vivo performance. BMP-2 was continuously released from the hybrid coating layer on the porous HA scaffold for up to 6 weeks. The hybrid coating containing BMP-2 showed significantly enhanced osteoblastic cell responses in comparison with the hybrid coating and HA substrate. Consequently, new bone formation was significantly increased within the hybrid coating containing BMP-2. These results reveal that the hybrid coating containing BMP-2 has the potential to be used as a bone implant, whose osteogenic properties are promoted by the release of BMP-2 in a controlled manner for a prolonged period of time.     

Effect of reaction pH on the photodegradation of model melanoidins

The effect was studied of the pH of the amino-carbonyl reaction on the photodegradation of model melanoidins. Nondialyzable model melanoidins were prepared from glucose and lysine with or without initial pH control to 7.0.: 2 mol/l phosphate buffer (buffer-melanoidin) and pH adjustment at the reaction start with NaHCO₃ (NaHCO₃-melanoidin). Melanoidin was also prepared from glucose and the lysine-Cu²⁺complex to investigate the difference of complexes between melanoidin and Cu²⁺ (Cu²⁺-melanoidin). Each melanoidin solution was irradiated with a Xe or tungsten-halogen lamp under dissolved oxygen or by the continuous supply of oxygen in a Cu²⁺/O₂ or ascorbic acid/Cu²⁺/O₂ system. The effects of the concentrations of Cu²⁺ and melanoidin, reaction pH value, and metal ion species on the decolorization rate in the Cu²⁺/O₂ system were investigated. The most effective factor for decolorization was found to be the melanoidin concentration. The decolorization rate was negligible when 14 g/l of Cu²⁺-melanoidin was photodegraded in the ascorbic acid/Cu²⁺/O₂ system under dissolved oxygen, although depolymerization was observed. Photodegradation of NaHCO₃-melanoidins in the Cu²⁺/O₂ system by the continuous supply of oxygen resulted in an increased decolorization rate, decreased molecular mass, production of low-molecular-weight compounds, release of free lysine, and pI change. The buffer- and Cu²⁺-melanoidins did not show changes in chemical characteristics similar to those of the NaHCO₃-melanoidin.     

Towards the automatic selection of optimal seam line locations when merging optical remote-sensing images

Image mosaicking is an important task in remote sensing due to the need for imagery with a greater spatial extent than provided by individual scenes. Merging of images requires the selection of a seam line within their area of overlap along which the scenes are merged. The seam line has a better chance of being invisible if it lies in regions where the images to be merged are very similar. The automatic detection of an optimal seam line is not a trivial task as it is difficult to find laterally continuous regions with high image similarity, and to identify image similarities when there are variations in the images, for example due to different illuminations or viewing directions, or shadow differences of tall structures. This article presents an automatic seam line location technique for remote-sensing images and achieves the following three objectives: to trace along the locations with minimal image difference so that the merged data set appears seamless; to avoid creating discontinuities within salient features within the images; and to ensure that the more accurate radiometric values that are associated with the least distance from the nadir point are better preserved in the mosaic image. Therefore, our method uses pixel-based image similarity measurement to choose the locations with high colour, edge and texture similarity; a region-based saliency map that is based on a human attention model to identify and avoid the areas with visibly dominant foreground objects; and location preference to encourage the seam line to lie as close as possible to an equal distance from the two nadir points of the images being merged. These measures are used as input to a cost function and the estimated costs are used to guide the tracing of the seam line in a dynamic programming algorithm. Our experiments demonstrate that the consideration of a combination of factors produces superior results to using just one or two of the variables as controls when merging high-resolution images containing complex structures.     

Effect of Wet Pretreatment on Interfacial Adhesion Energy of Cu-Cu Thermocompression Bond for 3D IC Packages

Quantitative analysis of the interfacial adhesion energy of Cu-Cu thermocompression bonds was performed using the four-point bending method with various wet pretreatment conditions. The evaluated interfacial adhesion energies for 1-μm-thick Cu bonding layers were 0.29 J/m², 1.28 J/m², 1.64 J/m², 1.17 J/m², and 0.43 J/m² for different acetic acid pretreatment times of 0 min, 1 min, 5 min, 10 min, and 15 min, respectively. There exists an optimum wet etch time for maximum adhesion strength. The change of surface properties with increasing wet etch time was believed to result in the variation of the interfacial adhesion energy. The decrease in interfacial adhesion energy after 5 min seems to result from a decrease in the plastic dissipation energy during interfacial crack propagation with thinner Cu film thickness caused by overetching.     

Biocompatibility of Fluor-Hydroxyapatite Bioceramics

Fluoridated hydroxyapatite (FHA) powders were fabricated by a solid-state reaction, and their dense bodies were obtained by sintering at 1350°C. The biological performance of FHAs was evaluated and compared with that of pure hydroxyapatite (HA). The fluoridation of FHAs was confirmed by the changes in their lattice parameters. Human osteoblast-like cells attached and proliferated well on all of the FHAs, including pure FA. The proliferation and differentiation levels of the cells on FHAs were similar to those on pure HA. This finding suggests that the FHAs possess cell viability and activity comparable to pure HA, and thus are potentially applicable as hard tissue substitutes.     

Antioxidant and anti-inflammatory activities of phenolic compounds extracted from lemon myrtle (Backhousia citriodora) leaves at various extraction conditions

Food Science and Biotechnology - Lemon myrtle leaves were extracted with ethanol at different temperatures (25, 50, and 80 °C) and times (2, 4, 6, and 10 h) to examine the...     

Lactobacillus plantarum ATG-K2 and ATG-K6 Ameliorates High-Fat with High-Fructose Induced Intestinal Inflammation

Obesity has become a worldwide health problem, and many significant inflammatory markers have been associated with the risk of side effects of obesity and obesity-related diseases. After a normal diet or high-fat diet with high-fructose water (HFHF) for 8 weeks, male Wistar rats were divided randomly into four experimental groups according to body weight. Next, for 8 weeks, a normal diet, HFHF diet, and HFHF diet with L. plantarum strains ATG-K2 or ATG-K6 were administered orally. Compared to the control group, the HFHF diet group showed significantly increased visceral fat, epididymal fat, and liver weight. The mRNA and protein expression levels of FAS and SREBP-1c were higher in the HFHF diet group than in the HFHF diet with L. plantarum strains ATG-K2 and ATG-K6. The HFHF diet with L. plantarum strain ATG-K2 showed significantly decreased inflammatory cytokine expression in the serum and small intestine compared to the HFHF diet group. Furthermore, histological morphology showed minor cell injury, less severe infiltration, and longer villi height in the small intestine ileum of the HFHF diet with L. plantarum strains groups than in the HFHF diet group. These results suggest that L. plantarum strains K2 and K6 may help reduce intestinal inflammation and could be used as treatment alternatives for intestinal inflammatory reactions and obesity.