Optical pulling force on a uniaxial anisotropic sphere by a high-order Bessel (vortex) beam.

Based on the generalized Lorenz-Mie theory (GLMT) and the scattering theory of uniaxial spheres, a theoretical approach is introduced to study the axial radiation force (AOF) exerted on a uniaxial anisotropic sphere illuminated by an on-axis high-order Bessel (vortex) beams (HOBVBs). Applying Maxwell's stress tensor, an analytical expression of the AOF on a uniaxial anisotropic sphere by the on-axis HOBVB is derived. The correctness of the theoretical and numerical results is verified by comparing the AOF on an isotropic sphere by a zero-order Bessel beam (ZOBB) with those results by a plane wave, Gaussian beam, and ZOBB. The focus of this study is to determine some conditions of the tractor beam, so as to realize the inverse motion of an anisotropic sphere through a Bessel beam. The range of optical pulling force (OPF) that can pull particles in reverse motion generated by zero-order and first-order Bessel beams is extended from isotropic spherical particles to anisotropic spherical particles. The effects of the sphere radius, conical angle, and especially electromagnetic anisotropy parameters on the OPF in water or a vacuum environment are discussed in detail. Moreover, the OPF exerted on the uniaxial anisotropic sphere illuminated by a HOBVB with l=2, 3, and 4 is also exhibited. It indicates that the HOBVB with l=2, 3 is also a good tractor beam for the uniaxial anisotropic sphere. The OPF generated by Bessel beams on uniaxial anisotropic spherical particles is not only affected by the conical angle and radius but is also significantly influenced by anisotropic parameters and topological charges. These properties of the OPF are different from those on an isotropic sphere. The theory and results are hopeful to provide an effective theoretical basis for the study of optical micromanipulation of biological and anisotropic complex particles by optical tractor (vortex) beams.

Light scattering of a uniform uniaxial anisotropic sphere by an on-axis high-order Bessel vortex beam.

Analytical solutions to the scattering of a uniform uniaxial anisotropic sphere illuminated by an on-axis high-order Bessel vortex beam (HOBVB) are investigated. Using the vector wave theory, the expansion coefficients of the incident HOBVB in terms of the spherical vector wave functions (SVWFs) are obtained. According to the orthogonality of the associated Legendre function and exponential function, more concise expressions of the expansion coefficients are derived. It can reinterpret the incident HOBVB faster compared with the expansion coefficients of double integral forms. The internal fields of a uniform uniaxial anisotropic sphere are proposed in the integrating form of the SVWFs by introducing the Fourier transform. The differences of scattering characteristics of a uniaxial anisotropic sphere illuminated by a zero-order Bessel beam, Gaussian beam, and HOBVB are exhibited. Influences of the topological charge, conical angle, and particle size parameters on the angle distributions of the radar cross section are analyzed in detail. The scattering and extinction efficiencies varied with the particle radius, conical angle, permeability, and dielectric anisotropy are also discussed. The results provide insights into the scattering and light-matter interactions and may find important applications in optical propagation and optical micromanipulation of biological and anisotropic complex particles.

Analysis of radiation force on a uniaxial anisotropic sphere by dual counter-propagating Gaussian beams.

Based on Maxwell's stress tensor and the generalized Lorenz-Mie theory, a theoretical approach is introduced to study the radiation force exerted on a uniaxial anisotropic sphere illuminated by dual counter-propagating (CP) Gaussian beams. The beams propagate with arbitrary direction and are expanded in terms of the spherical vector wave functions (SVWFs) in a particle coordinate system using the coordinate rotation theorem of the SVWFs. The total expansion coefficients of the incident fields are derived by superposition of the vector fields. Using Maxwell stress tensor analysis, the analytical expressions of the radiation force on a homogeneous absorbing uniaxial anisotropic sphere are obtained. The accuracy of the theory is verified by comparing the radiation forces of the anisotropic sphere reduced to the special cases of an isotropic sphere. In order to study the equilibrium state, the effects of beam parameters, particle size parameters, and anisotropy parameters on the radiation force are discussed in detail. Compared with the isotropic particle, the equilibrium status is sensitive to the anisotropic parameters. Moreover, the properties of optical force on a uniaxial anisotropic sphere in a single Gaussian beam trap and Gaussian standing wave trap are compared. It indicates that the CP Gaussian beam trap may more easily capture or confine the anisotropic particle. However, the radiation force exerted on an anisotropic sphere exhibits very different properties when the beams do not propagate along the primary optical axis. The influence of the anisotropic parameter on the radiation force by CP Gaussian beams is different from that of a single Gaussian beam. In summary, even for anisotropic particles, the Gaussian standing wave trap also exhibits significant advantages when compared with the single Gaussian beam trap. The theoretical predictions of radiation forces exerted on a uniaxial anisotropic sphere by dual Gaussian beams provide effective ways to achieve the improvement of optical tweezers as well as the capture, suspension, and high-precision delivery of anisotropic particles.

Production of Polyhydroxyalkanoates (PHAs) by Vibrio alginolyticus Strains Isolated from Salt Fields.

Vibrio alginolyticus is a halophilic organism usually found in marine environments. It has attracted attention as an opportunistic pathogen of aquatic animals and humans, but there are very few reports on polyhydroxyalkanoate (PHA) production using V. alginolyticus as the host. In this study, two V. alginolyticus strains, LHF01 and LHF02, isolated from water samples collected from salt fields were found to produce poly(3-hydroxybutyrate) (PHB) from a variety of sugars and organic acids. Glycerol was the best carbon source and yielded the highest PHB titer in both strains. Further optimization of the NaCl concentration and culture temperature improved the PHB titer from 1.87 to 5.08 g/L in V. alginolyticus LHF01. In addition, the use of propionate as a secondary carbon source resulted in the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). V. alginolyticus LHF01 may be a promising host for PHA production using cheap waste glycerol from biodiesel refining.

Metabolic engineering of Escherichia coli for the production of L-malate from xylose.

Malate is regarded as one of the key building block chemicals which can potentially be produced from biomass at a large scale. Although glucose has been extensively studied as the substrate for malate production, its high price and potential competition with food production are serious limiting factors. In this study, Escherichia coli was metabolically engineered to effectively produce malate from xylose, the second most abundant sugar component of lignocellulosic biomass. First, the biosynthetic route of malate was constructed by overexpressing D-tagatose 3-epimerase, L-fuculokinase, L-fuculose-phosphate aldolase, and aldehyde dehydrogenase A. Second, genes encoding malic enzyme, malate dehydrogenase, and fumarate hydratase were knocked out to eliminate malate consumption, resulting in a titer of 1.99 g/l malate and a yield of 0.47 g malate/g xylose. Third, glycolate oxidase and malate synthase were overexpressed to strengthen the conversion of glycolate to malate, which led to a titer of 4.33 g/l malate and a yield of 0.83 g malate/g xylose, reaching 93% of the theoretical yield. Finally, catalase HPII was overexpressed to decompose H2O2 and alleviate its toxicity, which improved cell growth and further boosted malate titer to 5.90 g/l with a yield of 0.80 g malate/g xylose. To the best of our knowledge, this is the first study to report efficient malate production from xylose as the carbon source.

Metabolic engineering of Escherichia coli for the synthesis of polyhydroxyalkanoates using acetate as a main carbon source.

BACKGROUND: High production cost of bioplastics polyhydroxyalkanoates (PHA) is a major obstacle to replace traditional petro-based plastics. To address the challenges, strategies towards upstream metabolic engineering and downstream fermentation optimizations have been continuously pursued. Given that the feedstocks especially carbon sources account up to a large portion of the production cost, it is of great importance to explore low cost substrates to manufacture PHA economically. RESULTS: Escherichia coli was metabolically engineered to synthesize poly-3-hydroxybutyrate (P3HB), poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB), and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) using acetate as a main carbon source. Overexpression of phosphotransacetylase/acetate kinase pathway was shown to be an effective strategy for improving acetate assimilation and biopolymer production. The recombinant strain overexpressing phosphotransacetylase/acetate kinase and P3HB synthesis operon produced 1.27 g/L P3HB when grown on minimal medium supplemented with 10 g/L yeast extract and 5 g/L acetate in shake flask cultures. Further introduction succinate semialdehyde dehydrogenase, 4-hydroxybutyrate dehydrogenase, and CoA transferase lead to the accumulation of P3HB4HB, reaching a titer of 1.71 g/L with a 4-hydroxybutyrate monomer content of 5.79 mol%. When 1 g/L of α-ketoglutarate or citrate was added to the medium, P3HB4HB titer increased to 1.99 and 2.15 g/L, respectively. To achieve PHBV synthesis, acetate and propionate were simultaneously supplied and propionyl-CoA transferase was overexpressed to provide 3-hydroxyvalerate precursor. The resulting strain produced 0.33 g/L PHBV with a 3-hydroxyvalerate monomer content of 6.58 mol%. Further overexpression of propionate permease improved PHBV titer and 3-hydroxyvalerate monomer content to 1.09 g/L and 10.37 mol%, respectively. CONCLUSIONS: The application of acetate as carbon source for microbial fermentation could reduce the consumption of food and agro-based renewable bioresources for biorefineries. Our proposed metabolic engineering strategies illustrate the feasibility for producing polyhydroxyalkanoates using acetate as a main carbon source. Overall, as an abundant and renewable resource, acetate would be developed into a cost-effective feedstock to achieve low cost production of chemicals, materials, and biofuels.

Analysis of lateral binding force exerted on a bi-sphere induced by an elliptic Gaussian beam.

Based on the generalized Lorentz-Mie theory (GLMT) and the localized approximation of the beam shape coefficients, we derived the expansions of incident elliptic Gaussian (EG) beams in terms of spherical vector wave functions (SVWFs). Utilizing multiple scattering (MS) equations and electromagnetic momentum (EM) theory, the lateral binding force (BF) exerted on a bi-sphere induced by an EG beam is calculated. Numerical effects of various parameters such as beam waist widths, beam polarization states, incident wavelengths, particle sizes, and material losses are analyzed and compared with the results of a circular Gaussian (CG) beam in detail. The observed dependence of the separation of optically bound particles on the incidence of an EG beam is in agreement with earlier theoretical predictions. Accurate investigation of BF induced by an EG beam could provide an effective test for further research on BF between more complex particles, which plays an important role in using optical manipulation on particle self-assembly.

Metabolic engineering of Escherichia coli for the synthesis of the quadripolymer poly(glycolate-co-lactate-co-3-hydroxybutyrate-co-4-hydroxybutyrate) from glucose.

Escherichia coli was metabolically engineered to effectively produce a series of biopolymers consisted of four types of monomers including glycolate, lactate, 3-hydroxybutyrate and 4-hydroxybutyrate from glucose as the carbon source. The biosynthetic route of novel quadripolymers was achieved by the overexpression of a range of homologous and heterologous enzymes including isocitrate lyase, isocitrate dehydrogenase kinase/phosphatase, glyoxylate/hydroxypyruvate reductase, propionyl-CoA transferase, ß-ketothiolase, acetoacetyl-CoA reductase, succinate semialdehyde dehydrogenase, 4-hydroxybutyrate dehydrogenase, CoA transferase and PHA synthase. In shake flask cultures using Luria-Bertani medium supplemented with glucose, the recombinant E. coli reached 7.10g/l cell dry weight with 52.60wt% biopolymer content. In bioreactor study, the final cell dry weight was 19.61g/l, containing 14.29g/l biopolymer. The structure of the produced polymer was chemically characterized by proton NMR analysis. Assessment of thermal and mechanical properties demonstrated that the quadripolymer possessed decreased crystallinity and improved toughness, in comparison to poly-3-hydroxybutyrate homopolymer. This is the first study reporting efficient microbial production of the quadripolymer poly(glycolate-co-lactate-co-3-hydroxybutyrate-co-4-hydroxybutyrate) from glucose.

Engineering Yarrowia lipolytica for poly-3-hydroxybutyrate production.

Strains of Yarrowia lipolytica were engineered to express the poly-3-hydroxybutyrate (PHB) biosynthetic pathway. The genes for ß-ketothiolase, NADPH-dependent acetoacetyl-CoA reductase, and PHB synthase were cloned and inserted into the chromosome of Y. lipolytica. In shake flasks, the engineered strain accumulated PHB to 1.50 and 3.84% of cell dry weight in complex medium supplemented with glucose and acetate as carbon source, respectively. In fed-batch fermentation using acetate as sole carbon source, 7.35 g/l PHB (10.2% of cell dry weight) was produced. Selection of Y. lipolytica as host for PHB synthesis was motivated by the fact that this organism is a good lipids producer, which suggests robust acetyl-CoA supply also the precursor of the PHB pathway. Acetic acid could be supplied by gas fermentation, anaerobic digestion, and other low-cost supply route.

Efficient utilization of pentoses for bioproduction of the renewable two-carbon compounds ethylene glycol and glycolate.

The development of lignocellulose as a sustainable resource for the production of fuels and chemicals will rely on technology capable of converting the raw materials into useful compounds; some such transformations can be achieved by biological processes employing engineered microorganisms. Towards the goal of valorizing the hemicellulose fraction of lignocellulose, we designed and validated a set of pathways that enable efficient utilization of pentoses for the biosynthesis of notable two-carbon products. These pathways were incorporated into Escherichia coli, and engineered strains produced ethylene glycol from various pentoses, including simultaneously from D-xylose and L-arabinose; one strain achieved the greatest reported titer of ethylene glycol, 40 g/L, from D-xylose at a yield of 0.35 g/g. The strategy was then extended to another compound, glycolate. Using D-xylose as the substrate, an engineered strain produced 40 g/L glycolate at a yield of 0.63 g/g, which is the greatest reported yield to date.

Biosynthesis of poly(glycolate-co-lactate-co-3-hydroxybutyrate) from glucose by metabolically engineered Escherichia coli.

Metabolically engineered Escherichia coli strains were constructed to effectively produce novel glycolate-containing biopolymers from glucose. First, the glyoxylate bypass pathway and glyoxylate reductase were engineered such as to generate glycolate. Second, glycolate and lactate were activated by the Megasphaera elsdenii propionyl-CoA transferase to synthesize glycolyl-CoA and lactyl-CoA, respectively. Third, ß-ketothiolase and acetoacetyl-CoA reductase from Ralstonia eutropha were introduced to synthesize 3-hydroxybutyryl-CoA from acetyl-CoA. At last, the Ser325Thr/Gln481Lys mutant of polyhydroxyalkanoate (PHA) synthase from Pseudomonas sp. 61-3 was over-expressed to polymerize glycolyl-CoA, lactyl-CoA and 3-hydroxybutyryl-CoA to produce poly(glycolate-co-lactate-co-3-hydroxybutyrate). The recombinant E. coli was able to accumulate the novel terpolymer with a titer of 3.90g/l in shake flask cultures. The structure of the resulting polymer was chemically characterized by proton NMR analysis. Assessment of thermal and mechanical properties demonstrated that the produced terpolymer possessed decreased crystallinity and improved toughness, in comparison to poly(3-hydroxybutyrate) homopolymer. This is the first study reporting efficient microbial production of poly(glycolate-co-lactate-co-3-hydroxybutyrate) from glucose.

Engineering a novel biosynthetic pathway in Escherichia coli for production of renewable ethylene glycol.

Ethylene glycol (EG) is an important commodity chemical with broad industrial applications. It is presently produced from petroleum or natural gas feedstocks in processes requiring consumption of significant quantities of non-renewable resources. Here, we report a novel pathway for biosynthesis of EG from the renewable sugar glucose in metabolically engineered Escherichia coli. Serine-to-EG conversion was first achieved through a pathway comprising serine decarboxylase, ethanolamine oxidase, and glycolaldehyde reductase. Serine provision in E. coli was then enhanced by overexpression of the serine-biosynthesis pathway. The integration of these two parts into the complete EG-biosynthesis pathway in E. coli allowed for production of 4.1 g/L EG at a cumulative yield of 0.14 g-EG/g-glucose, establishing a foundation for a promising biotechnology.

Light scattering of a Laguerre-Gaussian vortex beam by a chiral sphere.

Since the development of the generalized Lorenz-Mie theory, electromagnetic scattering by arbitrary beams has drawn growing interest. The Laguerre-Gaussian (LG) vortex beam is well known for its orbital angular momentum. With the aim of investigating the analytical solution to the scattering of a chiral sphere by a LG vortex beam, particular attention is paid to the expansion expression of the LG vortex beam. The expansion coefficients are derived based on the expansion of a Hermite Guassian beam as the LG vortex beam can be expressed as the superposition of Hermite Guassian modes. The numerical results of the incident beam expansion coefficients convergence and the scattered field comparison with the reference prove the validity of the theoretical analysis and computation codes. The results reveal that there exists an optimal sphere size for the maximum scattered field which is determined by the topological charge, beam waist radius, and beam center position. The investigation could provide a foundation for the optical manipulation of chiral particles by a LG vortex beam.

Inhibitory effect of cucurbitacin B on imiquimod-induced skin inflammation.

Psoriasis is a common skin disease, of which pathogenesis involves the increase of inflammatory reaction in epidermal cells. In an attempt to find therapeutics for psoriasis, we found that cucurbitacin B has an inhibitory potential on imiquimod-induced inflammation of keratinocytes. Cucurbitacin B significantly inhibited imiquimod-induced expression of crucial psoriatic cytokines, such as IL-8 and CCL20, via down-regulation of NF-κB and STAT3 signaling pathway in human keratinocytes. In addition, keratinocyte proliferation was markedly inhibited by cucurbitacin B. The potential beneficial effect of cucurbitacin B on psoriasis was further validated in imiquimod-induced psoriasiform dermatitis of experimental animal. Topical application of cucurbitacin B resulted in significant reduction of epidermal hyperplasia and inflammatory cytokines production, and ameliorated the psoriatic symptom. Taken together, these results suggest that cucurbitacin B may be a potential candidate for the treatment of psoriasis.

Enhanced production of poly-3-hydroxybutyrate by Escherichia coli over-expressing multiple copies of NAD kinase integrated in the host genome.

OBJECTIVES: With the help of attB-attP recombination technique, multiple copies of yfjB gene encoding the NAD kinase of Escherichia coli were inserted into the host chromosome to promote NADPH-dependent poly-3-hydroxybutyrate (PHB) production. RESULTS: The yfjB integration mutant E. coli T2 harbored a similar metabolic profile to that of the wild type control. When PHB biosynthesis operon was introduced, the yfjB integration mutant produced 3 g PHB l(-1) from 18.2 g glucose l(-1), while the wild type consumed 15.7 g glucose l(-1) to afford 2.34 g PHB l(-1) in 48 h of shake-flask cultivation. Transcriptional analysis showed that the transcription levels of genes within the PHB biosynthesis operon were increased by six to eightfold with yfj Bover-expression, which may be the primary reason for the improved PHB production. CONCLUSION: A practical method is demonstrated to construct genetically-stable strains harboring extra copies of NAD kinase to enhance NADPH-dependent reactions.

Genkwadaphnin induces reactive oxygen species (ROS)-mediated apoptosis of squamous cell carcinoma (SCC) cells.

Genkwadaphnin is a daphnane diterpene ester molecule isolated from the flower buds of Daphne genkwa. In the present study, we investigated the apoptosis-inducing effect of genkwadaphnin in squamous cell carcinoma (SCC) cells. Apoptosis was triggered in SCC12 cells following genkwadaphnin treatment in a time- and concentration-dependent manner. Genkwadaphnin treatment increased phosphorylation of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). Knockdown of JNK and p38 MAPK by recombinant adenovirus expressing microRNA (miR) resulted in significant inhibition of genkwadaphnin-induced apoptosis in SCC12 cells. Finally, pretreatment with the reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) markedly reduced SCC12 cell apoptosis, concomitant with significant inhibition of MAPK activation. These results indicate that genkwadaphnin has the potential to induce apoptosis in SCC cells, providing information on which to base further research with the aim of developing a cure for SCC.

Regional difference in sebum production by androgen susceptibility in human facial skin.

Androgens are important hormones that influence sebum production from the sebaceous glands. Human facial skin can be categorized as T- and U-zones, which are areas with high and low levels of sebum secretion, respectively. This study was performed to investigate whether there are topographical differences in androgen receptor (AR) expression related to regional variations in facial sebum secretion. The results of in vivo analysis indicated a statistically significant increase in AR expression in the sebaceous gland T-zones compared with the U-zones. In vitro experiments using human primary sebocytes also yielded similar results, with higher levels of AR protein and mRNA expression in T-zones. The results of this study suggested that differences in androgen susceptibility may be an important factor influencing regional differences in sebum production in human facial skin.

Glucocorticoid receptor enhances involucrin expression of keratinocyte in a ligand-independent manner.

In this study, we investigated the role of glucocorticoid receptor (GR) in epidermal keratinocytes. In adult normal human skin, GR was highly expressed in the upper layers of the epidermis. Consistent with normal skin, GR expression was increased after calcium treatment of HaCaT keratinocytes cultured in vitro, suggesting that GR is involved in keratinocyte differentiation process. Overexpression of GR using an adenovirus showed that expression of involucrin, an early differentiation marker of keratinocytes, was markedly increased due to GR overexpression. However, treatment with dexamethasone, a GR agonist, did not increase involucrin expression. Overexpression of GR led to phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinases (ERK) in the absence of glucocorticoid, suggesting that the GR effect on involucrin expression is related to activation of intracellular signaling cascades. This idea was supported by the fact that GR-mediated involucrin induction was abolished after treatment with JNK and ERK inhibitors. In addition, GR mutants lacking the ligand-binding domain increased involucrin expression concomitantly with increase of ERK phosphorylation. Together, these results suggest that GR modulates involucrin expression of keratinocytes by regulating the intracellular signaling network in a ligand-independent manner.

Geometric detection based on one-dimensional laser range profiles of dynamic conical target.

One-dimensional laser range profiles (LRPs) contain abundant information regarding the shape, size, and attitude of detected objects. For a dynamic conical target, the variation of its size and attitude could have a significant effect on the projections of LRP peaks. Ground coordinates, target coordinates, and incident field coordinates are established to compute the LRP of dynamic cones. In order to inverse the size, a genetic algorithm is adopted. The cone heights and half-cone angles of three different cones are inversed. Moreover, the results are used to inverse the attitude angles at any sampling time in order to verify accuracy of the theory. The inversion mentioned in this paper can be applied in any targets of arbitrary material, shape, and attitude with great efficiency.

Production of polyhydroxyalkanoates by engineered Halomonas bluephagenesis using starch as a carbon source.

A novel α-amylase Amy03713 was screened and cloned from the starch utilization strain Vibrio alginolyticus LHF01. When heterologously expressed in Escherichia coli, Amy03713 exhibited the highest enzyme activity at 45 °C and pH 7, maintained >50 % of the enzyme activity in the range of 25-75 °C and pH 5-9, and sustained >80 % of the enzyme activity in 25 % (w/v) of NaCl solution, thus showing a wide range of adapted temperatures, pH, and salt concentrations. Halomonas bluephagenesis harboring amy03713 gene was able to directly utilize starch. With optimized amylase expression, H. bluephagenesis could produce poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB). When cultured for PHB production, recombinant H. bluephagenesis was able to grow up to a cell dry weight of 11.26 g/L, achieving a PHB titer of 6.32 g/L, which is the highest titer that has been reported for PHB production from starch in shake flasks. This study suggests that Amy03713 is an ideal amylase for PHA production using starch as the carbon source in H. bluephagenesis.