Guo-Hua Wu

Ultrasound extraction of polysaccharides from mulberry leaves and their effect on enhancing antioxidant activity.

A Box-Behnken design (BBD) was applied to optimize the ultrasound-assisted extraction of polysaccharides from mulberry leaves. Under the optimum conditions of an extraction temperature of 57 °C, an extraction time of 80 min and a liquid/solid ratio of 53 mL/g, the mulberry leaf polysaccharide (MLP) yield was 6.92 ± 0.29%. Then, three fractions of MLPs were obtained by deproteinization, dialysis and decolorization. The carbohydrate content, FT-IR spectrum and monosaccharide composition of the MLPs were also investigated. The antioxidant activities of the three fractions were compared, and the results indicated that the antioxidant activities decreased with the increasing MLP purity. Therefore, highly concentrated MLPs were shown to have very little antioxidant activity. After quercetin (10 μg/mL) was added, the antioxidant activities were improved significantly. This result showed that MLPs and quercetin have a synergistic effect on the antioxidant activity. Although the MLPs have very little antioxidant activity alone, they greatly enhance the antioxidant activity of flavonoids. Thus, MLPs can be used as an antioxidant activity enhancer in the food industry.

Rapid determination of 1-deoxynojirimycin in Morus alba L. leaves by direct analysis in real time (DART) mass spectrometry.

A new method based on a Direct Analysis in Real Time (DART) ionization source coupled with triple quadrupole tandem mass spectrometry has been developed for rapid qualitative and quantitative analyses of 1-deoxynojirimycin (DNJ) in mulberry leaves. Two ions produced from DNJ, [M+H](+) (m/z 164) and [M-2H+H](+) (m/z 162), are observed using DART-MS in the positive ion mode. The peak areas of the two selected ions monitoring (SIM) signals of ([M+H](+) (m/z 164) and [M-2H+H](+) (m/z 162)) are integrated to determine the peak area for quantitative analyses. A reasonable linear regression equation is obtained in the range of 1.01 to 40.50 μg/mL, with a linear coefficient (R(2)) of 0.996. The limits of detection (LOD) and quantification (LOQ) of the method are 0.25 and 0.80 μg/mL, respectively. The range of recovery is shown to be 87.73-95.61%. The results derived from the developed DART-MS method are in good agreement with those from the conventional HPLC-FLD method. By contrast, DART-MS in SIM mode is a simple, rapid and high-throughput approach for the determination of the DNJ content in mulberry leaves. The present method is advantageous for the rapid screening of mulberry leaves containing high DNJ contents.

Robust composite silk fibers pulled out of silkworms directly fed with nanoparticles

This paper reports the impacts of direct feeding silkworms with different nanoparticles (Cu, Fe, and TiO2) on the morphology, structures, and mechanical properties of the resulting silk fiber (SF). The contents of the Cu nanoparticles were 38 times higher in the posterior silk glands and only 2-3 times higher in the SF and in the middle silk glands compared with the controlled groups. Significant changes of the surface morphology, structures, and diameter of the Cu nanoparticle fed SF have been observed, which are attributed to a slight SF protein reconstruction or conformational change in the mixture of silk fibroin and sericin in the silk glands. The resulting Cu-containing SF exhibits good tensile strength of 360MPa and reaches a strain of 38%, which are 89% and 36% higher than those of the natural SF. This study offers a new green strategy for the easy modification to achieve robust composite SF.

Preparation of a regenerated silk fibroin film and its adsorbability to azo dyes

In this work, a novel and sustainable biosorbent, regenerated silk fibroin film (rSFF) was successfully prepared and its adsorbability to azo dyes (acid yellow 11, naphthol orange and direct orange S) was measured. At optimal conditions, the adsorption capacity of rSFF for acid yellow 11 reached up to 59.71mg/g, which was 1.23-fold higher than that of raw silk fibroin fibers. More importantly, rSFF exhibited a high level of flexibility and functionality as well as a good shaping ability, which were crucial for its practical application. The SEM results showed that rSFF was a porous material, indicating that it had more available adsorption sites compared with raw silk fibroin fibers, which might contribute to the higher adsorption capacity of rSFF. Isotherm equilibrium studies revealed that the azo dye adsorption process followed the Langmuir model, indicating that rSFF was a structurally homogenous adsorbent. The recycle test showed that rSFF had potential to be reused in a number of treatment cycles. After five cycles, its adsorbability to acid yellow 11 remained as high as 47.20mg/g. Finally, a scale-up experiment was performed for rSFF, and the results indicated that it was feasible for rSFF to extend the practical application.

Modulation of the optical properties of D-π-A type azobenzene derivatives by changing the π-conjugated backbones: A theoretical study

The optical properties of two series of azobenzene derivatives were modulated by backbone modifications with the density functional theory (DFT) calculations. Compared to the short-chain molecule, the chromophore with an elongated π-bridge exhibits a greater extent of charge transfer during one-photon excitation and hence possesses a larger molecular first hyperpolarizability (β0). Meanwhile, an evident red-shift in the maximum absorption was observed after extension of the π-conjugated backbone. The tendency of the static β0 value derived from the two-state model is consistent with the result of the calculation at M06-2X/6–311++G(d,p) level by means of analytical derivative method. The dynamic perturbations were revealed to cause the obvious enhancement of the first hyperpolarizability. The more closer the foundational wavelength to two times the value of the maximum absorption in one-photon transition, the larger βRHS value is observed for the chromophore. The nonlinear optical (NLO) properties augment with the introduction of the THF solvents by comparing the gas-phase values. With increasing the length of conjugated bridge, the dynamic βRHS value increases more rapidly in THF solution than in vacuum.

Generic DART-MS platform for monitoring the on-demand continuous-flow production of pharmaceuticals: Advancing the quantitative protocol for caffeates in microfluidic biocatalysis

&NA; Today, continuous processing is regarded as an effective on‐demand production technique of pharmaceuticals. Homemade microreactors packed with immobilized lipase under continuous‐flow conditions were first applied to tailor the production of high‐value caffeic acid phenethyl ester (CAPE) from methyl caffeate (MC) and 2‐phenylethanol (PE) in cyclohexane via transesterification; however, this method is challenging due to the lack of a rapid platform for monitoring caffeates in microfluidic biocatalysis. The reactants were directly analyzed using Direct Analysis in Real Time Mass Spectrometry (DART‐MS), and the corresponding ionization parameters were investigated. Special ions produced from MC (parent ion m/z 192.87 and product ion m/z 133.44) and CAPE (parent ion m/z 282.93 and product ion m/z 178.87) were determined using DART‐MS2 in the negative ion mode. The peak areas of the select reaction monitoring (SRM) signals were calculated to develop the standard curves for quantitative analyses of the concentration. Reasonable linear regression equations of MC and CAPE were obtained in the range of 3.125–50.000 mg/L, with linear coefficients (R2) of 0.9515 and 0.9973, limits of detection (LOD) of 0.005 and 0.003 mg/L, limits of quantification (LOQ) of 0.02 and 0.01 mg/L, and recovery ranges of 92.50–97.11% and 90.11–97.60%, respectively. The results using DART–MS2 were in good agreement with those using conventional High‐Performance Liquid Chromatography with a UV detector (HPLC‐UV) and were successfully applied to monitor the kinetics constants and mass transfer coefficients in a continuous‐flow packed bed microreactor. Thus, the DART‐MS2 method is an efficient tool for analyzing caffeates in microfluidic biocatalysis with limited sample preparation and short operating time. Graphical abstract Figure. No caption available. HighlightsDART‐MS monitors continuous‐flow production of active pharmaceutical ingredients.Continuous‐flow microreactor packed with immobilized enzyme used to produce APIs.Simultaneous determination of MC and CAPE by DART‐MS2 at a speed of 40 s/sample.Results of DART‐MS2 were in good agreement with those using conventional HPLC‐UV.DART‐MS2 firstly used to measure kinetics and mass transfer coefficients in microreactors.

Light-induced self-assembly of bi-color CdTe quantum dots allows the discrimination of multiple proteins

We have found that the addition of proteins can greatly influence the light-induced self-assembly (LISA) behavior of bi-color thioglycolic acid (TGA)-capped CdTe Quantum Dots (QDs) and thus cause significant changes of their fluorescence (FL) signals (color and intensity), according to which a dual-channel FL sensor can be established for simultaneous discrimination of multiple proteins. The sensor is successfully used for the identification of ten native proteins and ten thermally denatured proteins and eight native proteins artificially added in human urine, respectively, during which process principal component analysis (PCA) is utilized to differentiate the targets based on their corresponding FL change patterns. This assay has provided a visual and simple method for the discrimination of various analytes, which may have great potential in the study of conformational changes of biomacromolecules and the analysis of real biological fluids.

Intrinsically reinforced silks obtained by incorporation of graphene quantum dots into silkworms

Silkworm silks have been widely used in a variety of fields due to their sensuousness, luster and excellent mechanical properties. Researchers have paid special attention in improving the mechanical properties of silks. In this work, Bombyx mori larval silkworms are injected with graphene quantum dots (GQDs) through a vascular injection to enhance mechanical properties of the silkworm silks. The GQDs can be incorporated into the silkworm silk gland easily due to hemolymph circulation and influence the spinning process of silkworm. The breaking strength, elongation at break and toughness modulus of the silks increase by 2.74, 1.33 and 3.62 times, respectively, by injecting per individual with 0.6 μg GQDs. Wide-angle X-ray scattering indicates that the size of β-sheet nanocrystals in GQDs-silks is smaller than that in control-silks. Infrared spectra suggest that GQDs confine the conformation transition of silk fibroin to β-sheet from random coil/α-helix, and the change of the size and content of β-sheet may be the reason for the improvement of the mechanical properties. The toxicity and safety limit of GQDs incorporated into each silkworm is also evaluated, and the results show that the upmost dose of GQDs per silkworm is 30.0 μg. The successful obtainment of reinforced silks by in vivo uptake of GQDs provides a promising route to produce high-strength silks.摘要家蚕蚕丝具有细腻、 光鲜以及优良的力学特性, 因而在诸多领域中都有广泛应用. 许多科学家对提高家蚕蚕丝力学性能的研究非常感兴趣. 本工作中, 我们通过血管注射的方式给家蚕幼虫注入了石墨烯量子点(GQDs), 并且得到了力学性能增强的蚕丝. GQDs可通过淋巴循环进入到家蚕的丝腺器官并影响家蚕的纺丝过程. 研究发现, 当家蚕的GQDs摄入量为0.6 μg/头时, 家蚕蚕丝的断裂强度、 断裂伸长率以及韧性模量可分别增强到原来的2.74, 1.33 和3.62倍. 广角X射线散射(WAXS)结果表明GQDs-蚕丝中的β-折叠纳米晶体的尺寸比起空白蚕丝有所降低, 红外光谱结果表明GQDs限制了丝素蛋白中无规则卷曲或者α-螺旋结构向β-折叠结构的构象转变. β-折叠结构的尺寸及含量的变化可能是引起蚕丝力学性能增强的原因所在. 我们还对GQDs的毒性以及单头家蚕摄入GQDs的安全限进行了评估, 结果发现家蚕摄入GQDs的上限为30.0 μg/头. 使家蚕直接摄入GQDs获得力学性能增强的蚕丝的方法为生产高强度蚕丝提供了一种有潜力的途径.

Effect of different planting areas on the chemical compositions and hypoglycemic and antioxidant activities of mulberry leaf extracts in Southern China

Guangdong, Guangxi and Chongqing are emerging sericulture areas in China where the production of mulberry leaves is huge. In order to identity high quality mulberry leaves that are suitable for healthy products to expand planting, 24 samples from three regions (Guangdong, Guangxi, Chongqing) in the south of China were quantified for two alkaloids (1-deoxynojirimycin and fagomine) and five phenols (chlorogenic acid, rutin, isoquercitrin, etc.) using high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Additionally, the total phenolic and total flavonoid contents, antioxidant and glycosidase inhibitory activities (hypoglycemic activity) were tested using different assays (DPPH, ABTS, FRAP) to comprehensively evaluate the quality of the mulberry leaves. The contents of DNJ and fagomine ranged from 0.401±0.003 to 5.309±0.036 mg/g and from 0.279±0.031 to 2.300±0.060 mg/g, respectively. The main phenolic constituents were chlorogenic acid, rutin and isoquercitrin, with chlorogenic acid present in the highest concentrations, ranging from 3.104±0.191 to 10.050±0.143 mg/g. The antioxidant activity exhibited a tendency as follows: Guangxi > Guangdong > Chongqing, except for two samples from Chongqing, which showed the highest antioxidant activity. Based on our study, mulberry leaves from Guangdong and Guangxi could be future sources of natural hypoglycemic and antioxidant products.