Sulfated Modification and Bioactivity Analysis of Polysaccharide from Porphyra

The polysaccharides were obtained by microwave-assisted enzymatic extraction from Porphyra, and then modified by sulphate method. Single factor and orthogonal experiments were used to optimize the sulfated modification process of polysaccharides, which were identified by Fourier transform infrared spectroscopy (FT-IR). The antioxidant and hypoglycemic activity changes of the polysaccharides modified by sulphate and chlorosulfonic acid-pyridine method were also studied. Results showed that the optimal technology parameters were the ratio of solid to liquid 1:80 g/mL, the mass ratio of Porphyra polysaccharide to ammonium sulfate 10:9 g/g, reaction time 33 min, and the maximum degree of substitution was 2.94. FT-IR showed that the characteristic absorption peaks of sulfate radical group appeared near 801 and 1123 cm−1, and the possible substitution position of sulfate radical group was C-6. The sulfate modification could significantly improve the scavenging ability of DPPH, O2− and OH free radicals and the inhibitory effect on α-glucosidase activity of the polysaccharides (P<0.05). The antioxidant and hypoglycemic activity of the polysaccharides modified by sulphate method were both higher than that by chlorosulfonic acid-pyridine method (P<0.05), indicating that sulphate method was applicable to modify the Porphyra polysaccharide. This study provides a theoretical basis for the further development of polysaccharides from Porphyra as a functional food

Preparation, Structural Characterization and Biological Activity of Phosphorylated Polysaccharide from Undaria pinnatifida Suringar

The polysaccharide purified from Undaria pinnatifida Suringar was phosphorylated using phosphate as a cross-linking agent. The structure of the phosphorylated polysaccharide was characterized by ultraviolet (UV) absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), periodate oxidation and Smith degradation, Congo red test, β-elimination reaction, and iodine-potassium iodide test, and the free radical scavenging capacity and hypoglycemic activity of the raw and modified polysaccharide were evaluated. The results showed that the substitution degree of phosphate was 9.26, and the characteristic absorption peaks of P=O and P–O–C appeared at 1 216 and 886 cm-1, indicating that the phosphorylation modification was successful. The maximum relative molecular mass of the phosphorylated polysaccharide was 94.4 × 103. It had a triple-stranded helical structure and was composed of glucopyranose unis linked together by β-glycosidic bonds. The polysaccharide and amino acids were linked together mainly by –O– glycopeptide bonds. The main linkages between monosaccharides were 1→3, 1→2,1→4 and 1→6 glycosidic bonds, the molar ratio was 0.494:0.504:0.002, and the sugar chain had a branched structure. The scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide anion radical (O2-·) and hydroxyl radical (·OH) and the α-glucosidase inhibitory activity of the polysaccharide were significantly increased by 34.76%, 12.30%, 76.05% and 3.70% after the phosphorylation modification (P < 0.05), indicating that phosphorylation modification enhanced the free radical scavenging capacity and hypoglycemic activity of the polysaccharide from Undaria pinnatifida Suringar

Intragenic DNA Methylation Regulates Insect Gene Expression and Reproduction through the MBD/Tip60 Complex

DNA methylation is an important epigenetic modification. However, the regulations and functions of insect intragenic DNA methylation remain unknown. Here, we demonstrate that a regulatory mechanism involving intragenic DNA methylation controls ovarian and embryonic developmental processes in Bombyx mori. In B. mori, DNA methylation is found near the transcription start site (TSS) of ovarian genes. By promoter activity analysis, we observed that 5′ UTR methylation enhances gene expression. Moreover, methyl-DNA-binding domain protein 2/3 (MBD2/3) binds to the intragenic methyl-CpG fragment and recruits acetyltransferase Tip60 to promote histone H3K27 acetylation and gene expression. Additionally, genome-wide analyses showed that the peak of H3K27 acetylation appears near the TSS of methyl-modified genes, and DNA methylation is enriched in genes involved in protein synthesis in the B. mori ovary, with MBD2/3 knockdown resulting in decreased fecundity. These data uncover a mechanism of gene body methylation for regulating insect gene expression and reproduction

Whole Genome Distribution and Ethnic Differentiation of Copy Number Variation in Caucasian and Asian Populations

Although copy number variation (CNV) has recently received much attention as a form of structure variation within the human genome, knowledge is still inadequate on fundamental CNV characteristics such as occurrence rate, genomic distribution and ethnic differentiation. In the present study, we used the Affymetrix GeneChip® Mapping 500K Array to discover and characterize CNVs in the human genome and to study ethnic differences of CNVs between Caucasians and Asians. Three thousand and nineteen CNVs, including 2381 CNVs in autosomes and 638 CNVs in X chromosome, from 985 Caucasian and 692 Asian individuals were identified, with a mean length of 296 kb. Among these CNVs, 190 had frequencies greater than 1% in at least one ethnic group, and 109 showed significant ethnic differences in frequencies (p<0.01). After merging overlapping CNVs, 1135 copy number variation regions (CNVRs), covering approximately 439 Mb (14.3%) of the human genome, were obtained. Our findings of ethnic differentiation of CNVs, along with the newly constructed CNV genomic map, extend our knowledge on the structural variation in the human genome and may furnish a basis for understanding the genomic differentiation of complex traits across ethnic groups

Estimation of Agricultural Total Factor Productivity in China: A Panel Cointegration Approach

This paper uses panel cointegration approach to estimate the agricultural total factor productivity (TFP) from 30 regions from 1978 to 2004 in China. The results of panel unit root find that all inputs and output variables are nonstationary series. Pedroni (1999) panel cointegration tests present the evidence supporting the existence of the long run cointegration relationship. This paper finds the estimator of FMOLS is better than OLS and DOLS. Agricultural total factor productivity is estimated based on Kao and Chiang (2000) panel coefficients estimation

Investigation of Induced Charge Mechanism on a Rod Electrode

Rod electrodes based on an electrostatic induction mechanism are widely used in various industrial applications, but the analytic solution of an induced charge mechanism on a metal rod electrode has not yet been systematically established. In this paper, the theoretical model of the induced charge on a rod electrode is obtained through the method of images. Then, the properties of the rod electrode under the action of the point charge are studied, including the induced charge density distribution on the rod electrode, the amount of the induced charge with different diameters and lengths of the electrode, and the effective space region induced by the electrode. On this basis, a theoretical model of the induced current on a rod electrode is established, which is used to study the induced current properties by a moving point charge. It is found that both the magnitude and bandwidth of the induced current increase with the increased point charge velocity. Finally, three experimental studies are conducted, and the experimental results show good consistency with the analysis of the theoretical model, verifying the correctness, and accuracy of the model. In addition, the induced charge mechanism studied in this paper can act as an effective basis for the rod electrode sensor design in terms of the optimal radius and length