VEGF基因油体表达系统构建及对拟南芥的遗传转化

为研究油体系统在植物中表达外源蛋白的优势,以油菜总DNA 为模板,通过PCR 得到油菜油体(Ycoil)及启动子序列(Ycprm)。同时,将多对合成的寡核苷酸链,通过PCR 方法拼接得到血管内皮生长因子全长基因(VEGF)。以此为基础,构建Ycoil、Ycprm、VEGF 融合表达载体p1390Ycprm-Ycoil-VEGF。将重组质粒转入农杆 菌GV3101,并用花浸染法对拟南芥进行浸染。在含潮霉素(20mg/L)的1/2MS 培养基上筛选转基因拟南芥种子(T0),获得了T1 代抗性植株,通过PCR 检测、SDS-PAGE 检测和Western blotting 检测,结果表明油菜油体及血管内皮生长因子的融合基因已经转入拟南芥中,并成功得到表达,转化率约为0.1%。     

Growth and persistence of Listeria monocytogenes isolates on the plant model Arabidopsis thaliana

While the majority of human listeriosis cases appear to be linked to consumption of processed ready-to-eat foods (e.g., deli meats), a few listeriosis outbreaks have been linked to consumption of contaminated vegetables. In this study, we assessed four isolates representing the major Listeria monocytogenes lineages for their abilities to attach to and grow on Arabidopsis thaliana, a well-characterized plant model. When plants were dipped for 5min into 3ml of water containing 8.8logCFU of L. monocytogenes and rinsed repeatedly, L. monocytogenes was recovered from the leaves at densities from 1.52 to 2.17logCFU/cm(2). Ten days after exposure, bacterial numbers had increased over initial numbers by 2.60-2.95logCFU/cm(2). Using L. monocytogenes expressing GFP, bacteria were visualized in the intercellular spaces of A. thaliana leaves, suggesting internalization through stomata. These data indicate that L. monocytogenes can rapidly attach to and multiply on plant surfaces and colonize intercellular spaces in A. thaliana leaves where it may be protected from sanitation treatments. When A. thaliana seeds were exposed to L. monocytogenes, between 4.23 and 4.57logCFU/cm(2) were recovered from leaves 7 days post-germination, suggesting that contaminated seeds can produce contaminated plants. Overall, our study demonstrates that prevention of L. monocytogenes contamination of plants throughout growing stages is critical, consistent with recommendations for other produce-transmitted foodborne pathogens.     

Sequence analysis of the right end of chromosome XV in Saccharomyces cerevisiae: An insight into the structural and functional significance of sub-telomeric repeat sequences

Approximately 3·9 kb of DNA, centromere proximal to the previously sequenced Y′ element at the right end of chromosome XV in Saccharomyces cerevisiae strain YP1, has been sequenced. A number of the known sub-telomeric repeat sequences were identified, including Y′, core X and STRs A, B. C and D. Several of these repeat elements contain potentially functional sequences. In addition, two other members of repeated gene families were identified. The first of these shows 61% and 60% DNA sequence identity to Enolases 1 and 2 respectively. The Enolase-like sequence appears to be species specific, with three copies being found in all strains of S. cerevisiae studied. The location of the three copies is the same for all strains. The second repeated sequence has homology with known open reading frames on chromosomes III, V and XI. There are five or six copies of this sequence in all S. cerevisiae and S. paradoxus strains studied and three in S. bayanus strains. The analysis of this region and comparison to sub-telomeric regions on other chromosomes gives some indication as to the potential functional and structural significance of sub-telomeric repeat sequences. In addition, these findings are consistent with the idea that sub-telomeric regions may be targets for unusual recombination events. The updated sequence has been deposited in the EMBL and GenBank databases under Accession Number M58718.     

Formate dehydrogenase gene of Arabidopsis thaliana is induced by formaldehyde and not by formic acid

Variability of expression of formate dehydrogenase (FDH) caused by uptake of C-1 compounds was examined by using Arabidopsis thaliana as a model plant. Effects of uptake of several C-1 compounds were evaluated by Northern blot analysis using cDNA of A. thaliana FDH prepared by cloning on the basis of known sequence. As a result, expression of the FDH gene in A. thaliana was not intensely influenced by formic acid, an inherent substrate for FDH, but strongly induced by its reduced form, formaldehyde.     

Insights into the effects of dynamic high-pressure microfluidization on the structural and rheological properties of rapeseed protein isolate

The application of dynamic high-pressure microfluidization (DHPM) provides interesting modifications in food structures. However, the effects of DHPM on the structural and rheological properties of rapeseed protein isolate (RPI) were scarcely investigated. In this study, the average hydrodynamic size of RPI treated by DHPM significantly declined from 239.2 nm to 170 nm with the pressure and time rising to 60 MPa and 2 min. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis found that DHPM did not affect the molecular mass of the RPI. The changes in the intrinsic fluorescence and circular dichroism spectra showed that tertiary and secondary structures of RPI were altered, as proved by the higher fluorescence intensity and greater conversion of random coils and β-sheets into α-helices compared with the control (unprocessed RPI). The spatial unfolding of the RPI structure and the dissociation of chemical bonds influenced its rheological behavior. All RPI suspensions (15%, w/v) processed by DHPM had lower apparent viscosity, moduli, higher gelling temperature (up to 69.7 °C) than control, and the differences in rheological performance were closely dependent on the treatment pressure and time. In conclusion, through this study of the effects of DHPM on RPI, DHPM was shown to be a potential method for modifying proteins and reducing the consistency of high-protein fluid foods.     

Insights into proteolytic processing of the major peanut allergen Ara h 2 by endogenous peanut proteases

BACKGROUND: The major peanut allergens are Ara h 1, Ara h 2 and Ara h 6. Proteolytic processing has been shown to be required for the maturation process of Ara h 6. The aim of this study was to examine whether Ara h 2 undergoes proteolytic processing and, if so, whether proteolytic processing influences its ability to bind human immunoglobulin E (IgE). RESULTS: Ara h 2 isolated from peanut extract under conditions of protease inhibition revealed a single additional peak for its two known isoforms (Ara h 2.01 and Ara h 2.02), corresponding to a C‐terminally truncated form lacking a dipeptide (RY). Ara h 2 isolated in the absence of protease inhibition, however, yielded two additional peaks, identified as C‐terminally truncated forms lacking either a dipeptide (RY) or a single tyrosine residue. The IgE‐binding capacity of the Ara h 2 truncated forms was not altered. CONCLUSION: Ara h 2 undergoes proteolytic processing by peanut proteases that involves C‐terminal removal of a dipeptide. Hence Ara h 2 isolated from peanut extract is a complex mixture of two isoforms expressed by different genes, Ara h 2.01 and Ara h 2.02, as well as truncated forms generated by the proteolytic processing of these isoforms. Copyright © 2010 Society of Chemical Industry     

Consideration of the evolution of the Saccharomyces cerevisiae MEL gene family on the basis of the nucleotide sequences of the genes and their flanking regions

Analysis of the DNA sequences of new members of the Saccharomyces cerevisiae MEL1-MEL10 gene family showed high homology between the members. The MEL gene family, α-galactosidase-coding sequences, have diverged into two groups; one consisting of MEL1 and MEL2 and the other of MEL3-MEL10. In two S. cerevisiae strains containing five or seven MEL genes each, all the genes are nearly identical, suggesting very rapid distribution of the gene to separate chromosomes. The sequence homology and the abrupt change to sequence heterogeneity at the centromere-proximal 3′ end of the MEL genes suggest that the distribution of the genes to new chromosomal locations has occurred partly by reciprocal recombination at solo delta sequences. We identified a new open reading frame sufficient to code for a 554 amino acid long protein of unknown function. The new open reading frame (Accession number Z37509) is located in the 3′ non-coding region of MEL3-MEL10 genes in opposite orientation to the MEL genes (Accession numbers Z37508, Z37510, Z37511). Northern analysis of total RNA showed no hybridization to a homologous probe, suggesting that the gene is not expressed efficiently if at all.     

Enantioselective Damage of Diclofop Acid Mediated by Oxidative Stress and Acetyl-CoA Carboxylase in Nontarget Plant Arabidopsis thaliana

Diclofop-methyl (DM) is a widely used chiral herbicide, which rapidly hydrolyzes to its major metabolite diclofop acid (DC) after application. With a carbon chiral center, DC not only is an important ingredient of herbicidal activity, but also has a long half-life in soil. Studies so far have only considered the activity of racemic DM in target organisms, and the enantioselective toxicity in nontarget plants of DM and DC has yet to be explored. In this study, the enantioselective phytotoxicity of DC mediated by oxidative stress and the key enzyme ACCase in the fatty acid synthesis system on the model plant Arabidopsis thaliana was investigated. Significant differences between the two enantiomers were observed in phytotoxicity including growth inhibition, oxidative damage and alteration of key genes expression of ACCase, with R-DC showing greater toxicity to Arabidopsis thaliana than S-DC. The results of molecular docking showed that there was a stronger affinity between R-DC and the target enzyme carboxyltransferase domain of ACCase, likely leading to the enantioselective phytotoxicity of DC. This study suggested that chirality of both parent compounds and metabolites should be considered to improve our understanding of the environmental fate and risks of chiral pesticides.     

Insights into the sorption properties of cutin and cutan biopolymers

Plant cuticles have been reported as highly efficient sorbents for organic compounds. The objective of this study was to elucidate the sorption and desorption behavior of polar and nonpolar organic compounds with the major structural components of the plant cuticle: the biopolymers cutin and cutan. The sorption affinity values of the studied compounds followed the order: phenanthrene > atrazine > chlorotoluron > carbamazepine. A higher sorption affinity of phenanthrene and atrazine to cutin was probably due to the higher level of amorphous paraffinic carbon in this biopolymer. Phenanthrene exhibited reversible sorption behavior and a high ratio of organic-carbon-normalized distribution coefficient (Koc) to carbon-normalized octanol-water partitioning coefficients (Kowc) with both biopolymers. This suggests that both biopolymers provide phenanthrene with a partition medium for hydrophobic interactions with the flexible long alkyl-chain moieties of the biopolymers. The low Koc/Kowc ratios obtained for the polar sorbates suggest that the polar sites in the biopolymers are not accessible for sorption interactions. Atrazine and carbamazepine exhibited sorption-desorption hysteresis with both sorbents, indicating that both sorbates interact with cutin and cutan via both hydrophobic and specific interactions. In general, the sorptive properties of the studied biopolymers were similar, signifying that the active sorption sites are similar even though the biopolymers exhibit different properties.     

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) determination of phase II metabolites of the mycotoxin zearalenone in the model plant Arabidopsis thaliana.

The biotransformation products of zearalenone, a Fusarium mycotoxin, were elucidated using the model plant Arabidopsis thaliana. After treatment of plant seedlings with 50 microM zearalenone, both the liquid media and the plant extracts were analysed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). An array of 17 different metabolites, most prominently glucosides, malonylglucosides, di-hexose- and hexose-pentose disaccharides of zearalenone, and alpha- and beta-zearalenol, were detected in the samples. Time courses for the different zearalenone metabolites were recorded and they give a closer insight into the metabolism kinetics. A scheme proposing the zearalenone metabolism in A. thaliana is given. The aspect of food safety regarding the (potential) occurrence of masked mycotoxins in agricultural commodities is discussed.     

反胶束萃取植物蛋白质结构与功能特性研究进展

该文综述国内外关于反胶束萃取技术分离得到的植物蛋白质结构与特性研究进展,阐述了反胶束萃取对植物蛋白质分子构象、微观结构、亚基构成、氨基酸组成的影响,以及结构改变引起蛋白质功能特性的差异;并提出反胶束萃取技术存在的问题及前景展望。     

热诱导下小麦蛋白结构与功能性质变化研究进展

小麦蛋白作为具有独特黏弹性的植物蛋白,在食品加工领域中应用广泛。加热是食品加工过程中常见的工艺过程,温度及物理协同作用是影响小麦蛋白结构及功能特性的主要因素,而热诱导下小麦蛋白的结构和功能性质的变化决定着小麦制品及小麦蛋白制品的品质,此外热加工体系中其他物质的加入对于增强小麦蛋白结构功能特性、丰富小麦蛋白制品种类及改善其品质发挥重要作用。本文综述了小麦蛋白的面筋蛋白网络和凝胶的形成机制,概述了不同热诱导方式如温度(温和热诱导和过热蒸汽热处理)、物理协同热诱导(挤压热诱导和超声处理)对小麦蛋白结构、功能性质及其加工制品品质的影响,介绍了热诱导加工体系中小麦蛋白与其他动植物蛋白、多糖、水分及盐离子的相互作用机制以及其产品加工的应用和品质变化,并针对小麦蛋白主要组分麦醇溶蛋白和麦谷蛋白对热诱导小麦蛋白结构、功能及产品品质的影响进行了分析和展望,以期为改善小麦蛋白在食品加工中的应用及品质改善提供理论参考。     

Insights into the structural characterisations,bioactivities and their correlations with water-soluble polysaccharides extracted from different pomelo (Citrus maxima Merr.) tissues

Pomelo (Citrus maxima Merr.), known as a famous fruit and folk medicine, is widely cultivated in China. Nonedible pomelo tissues contain peels, seeds, and segment membranes, which generally being discarded. Polysaccharides relationships among different pomelo tissues remain uncertain. Four water-soluble polysaccharides, PPPs, PSPs, FPPs and SMPs, were extracted from pomelo peels, seeds, pulps and segment membranes, respectively. Molecular structure and conformation were investigated by a combination of chemical and instrumental analyses. PPPs and FPPs were consisted of Ara, GalA, GlcA, Rha, Glc, Xyl and Gal, while PSPs and SMPs did not contain GalA and Gal. The average molecular weight (Mw) of PPPs, PSPs, FPPs and SMPs was 4.604 × 10⁵, 10.85 × 10⁵, 5.795 × 10⁵ and 16.06 × 10⁵ Da, respectively. PPPs, PSPs and SMPs all showed totally spherical structures, while FPPs primarily comprised linear chains. The structures–bioactivities correlations analysis revealed that low-Mw polysaccharides had strong DPPH•, OH• scavenging and HeLa cells inhibiting activities. These data revealed that the bioactivities of pomelo tissues polysaccharides were not a function of a single factor but a combination of various characteristics.     

功能性植物油脂的主要生理活性及应用

功能性植物油脂是一类具有特殊生理功能的植物油脂,具备优异的保健、药用功能,是普通食用动植物油脂的有益补充。文章重点分析了功能性植物油脂中多不饱和脂肪酸和磷脂的生理活性,并对几种有代表性的功能性植物油脂及应用进行了评述。     

氯化钾硫酸镁转化法生产硫酸钾的新工艺

利用有机溶剂析盐法分离水溶液中混合电解质的技术 ,开发了一种氯化钾、硫酸镁转化法生产硫酸钾的新工艺 ,与传统工艺相比 ,该工艺具有产品质量稳定 ,硫酸钾得率高 ,易操作等优点     

Microwave processing technology influences the functional and structural properties of fish gelatin

The objective of this study was to evaluate the effects of microwave processing technology (MPT, 240–800 W, 1 and 4 min) on the functional and structural properties of fish gelatin (FG). It showed that MPT could increase gel strength and texture properties of FG, especially for 240 W. MPT greatly increased emulsifying activity index (EAI) of FG, but decreased its emulsion stability index (ESI). Rheology results showed that MPT increased viscosity of FG, but decreased gelation times. Intrinsic fluorescence and Fourier transform infrared (FTIR) spectroscopy results indicated that MPT could unfold gelatin, contributing to the formation of H-bonds. Scanning electron microscopy (SEM) analysis revealed that low power and short time of MPT-treated gelatin gels had much more dense and less voids. This work provided guidance for the applications of MPT to improve the functional properties of FG, and the results show that MPT-treated FG can replace mammalian gelatin and meet the religious requirement.     

The applications of conventional and innovative mechanical technologies to tailor structural and functional features of dietary fibers from plant wastes: A review

Plant food wastes generated through the food chain have attracted increasing attention over the last few years not only due to critical environmental and economic issues but also as an available source of valuable components such as dietary fibers. However, the exploitation of plant waste remains limited due to the lack of appropriate processing technologies to recover and tailor fiber functionalities. Among the different technologies developed for waste valorization, mechanical techniques were suggested to be a promising and sustainable strategy to extract fibers with improved functionalities. In this context, the present review describes different mechanical technologies (conventional and innovative) with potential applications to produce micro/nanofibers from various plant residues, highlighting the operating principle as well as the main advantages and pitfalls. The impact on the structural, technological, and functional properties of fibrous materials is comprehensively discussed. The extent of fiber modification not only highly depended on the technology and operation conditions used but also on fiber composition and the application of posttreatments such as dehydration. Other variables, including economic and environmental issues such as equipment cost, energy demand, and eco-friendly features, are also reviewed. The outputs of this review can be used by both the industrial sector and academia to select a suitable combination of fiber and processing technology for designing novel foods with improved functionalities that fulfill market trends and consumer needs.     

New Insights into the High‐Pressure Processing of Meat and Meat Products

Abstract: For years, high‐pressure processing has been viewed as useful for pasteurizing food while maintaining the quality of fresh food. However, even at moderate pressure, this process is not without effects on food, especially on meat products. These effects are especially important because pressure greater than 400 MPa is generally necessary to achieve efficient microbial inactivation. In this review, recent advances in the understanding of the impacts of high pressure on the overall quality of raw and processed meat are discussed. Many factors, including meat product formulation and processing parameters, can influence the efficiency of high pressure in pasteurizing meat products. It appears that new strategies are applied either (i) to improve the microbial inactivation that results from high pressure while minimizing the adverse effects of high pressure on meat quality or (ii) to take advantage of changes in meat attributes under high pressure. Most of the time, multiple preservation factors or techniques are combined to produce safe, stable, and high‐quality food products. Among the new applications of high‐pressure techniques for meat and meat‐derivative products are their use in combination with temperature manipulation to texturize and pasteurize new meat products simultaneously.     

Oxidative cross-linking of potato proteins by fungal laccases: Reaction kinetics and effects on the structural and functional properties

Aiming at developing biocatalytic approach to modulate potato proteins functionalities, laccase-catalyzed oxidative cross-linking of potato proteins was investigated in terms of enzyme kinetics, reaction time course and product structural-functional properties. The catalytic efficiency (kcat/Km, mM⁻¹S⁻¹) of fungal laccases in oxidizing patatin-enriched potato protein (PAT, 0.010–0.748) was higher than that of potato protease inhibitors (PIs, 0.008–0.184). While PIs formed more efficiently oxidative cross-linked products. Cross-linking of potato proteins were achieved by laccase alone or by laccase-ferulic acid system; ferulic acid contributed to higher cross-linking extent and to the antioxidant activity of modified proteins. Potato proteins exhibited similar or slightly enhanced solubility upon cross-linking, except that highly cross-linked PIs (cross-linking extent >30%) obtained from Coriolus hirsutus laccase (LacCh)-treatments showed reduced solubility. General improvement in the emulsification property of potato proteins was observed upon cross-linking. Cross-linked potato proteins from LacCh-6 h treatment showed good foaming property; these proteins exhibited enhanced molecular flexibility and the characteristics of mild cross-linking extent (9.6–17.1%) with the accumulation of moderate molecular weight fraction (PAT:60–80 kDa, PIs:30–40 kDa). This study will lay foundations for the exploitation of potato proteins as functional ingredients.Industrial relevanceThe exploitation of novel proteins as functional ingredients is needed in order to meet the high demands for natural, healthy-oriented and sustainable food products. Laccase-catalyzed protein cross-linking is a promising green technology for tailoring the functionality of protein ingredients and achieving the desired textural/rheological quality of final products. The current study demonstrated the effectiveness of this enzymatic approach to enhance foaming and emulsifying properties of potato proteins. This approach can be adopted to modulate the functionality of other plant proteins and to develop plant proteins-based functional ingredients for various applications including stable delivery system, fat-replacing biopolymer matrix, meat analog/vegan products and gluten-replacement formulations.