Roles of flanking sequences in the binding between unimolecular parallel-stranded G-quadruplexes and ligands

G-quadruplexes attract more and more attention in recent years.Numerous small molecules which can induce or stabilize the formation of G-quadruplexes have been investigated on the purpose of anticancer drug development.As a motif existed in physiological condition,flanking sequences are an important part of G-quadruplexes but the study on the impact of flanking sequences on (G-quadruplex)-ligand binding is rarely reported.In this paper,the effects of flanking sequences on binding affinity between a series of unimolecular parallel-stranded G-quadruplex sequences derived from c-myc oncogene promoter (termed as c-myc G-quadruplexes) and their ligands are discussed in detail.The results showed that the flanking sequences on c-myc G-quadruplexes play key roles in (G-quadruplex)-ligand interaction.When a c-myc G-quadruplex is bound to its ligands,the flanking sequences might form a binding cavity above the terminal G-quartet,which could provide a suitable site for ligands to dock in.Moreover,the bases on flanking sequences could interact with ligand through π-π stacking,and finally form a sandwich-stacking mode (terminal G-quartet,ligand and bases on the flanking sequence).This mode could stabilize the (G-quadruplex)-ligand complex effectively and enhance the binding affinity dramatically.However,flanking sequences are also found to exhibit steric hindrance effect which could impede the (G-quadruplex)-ligand binding.     

(1→3)-α-D葡聚糖的季铵盐合成及其抗菌活性(1→3)-α-D葡聚糖的季铵盐合成及其抗菌活性

来源于Penicillium chrysongenum的碱溶性 (1→3)-α-D葡聚糖与缩水甘油基三甲基季铵盐酸盐（glycidyl trimethylammonium chloride, GTMAC）反应，生成葡聚糖季铵盐。IR图谱中季铵基团上的甲基的变角振动峰1480cm^-1、伸缩振动峰2872cm^-1变化明显，¹H-NMR表征确定季铵基团在糖环2、4位连接。该葡聚糖的最低抑菌浓度对大肠杆菌为1.0mg/mL，对金黄色葡萄球菌为2.0mg/mL。细胞质释放检测结果显示，葡聚糖季铵盐通过作用于细菌细胞膜而发挥抗菌作用。     

Effect of solvent on Se-modified ruthenium/carbon catalyst for oxygen reduction

Se-modified ruthenium supporting on carbon(Sex–Ru/C) electrocatalyst was prepared by solvothermal one-step synthesis method. The reaction mechanism was revealed after discussing impact of different solvents(i-propanol and EG) in solvotermal reaction. The result showed that the grain size of Se-modified ruthenium electrocatalyst was as small as 1 to 3 nm and highly dispersed on carbon surface. X-ray photoelectron spectroscopy(XPS) presented that selenium mainly existed in the catalyst in the form of elemental selenium and selenium oxides when the solvent was EG and i-propanol, respectively. The oxygen reduction reaction(ORR) performance was improved by appearance of selenium oxides.     

Sintering behavior of Cr in different atmospheres and its effect on the microstructure and properties of copper-based composite materials

Copper matrix composites consisting of chromium (Cr) or ferrochrome (Cr-Fe) as strengthening elements and molybdenum disulfide as a lubricant had been sintered in nitrogen and hydrogen atmosphere, respectively. Their morphology and energy-dispersive X-ray spectrometry (EDS) analysis showed that serious interaction occurred between MoS₂ and Cr (or Cr-Fe) particles when the samples were sintered in hydrogen atmosphere. Chromium sulfide compound (Cr_xS_y) was formed as a reaction product, which decreased the density and strength of the composites remarkably. This interaction was inhibited when the samples were sintered in nitrogen atmosphere; thus, the mechanical properties of the composites were improved.     

荧光法研究苯甲酸氮芥铕配合物与DNA的相互作用

 在Tris-HCl(pH7.2)介质中,研究了1个新的苯甲酸氮芥铕(Ⅲ)配合物(Eu(BANM)₃·H₂O)与DNA相互作用的荧光性能,表明此配合物可作为DNA定量测定的荧光试剂.此外以溴化乙锭(EB)为荧光探针,对配合物与DNA的结合机理进行了探讨.结果证明DNA与配合物之间存在插入和沟结合2种非共价作用方式,配合物与DNA的平均结合常数为7.19×10⁵.     

Arbuscular mycorrhizal formation of crucifer leaf mustard induced by flavonoids apigenin and daidzein

Flavonoids from legume root secretion may probably act as signal molecules for expression of Rhizobial “nod” nodulation genes and AM fungal symbiotic gene. Leaf mustard is a non-mycorrhizal plant; it does not contain flavonoids and other signal molecules. AM fungi could not infect the roots of leaf mustard and form a symbiont in nature,when it was treated with flavonoids (apigenin or daidzein).The results of trypan blue staining showed that two kinds of AM fungi (G intraradices and G mosseae) successfully infected the roots of non-mycorrhizal plant leaf mustard. AM fungi grew towards and colonized the roots of leaf mustard,producing young spores and completing the course of life.AM fungi are the only one kind of fungi with ALP activity.The result of ALP staining has also proved that AM fungi infected successfully the roots of leaf mustard. AM fungi (G intraradices and G mosseae) that existed in the roots of non-mycorrhizal plant leaf mustard were probed by nested PCR and special molecular probes. The above-mentioned proof chains have fully proved that flavonoids induced AM fungi (G intraradices and G mosseae) to infect non-mycorrhizal plant and establish symbiotic relationship.     

A wound-induced small polypeptide gene family is upregulated in soybean nodules

Small peptides function as key signals in processes, such as plant cell differentiation, organ development and defenses to biotic stresses. A large number of small peptide precursor genes have been predicted from the analysis of the soybean (Glycine max) whole genome DNA sequence. However, most of these genes have unknown characteristics and functions. In this report, we systemically searched for the gene families of small peptide precursors that are up-regulated in soybean nitrogen-fixing root nodules. We found 212 genes (encoding peptides shorter than 150 amino acids) that were up-regulated, and among them, 79 genes belong to 38 multiple-gene families, but the other 133 genes are unique. Twenty-eight of 38 families are conserved in Arabidopsis, but the other 10 only exist in legumes. We also identified 16 out of the 38 members of the wound-induced polypeptide (WIP) gene family to be upregulated in nitrogen-fixing nodules. We further analyzed homologs of WIP genes in Medicago, Lotus, Arabidopsis and Oryza species and found that a few homologous genes from Medicago truncatula and Lotus japonicus were also upregulated in their nodules and some WIP genes were induced by specific fungal pathogens on soybean and rice. Structure prediction indicated that all WIP prepropeptides contain a conserved DUF3774 domain (including two hydrophobic regions) and most of them have an N-terminal signal sequence. Fluorescence microscopy analysis of two WIP prepropeptides fused to GFP revealed that these proteins are located on the plasma membrane of tobacco leaf cells. Interestingly, 34 soybean WIP genes are clustered onto three soybean chromosomes, different from known peptide gene families (such as CLE). Among them, 11 highly identical genes are aligned on the 6th chromosome, 12 on the 12th, and 11 on the 13th chromosomes. Most of WIP genes from the 12th chromosome share the highest identities with their homologs on the 13th chromosome, suggesting that ancestral WIP genes could have originated from the 13th chromosome, then spread onto the 12th chromosome by chromosome homologous recombination; the new WIP genes could have existed in multiple copies by gene duplication which then spread onto the 6th chromosome. In Arabidopsis and Oryza species, half of the WIP genes are also aligned on one chromosome and showed higher identity with those from the soybean 12th and 13th chromosomes, suggesting that WIP genes originated from one common ancestor.     

Expression and antigen activity determination of human thyroid peroxidase in silkworm and yeast

In this study, we report the expression of human thyroid peroxidase (TPO) in silkworm larvae and Pichia pastoris GS115. Recombinant TPO is sequentially purified from the hemolymph of infected silkworm larvae and yeast using a Ni-NTA resin kit. The concentration of yield of recombinant TPO is 4.87 mg per thousand larvae and 40.83 mg per liter yeast culture. However, the recombinant TPO produced in silkworm show similar binding ability with the specific anti-TPO serum to standard human TPO purified from insect cells. The lower antigen activity indicates the TPO expressed in yeast is not suitable to be used as the coating antigen in enzyme linked immunosorbent assay (ELISA). The cost of TPO expressed in B. mori is about 1/4 that of in insect cells, and the cost of TPO purified from silkworm for ELISA is only 1/8 that of TPO produced from Sf9 cells. It indicates the BmNPV-silkworm expression system is a cost-effective platform for producing TPO with high antigen activity.     

A dynamic finite element model of human cervical spine with in vivo kinematic validation

Most previous cervical spine finite element （FE） models were validated using in vitro cadaver mea- surement data from literatures. Although in vitro mea- surement can provide valuable data for model verification, the in vivo mechanical and physiological conditions of the cervical spine during its natural motions cannot be reproduced in vitro. In this study, a human FE model of skull （CO） and spinal vertebrae （C1-T1） was developed. The in vivo kinematic characteristics of head and neck were obtained from optoelectronic system, and used for the validation of the FE model. The simulation resu]ts showed good agreement with the measured data in left/right lateral bending and left/right axial rotation, while discrepancy existed during flexion. The predicted segmental cervical vertebral angles were compared against data from previous in vivo experiment, too. Furthermore, the skin shift data from previous study was used to compensate the experimental measurement during flexion and left/right lateral bending. The results showed the model was successfully validated with the in vivo experimental data.     

Two forms of the membrane-bound state of the first C2 domain (C2A) of synaptotagminⅠand calcium-triggered membrane insertion

The synaptic vesicle protein synaptotagmin I(syt I) is a vesicle transmembrane protein present in synaptic vesicles, which has been proposed as the Ca^2 sensor that regulates secretion. The C2A domain is the membrane proximal part of its cytoplasmic domain. The interaction between C2A and lipid bilayer has been considered to be essential for triggering neurotransmitter release. In the present work, the measurements of membrane surface tension and surface concentration showed that the C2A domain of syt I exhibited two membrane-bound states: the surface adsorption state and the membrane insertion state. The surface absorption state formed in a Ca2~-independent manner with lower affinity, while the membrane insertion state formed with high affinity was only found in the presence of Ca^2 . Both the Ca^2 -independent and Ca^2 -dependent syt I membrane interactions required anionic phospholipids, such as phosphatidylserine (PS). When expressed into rat pheo-chromocytoma (PC12) cells and human embryonic kidney (HEK-293) cells, as demonstrated by immunofluorescence staining and subcellular fractionation, most of the C2A was found at the plasma membrane, even when the cells weredepleted of Ca^2 by incubation with EGTA. These resultssuggested a new molecular mechanism of syt I as a Ca^2 sensor in membrane fusion. Ca^2 -independent surface adsorption might attach syt I to the release site during the docking or priming step. When intracellular Ca^2 increased,syt I triggered the neurotransmitter release following the Ca^2 -dependent penetration into the target membrane.     

Protection of phosphatidylcholine to photosystem Ⅱ membrane during heat treatment

Photosystem Ⅱ membrane was reconstituted with phosphatidylcholine (PC) with different kinds of fatty acyl chains and the protection of PC to photosystem Ⅱ (PS Ⅱ)membrane during heat treatment was investigated using oxygen electrode, variable fluorescence and circular dichroism (CD) spectroscopy. Heat treatment decreased the oxygen evolution rate and the F′v/Fm′ ratio of PS Ⅱ membrane and influenced CD spectra of PS Ⅱ membrane, but PC inhibited the effect of heat treatment on the oxygen evolution rate, the F′v/F′m ratio and CD spectra of PS Ⅱ membrane. The results indicate that PC can protect PS Ⅱ membrane against heat treatment and the alterations in the unsaturated fatty acid extent in PC can cause the changes of the protection ability.     

A study of electron-shuttle mechanism in <Emphasis Type="Italic">Klebsiella pneumoniae</Emphasis> based-microbial fuel cells

In microbial fuel cell (MFC), the rate of electron transfer to anode electrode is a key intrinsic limiting factor on the power output of MFCs. Using Klebsiella pneumoniae (K. pneumoniae) strain L17 as biocatalyst, we studied the mechanism of electron shuttle via self-producing mediator in a cubic air-chamber MFC. To eliminate the influence of biofilm mechanism, the anode electrode was coated with microfiltration membrane (0.22 μm). Data showed that the microfiltration membrane coated and uncoated MFCs achie...     

SRO1 regulates heavy metal mercury stress response in Arabidopsis thaliana

Heavy metals in the environment are harmful limiting factors for the normal growth and development of plants. Here, we isolated and identified an Arabidopsis thaliana T-DNA insertion mutant, named srol-1, which showed a hyper-sensitive response to HgCl2. The SRO1 protein contains a WWE domain that mediates proteinprotein interactions. Under HgCl2 treatment, when compared with the wild-type plants, the growth of srol-1 was repressed dramatically and the number of true leaves was reduced and etiolated. The electrolyte leakage rates showed that cell membrane integrity in srol-1 was damaged more severely than in the wild type. DAB （3,5-diaminobenzidine） staining and confocal microscopy showed that Hg2＋ stress induced more hydrogen peroxide accumulation in srol-1 than in the wild type. The qRT-PCR results indicated that the expression of some abiotic stress-induced genes, such as L-ascorbate peroxidase （APX1）, was reduced under oxidative or Hg2＋ stress. Transgenic plants containing a GFP：：SRO1 fusion protein showed that SRO1 was localized in the nucleus of the cells. SRO1 was shown to be expressed in various tissues, and was most highly expressed in the vigorous tissues. Our results suggest thatSRO1 may play an important role in the stress response of A. thaliana to heavy metals.     

mLLDPE/LDPE共混物相结构的研究

采用SAXS方法研究了不同配比的茂金属催化聚乙烯（mLLDPE）/低密度聚乙烯（LDPE）共混物的界面层厚度σ_b、Porod指数α、分散相尺寸a_c值、积分不变量Q值等相结构参数。研究结果表明,共混物中两相具有部分相容性,分散相以片状存在;当共混质量比为80/20和20/80时,显示良好的混合均匀性。     

MoFLP1, encoding a novel fungal fasciclin-like protein, is involved in conidiation and pathogenicity in Magnaporthe oryzae

Fasciclin family proteins have been identified as cell adhesion molecules in various organisms. In this study, a novel Magnaporthe oryzae fasciclin-like protein encoding gene, named MoFLP1, was isolated from a subtractive suppressive cDNA library and functionally analyzed. Sequence analysis showed that the MoFLP1 gene contains an open reading frame (ORF) of 1050 nucleotides encoding 349 amino acids with a calculated molecular weight of 35.85 kDa and a pI of 7.76. The deduced MoFLP1 protein contains a 17-amino acid secretion signal sequence and an 18-amino acid sequence with the characteristics of a glycosylphosphotidylinositol (GPI) anchor additional signal at its N- and C-terminuses, respectively. Potential N-glycosylation sites and domains involving cell adhesion were also identified in MoFLP1. Sequence analysis and subcellular localization by the expression of MoFLP1-GFP fusion construct in M. oryzae indicated that the MoFLP1 protein is probably localized on the vacuole membrane. Two MoFLP1 null mutants generated by targeted gene disruption exhibited marked reduction of conidiation, conidial adhesion, appressorium turgor, and pathogenicity. Our results indicate that fasciclin proteins play important roles in fungal development and pathogenicity in M. oryzae.     

v-Fos transformation effector binds with CD2 cytoplasmic tail

The CD2 molecule, an adhesive and co-stimulating molecule, expresses virtually on all T lymphocytes, thymocytes, as well as natural killer cells, playing an important role in thymus development, T cell activation and apoptosis[1―3]. CD2 molecule consists of an ex- tracellular region with two Ig-like domains, a single membrane-spanning domain, and a positively charged proline-rich cytoplasmic tail, which is highly conserved between different species[1,4―7]. The functions of CD2 in signal t…     

Critical electronic structures controlling phase transitions induced by lithium ion intercalation in molybdenum disulphide

We report on first-principles studies of lithium-intercalation-induced structural phase transitions in molybdenum disulphide (MoS2 ), a promising material for energy storage in lithium ion batteries. It is demonstrated that the inversion-symmetry-related Mo-S p-d covalence interaction and the anisotropy of d-band hybridization are the critical factors influencing the structural phase transitions upon Li ion intercalation. Li ion intercalation in 2H-MoS2 leads to two competing effects, i.e. the 2H-to-1T transition due to the weakening of Mo-S p-d interaction and the D 6h crystal field, and the charge-density-wave transition due to the Peierls instability in Li-intercalated 2H phase. The stabilization of charge density wave in Li-intercalated MoS2 originates from the enhanced electron correlation due to nearest-neighbor Mo-Mo d-d covalence interaction, conforming to the extended Hubbard model. The magnitude of charge density wave is affected by Mo-S p-d covalence interaction and the anisotropy of d-band hybridization. In 1T phase of Li-intercalated MoS2 , the strong anisotropy of d-band hybridization contributes to the strong Fermi surface nesting while the d-band nonbonding with S-p facilities effective electron injection.     

魔芋葡甘聚糖/纳米四氧化三铁复合溶胶的流变性能

为了研究魔芋葡甘聚糖/纳米Fe_3O_4_静电纺丝膜,运用流变仪分析纳米Fe_3O_4对KGM溶胶流变性能的影响,以期为制备复合的纺丝液的浓度和配比提供了指导。结果表明:KGM/纳米Fe_3O_4复合溶胶是一种假塑性流体;复合溶胶的粘度、线性粘弹区域范畴、屈服应力值、模量等四个指标均与纳米Fe_3O_4掺杂比的掺杂比呈正比关系,从剪切性质分析其体系纳米Fe_3O_4质量浓度不应超过1.2%。通过频率扫描分析,纳米Fe_3O_4与KGM之间存在相互作用,随着纳米Fe_3O_4粒子含量的增加使得与KGM作用增加,从而使体系形成稳定网络结构,使复合溶胶的稳定性更高,因此将魔芋葡甘聚糖/纳米Fe_3O_4制备静电纺丝膜具有一定可行性。     

DEX1, a plasma membrane-localized protein, functions in microspore development by affecting CalS5 expression in Arabidopsis thaliana

Microsporogenesis in flowering plants plays important roles in sexual reproduction. It has been reported that DEFECTIVE IN EXINE FORMATION1 (DEX1) is essential for exine pattern formation in Arabidopsis thaliana. However, the functions of DEX1 in regulating microspore development are largely not understood. In this study, we show that DEX1 is strongly expressed in the tapetum by using RNA in situ hybridization. dex1 microspores were degenerated and aborted after release from the tetrads. The callose wall in tetrads was thinner in the dex1 mutant than in the wild type, suggesting that DEX1 affects callose formation at the tetrad stage during anther development. RT-PCR and real-time PCR analyses showed that CalS5, which plays an important role in callose synthesis during microspore development, was greatly down-regulated in dex1 plants. DEX1 encodes a membrane protein with one transmembrane domain, one intracellular domain and one extracellular domain. Collectively, our results demonstrate that DEX1 is essential for microspore development, possibly by regulating the expression of CalS5.