腐殖酸对矿物结合汞环境迁移性的影响及其机制研究

腐殖酸对矿物结合汞环境迁移活性 (挥发性 ,植物迁移活性及水迁移活性 )兼具抑制与活化的双重效应。富里酸对铁锰氧化物结合汞无论是挥发活性还是植物迁移活性及水迁移活性均表现极显著的促进效应 ,而酸性淋溶将加速富里酸对硅酸盐粘土矿物结合汞的环境迁移的活化进程 ;灰色胡敏酸对矿物结合汞的活化效应较弱 ,并更易于对矿物汞环境活性表现抑制作用。棕色胡敏酸性质与影响介于富里酸与灰色胡敏酸之间。腐殖酸作用下 ,矿物结合汞的环境迁移形态发生了改变 :元素态汞、游离的有机结合态汞和溶解态无机汞依次成为其发生大气环境迁移、土壤垂直水迁移和植物迁移最有效的形态。     

小麦淀粉粒束缚淀粉合成酶基因多态性的分子鉴定

运用6％的SDS-PAGE对14个小麦品种成熟籽粒Wx蛋白的多态性进行了鉴定,结果表明,14个小麦品种根据其Wx蛋白的缺失情况可分为6种组合类型。另外,根据Wx-A1、Wx-D1和Wx-D1这3个位点基因序列和变异情况分别设计了PCR引物,扩增结果表明：Wx-A1位点突变材料扩增产物为327bp,正常材料中扩增不到该特异带;在Wx-B1位点扩增出187bp目标带,突变材料没有该扩增产物;在Wx-D1位点扩增出约700bp目标带,突变材料没有该特异带。与前人的研究结果相比,Wx-B1引物在3个位点的扩增产物长度更短,差异更大,在2％琼脂糖胶上即可清楚分开,缩短了鉴定时间,提高了效率,为大规模筛选优质面条小麦品种提供了可能。     

Structural studies and model membrane interactions of two peptides derived from bovine lactoferricin.

The powerful antimicrobial properties of bovine lactoferricin (LfcinB) make it attractive for the development of new antimicrobial agents. An 11-residue linear peptide portion of LfcinB has been reported to have similar antimicrobial activity to lactoferricin itself, but with lower hemolytic activity. The membrane-binding and membrane-perturbing properties of this peptide were studied together with an amidated synthetic version with an added disulfide bond, which was designed to confer increased stability and possibly activity. The antimicrobial and cytotoxic properties of the peptides were measured against Staphylococcus aureus and Escherichia coli and by hemolysis assays. The peptides were also tested in an anti-cancer assay against neuroblastoma cell lines. Vesicle disruption caused by these LfcinB derivatives was studied using the fluorescent reporter molecule calcein. The extent of burial of the two Trp residues in membrane mimetic environments were quantitated by fluorescence. Finally, the solution NMR structures of the peptides bound to SDS micelles were determined to provide insight into their membrane bound state. The cyclic peptide was found to have greater antimicrobial potency than its linear counterpart. Consistent with this property, the two Trp residues of the modified peptide were suggested to be embedded deeper into the membrane. Although both peptides adopt an amphipathic structure without any regular alpha-helical or beta-sheet conformation, the 3D-structures revealed a clearer partitioning of the cationic and hydrophobic faces for the cyclic peptide.     

NaCl胁迫对菜用大豆种子多胺代谢的影响

采用蛭石栽培,在100 mmol·L-1NaCl胁迫下,对耐盐性不同的两个品种菜用大豆种子的丙二醛(MDA)含量和多胺(PAs)代谢进行了研究.结果表明:NaCl胁迫显著增加了菜用大豆种子的MDA含量,但耐盐品种‘绿领特早’(LL)的增幅低于盐敏感品种‘理想高产95-1’(LX).与LX相比,LL种子在整个NaCl胁迫期间均维持了相对较高的游离态精胺(Spm)、结合态Spm、结合态亚精胺(Spd)、束缚态Spd和束缚态腐胺(Put)含量,较高的(Spd +Spm )/Put 和(cPAs+bPAs)/fPAs值及较低的Put/PAs值,在胁迫中、后期(9～15 d)维持了相对较高的游离态Spd含量;胁迫期间,LL的精胺酸脱羧酶(ADC)长时期(6～15 d)保持相对较高的活性,而多胺氧化酶(PAO)则长时期(6～15 d)维持相对较低的活性.综上,LL具有较强的多胺合成能力及较强的Put向Spd和Spm以及游离态多胺向结合态和束缚态多胺转化的能力,进而有效抑制了细胞的膜脂过氧化,这可能是其耐盐性较强的重要原因之一.     

Phytotoxic conjugates of indole-3-acetic acid: potential agents for biochemical selection of mutants in conjugate hydrolysis

Two strategies for selection of plant mutants altered in their ability to hydrolyze IAA conjugates are described. The rationale for both strategies is to form a conjugate between two chemical moieties in which one moiety is a toxin. The first strategy makes use of a toxic auxin analogue. For this approach a series of halogenated IAA analogues were tested for toxic properties to Lemna gibba and Zea mays. Several halogenated analogues were toxic, but only 5-Br-IAA was highly toxic to both species. The second strategy required a toxic compound with suitable functional groups to allow IAA conjugation. The mycotoxin patulin was found to be a suitable candidate. Uptake and hydrolysis of IAA-conjugates was studied in order to better define the conditions required for conjugate analogues to be effectively employed for selections.     

MBOAT7-driven lysophosphatidylinositol acylation in adipocytes contributes to systemic glucose homeostasis

We previously demonstrated that antisense oligonucleotide-mediated knockdown of Mboat7, the gene encoding membrane bound O-acyltransferase 7, in the liver and adipose tissue of mice promoted high fat diet-induced hepatic steatosis, hyperinsulinemia, and systemic insulin resistance. Thereafter, other groups showed that hepatocyte-specific genetic deletion of Mboat7 promoted striking fatty liver and NAFLD progression in mice but does not alter insulin sensitivity, suggesting the potential for cell autonomous roles. Here, we show that MBOAT7 function in adipocytes contributes to diet-induced metabolic disturbances including hyperinsulinemia and systemic insulin resistance. We generated Mboat7 floxed mice and created hepatocyte- and adipocyte-specific Mboat7 knockout mice using Cre-recombinase mice under the control of the albumin and adiponectin promoter, respectively. Here, we show that MBOAT7 function in adipocytes contributes to diet-induced metabolic disturbances including hyperinsulinemia and systemic insulin resistance. The expression of Mboat7 in white adipose tissue closely correlates with diet-induced obesity across a panel of ∼100 inbred strains of mice fed a high fat/high sucrose diet. Moreover, we found that adipocyte-specific genetic deletion of Mboat7 is sufficient to promote hyperinsulinemia, systemic insulin resistance, and mild fatty liver. Unlike in the liver, where Mboat7 plays a relatively minor role in maintaining arachidonic acid-containing PI pools, Mboat7 is the major source of arachidonic acid-containing PI pools in adipose tissue. Our data demonstrate that MBOAT7 is a critical regulator of adipose tissue PI homeostasis, and adipocyte MBOAT7-driven PI biosynthesis is closely linked to hyperinsulinemia and insulin resistance in mice.     

On Relative Precision in Stratified Sampling for a Mean with Fixed Cost

This paper considers the extrema of the relative precision (R. P.), or the ratio of the variance of optimum allocation to that of proportional allocation in stratified sampling for a mean (=Y) or total (=Y) when there is a fixed cost C=c_o+σn_hc_h over L strata. The upper bound of R. P. is shown to be equal to unity, though the lower bound can be negative while approaching zero if the finite population size N→∞. Numerical results (cf. Table) when the upper bound of R. P. = 1 is attained are included for the cases L≦4 with various combinations of {W_h}, {c_h} and a fixed cost C; these give the appropriate sample sizes (=n_p) determined for proportional sampling in the cases of finite populations of sizes N=5000, 10,000 respectively.     

Extending the diffuse layer model of surface acidity behaviour: III. Estimating bound site activity coefficients

Abstract

Although detailed thermodynamic analyses of the 2-pK diffuse layer surface complexation model generally specify bound site activity coefficients for the purpose of accounting for those non-ideal excess free energies contributing to bound site electrochemical potentials, in application these terms are ignored based on one or more of the following assumptions: (1) bound site activity coefficients cancel out in the mass action quotients; (2) bound sites display ideal behaviour; and/or (3) these energies are already included in the exponential Boltzmann terms. In this work it is demonstrated that the bound site charging energy terms discussed in the two previous papers in this series have both conceptual and computational analogies to the charging energy contribution to the activity coefficients obtained from the Debye–Huckel Limiting Law. On high charge density colloidal particles at constant counterion condensation (τ), these charging energies can be related to the surface potential (ψ) by: ΔG_charging = (1 – τ)Fψ (where F is the Faraday constant). If one assumes a maximum practical accuracy of ± 10% in experimental estimates of ψ, then it is suggested that charging energies are likely to be experimentally indiscernible under conditions where τ > 0.9. These findings support the historical practice of ignoring bound site activity coefficients with the 2-pK diffuse layer surface complexation model in the following situations: for spherical particles with a radius ≥ 0.1 μm at ionic strengths ≥ 0.001 M (1 : 1), and for spherical particles with a radius >0.01 μm at an ionic strength >0.1 M (1 : 1). In contrast, charging energies (and non-ideal behaviour) are predicted to be significant at all charge densities and ionic strengths for spherical particles with a radius of 0.001 μm.