DNA damage in the early primordial anther is closely correlated with stamen arrest in the female flower of cucumber (<Emphasis Type="Italic">Cucumis sativus</Emphasis> L.)

To investigate the regulatory mechanisms of sex expression in cucumber, morphological observations and biochemical analyses were carried out on inappropriate stamen development of female flowers of cucumber. It was found that developmental arrest of the inappropriate stamen mainly occurs at the anther primordium. This arrest is closely correlated with DNA damage, as detected by TUNEL assay, and might result from anther-specific DNase activation. It was also found that the DNA damage does not lead to cell degeneration, although chromatin condensation is observed in the anther primordia.Abbreviations DAPI 4,6-diamidine-2-phenylindole dihydrochloride - MTT 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide - PCD programmed cell death - TUNEL TdT-mediated dUTP nick-end labeling     

白芨的组培快繁(简报)

本文扼要地阐述了以白芨种子为培养材料,经筛选的培养基诱导、分化、生长,最终可获得苗质好、性状均一的白芨;为进一步研究快速繁殖白芨提供参考.     

MD Simulations and first principles to evaluate the role of binary Fe–V alloys layer on the radiation resistance in the alpha-iron

Radiation damage in reactor materials caused by the collision of the fast neutrons has a great impact on the reliability and safety of nuclear reactors. The element vanadium has attracted interest in many fields due to its advantageous properties in alloys. Thus, molecular dynamics simulation (MD) and first-principles calculation have been executed here to explore the radiation-resistant properties of five materials adding a layer in the bulk (pure iron and four types of Fe–V alloys containing 10%-40% V). The following results were inferred from these simulations. Firstly, the number of Frenkel pairs (FPs) at the stable quenching stage in the bulk decreases when the Fe–V alloy is added as an anti-radiation layer to the bulk. These benefits are evident for the Fe₈₀V₂₀ and alloy layers with more vanadium. The main reason is that the Fe–V binding energy is greater than the Fe-Fe binding energy, which can make the Primary Knock-On atom (PKA) lose more energy at the Fe–V alloy layer. Secondly, the average value of point-defect, cluster and defect clustered fractions in the bulk of Fe–V alloy is smaller than that in the pure iron at the stable quenching stage, especially for the Fe₈₀V₂₀ alloy.     

Rapid determination of gatifloxacin in biological samples and pharmaceutical products using europium‐sensitized fluorescence spectrophotometry

A europium‐sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of gatifloxacin (GFLX). The GFLX–Eu³⁺–SDBS system was studied and it was found that SDBS significantly enhanced the fluorescence intensity of the GFLX–Eu³⁺ complex (about 25‐fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 338 and 617 nm, pH 7.5, 3.0 × 10^–6 mol/L europium(III), and 5.0 × 10^–5 mol/L SDBS. The enhanced fluorescence intensity of the system (ΔI_f) showed a good linear relationship with the concentration of GFLX over the range 1.0 × 10^–8–8.0 × 10^–7 mol/L with a correlation coefficient of 0.9990. The detection limit (S:N = 3) was determined as 1.0 × 10^–9 mol/L. This method has been successfully applied for the determination of GFLX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range and good stability. The luminescence mechanism of the system is also discussed in detail. Copyright © 2008 John Wiley & Sons, Ltd.     

Osmolyte-induced protein folding free energy changes

Upon addition of protecting osmolyte to an aqueous solution of an intrinsically unstructured protein, spectral observables are often seen to change in a sigmoid fashion as a function of increasing osmolyte concentration. Commonly, such data are analyzed using the linear extrapolation model (LEM), a method that defines a scale from 0%-100% folded species at each osmolyte concentration by means of extending pre- and post-folding baselines into the transition region. Defining the 0%-100% folding scale correctly for each osmolyte is an important part of the analysis, leading to evaluation of the fraction of folded protein existing in the absence of osmolytes. In this study, we used reduced and carboxyamidated RNase T1 (RCAM-T1) as an intrinsically unstructured protein, and determined the thermodynamic stability of RCAM-T1 induced by naturally occurring osmolytes. Because the folded fraction of the protein population determined by experiments of thermal and urea-induced denaturation is nonzero in the absence of osmolytes at 15 degrees C, the commonly used LEM can lead to false values of DeltaG[stackD-->N0] for protein folding due to the arbitrary assumption that the protein is 100% unfolded in the presence of buffer alone. To correct this problem, titration of the protein solution with urea and extrapolating back to zero urea concentration gives the spectral value for 100% denatured protein. With fluorescence as the observable we redefine F/F0 to F/F0extrap = 1.0 and require that the denatured-state baseline have this value as its intercept. By so doing, the 0%-100% scale-corrected DeltaG[D-->N0] values of RCAM-T1 folding in the presence of various osmolytes are then found to be identical, with small error, demonstrating that DeltaG[D-->N0] is independent of the osmolytes used. Such a finding is an important step in validating this quantity derived from the LEM as having the properties expected of an authentic thermodynamic parameter. The rank order of osmolyte efficacies in stabilizing RCAM-T1 is sarcosine > sucrose > sorbitol > proline > betaine > glycerol.     

Apple Sucrose Transporter SUT1 and Sorbitol Transporter SOT6 Interact with Cytochrome b5 to Regulate Their Affinity for Substrate Sugars

Sugar transporters are central machineries to mediate cross-membrane transport of sugars into the cells, and sugar availability may serve as a signal to regulate the sugar transporters. However, the mechanisms of sugar transport regulation by signal sugar availability remain unclear in plant and animal cells. Here, we report that a sucrose transporter, MdSUT1, and a sorbitol transporter, MdSOT6, both localized to plasma membrane, were identified from apple (Malus domestica) fruit. Using a combination of the split-ubiquitin yeast two-hybrid, immunocoprecipitation, and bimolecular fluorescence complementation assays, the two distinct sugar transporters were shown to interact physically with an apple endoplasmic reticulum-anchored cytochrome b5 MdCYB5 in vitro and in vivo. In the yeast systems, the two different interaction complexes function to up-regulate the affinity of the sugar transporters, allowing cells to adapt to sugar starvation. An Arabidopsis (Arabidopsis thaliana) homolog of MdCYB5, AtCYB5-A, also interacts with the two sugar transporters and functions similarly. The point mutations leucine-73 → proline in MdSUT1 and leucine-117 → proline in MdSOT6, disrupting the bimolecular interactions but without significantly affecting the transporter activities, abolish the stimulating effects of the sugar transporter-cytochrome b5 complex on the affinity of the sugar transporters. However, the yeast (Saccharomyces cerevisiae) cytochrome b5 ScCYB5, an additional interacting partner of the two plant sugar transporters, has no function in the regulation of the sugar transporters, indicating that the observed biological functions in the yeast systems are specific to plant cytochrome b5s. These findings suggest a novel mechanism by which the plant cells tailor sugar uptake to the surrounding sugar availability.     

叶绿体基因组进化的速率和方式

叶绿体是植物细胞重要的细胞器,叶绿体基因组被广泛用于系统进化的研究。对叶绿体基因组进化的速度和方式进行了介绍,并对造成其特异的点突变的原因进行了一定的分析。     

轮状病毒疫苗研究进展及其转基因植物疫苗的开发前景

轮状病毒是目前婴幼儿秋冬季腹泻的最主要病原物,作者通过轮状病毒减毒株疫苗,亚单位疫苗和DNA疫苗研究进展的综合分析,指出了减毒株疫苗在实际应用中存在的弊端,论述了开发新型轮状病毒疫苗,特别是转基因植物疫苗的必要性和可行性。     

Differentiating the 2,3-diols of glucopyranosides by 4,6-O-benzylidene-protected-1,2-d-glucopyranosylorthoesters strategy

A facile and efficient method to differentiate the 2,3-diols of glucopyranosides based on 1,2-orthoesters strategy was developed. Stable thioglucosides were employed as the starting materials to prepare the corresponding 1,2-orthoesters. When treated with HCl aqueous solution and followed with Et₃N, differentiation of the 2,3-diols was efficiently achieved along with the generation of a convertible anomeric hydroxyl group. In addition, an easy and practical method based on NOE was proposed to determine whether the 1,2-orthoesters were endo-type or exo-type.