Assessment of lead availability in soils contaminated by mine spoil

The uptake of lead by two contrasting plant species, radish and red fescue, grown in soils contaminated by mine spoil was investigated. Uptake was found to be poorly correlated either with pH or total Pb concentration in the soils. By contrast, a good correlation was obtained, particularly for red fescue, between Pb uptake and Pb concentration in the solution of equilibrated soil suspensions over a wide range of soil pH, total soil Pb and soil solution Pb concentration.Calculations suggested a similar order of magnitude in the total amounts of Pb taken up by the plants and Pb in the soil solution of the root zone, justifying the latter as a good index of Pb-availability. ei]Section editor: A C Borstlap     

Evaluation of polysulfone hollow fibres and ceramic suction samplers as devices for the in situ extraction of soil solution

An investigation was carried out to assess the potential of using polysulfone hollow fibres for the extraction of soil solution. In comparison to ceramic suction samplers the fibres were shown to contain very low levels of potential contaminants and a low exchange capacity. Carry over between individual samples was negligible permitting the accurate monitoring of temporal changes in solution chemistry. Their flexible and root sized nature makes them ideal for sampling small soil volumes. Some concern however remains about retention of colloidal Fe at the fibre interface. When comparing the soil solution of samples extracted with polysulfone fibres with those extracted by ceramic suction samplers, no significant differences in solute concentrations were observed. No sample contamination resulting from dissolution of Al or Si from the ceramic cup was detected. Analysis of soil solutions collected over a number of extractions, and during and after a rainfall event showed concentrations of elements in solution to remain relatively constant with time.     

Conformational properties of the —35 region of the trp promoter in solution: comparison of the wild-type sequence with an AT transversion

The majority of the ¹H NMR resonances of the protons in a tetradecamer containing the —35 region of the trp promoter d(GCTGTTGACAATTA): d(TAATTGTCAACAGC) and in the TA transversion have been assigned. The conformational properties of the nucleotides have been determined and compared in the two duplexes. Analysis of spin-spin coupling and NOES shows that all sugar puckers are in the south domain (i.e. near C2 endo) and the glycosidic torsion angles are anti (110°). The NMR data are consistent with the duplex being in the B family of conformations. Significant differences in chemical shifts between the two molecules were observed only for nearest neighbours to the transversion site, suggesting the absence of long range conformational effects. This was confirmed by the similarity of coupling constants and NOEs. Other properties are also not greatly affected at positions more than two base pairs from the mutation site. These results are consistent with the hypothesis that unconstrained oligonucleotides are highly flexible, and can readily accommodate significant perturbations of the local structure, such as a transversion.     

In vitro culture of vanhoutte's spirea explants from ‘secondary cultures’ and dormant stems forced in solutions containing plant growth regulators

Explants from new growth of forced dormant stems and secondary cultures of Vanhoutte's spirea were cultured on Linsmaier and Skoog (L.S.) medium containing benzyladenine (BA), indoleacetic acid (IAA), thidiazuron (TDZ), and zeatin. The dormant stems were forced by immersing their basal portions in forcing solutions containing 626 µM 8-hydroxyquinoline citrate (8-HQC) and 2% sucrose. BA and gibberellic acid (GA₃) were also added into the forcing solutions to determine if explants obtained from the new growth will benefit from this treatment when culturedin vitro.L.S. medium supplemented with 5 µM BA alone, 5 µM BA plus 1 or 5 µM IAA, and 0.5 or 0.75 µM TDZ alone produced the best shoot proliferation for both sources of explants. BA and GA₃ appeared to be taken up from the forcing solution by the new softwood growth. BA in the forcing solution stimulatedin vitro shoot proliferation in different degrees depending on the period of treatment, while GA₃ caused lessin vitro shoot proliferation. It is proposed that forcing solutions containing plant growth regulators (P.G.R.) are a useful approach for manipulating responses of plant tissues culturedin vitro.     

The structure of duplex DNA in the nucleosome core particle: An alternative model

Many studies indirectly indicate that the conformation ofin vivo duplex DNA is the double helix. The most direct view, from the X-ray analysis of the nucleosome core particle, has also been interpreted in terms of the double helix structure. However, an alternative possibility exists; that the duplex adopts a metastable side-by-side conformation which readily converts to the double helix on removal of protein. Evidence for the existence of this conformation has been obtained from a reanalysis of the electron density map for the nucleosome particle.     

Thermal stability and conformational transitions of scrapie amyloid (prion) protein correlate with infectivity.

The scrapie amyloid (prion) protein (PrP27-30) is the protease-resistant core of a larger precursor (PrPSc) and a component of the infectious scrapie agent; the potential to form amyloid is a result of posttranslational event or conformational abnormality. The conformation, heat stability, and solvent-induced conformational transitions of PrP27-30 were studied in the solid state in films by CD spectroscopy and correlated with the infectivity of rehydrated and equilibrated films. The exposure of PrP27-30 in films to 60 degrees C, 100 degrees C, and 132 degrees C for 30 min did not change the beta-sheet secondary structure; the infectivity slightly diminished at 132 degrees C and correlated with a decreased solubility of PrP27-30 in sodium dodecyl sulfate (SDS), probably due to cross-linking. Exposing PrP27-30 films to formic acid (FA), trifluoroacetic acid (TFA), trifluoroethanol (TFE), hexafluoro-2-propanol (HFIP), and SDS transformed the amide CD band, diminished the mean residue ellipticity of aromatic bands, and inactivated scrapie infectivity. The convex constraint algorithm (CAA) deconvolution of the CD spectra of the solvent-exposed and rehydrated solid state PrP27-30 identified five common spectral components. The loss of infectivity quantitatively correlated with a decreasing proportion of native, beta-pleated sheet-like secondary structure component, an increasing amount of alpha-helical component, and an increasingly disordered tertiary structure. The results demonstrate the unusual thermal stability of the beta-sheet secondary structure of PrP27-30 protein in the solid state. The conformational perturbations of PrP27-30 parallel the changes in infectivity and suggest that the beta-sheet structure plays a key role in the physical stability of scrapie amyloid and in the ability to propagate and replicate scrapie.     

Conformational analysis of protein structures derived from NMR data

A study is presented of the conformational characteristics of NMR-derived protein structures in the Protein Data Bank compared to X-ray structures. Both ensemble and energy-minimized average structures are analyzed. We have addressed the problem using the methods developed for crystal structures by examining the distribution of ?, Ψ, and χ angles as indicators of global conformational irregularity. All these features in NMR structures occur to varying degrees in multiple conformational states. Some measures of local geometry are very tightly constrained by the methods used to generate the structure, e.g., proline ? angles, α-helix ?, Ψ angles, ω angles, and C_α chirality. The more lightly restrained torsion angles do show increasead clustering as the number of overall experimental observations increases. ?, Ψ, and χ₁ angle conformational heterogeneity is strongly correlated with accessibility but shows additional differences which reflect the differing number of observations possible in NMR for the various side chains (e.g., many for Trp, few for Ser). In general, we find that the core is defined to a notional resolution of 2.0 to 2.3 Å. Of real interest is the behavior of surface residues and in particular the side chains where multiple rotameric states in different structures can vary from 10% to 88%. Later generation structures show a much tighter definition which correlates with increasing use of J-coupling information, stereospecific assignments, and heteronumclear techniques. A suite of programs is being developed to address the special needs of NMR-derived structures which will take into account the existence of increased mobility in solution. © 1993 Wiley-Liss, Inc.     

蛋白质侧链的预测

根据Ｄｅｓｍｅｔ的死端排除定则制作了一种蛋白质侧链观测的快速软件系统,用一批实例结构数据和不同的侧链转子来检验上定则的可行性;并讨论预测的ＲＭＳ与溶剂可及性和结构元素的关系。     

用Reinecke盐液曝光计检测树冠内的光合有效辐射

1 引言 传统的植物光合生理生态研究中,多用照度计来测定光照指标,它以人眼对光亮度的响应特性为基础,与植物叶片对光照的响应曲线差异很大;而太阳光谱中只有400—700nm的波段才是光合有效辐射     

不同预处理对小鼠粪样菌群高通量测序分析结果的影响

应用高通量测序技术比较不同预处理对小鼠粪样菌群结构的影响,以期为后续相关研究提供参考依据。采集昆明小鼠新鲜粪样,分为原始粪样组、生理盐水处理组和PBS处理组,提取粪样DNA,采用Illumina MiSeq平台进行测序对3组样本的16S rRNA V3~V4区基因文库进行生物信息学分析。结果显示,3组样本拥有共同的OTUs 188个,不同预处理对粪样微生物多样性和丰度产生影响,生理盐水处理组、PBS处理组和原始粪样组分别检出14、11、12个门,3组样本共有门11个;分别检出24、21、21个纲,3组样本共有纲20个;分别检出62、55、59个科,3组样本共有科26个;分别检出147、126、137个属,3组样本共有属117个。总体来看,生理盐水处理组微生物多样性和丰度相对最高,原始粪样组次之,PBS处理组最低。粪样经生理盐水处理后,能在一定程度上提高肠道菌群检测的准确性。