纳米材料在生物医学检测中的应用

纳米技术的兴起,对生物医学领域的变革产生了深远的影响。纳米材料是纳米技术发展的重要基础,它具有许多传统材料所不具备的独特的理化性质,因此在生物医学、传感器等重要技术领域有着广泛的应用前景。对几类常见的纳米材料包括纳米金、量子点、磁性纳米粒子、碳纳米管和硅纳米线在蛋白质、DNA、金属离子以及生物相关分子检测方面的应用进行综述。     

水稻硅转运蛋白研究进展

硅是促进水稻生长和维持持续生产的重要营养元素,它有助于提高植物抗病虫害、抗倒伏以及抗生物和非生物胁迫的能力。硅能改善水稻的形态结构,提高产量和品质,还可以提高氮、磷利用率,减轻一些重金属的毒害作用。综述了水稻硅吸收运输有关的输入转运蛋白Lsi1、输出转运蛋白Lsi2和运输蛋白Lsi6表达和功能。同时,对这些转运蛋白的应用前景进行了展望。     

A spotlight on “established”, as opposed to “newcomer”, Americans

By elaborating upon the idea of “relational assimilation”, Tomas Jimenez alters the dominant lens through which social scientists, and especially sociologists, have understood the concept of assimilation and the effects of immigration. In this highly readable and thoughtful book, we are asked to conceive of this kind of assimilation as one which involves “the give-and-take of adjustment”, not just a one-way route by which “newcomers” must adapt to settings populated by “established” members of the population. According to the author, ongoing forms of immigration and its resulting diversity actually change the regional self-understandings of those who are already living in those settings.     

Silicon-mediated changes of some physiological and enzymatic parameters symptomatic for oxidative stress in spinach and tomato grown in sodic-B toxic soil

We investigated effect of silicon (Si) on the growth, uptake of sodium (Na), chloride (Cl), boron (B), stomatal resistance (SR), lipid peroxidation (MDA), membrane permeability (MP), lipoxygenase (LOX) activity, proline (PRO) accumulation, H₂O₂ accumulation, non-enzymatic antioxidant activity (AA) and the activities of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) of spinach and tomato grown in sodic-B toxic soil. Si applied to the sodic-B toxic soil at 2.5 and 5.0 mM concentrations significantly increased the Si concentration in the plant species and counteracted the deleterious effects of high concentrations of Na, Cl and B on root and shoot growth by lowering the accumulation of these elements in the plants. Stomatal resistance, MP, MDA and the concentrations of H₂O₂ and PRO were higher in the plants grown in sodic-B toxic soil without Si: LOX activity of excised leaves of both species was increased by Si. Antioxidant activities of both species were significantly affected by Si, with the activities of SOD, CAT and APX decreased and AA increased by applied Si. For most of the parameters measured, it was found that 5 mM Si was more effective than the 2.5 mM Si. Based on the present work, it can be concluded that Si alleviates sodicity and B toxicity of the plants grown in sodic-B toxic soil by preventing both oxidative membrane damage and also translocation of Na, Cl and B from root to shoots and/or soil to plant, and lowering the phytotoxic effects of Na, Cl and B within plant tissues. It was concluded that tomato was more responsive to Si than spinach since it was more salt sensitive than spinach. To our knowledge, this is the first report that Si improves the combined salt and B tolerance of spinach and tomato grown in naturally sodic-B toxic soil, and which describes membrane-related parameters and antioxidant responses.     

Hydroalumination of bis(alkynyl)germanes and -silanes: Generation of a chelating Lewis-acid and observation of a dismutation reaction

Treatment of diphenyl-di(phenylethynyl)germane with two equivalents of di(tert-butyl)aluminum hydride afforded the corresponding dialkenyl derivative, Ph₂Ge[C(AltBu₂)C(H)-Ph]₂ (1) by dual hydroalumination. The aluminum atoms of 1 are attached to the carbon atoms in α-position to germanium. They are coordinatively unsaturated and are able to act as chelating Lewis-acids and to coordinate donors such as chloride or bromide anions in a chelating manner (2, 3). The analogous reaction of the corresponding silicon-centered dialkyne with two equivalents of dimethylaluminum hydride gave a mixture of unknown compounds. Interestingly, equimolar quantities of the hydride and the dialkyne resulted in dismutation and the formation of the unprecedented compound MeAl[C(CH-Ph)-SiPh₂-CC-Ph]₂ (4). Compound 4 has two alkenyl groups bonded to the central aluminum atom and a terminal alkynyl group attached to each silicon atom. An attempt to reduce the remaining triple bonds by reaction with di(tert-butyl)aluminum hydride resulted in cleavage and isolation of the monoalkenyl compound tBu₂Al-C[C(H)-Ph]-SiPh₂-CC-Ph (5). The molecular structure of 5 showed a close interaction between the α-carbon atom of the triple bond and the coordinatively unsaturated aluminum atom.     

Sodium Zeolite A Supplementation and Its Impact on the Skeleton of Dairy Calves

Twenty calves were placed on study at 3 days of age and were placed according to birth order into one of two groups: SS, which received 0.05% BW sodium zeolite A (SZA) added to their milk replacer, and CO, which received only milk replacer. Blood samples were taken on days 0, 30, and 60 for osteocalcin (OC) and deoxypyridinoline (DPD) analysis. On day 60, the calves were euthanized, and synovial fluid, articular cartilage, and both fused metacarpals were collected for bone quality analyses such as architecture and mechanical properties, mineral composition, and glycosaminoglycan concentration. There were no differences in OC concentrations because of treatment (p = 0.12), and CO calves had lower DPD concentrations than SS calves (p = 0.01), but the OC-to-DPD ratio was not different between treatments (p = 0.98). No differences in bone architecture or mechanical properties were detected. SZA supplementation increased cortical bone (p = 0.0002) and articular cartilage (p = 0.05) aluminum content. Glycosaminoglycan concentrations were not different in synovial fluid or cartilage. Supplementation of SZA appeared to alter the rate of bone turnover without altering bone strength. Aluminum concentrations in the bone and cartilage increased, which may be a concern, although the long-term consequences of such remain to be determined.     

Highly sensitive measurements of PNA-DNA hybridization using oxide-etched silicon nanowire biosensors

The highly sensitive and sequence-specific detection of single-stranded oligonucleotides using nonoxidized silicon nanowires (SiNWs) is demonstrated. To maximize device sensitivity, the surface of the SiNWs was functionalized with a densely packed organic monolayer via hydrosilylation, subsequently immobilized with peptide nucleic acid (PNA) capable of recognizing the label-free complementary target DNA. Because of the selective functionalization of the SiNWs, binding competition between the nanowire and the underlying oxide is avoided. Transmission electron microscopy was conducted to clearly differentiate the SiNW surface before and after removal of SiO₂. Fluorescence microscopy was used to further realize the selectivity of the oxide-etched chemistry on the SiNWs and sequence specificity of PNA-DNA hybridization. The concentration-dependent resistance change measurements upon hybridization of PNA-DNA show that detection limit down to 10 fM can be obtained. The SiNW devices also reveal the capability of an obvious discrimination against mismatched sequences. Among several efforts being made to improve detection sensitivity, this work addresses one significant issue regarding surface functionalization which enables highly sensitive biomolecular sensing with SiNWs.     

Dibutylsilylene-pentose bis-chelates: on the glycoses' binding sites for strongly Lewis-acidic centres

Excess di(tert-butyl)silylene (DTBS) bis(trifluoromethanesulfonate) formed bis-DTBS derivatives with the four aldopentoses (arabinose, lyxose, ribose and xylose). The structure of the bis-chelates was affected by the bulk of the DTBS groups and the requirement of flat silacycles in the case of five-membered chelate rings. These restrictions resulted in unusual cyclic bis-chelates for ribofuranose (κO^1,5,κO^2,3 bis-chelate) and lyxopyranose (κO^1,4,κO^2,3 bis-chelate of a twisted boat conformation). Most importantly, all aldopentoses formed bis-chelates of their open-chain aldehydo isomers. The bis-chelates of aldehydo-arabinose and -xylose were κO^2,3,κO^4,5-bonded and thus exhibited five-membered chelate rings. The bis-chelates of aldehydo-lyxose and -ribose were κO^2,4,κO^3,5-bonded and resembled six-membered chelate rings. For lyxose, the aldehydo bis-chelate was isolated as a solid. The molecular structures were assigned by a combined ¹H, ¹³C, and ²⁹Si NMR spectroscopic approach, which was supported by X-ray analyses on crystals of the bis-DTBS chelates of κO^1,2,κO^3,5-bonded rac-xylofuranose, κO^1,5,κO^2,3-bonded d-ribofuranose, and κO^2,4,κO^3,5-bonded aldehydo-d-lyxose.     

A surface modification strategy on silicon nitride for developing biosensors

A surface modification strategy for the use of giant magnetoresistive materials in the detection of protein-protein interactions is developed. This modification strategy is based on silanization of semiconductive materials. A native silicon nitride surface was treated with concentrated hydrofluoric acid to improve surface homogeneity. Nano-strip was used to oxidize silicon nitride to form a hydrophilic layer. Aminopropyltriethoxysilane was subsequently used to functionalize the treated surfaces to form amine groups, which were further activated with glutaraldehyde to introduce a layer of aldehyde groups. The effectiveness of this modification strategy was validated by chemiluminescence immunoassays of purified 6x His-HrpW of Pseudomonas syringae pv. tomato DC3000 and human transferrin. Signals with intensities related to concentrations of these two immobilized model proteins were observed. The modified surface was also validated by a more complex system: intercellular proteins secreted by DC3000. HrpW in these protein mixtures was successfully recognized by anti-HrpW antibodies when mixed proteins were immobilized onto activated surfaces. This surface modification strategy provides a platform onto which proteins can be directly immobilized for biosensor and protein array applications.     

Importance of biological and abiotic factors for geochemical cycling in a freshwater eutrophic lake

Here we report the results of a comprehensive biogeochemical monitoring of Rostherne Mere in 1998, including changes in dissolved oxygen, organic carbon and nitrogen, nitrate/nitrite, ammonia, Al, Na, S, K, Mg, Ca, Si, Fe, Mn, orthophosphate, particulate N & P, suspended solids, temperature, pH, chlorophyll-a and zooplankton. The results demonstrated the major influence of primary producers on the overall geochemical cycling of N, P and Si, and suggested that the significance of zooplankton might have been previously underestimated. For major anions and cations, however, the influence of biota on lake water concentrations appeared to be negligible, reflecting the fact that these chemicals were present far in excess of plankton requirements. Thus changes in concentrations of Ca, K, Na, Mg and S were rather limited and must have reflected changes in hydrological and meteorological parameters. K, however, demonstrated a transitional pattern, reflecting some influence of biological uptake. During the stratification period, the slow processes of bacterial decomposition in the hypolimnion gradually released chemicals contained in the materials accumulated in the bottom layer, remarkably increasing the concentrations of dissolved compounds of those elements present in amounts comparable with the pool stored in the sedimenting detritus (e.g. orthophosphate P, ammonia N, Si and DOC). The decomposition also resulted in a drop in the redox potential, followed by partial denitrification and chemical release from the sediments. The hypolimnion of the Mere was confirmed to remain at the stage of Mn release, characterised by accumulation of DOC, orthophosphates, ammonia and initial stages of denitrification. High levels of P released from the sediments during the stratification period suggest that the lake’s recovery after sewage diversion might be further delayed.