网格蛋白介导的内吞作用机制

受体介导的内吞作用是目前公认的生物体摄取生物大分子的途径,而网格蛋白介导的内吞又是最主要的受体介导方式.结合国内外最新报道,介绍了网格蛋白和衔接蛋白的结构、分子特性和功能;从衔接蛋白、网格蛋白的招募;包被小凹的内陷、缢缩和包被液泡的芽殖和包被液泡的脱壳等过程,阐释了网格蛋白介导的内吞作用机制.     

Intermediate organelles of the plant secretory pathway: identity and function

The secretory pathway of eukaryotic cells comprises a network of organelles that connects three large membranes, the plasma membrane, the vacuole and the endoplasmic reticulum. The Golgi apparatus and the various post-Golgi organelles that control vacuolar sorting, secretion and endocytosis can be regarded as intermediate organelles of the endocytic and biosynthetic routes. Many processes in the secretory pathway have evolved differently in plants and cannot be studied using yeast or mammalian cells as models. The best characterized organelles are the Golgi apparatus and the prevacuolar compartment, but recent work has shed light on the role of the trans Golgi network, which has to be regarded as a separate organelle in plants. In this study, we wish to highlight recent findings regarding the late secretory pathway and its crosstalk with the early secretory pathway as well as the endocytic route in plants. Recently published findings and suggested models are discussed within the context of known features of the equivalent pathway in other eukaryotes.     

Palladium exposure of barley: uptake and effects

Motor vehicles are now equipped with exhaust gas catalytic converters containing rare metals, such as palladium (Pd), platinum and rhodium, as catalytic active materials, leading to significantly increased emission of these metals. Compared with platinum and rhodium, low concentrations of Pd have been shown to have more serious effects on cells and organisms. In the present study, uptake of Pd by barley and behaviour of Pd nanoparticles in nutrient solutions used to grow plants were observed in order to develop a model of Pd exposure of plant systems. Pd determination was performed using a selective separation and pre-concentration procedure, which was further developed for this study, and coupled to graphite furnace atomic absorption spectrometry. The results show that uptake of Pd depends on Pd particle diameter. Compared to other toxic metals, like mercury, Pd causes stress effects in leaves at lower concentrations in nutrient solutions. Furthermore, Pd particles are dissolved at different rates, depending on size, in the nutrient solution during plant growth.     

Assembly of non-natural electron transfer conduits in the cytochrome P450 system: a critical assessment and update of artificial redox constructs amenable to exploitation in biotechnological areas

The high plasticity of the active-site cavity of cytochromes P450, permitting reactivity toward a vast array of compounds, makes these enzymes attractive targets for biotechnological application. Escalating attention in this area is driven by remarkable progress in the rational design by DNA shuffling of self-sufficient, multi-domain P450/electron donor constructs simplifying the composition of biocatalytic systems. Moreover, versatile approaches were undertaken to supersede the well-established, NAD(P)H-steered proteinaceous redox chains by cost-effective alternative electron transfer conduits constituted of organometallic mediators or photoactivatable redox triggers. Electrochemical techniques have proven particularly useful: employing different types of carbon- and metal-based electrodes for the fabrication of biosensors, the continuing challenge was to optimize the conductive properties of these devices by creating biocompatible interfaces for transferring electrons between sensor surfaces and redox proteins. The present review provides a critical update of the most significant breakthroughs in innovative manipulation of the redox machinery, giving an impulse to exploitation of P450s in fields such as the production of fine chemicals, drug processing, medicinal diagnostics and remediation of biotopes contaminated with harmful environmental pollutants.     

A sensitive voltammetric sensor for determination of synthetic corticosteroid triamcinolone, abused for doping

Edge plane pyrolytic graphite electrode (EPPGE) modified with single-wall carbon nanotubes (SWNTs) has been used as a sensor to determine triamcinolone, abused by athletes for doping. A comparison of the voltammetric behavior between SWNTs modified EPPGE and fullerene – C₆₀-modified EPPGE indicated that SWNTs modified EPPGE is more sensitive. The electrode exhibited an effective catalytic response with good reproducibility and stability. The effect of several parameters such as pH, square wave frequency and steroid concentration were studied. The square wave voltammetric response of the electrode to triamcinolone is linear in the range 0.1–25 nM with a detection limit and sensitivity of 8.9 × 10⁻¹⁰ M and 2.06 μA nM⁻¹, respectively. The method was applied for the determination of triamcinolone in several commercially available pharmaceuticals and real urine samples obtained from patients undergoing pharmacological treatment with triamcinolone. A comparison of the observed results with HPLC analysis indicated a good agreement. The product obtained after reduction of triamcinolone was also characterized using ¹H NMR and GC–MS and the site of reduction is found to be carbonyl group at position 20. The method described is rapid, simple and accurate and can be easily applied for detecting cases of doping.     

Hydrophilic polydopamine‐coated magnetic graphene nanocomposites for highly efficient tryptic immobilization

In this work, polydopamine‐coated magnetic graphene (MG@PDA) nanocomposites were synthesized by a facile method. Trypsin was then directly immobilized on the surface of the nanocomposites through simple PDA chemistry with no need for introducing any other coupling groups. The as‐made MG@PDA nanocomposites inherit not only the large surface area of graphene which makes them capable of immobilizing high amount of trypsin (up to 0.175 mg/mg), but also the good hydrophilicity of PDA which greatly improves their biocompatibility. Moreover, the strong magnetic responsibility makes them easy to be separated from the digested peptide solution when applying a magnetic field. The feasibility of the trypsin‐immobilized MG@PDA (MG@PDA‐trypsin) nanocomposites for protein digestion was investigated and the results indicated their high digestion efficiency in a short digestion time (10 min). In addition, the reusability and stability of the MG@PDA‐trypsin nanocomposites were also tested in our work. To further confirm the efficiency of MG@PDA‐trypsin nanocomposites for proteome analysis, they were applied to digest proteins extracted from skimmed milk, followed by nano RPLC‐ESI‐MS/MS analysis, and a total of 321 proteins were identified, much more than those obtained by 16‐h in‐solution digestion (264 proteins), indicating the great potential of MG@PDA‐trypsin nanocomposites as the supports for high‐throughput proteome study.     

A reusable amperometric biosensor based on a novel silver-epoxy electrode for immunoglobulin detection

A renewable immunosensor consisting of an `epoxygraphite' biocomposite containing silver and tetracyanoquinodimethane (TCNQ) is described. These compounds enhance conductivity allowing the use of a smaller potential (0.28 v) which, in turn, enhances selectivity. This sensor, which may be renewed by simple polishing of its surface, was employed to detect human IgG using peroxidase-coupled anti-human IgG.     

Direct competitive chemiluminescence immunoassays based on gold‐coated magnetic particles for detection of chloramphenicol

Direct competitive chemiluminescence immunoassays (CLIA) based on gold‐coated magnetic nanospheres (Au‐MNPs) were developed for rapid analysis of chloramphenicol (CAP). The Au‐MNPs were modified with carboxyl groups and amino groups by 11‐mercaptoundecanoic acid (MUA) and cysteamine respectively, and then were respectively conjugated with CAP base and CAP succinate via an activating reaction using 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N‐hydroxysuccinimide (NHS). NSP‐DMAE‐NHS, a new and effective luminescence reagent, was employed to label anti‐CAP antibody (mAb) as a tracer in direct CLIA for CAP detection using a ‘homemade’ luminescent measurement system that was set up with a photomultiplier tube (PMT) and a photon counting unit linked to a computer. The sensitivities and limits of detection (LODs) of the two methods were obtained and compared according to the inhibition curves. The 50% inhibition concentration (IC₅₀) values of the two methods were about 0.044 ng/mL and 0.072 ng/mL respectively and LODs were approximately 0.001 ng/mL and 0.006 ng/mL respectively. To our knowledge, they were much more sensitive than any traditional enzyme‐linked immunosorbent assay (ELISA) ever reported. Moreover, the new luminescence reagent NSP‐DMAE‐NHS is much more sensitive and stable than luminol and its derivatives, contributing to the sensitivity enhancement. Copyright © 2015 John Wiley & Sons, Ltd.     

手性环方铂络合物与DNA相互作用中的分子识别

用生物微量热技术及ＤＮＡＴｍ测量研究了手性不同的三种环方铂络合物与小牛胸腺ＤＮＡ（２００ｂｐ）作用中的特异性,发现Ｒ,Ｒ构型的与ＤＮＡ作用最强,这与癌细胞的体外筛选结果相一致．而且通过ＨＰＬＣ及１３Ｃ－ＮＭＲ研究为环方铂络合物与ＤＮＡ作用的分子机理分析找到了直接的证据．