纳米颗粒增强酶生物传感器性能的研究进展

简要介绍生物传感器的原理及分类,并且对纳米颗粒增强酶生物传感器的研究现状进行了评述,尤其是纳米颗粒对葡萄糖生物传感器和尿酸酶生物传感器的增强作用,并对我国生物传感器的发展方向做了展望。     

Theaflavin ameliorates cerebral ischemia-reperfusion injury in rats through its anti-inflammatory effect and modulation of STAT-1

Theaflavin, a major constituent of black tea, possesses biological functions such as the antioxidative, antiviral, and anti-inflammatory ones. The purpose of this study was to verify whether theaflavin reduces focal cerebral ischemia injury in a rat model of middle cerebral artery occlusion (MCAO). Male Sprague-Dawley rats were anesthetized and subjected to 2 hours of MCAO followed 24 hours reperfusion. Theaflavin administration (5, 10, and 20 mg/kg, i.v.) ameliorated infarct and edema volume. Theaflavin inhibited leukocyte infiltration and expression of ICAM-1, COX-2, and iNOS in injured brain. Phosphorylation of STAT-1, a protein which mediates intracellular signaling to the nucleus, was enhanced 2-fold over that of sham group and was inhibited by theaflavin. Our study demonstrated that theaflavin significantly protected neurons from cerebral ischemia-reperfusion injury by limiting leukocyte infiltration and expression of ICAM-1, and suppressing upregulation of inflammatory-related prooxidative enzymes (iNOS and COX-2) in ischemic brain via, at least in part, reducing the phosphorylation of STAT-1.     

The interaction between tylophorine B and TMV RNA

Tylophorine B exhibits 60% inhibition against tobacco mosaic virus (TMV) at a concentration of 1.0 x 10(-6) g/ml. In our study, high affinity for TMV RNA and assembly origin of TMV RNA (oriRNA) was revealed, accompanied by the conformational change of RNA. Considering that TMV assembly begins with the specific recognition by the coat protein aggregate of oriRNA, and that tylophorine B has favorable interaction with oriRNA, we speculate that tylophorine B likely exerts its virus inhibition by binding to oriRNA and interfering with virus assembly initiation. This work may shed light on the possible molecular inhibition mechanism against TMV by tylophorine B, and provide clues in rational design of sequence-specific RNA binding antivirus drugs.     

Hetaryl imidazoles: a novel dual inhibitors of VEGF receptors I and II

A novel potent derivatives of hetaryl imidazoles were described as inhibitors of vascular endothelial growth factor receptor II (VEGFR-2). Several compounds display VEGFR-2 inhibitory activity reaching IC(50)<100 nM in both enzymatic and cellular assays. The compounds also inhibit the related tyrosine kinase, VEGFR-1. By controlling the substitution pattern on the 5-carboxamido functionality, both dual and specific VEGFR-2 thiazoles were identified.     

Habitat choice and seed–seedling conflict of Spartina alterniflora on the coast of China

To elucidate the seed–seedling conflict and the process of habitat choices during the expansion of S. alterniflora, densities of seeds and seedlings in three different habitats, foreland, Spartina meadow, and canopy gap patch, were measured. Statistical analyses of these measurements were performed to investigate the interaction between seeds or seedlings and environmental factors. Also, the process of habitat choice during the expansion of S. alterniflora was explored. The results show that, in the upper soil seed bank (0–5 cm), both the ratio of germinated seeds and the ratio of survival seedlings to total seeds do not differ significantly among the three habitats. However, in the lower soil seed bank (5–10 cm), these ratios differ significantly, suggesting the seed–seedling conflict of S. alterniflora generally occurs in the lower soil seed bank. The remarkable conflict occurs in the meadow habitat. Greenhouse experiments indicate that the germination rate decreases significantly and the mortality of pre-emerged seedlings increases significantly with increasing burial depth. The maximal burial depth of emerged seedlings varies with sediment types. Comparisons of burial depth effects on seedling height, mesocotyl length, coleoptile length, and root length show that the major responses of S. alterniflora pre-emerged seedlings to the burial treatments are the elongation of coleoptiles and mesocotyls, which favor seedling survival by enhancing aeration and accelerating emergence. These results suggest that burial treatment is a key selection factor, which leads to the seed–seedling conflict in recruitment of S. alterniflora population, and directly affects the expansion rate and the area infected by S. alterniflora. Handling editor: S. M. Thomaz Ziwang Deng: co-first author.     

Hydrogen sulfide prevents hypoxia-induced apoptosis via inhibition of an H(2)O(2)-activated calcium signaling pathway in mouse hippocampal neurons

Hydrogen sulfide (H(2)S), an endogenous gaseous mediator, has been shown to exert protective effects against damage to different organs in the human body caused by various stimuli. However, the potential effects of H(2)S on hypoxia-induced neuronal apoptosis and its mechanisms remain unclear. Here, we exposed mouse hippocampal neurons to hypoxic conditions (2% O(2), 5% CO(2) and 93% N(2) at 37°C) to establish a hypoxic cell model. We found that 4-h hypoxia treatment significantly increased intracellular reactive oxygen species (ROS) levels, and pretreatment with NaHS (a source of H(2)S) for 30min suppressed hypoxia-induced intracellular ROS elevation. The hypoxia treatment significantly increased cytosolic calcium ([Ca(2+)](i)), and pretreatment with NaHS prevented the increase in [Ca(2+)](i). Additionally, polyethylene glycol (PEG)-catalase (a H(2)O(2) scavenger) but not PEG-SOD (an O(2)(-) scavenger) conferred an inhibitory effect similar to H(2)S on the hypoxia-induced increase in [Ca(2+)](i). Furthermore, we found that pretreatment with NaHS could significantly inhibit hypoxia-induced neuronal apoptosis, which was also inhibited by PEG-catalase or the inositol 1,4,5-triphosphate (IP(3)) receptor blocker xestospongin C. Taken together, these findings suggest that H(2)S inhibits hypoxia-induced apoptosis through inhibition of a ROS (mainly H(2)O(2))-activated Ca(2+) signaling pathway in mouse hippocampal neurons.     

Roles for receptors, pheromones, G proteins, and mating type genes during sexual reproduction in Neurospora crassa

Here we characterize the relationship between the PRE-2 pheromone receptor and its ligand, CCG-4, and the general requirements for receptors, pheromones, G proteins, and mating type genes during fusion of opposite mating-type cells and sexual sporulation in the multicellular fungus Neurospora crassa. PRE-2 is highly expressed in mat a cells and is localized in male and female reproductive structures. Δpre-2 mat a females do not respond chemotropically to mat A males (conidia) or form mature fruiting bodies (perithecia) or meiotic progeny (ascospores). Strains with swapped identity due to heterologous expression of pre-2 or ccg-4 behave normally in crosses with opposite mating-type strains. Coexpression of pre-2 and ccg-4 in the mat A background leads to self-attraction and development of barren perithecia without ascospores. Further perithecial development is achieved by inactivation of Sad-1, a gene required for meiotic gene silencing. Findings from studies involving forced heterokaryons of opposite mating-type strains show that presence of one receptor and its compatible pheromone is necessary and sufficient for perithecial development and ascospore production. Taken together, the results demonstrate that although receptors and pheromones control sexual identity, the mating-type genes (mat A and mat a) must be in two different nuclei to allow meiosis and sexual sporulation to occur.     

Structural and Biochemical Characterization of the Human Cyclophilin Family of Peptidyl-Prolyl Isomerases

Peptidyl-prolyl isomerases catalyze the conversion between cis and trans isomers of proline. The cyclophilin family of peptidyl-prolyl isomerases is well known for being the target of the immunosuppressive drug cyclosporin, used to combat organ transplant rejection. There is great interest in both the substrate specificity of these enzymes and the design of isoform-selective ligands for them. However, the dearth of available data for individual family members inhibits attempts to design drug specificity; additionally, in order to define physiological functions for the cyclophilins, definitive isoform characterization is required. In the current study, enzymatic activity was assayed for 15 of the 17 human cyclophilin isomerase domains, and binding to the cyclosporin scaffold was tested. In order to rationalize the observed isoform diversity, the high-resolution crystallographic structures of seven cyclophilin domains were determined. These models, combined with seven previously solved cyclophilin isoforms, provide the basis for a family-wide structure∶function analysis. Detailed structural analysis of the human cyclophilin isomerase explains why cyclophilin activity against short peptides is correlated with an ability to ligate cyclosporin and why certain isoforms are not competent for either activity. In addition, we find that regions of the isomerase domain outside the proline-binding surface impart isoform specificity for both in vivo substrates and drug design. We hypothesize that there is a well-defined molecular surface corresponding to the substrate-binding S2 position that is a site of diversity in the cyclophilin family. Computational simulations of substrate binding in this region support our observations. Our data indicate that unique isoform determinants exist that may be exploited for development of selective ligands and suggest that the currently available small-molecule and peptide-based ligands for this class of enzyme are insufficient for isoform specificity.

Enhanced version

This article can also be viewed as an enhanced version in which the text of the article is integrated with interactive 3-D representations and animated transitions. Please note that a Web plugin is required to access this enhanced functionality. Instructions for the installation and use of the web plugin are available in Text S1.