近年来出现的几类新概念动物疫苗

动物疫病流行广泛、传播迅速,严重危害养殖业的发展。疫苗接种是预防和控制动物传染病最有效的策略之一。目前,随着生物技术的发展和疫病防控的需要,安全、高效、广谱、用量少、具有标记特征的新型疫苗成为研发重点。文中就近年来出现的黏膜疫苗、长效与速效疫苗、嵌合疫苗、纳米颗粒疫苗等新概念动物疫苗的发展、应用及优缺点进行了评述,并提出了其发展方向,以期为动物疫苗的研发提供借鉴。     

DNA Methylation Effects on Tetra-Nucleosome Compaction and Aggregation

DNA CpG methylation has been associated with chromatin compaction and gene silencing. Whether DNA methylation directly contributes to chromatin compaction remains an open question. In this study, we used fluorescence fluctuation spectroscopy (FFS) to evaluate the compaction and aggregation of tetra-nucleosomes containing specific CpG patterns and methylation levels. The compactness of both unmethylated and methylated tetra-nucleosomes is dependent on DNA sequences. Specifically, methylation of the CpG sites located in the central dyad and the major grooves of DNA seem to have opposite effects on modulating the compactness of tetra-nucleosomes. The interactions among tetra-nucleosomes, however, seem to be enhanced because of DNA methylation independent of sequence contexts. Our finding can shed light on understanding the role of DNA methylation in determining nucleosome positioning pattern and chromatin compactness.     

Nonreductive chemical release of intact N-glycans for subsequent labeling and analysis by mass spectrometry

A novel strategy is proposed, using cost-saving chemical reactions to generate intact free reducing N-glycans and their fluorescent derivatives from glycoproteins for subsequent analysis. N-Glycans without core α-1,3-linked fucose are released in reducing form by selective hydrolysis of the N-type carbohydrate–peptide bond of glycoproteins under a set of optimized mild alkaline conditions and are comparable to those released by commonly used peptide-N-glycosidase (PNGase) F in terms of yield without any detectable side reaction (peeling or deacetylation). The obtained reducing glycans can be routinely derivatized with 2-aminobenzoic acid (2-AA), 1-phenyl-3-methyl-5-pyrazolone (PMP), and potentially some other fluorescent reagents for comprehensive analysis. Alternatively, the core α-1,3-fucosylated N-glycans are released in mild alkaline medium and derivatized with PMP in situ, and their yields are comparable to those obtained using commonly used PNGase A without conspicuous peeling reaction or any detectable deacetylation. Using this new technique, the N-glycans of a series of purified glycoproteins and complex biological samples were successfully released and analyzed by electrospray ionization mass spectrometry (ESI–MS) and tandem mass spectrometry (MS/MS), demonstrating its general applicability to glycomic studies.     

Ecological Risk Assessment of Provincial Land-Use Overall Planning in China

The method evaluating the ecological risk for provincial land-use overall planning is introduced so as to construct an environment-friendly land-use pattern. The ecological risk degree is determined by risk source intensity and ecological vulnerability degree. In order to quantify them, the calculation process, classification standard, and acceptability analysis are established. With an example, it evaluates the ecological risk of land-use overall planning in Sichuan Province. The results show: (1) the implementation of planning can reduce the potential ecological risk effectively, and the whole ecological risk level is on the decline during the planning period; (2) the spatial difference of ecological risk is significant. However, the basic pattern of ecological risks, which is higher in the east and lower in the west, has not changed after the planning implementation, and the higher risk areas mainly distribute in the economically developed and densely populated areas; (3) according to the spatiotemporal characteristics, the emphasis of ecological risk prevention and control can be identified, and some countermeasures can be suggested in order to decrease the potential adverse effects. The method proposed in the article can provide decision basis for provincial land-use overall planning, and is helpful to ecological risk analysis of other planning.     

Structural insights into the T6SS effector protein Tse3 and the Tse3–Tsi3 complex from Pseudomonas aeruginosa reveal a calcium‐dependent membrane‐binding mechanism

The opportunistic pathogen Pseudomonas aeruginosa uses the type VI secretion system (T6SS) to deliver the muramidase Tse3 into the periplasm of rival bacteria to degrade their peptidoglycan (PG). Concomitantly, P. aeruginosa uses the periplasm‐localized immunity protein Tsi3 to prevent potential self‐intoxication caused by Tse3, and thus gains an edge over rival bacteria in fierce niche competition. Here, we report the crystal structures of Tse3 and the Tse3–Tsi3 complex. Tse3 contains an annexin repeat‐like fold at the N‐terminus and a G‐type lysozyme fold at the C‐terminus. One loop in the N‐terminal domain (Loop 12) and one helix (α9) from the C‐terminal domain together anchor Tse3 and the Tse3–Tsi3 complex to membrane in a calcium‐dependent manner in vitro, and this membrane‐binding ability is essential for Tse3's activity. In the C‐terminal domain, a Y‐shaped groove present on the surface likely serves as the PG binding site. Two calcium‐binding motifs are also observed in the groove and these are necessary for Tse3 activity. In the Tse3–Tsi3 structure, three loops of Tsi3 insert into the substrate‐binding groove of Tse3, and three calcium ions present at the interface of the complex are indispensable for the formation of the Tse3–Tsi3 complex.     

Dimeric Ube2g2 simultaneously engages donor and acceptor ubiquitins to form Lys48‐linked ubiquitin chains

Cellular adaptation to proteotoxic stress at the endoplasmic reticulum (ER) depends on Lys48‐linked polyubiquitination by ER‐associated ubiquitin ligases (E3s) and subsequent elimination of ubiquitinated retrotranslocation products by the proteasome. The ER‐associated E3 gp78 ubiquitinates misfolded proteins by transferring preformed Lys48‐linked ubiquitin chains from the cognate E2 Ube2g2 to substrates. Here we demonstrate that Ube2g2 synthesizes linkage specific ubiquitin chains by forming an unprecedented homodimer: The dimerization of Ube2g2, mediated primarily by electrostatic interactions between two Ube2g2s, is also facilitated by the charged ubiquitin molecules. Mutagenesis studies show that Ube2g2 dimerization is required for ER‐associated degradation (ERAD). In addition to E2 dimerization, we show that a highly conserved arginine residue in the donor Ube2g2 senses the presence of an aspartate in the acceptor ubiquitin to position only Lys48 of ubiquitin in proximity to the donor E2 active site. These results reveal an unanticipated mode of E2 self‐association that allows the E2 to effectively engage two ubiquitins to specifically synthesize Lys48‐linked ubiquitin chains.