多产柴油的催化裂化动力学模型

在已开发的重油催化裂化十一集总动力学模型的基础上，对参数估计方法进行了改进，建立了一步法确定模型动力学参数的方法，并通过一步法得到了MLC-500催化剂多产柴油裂化的动力学参数，模型的实验室验证表明，动力学参数是可靠的。     

Metabolic priming by a secreted fungal effector

Maize smut caused by the fungus Ustilago maydis is a widespread disease characterized by the development of large plant tumours. U. maydis is a biotrophic pathogen that requires living plant tissue for its development and establishes an intimate interaction zone between fungal hyphae and the plant plasma membrane. U. maydis actively suppresses plant defence responses by secreted protein effectors. Its effector repertoire comprises at least 386 genes mostly encoding proteins of unknown function and expressed exclusively during the biotrophic stage. The U. maydis secretome also contains about 150 proteins with probable roles in fungal nutrition, fungal cell wall modification and host penetration as well as proteins unlikely to act in the fungal-host interface like a chorismate mutase. Chorismate mutases are key enzymes of the shikimate pathway and catalyse the conversion of chorismate to prephenate, the precursor for tyrosine and phenylalanine synthesis. Root-knot nematodes inject a secreted chorismate mutase into plant cells likely to affect development. Here we show that the chorismate mutase Cmu1 secreted by U. maydis is a virulence factor. The enzyme is taken up by plant cells, can spread to neighbouring cells and changes the metabolic status of these cells through metabolic priming. Secreted chorismate mutases are found in many plant-associated microbes and might serve as general tools for host manipulation.     

Nesprin interchain associations control nuclear size

Nesprins-1/-2/-3/-4 are nuclear envelope proteins, which connect nuclei to the cytoskeleton. The largest nesprin-1/-2 isoforms (termed giant) tether F-actin through their N-terminal actin binding domain (ABD). Nesprin-3, however, lacks an ABD and associates instead to plectin, which binds intermediate filaments. Nesprins are integrated into the outer nuclear membrane via their C-terminal KASH-domain. Here, we show that nesprin-1/-2 ABDs physically and functionally interact with nesprin-3. Thus, both ends of nesprin-1/-2 giant are integrated at the nuclear surface: via the C-terminal KASH-domain and the N-terminal ABD-nesprin-3 association. Interestingly, nesprin-2 ABD or KASH-domain overexpression leads to increased nuclear areas. Conversely, nesprin-2 mini (contains the ABD and KASH-domain but lacks the massive nesprin-2 giant rod segment) expression yields smaller nuclei. Nuclear shrinkage is further enhanced upon nesprin-3 co-expression or microfilament depolymerization. Our findings suggest that multivariate intermolecular nesprin interactions with the cytoskeleton form a lattice-like filamentous network covering the outer nuclear membrane, which determines nuclear size.     

Morphology and growth variation of Agropyron Smithii RYDB. (western wheatgrass) at different salinity levels

The purpose of this study was to determine the morphology and growth responses of Agropyron smithii Rydb. To various saline environments as evaluated in the laboratory. Agropyron smithii Rydb. (Rosana) seeds were germinated, transplanted into nutrient solutions with NaCl concentrations of 0, 50, 100, 150, and 200 m M , and grown for 80 days. Plant height, length of culm, and number of culms per plant were significantly reduced by the presence of NaCl in the nutrient solutions. As the external NaCl concentrations increased, values of root and plant ratio and leaf dry/fresh mass ratio increased significantly; biomass decreased significantly. However, the stomatal index, number of leaves per culm, and ratio of leaf length to leaf width were not significantly affected by the presence of NaCl.     

Dominant missense mutations in ABCC9 cause Cantú syndrome

Cantú syndrome is characterized by congenital hypertrichosis, distinctive facial features, osteochondrodysplasia and cardiac defects. By using family-based exome sequencing, we identified a de novo mutation in ABCC9. Subsequently, we discovered novel dominant missense mutations in ABCC9 in 14 of the 16 individuals with Cantú syndrome examined. The ABCC9 protein is part of an ATP-dependent potassium (K(ATP)) channel that couples the metabolic state of a cell with its electrical activity. All mutations altered amino acids in or close to the transmembrane domains of ABCC9. Using electrophysiological measurements, we show that mutations in ABCC9 reduce the ATP-mediated potassium channel inhibition, resulting in channel opening. Moreover, similarities between the phenotype of individuals with Cantú syndrome and side effects from the K(ATP) channel agonist minoxidil indicate that the mutations in ABCC9 result in channel opening. Given the availability of ABCC9 antagonists, our findings may have direct implications for the treatment of individuals with Cantú syndrome.     

Positive selection of CD4+ thymocytes controlled by MHC class II gene products

The mature T-cell antigen receptor repertoire is characterized by lack of reactivity to self-components as well as by preferential reactivity to foreign antigens in the context of polymorphic self-proteins encoded within the major histocompatibility complex. Whereas the former characteristic (referred to as negative selection or tolerance) is associated with intrathymic deletion of T cells expressing T-cell antigen receptor beta-chain variable (V beta) domains, which confer a preferential reactivity to self antigens, the existence of the latter (referred to as positive selection or MHC restriction) has so far only been inferred indirectly from functional studies. We show here that intrathymic deletion of V+beta 6 T cells (reactive with a self-antigen encoded by the Mlsa locus) is controlled by polymorphic MHC class II determinants. Furthermore, in mice lacking expression of Mlsa, the same class II MHC loci control the frequency of occurrence of V+beta 6 cells among mature CD4+ T lymphocytes. These data are direct evidence for positive selection by MHC determinants in the thymus in unmanipulated animals.     

Uncoupling of hypomyelination and glial cell death by a mutation in the proteolipid protein gene.

Proteolipid protein (PLP; M(r) 30,000) is a highly conserved major polytopic membrane protein in myelin but its cellular function remains obscure. Neurological mutant mice can often provide model systems for human genetic disorders. Mutations of the X-chromosome-linked PLP gene are lethal, identified first in the jimpy mouse and subsequently in patients with Pelizaeus-Merzbacher disease. The unexplained phenotype of these mutations includes degeneration and premature cell death of oligodendrocytes with associated hypomyelination. Here we show that a new mouse mutant rumpshaker is defined by the amino-acid substitution Ile-to-Thr at residue 186 in a membrane-embedded domain of PLP. Surprisingly, rumpshaker mice, although myelin-deficient, have normal longevity and a full complement of morphologically normal oligodendrocytes. Hypomyelination can thus be genetically separated from the PLP-dependent oligodendrocyte degeneration. We suggest that PLP has a vital function in glial cell development, distinct from its later role in myelin assembly, and that this dichotomy of action may explain the clinical spectrum of Pelizaeus-Merzbacher disease.