碳纳米管膜的制备及其研究进展

碳纳米管众多优良性质,并不仅仅体现在单根碳纳米管中,更多的是在大量的碳纳米管的集中体现,即碳纳米管膜的性质与应用。本文根据碳纳米管膜中碳纳米管的排列方式不同,详细介绍了无序碳纳米管膜、水平有序碳纳米管膜及垂直有序碳纳米管膜的制备方法、应用现状及其面临的挑战。     

碳纳米管场致电子发射研究进展

碳纳米管（CNTs）具有独特的电子、化学、力学特性,且易制备,作为冷阴极场发射材料在平板显示领域有潜在的应用价值而引起了人们的极大兴趣。本文简单介绍了几种改善碳纳米管薄膜场致电子发射特性的实验方法研究进展,并对碳纳米管场发射显示器研究进展进行了综述。     

Light emission of double-walled carbon nanotube filaments doped with yttrium and europium

As the potential applications of carbon nanotubes in the field of electroluminescence,elements yttrium and europium were introduced to modify the emission properties of double-walled carbon nanotubes(DWNTs)to obtain higher efficacy and other properties.The light emission spectrum of the Y-Eu-doped DWNT filament is suppressed in the near-infrared range,while enhanced in the mid-infrared range.The doped DWNT filament can reach higher efficacy than that of the pure DWNT filament at the same input power and can...     

Dps-like proteins: structural and functional insights into a versatile protein family

Dps-like proteins are key factors involved in the protection of prokaryotic cells from oxidative damage. They act by either oxidizing iron to prevent the formation of oxidative radicals or by forming Dps-DNA complexes to physically protect DNA. All Dps-like proteins are characterized by a common three-dimensional architecture and are found as spherical dodecamers with a hollow central cavity. Despite their structural similarities, recent biochemical and structural data have suggested different functions among members of the family that range from protection inside the cells in response to various stress signals to adhesion and virulence during bacterial infections. Moreover, the Dps-like proteins have lately attracted considerable interest in the field of nanotechnology owing to their ability to act as protein cages for iron and various other metals. A better understanding of their function and mechanism could therefore lead to novel applications in biotechnology and nanotechnology.     

DING proteins: numerous functions, elusive genes, a potential for health

DING proteins, named after their conserved N-terminus, form an overlooked protein family whose members were generally discovered through serendipity. It is characterized by an unusually high sequence conservation, even between distantly related species, and by an outstanding diversity of activities and ligands. They all share a demonstrated capacity to bind phosphate with high affinity or at least a predicted phosphate-binding site. However, DING protein genes are conspicuously absent from databases. The many novel family members identified in recent years have confirmed that DING proteins are ubiquitous not only in animals and plants but probably also in prokaryotes. At the functional level, there is increasing evidence that they participate in many health-related processes such as cancers as well as bacterial (Pseudomonas) and viral (HIV) infections, by mechanisms that are now beginning to be understood. They thus represent potent targets for the development of novel therapeutic approaches, especially against HIV. The few genomic sequences that are now available are starting to give some clues on why DING protein genes and mRNAs are well conserved and difficult to clone. This could open a new era of research, of both fundamental and applied importance.     

Sugar-mimicking glycosidase inhibitors: bioactivity and application

A large number of compounds mimicking the structures of monosaccharides or oligosaccharides have been discovered from natural sources. Such sugar mimics inhibit carbohydrate-degrading enzymes because of a structural resemblance to the sugar moiety of the natural substrate. Carbohydrate-degrading enzymes are involved in a wide range of important biological processes, such as intestinal digestion, posttranslational processing of the sugar chain of glycoproteins, their quality control mechanisms, lysosomal catabolism of glycoconjugates, and some viral infections. It has now been realized that inhibitors of the enzymes have enormous therapeutic potential in diabetes and lysosomal storage disorders. In this review, the general bioactivity, current applications, and the prospects for new therapeutic applications are described. Received 27 August 2008; received after revision 08 November 2008; accepted 03 December 2008     

Anti-infective properties of bacteriocins: an update

Bacteriocin production is a widespread phenomenon among bacteria. Bacteriocins hold great promise for the treatment of diseases caused by pathogenic bacteria and could be used in the future as alternatives to existing antibiotics. The anti-infective potential of bacteriocins for inhibiting pathogens has been shown in various food matrices including cheese, meat, and vegetables. However, their inhibition of pathogens in vivo remains unclear and needs more investigation, due mainly to difficulties associated with demonstrating their health benefits. Many bacteriocins produced by established or potential probiotic organisms have been evaluated as potential therapeutic agents and interesting findings have been documented in vitro as well as in a few in vivo studies. Some recent in vivo studies point to the efficacy of bacteriocin-based treatments of human and animal infections. While further investigation remains necessary before the possibilities for bacteriocins in clinical practice can be described more fully, this review provides an overview of their potential applications to human and veterinary health.     

Lysozyme activates Enterococcus faecium to induce necrotic cell death in macrophages

Enterococci are commensal organisms in the alimentary tract. However, they can cause a variety of life-threatening infections, especially in nosocomial settings. We hypothesized that induction of cell death might enable these facultative pathogenic bacteria to evade the innate immune response and to cause infections of their host. We demonstrate that E. faecium when exposed to lysozyme induces cell death in macrophages in vitro and in vivo. Flow cytometric analyses of J774A.1 macrophages infected with E. faecium revealed loss of cell membrane integrity indicated by uptake of propidium iodide and decrease of the inner mitochondrial transmembrane potential ΔΨ_m. Inhibition of caspases, treatment of macrophages with cytochalasin D, or rifampicin did not prevent cells from dying, suggesting cell death mechanisms that are independent of caspase activation, bacterial uptake, and intracellular bacterial replication. Characteristics of necrotic cell death were demonstrated by both lack of procaspase 3 activation and cell shrinkage, electron microscopy, and release of lactate dehydrogenase. Pretreatment of E. faecium with lysozyme and subsequently with broad spectrum protease considerably reduced cell death, suggesting that a bacterial surface protein is causative for cell death induction. Moreover, in a mouse peritonitis model we demonstrated that E. faecium induces cell death of peritoneal macrophages in vivo. Altogether, our results show that enterococci, under specific conditions such as exposure to lysozyme, induce necrotic cell death in macrophages, which might contribute to disseminated infections by these facultative pathogenic bacteria.     

Oxazolidinones: a novel class of antibiotics

Oxazolidinones are a novel class of synthetic antimicrobial agents which have now entered phase III clinical trials. The most promising feature of these compounds is their oral activity against multidrug-resistant Gram-positive bacteria which have created tremendous therapeutic problems in recent years. In addition, development of resistance in vitro has so far remained below detectable levels. Different from many antibacterial agents used in the treatment of human infections, oxazolidinones do not block bacterial protein synthesis at the level of polypeptide chain elongation but rather seem to interfere with initiation of translation. Both binding of formylmethionine-transfer RNA to initiation complexes as well as release of formylmethioninepuromycin from initiation complexes have been reported to be targets for oxazolidinones. The major binding sites of oxazolidinones are the large (50S) ribosomal subunits.     

Glutathione synthetase deficiency

Glutathione (GSH), one of the most important antioxidants in the eukaryotic organism, is synthesized in a two-step procedure where the last step is catalysed by the enzyme glutathione synthetase (GSS). GSS deficiency is inherited autosomal recessively, and patients with this disease can be divided into three groups, according to their clinical phenotype. Mildly affected patients have mutations affecting the stability of the enzyme, causing a compensated haemolytic anaemia; moderately affected patients have, in addition, metabolic acidosis; and severely affected patients also develop neurological defects and show increased susceptibility to bacterial infections. Moderately and severely affected patients have mutations that compromise the catalytic properties of the enzyme. 5-Oxoprolinuria appears in all three groups, but is more pronounced in the two latter groups. Today, no cure can be offered these patients; they are given vitamins C and E to boost their antioxidant levels, and bicarbonate to correct metabolic acidosis.Received 20 April 2005; received after revision 19 May 2005; accepted 20 May 2005     

Protein N-terminal methionine excision

N-terminal methionine excision (NME) is the major proteolytic pathway responsible for the diversity of N-terminal amino acids in proteins. Dedicated NME components have been identified in all organisms, in all compartments in which protein synthesis occurs: cytoplasm, plastids and mitochondria. Recent studies have revealed that NME is regulated at various levels and plays an important role in controlling protein turnover. NME is essential in Eubacteria and lower eukaryotes and is the target of many natural and synthetic inhibitors. Such inhibitors have considerable potential for use in the treatment of various human diseases, from cancer to bacterial and parasitic infections.Received 19 December 2003; received after revision 21 January 2004; accepted 4 February 2004     

Knowledge translation: airway epithelial cell migration and respiratory diseases

Airway epithelial cell migration is essential for lung development and growth, as well as the maintenance of respiratory tissue integrity. This vital cellular process is also important for the repair and regeneration of damaged airway epithelium. More importantly, several lung diseases characterized by aberrant tissue remodeling result from the improper repair of damaged respiratory tissue. Epithelial cell migration relies upon extracellular matrix molecules and is further regulated by numerous local, neuronal, and hormonal factors. Under inflammatory conditions, cell migration can also be stimulated by certain cytokines and chemokines. Many well-known environmental factors involved in the pathogenesis of chronic lung diseases (e.g., cigarette smoking, air pollution, alcohol intake, inflammation, viral and bacterial infections) can inhibit airway epithelial cell migration. Further investigation of cellular and molecular mechanisms of cell migration with advanced techniques may provide knowledge that is relevant to physiological and pathological conditions. These studies may eventually lead to the development of therapeutic interventions to improve lung repair and regeneration and to prevent aberrant remodeling in the lung.     

Phagocytes,phagocytose et défense de l'organisme contre les infections

Summary After the evocation of classic notions about morphology and physiology of free and fixed phagocytes, and their role in the defense of organism against infections, writers give new observations on two principal points.1. They show that polysaccharids, to which the grampositive bacteria owe their specificity, are the most important agents responsable of the migration of polymorphonuclear leucocytes in inflamed connective tissue.2. They show that bacterial endotoxins, nature of which is glucido-lipido-polypeptidic, and which are also antigens O complets of gram-negative micro-organisms, appear able to stop the coming of polymorphonuclears in inflamed connective tissues. The endotoxins kill not leukocytes; they are not leucocidins, but they prevent diapedesis through a mechanism still obscure. For this reason, they favour the development of infections.Ultimately, writers tell how the two great theories of immunity, cellular theory ofMetchnikoff and humoral theory of german authors, can mary together: in vivo, phagocytes have the first and also the last word to kill bacteria, but their work is very much easier after opsonization with antibodies.     

Synsthesis and RES-stimulating activity of bacterial cell-wall peptidoglycan peptides related to FK-156

Summary The bacterial cell-wall peptidoglycan peptides and related compounds coupled with some fatty acids were synthesized, and their immunostimulating property was examined by carbon clearance assay. All the new compounds (2–6) proved to possess significant potencies superior to that of FK-156 (1).Acknowledgment. We are grateful to Dr J. Mori and his coworkers for the biological assays.     

Molecular recognition of microbial lipid-based antigens by T cells

The immune system has evolved to protect hosts from pathogens. T cells represent a critical component of the immune system by their engagement in host defence mechanisms against microbial infections. Our knowledge of the molecular recognition by T cells of pathogen-derived peptidic antigens that are presented by the major histocompatibility complex glycoproteins is now well established. However, lipids represent an additional, distinct chemical class of molecules that when presented by the family of CD1 antigen-presenting molecules can serve as antigens, and be recognized by specialized subsets of T cells leading to antigen-specific activation. Over the past decades, numerous CD1-presented self- and bacterial lipid-based antigens have been isolated and characterized. However, our understanding at the molecular level of T cell immunity to CD1 molecules presenting microbial lipid-based antigens is still largely unexplored. Here, we review the insights and the molecular basis underpinning the recognition of microbial lipid-based antigens by T cells.     

Heat shock proteins in autoimmune disease. From causative antigen to specific therapy?

Heat shock proteins (hsp) are highly conserved from bacteria to man. Bacterial hsp, with approximate molecular weights of 60 kDa (hsp60), are immunodominant antigens that are immunologically cross-reactive with their mammalian counterparts. Hsp molecules are therefore useful in studies of fundamental questions concerning immune responses to foreign as opposed to self antigens. The finding that immune responses to hsp are associated with both experimentally-induced and spontaneous autoimmune diseases in animals has prompted intensive research to assess the role of bacterial hsp as the etiological agents involved in the development of autoimmune diseases. Recent evidence from animal models of autoimmune disease has clearly demonstrated the involvement of hsp in both the pathogenesis and the immunoregulation of autoimmune diseases. Studies with arthritogenic and diabetogenic T cell clones have identified immunogenic epitopes of hsp. These have been shown to ameliorate adjuvant arthritis in Lewis rats, and insulin-dependent diabetes mellitus (IDDM) in non-obese diabetic (NOD) mice. Such studies may have important therapeutic implications for the future treatment of human autoimmune disease.     

Vitamin C and the immune response.

The inclusion of vitamin C in the drinking water of BALB/c mice was without effect on the humoral antibody response to sheep red blood cells and bacterial lipopolysaccharide. However, there was a significantly increased cell-mediated immune response as determined by increased T-lymphocyte responses to concanavalin A. This might suggest a mechanism, along with interferon enhancement, for the possible protection by vitamin C against some viral infections.     

单一导电性能的单壁碳纳米管的分离

本文首先简单介绍了单壁碳纳米管的化学结构与导电性性能之间的关系，然后就单壁碳纳米管研究中的一个重要难题，即如何分离金属型和半导体型，概述了目前主要的分离方法和研究结果。