Epitope mapping by a method that requires no amino acid sequence information.

A simple, rapid method of epitope mapping has been developed that avoids the often cumbersome requirement of obtaining amino acid sequence information. The protein antigen is digested with various concentrations of carboxypeptidase into a nearly continuous series of polypeptides of different molecular weights, all containing a common N-terminus. The peptides are separated by polyacrylamide gel electrophoresis and then transferred to nitrocellulose paper. After developing the blot with the antibody to be mapped, a nearly continuous stain is observed extending from the position of the intact antigen to the molecular weight of the smallest N-terminal fragment still containing the antibody's epitope. By noting the molecular weight where the stain terminates, the position of the epitope relative to the N-terminus can be determined. Using this methodology, and taking special precautions to inhibit all endoproteinases in the carboxypeptidase preparation, the previously mapped epitopes of six nonoverlapping antibodies to the erythrocyte anion transporter were confirmed.     

Growth Type and Functional Trajectories: An Empirical Study of Urban Expansion in Nanjing,China

Drawing upon the Landsat satellite images of Nanjing from 1985, 1995, 2001, 2007, and 2013, this paper integrates the convex hull analysis and common edge analysis at double scales, and develops a comprehensive matrix analysis to distinguish the different types of urban land expansion. The results show that Nanjing experienced rapid urban expansion, dominated by a mix of residential and manufacturing land from 1985 to 2013, which in turn has promoted Nanjing’s shift from a compact mononuclear city to a polycentric one. Spatial patterns of three specific types of growth, namely infilling, extension, and enclave were quite different in four consecutive periods. These patterns result primarily from the existing topographic constraints, as well as government-oriented urban planning and policies. By intersecting the function maps, we also reveal the functional evolution of newly-developed urban land. Moreover, both self-enhancing and mutual promotion of the newly developed functions are surveyed over the last decade. Our study confirms that the integration of a multi-scale method and multi-perspective analysis, such as the spatiotemporal patterns and functional evolution, helps us to better understand the rapid urban growth in China.     

Glucose biosensor based on electrodeposited platinum nanoparticles and three-dimensional porous chitosan membranes

The chitosan with three-dimensional porous structure greatly increased the effective electrode surface for loading of platinum nanoparticles and promoted efficient electron transfer. The resulting biosensor had a response time (within 5 s) and a linear response from 6 μM to 4.2 mM glucose with a detection limit of 2 μM (S/N = 3). Moreover, the methodology can be applied for the immobilization of other enzymes.     

Secretion of the STA3 heat-stable enterotoxin of Escherichia coli: extracellular delivery of Pro-STA is accomplished by either Pro or STA

The methanol-soluble, heat-stable enterotoxin of Escherichia coli is a protease-resistant extracellular peptide which is synthesized as a 72-amino-acid precursor Pre-Pro-STA3. The specific roles of Pre (19 amino acids), Pro (34 amino acids) and STA3 (19 amino acids) in the secretion process were studied by functionally deleting each of the three domains. Deletion of the Pre signal sequence resulted in a short-lived cell-associated molecule with an M(r) equivalent to that of Pro-STA3. Deletion of Pro (i.e., Pre-STA3) resulted in the rapid extracellular accumulation of STA3; the periplasmic intermediate found in the secretion of the wild-type toxin was undetected. Deletion of the STA3 domain resulted in a cell-associated Pre-Pro peptide; with time this form converted to periplasmic Pro which later became extracellular. When DNA encoding either STA3, by itself, or Pro-STA3 (lacking the signal peptide) was expressed, these peptides were degraded intracellularly, with no periplasmic or extracellular forms detected. The results presented demonstrate that the signal peptide (Pre) is essential even for the export of small peptides to the periplasm, and that its absence causes the STA3 domain to become susceptible to intracellular proteases. The rapid degradation of intracellular STA3 indicates that its proteolytic resistance is acquired in a compartment other than the cytoplasm. The results also show that after the Pre domain is proteolytically cleaved from Pre-STA3 and Pre-Pro, the STA3 and Pro peptides can exit to the culture supernatant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Strategies for farmers and policy makers to control nitro-gen losses whilst maintaining crop production

The nitrogen (N) cycle is essentially 'leaky'. The losses of small amounts of nitrate to waters and of ammonia and nitrous oxide to the atmosphere are a part of the global biogeo-chemical N cycle. However, intensive agricultural production, industry and vehicle use have more than doubled the amount of 'reactive' N in the environment, resulting in eutrophication, ecosystem change and health concerns. Research has identified agricultural practices that cause large losses of N and, in some cases, developed solutions. This paper discusses the problems of maintaining productivity while reducing N losses, compares conventional with low input (integrated) and organic farming systems, and discusses wider options. It also looks at the need to integrate studies on N with other environmental impacts, set in the context of the whole farm system, to provide truly sustainable agricultural systems.     

Anti-biofouling property studies on carboxyl-modified multi-walled carbon nanotubes filled PDMS nanocomposites

Polydimethylsiloxane (PDMS) with exceptional fouling-release properties is extremely susceptible to the microfouling resulted from the colonization of the pioneer microorganisms in the marine environment. In this study, six carboxyl-modified multi-walled carbon nanotubes (cMWNTs) nanoparticles were incorporated into the PDMS matrix, respectively, in order to produce the cMWNTs-filled PDMS nanocomposites (CPs) with improved antifouling (AF) properties. The AF properties of the six CPs were examined via the field assays conducted in Weihai, China. The effects of the anti-biofouling potential of the CPs (i.e. the P₃ surface) on the colonization of the pioneer prokaryotic and eukaryotic microbes were investigated using the single-stranded conformation polymorphism technique via the comparison of the diversity indices. Different CPs have displayed differential and better AF properties as compared to that of the unfilled PDMS (P₀). The P₃ surface has exhibited exceptional anti-biofouling capacity compared with the other CPs surfaces, which can effectively prevent biofouling for more than 14 weeks in the field. The SSCP analysis revealed that the P₃ surface may have significant modulating effect on the pioneer microbial communities. The pioneer eukaryotic microbes seemed more susceptible than the pioneer prokaryotic microbes to be subjected to the major perturbations exerted by the P₃ surface. The dramatically reduced eukaryotic-microbial diversity may contribute to the impeding and weakening of the development and growth of the biofilm. The P₃ surface has the potential to be used for future maritime applications.     

ERp57 is up‐regulated in free fatty acids‐induced steatotic L‐02 cells and human nonalcoholic fatty livers

Pathogenesis of nonalcoholic fatty liver disease (NAFLD) is not clear. In this study we aimed to identify proteins involved in NAFLD development in free fatty acids (FFA)‐induced hepatosteatotic cells and in human liver biopsies. Steatosis was induced by incubating a normal human hepatocyte‐derived cell line L‐02 with FFA. Differentially expressed proteins in the steatotic cells were analyzed by two‐dimensional gel electrophoresis‐based proteomics. Involvement of one of the up‐regulated proteins in steatosis was characterized using the RNA interference approach with the steatotic cells. Protein expression levels in liver biopsies of patients with NAFLD were assessed by immunohistochemistry. Proteomic analysis of L‐02 steatotic cells revealed the up‐regulation of ERp57, a condition not previously implicated in NAFLD. Knockdown of ERp57 expression with siRNA significantly reduced fat accumulation in the steatotic cells. ERp57 expression was detected in 16 out of 17 patient biopsies and correlated with inflammation grades or fibrosis stages, while in 5 normal biopsies ERp57 expression was not detectable in hepatocytes. In conclusion, ERp57 was up‐regulated in FFA‐induced steatotic hepatic cells and in NAFLD patient livers and demonstrated steatotic properties in cultured cells. Further investigations are warranted to verify the involvement of ERp57 in NAFLD development. J. Cell. Biochem. 110: 1447–1456, 2010. © 2010 Wiley‐Liss, Inc.