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An analysis of the structural modification during synthesis of prion protein PrP(Sc) involved the application of nondenaturing techniques to purify PrP(Sc) from the cellular prion protein PrPC, and the definition of their secondary structures. The transformation of alpha-helices into beta-sheets is involved in the formation of PrPSc, and an unknown chemical change in a small portion of PrPSc may trigger this mechanism.

Structural analysis based on comparisons of the amino acid sequences of 11 mammalian and 1 avian prion proteins (PrP) predicted four alpha-helical structures. To test the prediction, peptides homologous to portions of the Syrian hamster prion proteins (PrP) sequence were synthesized. Contrary to predictions, three of the four structures formed amyloids. The findings indicate that the conversion of the cellular PrP isoform to the scrapie isoform could be due to the transition of alpha helices to beta-sheets.If such is the case, prion diseases could be considered as disorders of proteinconformations.

Background: Peptide amphiphiles (PAs) are a class of amphiphilic molecules able to self-assemble into nanomaterials that have shown efficient in vivo targeted delivery. Understanding the interactions of PAs with cells and the mechanisms of their internalization and intracellular trafficking is critical in their further development for therapeutic delivery applications. Methodology/Principal Findings: PAs of a novel, cell- and tissue-penetrating peptide were synthesized possessing two different lipophilic tail architectures and their interactions with prostate cancer cells were studied in vitro. Cell uptake of peptides was greatly enhanced post-modification. Internalization occurred via lipid-raft mediated endocytosis and was common for the two analogs studied. On the contrary, we identified the non-peptidic part as the determining factor of differences between intracellular trafficking and retention of PAs. PAs composed of di-stearyl lipid tails linked through poly(ethylene glycol) to the peptide exhibited higher exocytosis rates and employed different recycling pathways compared to ones consisting of di-palmitic-coupled peptides. As a result, cell association of the former PAs decreased with time. Conclusions/Significance: Control over peptide intracellular localization and retention is possible by appropriate modification with synthetic hydrophobic tails. We propose this as a strategy to design improved peptide-based delivery systems. [ABSTRACT FROM AUTHOR]

When photosystem II (PSII) is exposed to excess light, singlet oxygen (¹O2) formed by the interaction of molecular oxygen with triplet chlorophyll. Triplet chlorophyll is formed by the charge recombination of triplet radical pair ³[P680•+ Pheo] •- in the acceptor-side photoinhibition of PSII. Here, we provide evidence on the formation of ¹O2 in the donor side photoinhibition of PSII. Light-induced ¹O2 production in Tris-treated PSII membranes was studied by electron paramagnetic resonance (EPR) spin-trapping spectroscopy, as monitored by TEMPONE EPR signal. Light-induced formation of carbon-centered radicals (R•) was observed by POBN-R adduct EPR signal. Increased oxidation of organic molecules at high pH enhanced the formation of TEMPONE and POBN-R adduct EPR signals in Tris-treated PSII membranes. Interestingly, the scavenging of R• by propyl gallate significantly suppressed ¹O2. Based on our results, it is concluded that ¹O2 formation correlates with R• formation on the donor side of PSII due to oxidation of organic molecules (lipids and proteins) by long-lived P680•+/TyrZ•. It is proposed here that the Russell mechanism for the recombination of two peroxyl radicals formed by the interaction of R• with molecular oxygen is a plausible mechanism for ¹O2 formation in the donor side photoinhibition of PSII. [ABSTRACT FROM AUTHOR]

Peptide-based packaging systems show great potential as safer drug delivery systems. They overcome problems associated with lipid-based or viral delivery systems, vis-a-vis stability, specificity, inflammation, antigenicity, and tune-ability. Here, we describe a set of 15 & 23-residue branched, amphiphilic peptides that mimic phosphoglycerides in molecular architecture. These peptides undergo supramolecular self-assembly and form solvent-filled, bilayer delimited spheres with 50-200 nm diameters as confirmed by TEM, STEM and DLS. Whereas weak hydrophobic forces drive and sustain lipid bilayer assemblies, these all-peptide structures are stabilized potentially by both hydrophobic interactions and hydrogen bonds and remain intact at low micromolar concentrations and higher temperatures. A linear peptide lacking the branch point showed no self-assembly properties. We have observed that these peptide vesicles can trap fluorescent dye molecules within their interior and are taken up by N/N 1003A rabbit lens epithelial cells grown in culture. These assemblies are thus potential drug delivery systems that can overcome some of the key limitations of the current packaging systems. [ABSTRACT FROM AUTHOR]

Background: Celiac disease (CD) is an intestinal inflammatory condition that develops in genetically susceptible individuals after exposure to dietary wheat gliadin. The role of post-translational modifications of gliadin catalyzed by tissue transglutaminase (tTG) seems to play a crucial role in CD. However, it remains to be established how and where tTG is activated in vivo. We have investigated whether gliadin peptides modulate intracellular Ca2+ homeostasis and tTG activity. Methods/Principal Findings: We studied Ca2+ homeostasis in Caco-2 cells by single cell microfluorimetry. Under our conditions, A-gliadin peptides 31-43 and 57-68 rapidly mobilized Ca2+ from intracellular stores. Specifically, peptide 31-43 mobilized Ca2+ from the endoplasmic reticulum (ER) and mitochondria, whereas peptide 57-68 mobilized Ca2+ only from mitochondria. We also found that gliadin peptide-induced Ca2+ mobilization activates the enzymatic function of intracellular tTG as revealed by in situ tTG activity using the tTG substrate pentylamine-biotin. Moreover, we demonstrate that peptide 31-43, but not peptide 57-68, induces an increase of tTG expression. Finally, we monitored the expression of glucose- regulated protein-78 and of CCAAT/enhancer binding protein-homologous protein, which are two biochemical markers of ER-stress, by real-time RT-PCR and western blot. We found that chronic administration of peptide 31-43, but not of peptide 57-68, induces the expression of both genes. Conclusions: By inducing Ca2+ mobilization from the ER, peptide 31-43 could promote an ER-stress pathway that may be relevant in CD pathogenesis. Furthermore, peptides 31-43 and 57-68, by activating intracellular tTG, could alter inflammatory key regulators, and induce deamidation of immunogenic peptides and gliadin-tTG crosslinking in enterocytes and specialized antigen-presenting cells. [ABSTRACT FROM AUTHOR]

The ability to regulate protein levels in live cells is crucial to understanding protein function. In the interest of advancing the tool set for protein perturbation, we developed a protein destabilizing domain (DD) that can confer its instability to a fused protein of interest. This destabilization and consequent degradation can be rescued in a reversible and dose-dependent manner with the addition of a small molecule that is specific for the DD, Shield-1. Proteins encounter different local protein quality control (QC) machinery when targeted to cellular compartments such as the mitochondrial matrix or endoplasmic reticulum (ER). These varied environments could have profound effects on the levels and regulation of the cytoplasmically derived DD. Here we show that DD fusions in the cytoplasm or nucleus can be efficiently degraded in mammalian cells; however, targeting fusions to the mitochondrial matrix or ER lumen leads to accumulation even in the absence of Shield-1. Additionally, we characterize the behaviour of the DD with perturbants that modulate protein production, degradation, and local protein QC machinery. Chemical induction of the unfolded protein response in the ER results in decreased levels of an ER-targeted DD indicating the sensitivity of the DD to the degradation environment. These data reinforce that DD is an effective tool for protein perturbation, show that the local QC machinery affects levels of the DD, and suggest that the DD may be a useful probe for monitoring protein quality control machinery. [ABSTRACT FROM AUTHOR]

In the present work, we developed the Fc-III tagged protein expression system for protein purification and detection. The Fc-III sequence encodes for a 13 residue peptide and this peptide is cyclized by disulfide bond formation when the fusion protein is expressed. The Fc-III-fusion proteins selectively bind to immunoglobulin Fc domains (IgG-Fc) expressed from E. coli. We showed the efficient purification of Fc-III tagged proteins by immobilized non-native IgG- Fc and the detection of the cellular locations of fusion proteins by fluorescent-conjugated IgG-Fc. Our results prove that Fc-III tagged protein expression system is a simple and efficient tool for protein purification and detection and is a useful addition to the biochemistry and proteomics toolbox. [ABSTRACT FROM AUTHOR]

In grapevine Vitis vinifera L. cv Pinot noir, the Pathogenesis-Related (PR) proteins CHI4D and TL3 are among the most abundant extractable PR proteins of ripe berries and accumulate during berry ripening from véraison until full maturation. Evidence was supplied in favor of the involvement of these two protein families in plant defense mechanisms and plant development. In order to better understand CHI4D and TL3 function in grapevine, we analyzed their temporal and spatial pattern of expression during maturation and after an abiotic stress (UV-C) by in situ hybridization (ISH) and immunohistolocalization. In ripening berries, CHI4D and TL3 genes were mainly expressed in the exocarp and around vascular bundles of the mesocarp. In UV-C exposed berries, CHI4D and TL3 gene expression was strongly induced before ve´raison. Corresponding proteins localized in the exocarp and, to a lesser extent, around vascular bundles of the mesocarp. The spatial and temporal accumulation of the two PR proteins during berry maturation and after an abiotic stress is discussed in relation to their putative roles in plant defense. [ABSTRACT FROM AUTHOR]

Paddy soils are classified as wetlands which play a vital role in climatic change and food production. Soil carbon (C), especially soil organic C (SOC), in paddy soils has been received considerable attention as of recent. However, considerably less attention has been given to soil inorganic carbon (SIC) in paddy soils and the relationship between SOC and SIC at interface between soil and the atmosphere. The objective of this research was to investigate the utility of applying Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) to explore SOC and SIC present near the surface (0-10 µm) of paddy soils. The FTIR-PAS spectra revealed an unique absorption region in the wavenumber range of 1,350-1,500 cm-1 that was dominated by C-O (carbonate) and C-H bending vibrations (organic materials), and these vibrations were used to represented SIC and SOC, respectively. A circular distribution between SIC and SOC on the surface of paddy soils was determined using principal component analysis (PCA), and the distribution showed no significant relationship with the age of paddy soil. However, SIC and SOC were negatively correlated, and higher SIC content was observed near the soil surface. This relationship suggests that SIC in soil surface plays important roles in the soil C dynamics. [ABSTRACT FROM AUTHOR]

The medical use of non-thermal physical plasmas is intensively investigated for sterilization and surface modification of biomedical materials. A further promising application is the removal or etching of organic substances, e.g., biofilms, from surfaces, because remnants of biofilms after conventional cleaning procedures are capable to entertain inflammatory processes in the adjacent tissues. In general, contamination of surfaces by micro-organisms is a major source of problems in health care. Especially biofilms are the most common type of microbial growth in the human body and therefore, the complete removal of pathogens is mandatory for the prevention of inflammatory infiltrate. Physical plasmas offer a huge potential to inactivate micro-organisms and to remove organic materials through plasma-generated highly reactive agents. Method: In this study a Candida albicans biofilm, formed on polystyrene (PS) wafers, as a prototypic biofilm was used to verify the etching capability of the atmospheric pressure plasma jet operating with two different process gases (argon and argon/oxygen mixture). The capability of plasma-assisted biofilm removal was assessed by microscopic imaging. Results: The Candida albicans biofilm, with a thickness of 10 to 20 mm, was removed within 300 s plasma treatment when oxygen was added to the argon gas discharge, whereas argon plasma alone was practically not sufficient in biofilm removal. The impact of plasma etching on biofilms is localized due to the limited presence of reactive plasma species validated by optical emission spectroscopy. [ABSTRACT FROM AUTHOR]

The proteome of the marine bacterium Photobacterium angustum S14 was exposed to UVB and analyzed by the implementation of both the post-digest ICPL labeling method and 2D-DIGE technique using exponentially growing cells. A total of 40 and 23 proteins were quantified in all replicates using either the ICPL or 2D-DIGE methods, respectively. By combining both datasets from 8 biological replicates (4 biological replicates for each proteomics technique), 55 proteins were found to respond significantly to UVB radiation in P. angustum. A total of 8 UVB biomarkers of P. angustum were quantified in all replicates using both methods. Among them, the protein found to present the highest increase in abundance (almost a 3-fold change) was RecA, which is known to play a crucial role in the so-called recombinational repair process. We also observed a high number of antioxidants, transport proteins, metabolism-related proteins, transcription/ translation regulators, chaperonins and proteases. We also discuss and compare the UVB response and global protein expression profiles obtained for two different marine bacteria with trophic lifestyles: the copiotroph P. angustum and oligotroph Sphingopyxis alaskensis. [ABSTRACT FROM AUTHOR]

Enzyme catalyzed conversion of plant biomass to sugars is an inherently inefficient process, and one of the major factors limiting economical biofuel production. This is due to the physical barrier presented by polymers in plant cell walls, including semi-crystalline cellulose, to soluble enzyme accessibility. In contrast to the enzymes currently used in industry, bacterial cellulosomes organize cellulases and other proteins in a scaffold structure, and are highly efficient in degrading cellulose. To mimic this clustered assembly of enzymes, we conjugated cellulase obtained from Trichoderma viride to polystyrene nanospheres (cellulase:NS) and tested the hydrolytic activity of this complex on cellulose substrates from purified and natural sources. Cellulase:NS and free cellulase were equally active on soluble carboxymethyl cellulose (CMC); however, the complexed enzyme displayed a higher affinity in its action on microcrystalline cellulose. Similarly, we found that the cellulase:NS complex was more efficient in degrading natural cellulose structures in the thickened walls of cultured wood cells. These results suggest that nanoparticle-bound enzymes can improve catalytic efficiency on physically intractable substrates. We discuss the potential for further enhancement of cellulose degradation by physically clustering combinations of different glycosyl hydrolase enzymes, and applications for using cellulase:NS complexes in biofuel production. [ABSTRACT FROM AUTHOR]

Many lines of evidence suggest an interaction between glycosaminoglycans (GAGs) and the PrP proteins as well as a possible role for GAGs in prion disease pathogenesis. In this work, we sought to determine whether the PrP. GAG interaction affects the incorporation of PrPSc (the scrapie isoform of PrP) to normal cells. This may be the first step in prion disease pathogenesis. To this effect, we incubated proteinase K-digested hamster scrapie brain homogenates with several lines of Chinese hamster ovary (CHO) cells in the presence or absence of heparin. Our results show that over a large range of PrPSc concentrations the binding of PrPSc to wild type CHO cells, which do not express detectable PrP, was equivalent to the binding of PrPSc to CHO cells overexpressing PrP. A significant part of PrPSc binding to both lines could be inhibited by heparin. Additional evidence that PrPSc binding to cells was dependent on the presence of GAGs could be concluded from the fact that the binding of PrPSc to CHO cells missing GAGs on the cell surface was significantly reduced. Interestingly, preincubation of scrapie brain homogenate with heparin before intraperitoneal inoculation into normal hamsters resulted in a significant delay in prion disease manifestation. [ABSTRACT FROM AUTHOR]