Optimized Silica-Binding Peptide-Mediated Delivery of Bactericidal Lysin Efficiently Prevents Staphylococcus aureus from Adhering to Device Surfaces

Staphylococcal-associated device-related infections (DRIs) represent a significant clinical challenge causing major medical and economic sequelae. Bacterial colonization, proliferation, and biofilm formation after adherence to surfaces of the indwelling device are probably the primary cause of DRIs. To address this issue, we incorporated constructs of silica-binding peptide (SiBP) with ClyF, an anti-staphylococcal lysin, into functionalized coatings to impart bactericidal activity against planktonic and sessile Staphylococcus aureus. An optimized construct, SiBP1-ClyF, exhibited improved thermostability and staphylolytic activity compared to its parental lysin ClyF. SiBP1-ClyF-functionalized coatings were efficient in killing MRSA strain N315 (>99.999% within 1 h) and preventing the growth of static and dynamic S. aureus biofilms on various surfaces, including siliconized glass, silicone-coated latex catheter, and silicone catheter. Additionally, SiBP1-ClyF-immobilized surfaces supported normal attachment and growth of mammalian cells. Although the recycling potential and long-term stability of lysin-immobilized surfaces are still affected by the fragility of biological protein molecules, the present study provides a generic strategy for efficient delivery of bactericidal lysin to solid surfaces, which serves as a new approach to prevent the growth of antibiotic-resistant microorganisms on surfaces in hospital settings and could be adapted for other target pathogens as well.     

佛山世纪莲体育场预应力工程施工技术

佛山世纪莲体育场工程,设计采用无粘结预应力混凝土环向楼面、有粘结预应力混凝土大斜柱、有粘结预应力混凝土大承台和预应力抗拔锚杆多项预应力技术,介绍了技术难点与采取的施工措施。     

一种化学结合方式下新型耐火泥浆的研制与应用

分析了传统耐火泥浆存在的缺陷,介绍了以化学结合剂为结合方式的二种新型耐火泥浆的研制方法。新型泥浆与传统的泥浆相比有许多突出的物理化学性能,具有施工简便、作业性好,已经成功用于多种高温炉窑。     

Fractionation at pilot-plant scale of an haemoglobin hydrolysate by strong anionic exchange chromatography Application to the preparation of an amphiphilic peptide

The development and the scale-up of high performance anion chromatography to obtain 1 milligram to 1 gram yields of a peptide fraction from a complex peptic haemoglobin hydrolysate is described here. The chromatographic conditions were developed using a 1 cm³ Mono Q analytical column and progressively scaled-up to a 6 dm³ Q Sepharose Fast Flow column. For easy recovery of peptide and easy adjustment of conditions for final purification, a volatile buffer, ethanolamine/HCl buffer 20 mmol dm⁻³, pH 10·5, was employed; desalting was carried out by a pilot-plant scale electrodialysis which permitted the elimination of 99% NaCl without important loss of peptide (less than 15%). A combination of these techniques with reverse phase HPLC proved a useful strategy for fractionation of a complex peptide mixture and enabled pure peptides to be obtained in sufficient quantities for further analyses and biological tests. The example of preparation and purification of an amphiphilic peptide is described. Its ability to solubilize an insoluble photosensitizer, protoporphyrin IX, was determined in order to study its utilization as a carrier for photochemotherapy. © 1998 SCI.     

Enzyme activities in cocoa beans during fermentation

The activities of endoprotease, aminopeptidase, carboxypeptidase, invertase (cotyledon and pulp), polyphenol oxidase and glycosidases were studied during heap fermentation of ICS-95 cocoa beans. These enzymes are of key importance in flavour precursor formation and in pigment degradation during cocoa fermentation. Optimal extraction and assay conditions were established to characterise the enzymes reactions and to quantify and compare enzyme activities during cocoa fermentation. The enzymes exhibited large differences in pH optima and stability during fermentation. Aminopeptidase, invertase (cotyledon and pulp) and polyphenol oxidase were strongly inactivated, carboxypeptidase was partly inactivated, whereas endoprotease and glycosidases remained active throughout the fermentation. Since many enzymes are inactivated during fermentation, it is generally recognised that the actual period of enzyme action is short. Although our results confirmed total inactivation for some enzymes, we show that several key enzymes are not completely inactivated during fermentation. Therefore, some enzyme reactions can continue throughout the whole fermentation process. Only polyphenol oxidase was strongly inactivated during sun and artificial drying of the beans. The other enzymes were stable during the drying process. Enzymes like endoprotease and glycosidases are still active in properly fermented and dried beans. © 1998 SCI.     

Application of Immobilized α-Chymotrypsin to Peptide Synthesis in Frozen Aqueous Systems

In order to combine the high potential of frozen state peptide synthesis and the advantages of the application of immobilized proteases, the capability of carrier-bound α-chymotrypsin (CT, EC 3.4.21.1) to form peptide bonds in frozen aqueous reaction mixtures was investigated. The properties of the support materials strongly influenced the peptide yields. CT bound to rather hydrophobic supports catalysed peptide synthesis as effectively as the soluble enzyme. The immobilized enzyme preparations could be successfully re-used at least 15 times. Peptide synthesis catalysed by immobilized chymotrypsin was also studied in low water organic reaction mixtures at sub-zero temperatures. The advantages and limitations of the different approaches are discussed. © 1997 SCI.     

Antifungal Peptides and Proteins to Control Toxigenic Fungi and Mycotoxin Biosynthesis

The global challenge to prevent fungal spoilage and mycotoxin contamination on food and feed requires the development of new antifungal strategies. Antimicrobial peptides and proteins (AMPs) with antifungal activity are gaining much interest as natural antifungal compounds due to their properties such as structure diversity and function, antifungal spectrum, mechanism of action, high stability and the availability of biotechnological production methods. Given their multistep mode of action, the development of fungal resistance to AMPs is presumed to be slow or delayed compared to conventional fungicides. Interestingly, AMPs also accomplish important biological functions other than antifungal activity, including anti-mycotoxin biosynthesis activity, which opens novel aspects for their future use in agriculture and food industry to fight mycotoxin contamination. AMPs can reach intracellular targets and exert their activity by mechanisms other than membrane permeabilization. The mechanisms through which AMPs affect mycotoxin production are varied and complex, ranging from oxidative stress to specific inhibition of enzymatic components of mycotoxin biosynthetic pathways. This review presents natural and synthetic antifungal AMPs from different origins which are effective against mycotoxin-producing fungi, and aims at summarizing current knowledge concerning their additional effects on mycotoxin biosynthesis. Antifungal AMPs properties and mechanisms of action are also discussed.     

Origin of Increased Solvent Accessibility of Peptide Bonds in Mutual Synergetic Folding Proteins

Mutual Synergetic Folding (MSF) proteins belong to a recently discovered class of proteins. These proteins are disordered in their monomeric but ordered in their oligomeric forms. Their amino acid composition is more similar to globular proteins than to disordered ones. Our preceding work shed light on important structural aspects of the structural organization of these proteins, but the background of this behavior is still unknown. We suggest that solvent accessibility is an important factor, especially solvent accessibility of the peptide bonds can be accounted for this phenomenon. The side chains of the amino acids which form a peptide bond have a high local contribution to the shielding of the peptide bond from the solvent. During the oligomerization step, other non-local residues contribute to the shielding. We investigated these local and non-local effects of shielding based on Shannon information entropy calculations. We found that MSF and globular homodimeric proteins have different local contributions resulting from different amino acid pair frequencies. Their non-local distribution is also different because of distinctive inter-subunit contacts.     

Gene Expression Data Mining Reveals the Involvement of GPR55 and Its Endogenous Ligands in Immune Response,Cancer, and Differentiation

G protein-coupled receptor 55 (GPR55) is a recently deorphanized lipid- and peptide-sensing receptor. Its lipidic endogenous agonists belong to lysoglycerophospholipids, with lysophosphatidylinositol (LPI) being the most studied. Peptide agonists derive from fragmentation of pituitary adenylate cyclase-activating polypeptide (PACAP). Although GPR55 and its ligands were implicated in several physiological and pathological conditions, their biological function remains unclear. Thus, the aim of the study was to conduct a large-scale re-analysis of publicly available gene expression datasets to identify physiological and pathological conditions affecting the expression of GPR55 and the production of its ligands. The study revealed that regulation of GPR55 occurs predominantly in the context of immune activation pointing towards the role of the receptor in response to pathogens and in immune cell lineage determination. Additionally, it was revealed that there is almost no overlap between the experimental conditions affecting the expression of GPR55 and those modulating agonist production. The capacity to synthesize LPI was enhanced in various types of tumors, indicating that cancer cells can hijack the motility-related activity of GPR55 to increase aggressiveness. Conditions favoring accumulation of PACAP-derived peptides were different than those for LPI and were mainly related to differentiation. This indicates a different function of the two agonist classes and possibly the existence of a signaling bias.     

Effects of ion polarizability and oxygen vacancy on microwave dielectric properties of fluorite-structured Ce1−xCaxO2−x

X-ray diffractometer with Rietveld refinement and Raman spectroscopy were used for phase analysis. Ca doping results in decreased ε_r (24.09–21.52), Q × f (68 914–40 110 GHz), and τ_f (−50.0 ppm/°C to −60.2 ppm/°C) all decrease, which obviously does not conform to the mutual constraint relationship among the three parameters of microwave dielectric properties. The ε_r of Ce_1−xCa_xO_2−x ceramics is affected by the ion polarizability and the Ce rattling and valence states, among which the rattling of Ce cations plays a dominant role. The presence of oxygen vacancies in Ce_1−xCa_xO_2−x ceramics explains the decrease in Q × f. The τ_ε, ε_r, and α_L are responsible for the decrease in τ_f, especially for the τ_αm-3α_L values.