Search results for "Oligomer"

Regulation of the inflammatory response by tin protoporphyrin IX in the rat anterior cruciate ligament transection model of osteoarthritis

2010

The purpose of this study was to investigate several inflammatory mediators and cartilage degradation molecules as possible biomarkers of joint lesion in the anterior cruciate ligament transection (ACLT) model of osteoarthritis in rats. We also assessed whether the treatment with the anti-inflammatory agent tin protoporphyrin IX (SnPP) reduces the progression of disease. Our results indicate that serum levels of interleukin (IL)-6 and PGE2 are significantly increased in ACLT rats 10 weeks after surgery, whereas the increases in IL-1β and tumor necrosis-α were not significant. In addition, our data suggest that IL-17 is the main pro-inflammatory cytokine in the ACLT joint. We have shown that…

Structural Characterization of Isomeric Dimers from the Oxidative Oligomerization of Catechol with a Biomimetic Catalyst

2007

In a previous paper, it has been reported about the formation of catechol di-, tri- and tetramers within an oxidative polymerization catalyzed by synthetic water-soluble iron-porphyrin as an efficient alternative to bio-labile natural peroxidase. It has also been demonstrated the occurrence of both C-C and C-O-C coupling mechanisms. However, since the coupling products were determined by mass spectroscopy, the exact bonding position could not have been precisely ascertained for the C-C bonded isomeric dimers that are the dominant products of catechol oligomerization. Therefore, here isolation and characterization of catechol isomeric dimers, obtained by oxidative coupling under the catalysi…

Powerful Fluoroalkoxy Molybdenum(V) Reagent for Selective Oxidative Arene Coupling Reaction

2013

We introduce the novel fluoroalkoxy molybdenum(V) reagent 1 which has superior reactivity and selectivity in comparison to MoCl5 or the MoCl5 /TiCl4 reagent mixture in the oxidative coupling reactions of aryls. Common side reactions, such as chlorination and/or oligomer formation, are drastically diminished creating a powerful and useful reagent for oxidative coupling. Theoretical treatment of the reagent interaction with 1,2-dimethoxybenzene-type substrates indicates an inner-sphere electron transfer followed by a radical cationic reaction pathway for the oxidative-coupling process. EPR spectroscopic and electrochemical studies, X-ray analyses, computational investigations, and the experim…

Streptolysin O: the C-terminal, tryptophan-rich domain carries functional sites for both membrane binding and self-interaction but not for stable oli…

2001

AbstractStreptolysin O belongs to the class of thiol-activated toxins, which are single chain, four-domain proteins that bind to membranes containing cholesterol and then assemble to form large oligomeric pores. Membrane binding involves a conserved tryptophan-rich sequence motif located within the C-terminally located domain 4. In contrast, sites involved in oligomerization and pore formation have been assigned to domains 1 and 3, respectively. We here examined the functional properties of domain 4, which was recombinantly expressed with an N-terminal histidine tag for purification and an additional cysteine residue for covalent labeling. The fluorescently labeled fragment readily bound to…

Assembly mechanism of the oligomeric streptolysin O pore: the early membrane lesion is lined by a free edge of the lipid membrane and is extended gra…

1998

Streptolysin O (SLO) is a bacterial exotoxin that binds to cell membranes containing cholesterol and then oligomerizes to form large pores. Along with rings, arc-shaped oligomers form on membranes. It has been suggested that each arc represents an incompletely assembled oligomer and constitutes a functional pore, faced on the opposite side by a free edge of the lipid membrane. We sought functional evidence in support of this idea by using an oligomerization-deficient, non-lytic mutant of SLO. This protein, which was created by chemical modification of a single mutant cysteine (T250C) with N-(iodoacetaminoethyl)-1-naphthylamine-5-sulfonic acid, formed hybrid oligomers with active SLO on memb…

1979

The demixing behavior of 20 representatives of the system oligo(dimethylsiloxane)/oligo(propylene glycol) (ODMS/OPG)1 is investigated at pressures up to 1 500 bar. The degrees of oligomerization range from 2 to 5 for the first and from 1 to 57, 6 for the second component. The experimental results are compared with those for the previously studied system oligoisobutene/oligo(propylene glycol) (OIB/OPG). In both cases the observed upper critical temperatures Tc increase with the number of monomeric units of the less polar component, whereas they run through a minimum when the number of monomeric units of the glycol is raised. For the present system the Tc values are found to be considerably h…

Structure optimization of azobenzene oligomers for holography

2005

Azobenzene oligomer layers with side chain chromofore groups (ChG) has been experimentally studied to optimize scalar and vector hologram recording at 633 nm. ChG with different acceptors (Br, NO2, H, CN) and different bonding type to the matrix (dispersed without bonding or with covalent bonding) were used. The influence of oligomer matrix (polyvinylbuthirol, tolyle, hexamethylene, polyvinylpirolidone, double matrix) and spacers was also studied. The best results (the maximal diffraction efficiency of 7.9% and the minimal specific recording energy of 0.38 J/(cm2 %)) are obtained for ChG with one NO2 acceptor group covalently bonded to tolyle matrix. Double matrix considerably decreases the…

Irreversible formation of intermediate BSA oligomers requires and induces conformational changes.

2004

Understanding the relation between protein conformational changes and aggregation, and the physical mechanisms leading to such processes, is of primary importance, due to its direct relation to a vast class of severe pathologies. Growing evidence also suggests that oligomeric intermediates, which may occur early in the aggregation pathway, can be themselves pathogenic. The possible cytotoxicity of oligomers of non-disease-associated proteins adds generality to such suggestion and to the interest of studies of oligomer formation. Here we study the early stages of aggregation of Bovine Serum Albumin (BSA), a non pathogenic protein which has proved to be a useful model system. Dynamic light sc…

Valorization of apple peels through the study of the effects on the amyloid aggregation process of ?-casein

2021

Waste valorization represents one of the main social challenges when promoting a circular economy and environmental sustainability. Here, we evaluated the effect of the polyphenols extracted from apple peels, normally disposed of as waste, on the amyloid aggregation process of ?-casein from bovine milk, a well-used amyloidogenic model system. The effect of the apple peel extract on protein aggregation was examined using a thioflavin T fluorescence assay, Congo red binding assay, circular dichroism, light scattering, and atomic force microscopy. We found that the phenolic extract from the peel of apples of the cultivar "Fuji", cultivated in Sicily (Caltavuturo, Italy), inhibited ?-casein fib…

Introduction and Technical Survey: Protein Aggregation and Fibrillogenesis

2012

In this chapter we provided the overall background to the subject of protein aggregation and fibrillogenesis in amyloidogenesis, with introduction and brief discussion of the various topics that are included with the coming chapters. The division of the book into basic science and clinical science sections enables correlation of the topics to be made. The many proteins and peptides that have currently been found to undergo fibrillogenesis are tabulated. A broad technical survey is made, to indicate the vast array of techniques currently available to study aspects of protein oligomerization, aggregation and fibrillogenesis. These are split into three groups and tabulated, as the microscopica…