Search results for "aggregation."
showing 10 items of 544 documents
Inactivation and structural changes of polyphenol oxidase in quince ( Cydonia oblonga Miller) juice subjected to ultrasonic treatment
2020
Background Polyphenol oxidase (PPO) is considered a problem in the food industry because it starts browning reactions during fruit and vegetable processing. Ultrasonic treatment is a technology used to inactivate the enzyme; however, the mechanism behind PPO inactivation is still unclear. For this reason, the inactivation, aggregation, and structural changes in PPO from quince juice subjected to ultrasonic treatments were investigated. Different intensities and times of ultrasonic treatment were used. Changes in the activity, aggregation, conformation, and structure of PPO were investigated through different structural analyses. Results Compared to untreated juice, the PPO activity in treat…
Combined spectroscopic and theoretical analysis of the binding of a water-soluble perylene diimide to DNA/RNA polynucleotides and G-quadruplexes.
2021
We present here a combined spectroscopic and theoretical analysis of the binding of N,N’-bis(2-(1-piperazino)ethyl)-3,4,9,10-perylenetetracarboxylic acid diimide dichloride (PZPERY) to different biosubstrates. Absorbance titrations and circular dichroism experiments, melting studies and isothermal calorimetry (ITC) titrations reveal a picture where the binding to natural double-stranded DNA is very different from that to double and triple-stranded RNAs (poly(A)∙poly(U) and poly(U)∙poly(A)⁎poly(U)). As confirmed also by the structural and energetic details clarified by density functional theory (DFT) calculations, intercalation occurs for DNA, with a process driven by the combination of aggr…
Carnosine Inhibits Aβ42Aggregation by Perturbing the H-Bond Network in and around the Central Hydrophobic Cluster
2013
Aggregation of the amyloid-β peptide (Aβ) into fibrillar structures is a hallmark of Alzheimer's disease. Thus, preventing self-assembly of the Aβ peptide is an attractive therapeutic strategy. Here, we used experimental techniques and atomistic simulations to investigate the influence of carnosine, a dipeptide naturally occurring in the brain, on Aβ aggregation. Scanning force microscopy, circular dichroism and thioflavin T fluorescence experiments showed that carnosine does not modify the conformational features of Aβ42 but nonetheless inhibits amyloid growth. Molecular dynamics (MD) simulations indicated that carnosine interacts transiently with monomeric Aβ42 by salt bridges with charge…
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…
Copper(ii) and zinc(ii) dependent effects on Aβ42 aggregation: a CD, Th-T and SFM study
2013
A? aggregation is a central event in Alzheimer's disease (AD). In vitro evidence indicates that A? aggregation and fibrillogenesis are significantly influenced by the employed experimental conditions. Indeed, although it is widely established that metal ions, such as copper and zinc, have significant effects on the A? aggregation process, their actual role in A? fibrillogenesis is still debated. In this work the effects of a molar excess of zinc(ii) and/or copper(ii) ions on the A?42 aggregation process and the morphology of the resultant aggregates have been compared in samples exhibiting different initial conformations. CD spectroscopy, Th-T-induced fluorescence and Scanning Force Microsc…
Bovine Serum Albumin protofibril-like aggregates formation: Solo but not simple mechanism
2011
We report an experimental study on the model protein Bovine Serum Albumin (BSA), with the aim of elucidating the mechanisms by which a fully folded globular protein undergoes different aggregation pathways leading to the formation of amyloid fibrils or amorphous aggregates. We observe thermally induced formation of fibrillar structures at pH far from the protein isoelectric point. The increase of electrostatic repulsion results in protein destabilization and in modifications of inter and intra-molecular interactions leading to the growth of fibril-like aggregates stabilized by inter-molecular-β sheets. The aggregation kinetics is studied by means of fluorescence techniques, light scattering…
Thermal aggregation and ion-induced cold-gelation of bovine serum albumin
2009
Protein cold-gelation has recently received particular attention for its relevance in bio and food technology. In this work, we report a study on bovine serum albumin cold-gelation induced by copper or zinc ions. Metal-induced cold-gelation of proteins requires two steps: during the first one, the heat treatment causes protein partial unfolding and aggregation; then, after cooling the solution to room temperature, gels are formed upon the addition of metal ions. The thermally induced behaviour has been mainly investigated through different techniques: Fourier transform infrared (FTIR) spectroscopy, circular dichroism, dynamic light scattering (DLS) and rheology. Data have shown that the agg…
Two Latent and Two Hyperstable Polymeric Forms of Human Neuroserpin
2010
AbstractHuman neuroserpin (hNS) is a serine protease inhibitor that belongs to the serpin superfamily and is expressed in nervous tissues. The serpin fold is generally characterized by a long exposed loop, termed the reactive center loop, that acts as bait for the target protease. Intramolecular insertion of the reactive center loop into the main serpin β-sheet leads to the serpin latent form. As with other known serpins, hNS pathological mutants have been shown to accumulate as polymers composed of quasi-native protein molecules. Although hNS polymerization has been intensely studied, a general agreement about serpin polymer organization is still lacking. Here we report a biophysical chara…
Identification and isolation of the primary aggregation factor from the cell membrane of the sponge Geodia cydonium
1985
The primary aggregation factor (pAF) of sponge cells is a glycoprotein that is firmly associated with the cell membrane. Polyspecific antibodies (anti-GM) prepared from sera raised against membranes of cells from the siliceous sponge Geodia cydonium were found to inhibit initial aggregation of homologous cells. The inhibition of aggregation, caused by anti-GM was neutralized by pAF. The pAF had been successfully solubilized and enriched by affinity chromatography, gel filtration and density gradient centrifugation, if checked by polyacrylamide gel electrophoresis in the presence of urea. The Mr of the native pAF was approximately 40 000 as estimated by gel filtration; under denaturing condi…
Oral Glycoprotein IIb/IIa Antagonists for Unstable Angina — Is There Still a Chance for the Oral Substances?
2001
The intravenous glycoprotein IIb/IIIa antagonists abciximab, tirofiban and eptifibatide are well accepted for the therapy of patients with unstable angina and/or as concomitant medication during coronary interventions. Despite the fact that these drugs are not used in all patients presenting with unstable angina during coronary interventions, the scientific evidence is overwhelming including the substantial reduction in mortality 3 years after utilisation of abciximab for coronary interventions in patients with unstable angina. In addition to these two indications, intravenous glycoprotein IIb/IIIa antagonists are currently being investigated for use in patients undergoing carotid artery in…