Search results for "Protein aggregation"
showing 10 items of 128 documents
Thermal Aggregation of Bovine Serum Albumin in Trehalose and Sucrose Aqueous Solutions
2012
We report results of static and dynamic light scattering measurements performed on bovine serum albumin (BSA) in saccharide (trehalose and sucrose) solutions. Our aim is to study the effects of the two disaccharides on the first steps of thermal aggregation of BSA in aqueous solutions at two protein concentrations (1 and 30 mg/mL) at increasing sugar/water ratio. Results show that sugars modify early stages of aggregation mainly by perturbing the thermodynamic behavior of the solvent (i.e., general solvent effects) without involving direct, specific sugar-protein interactions. This agrees with current hypotheses on sugar action in protein solutions. (1-3) The linear correlation detected bet…
Thermal Denaturation of Pea Globulins (Pisum sativum L.)—Molecular Interactions Leading to Heat-Induced Protein Aggregation
2013
The heat-induced denaturation and aggregation of mixed pea globulins (8%, w/w) were investigated using differential scanning calorimetry (DSC), SDS-PAGE, and size-exclusion chromatography (SEC-HPLC). DSC data showed that the pea proteins denaturation temperature (T(d)) was heating-rate dependent. The T(d) value decreased by about 4 °C by lowering the heating rate from 10 to 5 °C/min. The SDS-PAGE analysis revealed that protein denaturation upon heating at 90 °C was mainly governed by noncovalent interaction. The SEC-HPLC measurements indicated that low-denatured legumin (≈350-410 kDa) and vicilin/convicilin (≈170 kDa) globulins were heat-denatured and most of their subunits reassociated int…
Dimerization of visinin-like protein 1 is regulated by oxidative stress and calcium and is a pathological hallmark of amyotrophic lateral sclerosis
2014
AbstractRedox control of proteins that form disulfide bonds upon oxidative challenge is an emerging topic in the physiological and pathophysiological regulation of protein function. We have investigated the role of the neuronal calcium sensor protein visinin-like protein 1 (VILIP-1) as a novel redox sensor in a cellular system. We have found oxidative stress to trigger dimerization of VILIP-1 within a cellular environment and identified thioredoxin reductase as responsible for facilitating the remonomerization of the dimeric protein. Dimerization is modulated by calcium and not dependent on the myristoylation of VILIP-1. Furthermore, we show by site-directed mutagenesis that dimerization is…
Fluctuation Methods To Study Protein Aggregation in Live Cells: Concanavalin A Oligomers Formation
2011
Prefibrillar oligomers of proteins are suspected to be the primary pathogenic agents in several neurodegenerative diseases. A key approach for elucidating the pathogenic mechanisms is to probe the existence of oligomers directly in living cells. In this work, we were able to monitor the process of aggregation of Concanavalin A in live cells. We used number and brightness analysis, two-color cross number and brightness analysis, and Raster image correlation spectroscopy to obtain the number of molecules, aggregation state, and diffusion coefficient as a function of time and cell location. We observed that binding of Concanavalin A to the membrane and the formation of small aggregates paralle…
Heterogeneity of aggregates in the fibrillation mechanisms of proteins probed by time resolved fluorescence
2010
Under appropriate conditions almost all proteins are able to aggregate to form long, well-ordered and beta-sheet rich arrays known as amyloid fibrils. The formation of such structures involves complex intra and intermolecular interactions modulated by the structure and dynamics of the native protein, and by the physico-chemical properties of the solvent. Multiple interactions and cross-feedback during the aggregation pathway cause different ultimate aggregates’ morphologies and the possible simultaneous occurrence of multiple species. The structural definition of such assemblies is complicated by the polymorphism of the amyloid fibrils. Aim of this study is to inquire on the different natur…
Impact of Chaperonopathies in Protein Homeostasis and Beyond
2013
Chaperones have functions other than those classically attributed to them pertaining to protein homeostasis. These “other” non-canonical functions are the focus of chapter 8. The close interaction of the chaperoning and the immune systems and the impact of their malfunctioning on aging and cancer are highlighted. Conversely, the impact of ageing and cancer on the two systems is also underscored. The connections between stress, protein damage (including chaperones), protein misfolding, protein aggregation and precipitation, and tissue degeneration, are analyzed, indicating that all these processes are aggravated by a decline in chaperoning potential with aging (chaperonopathies of the aged) …
Sigma-1 Receptor Activation Induces Autophagy and Increases Proteostasis Capacity In Vitro and In Vivo
2019
Dysfunction of autophagy and disturbed protein homeostasis are linked to the pathogenesis of human neurodegenerative diseases and the modulation of autophagy as the protein clearance process has become one key pharmacological target. Due to the role of sigma-1 receptors (Sig-1R) in learning and memory, and the described pleiotropic neuroprotective effects in various experimental paradigms, Sig-1R activation is recognized as one potential approach for prevention and therapy of neurodegeneration and, interestingly, in amyotrophic lateral sclerosis associated with mutated Sig-1R, autophagy is disturbed. Here we analyzed the effects of tetrahydro-N,N-dimethyl-2,2-diphenyl-3-furanmethanamine hyd…
Quantification of HSP27 and HSP70 Molecular Chaperone Activities
2011
Stress-inducible heat-shock proteins (HSPs, like HSP70 and HSP27) are molecular chaperones that -protect cells from stress damage by keeping cellular proteins in a folding competent state and preventing them from irreversible aggregation. HSP27 and HSP70 chaperone activities are useful indicators to test chemical products and physical stress impact on protein denaturation, to select HSP inhibitors, or to -determine the implication of the chaperone function in other HSP activities, such as apoptosis. We have developed two simple and fast chaperone activity tests for HSP27 and HSP70 that we initially set up to test the effect of potential HSP inhibitors obtained after screening of chemical an…
The role of pH on instability and aggregation of sickle hemoglobin solutions
2004
Understanding the physical basis of protein aggregation covers strong physical and biomedical interests. Sickle hemoglobin (HbS) is a point-mutant form of normal human adult hemoglobin (HbA). It is responsible for the first identified "molecular disease," as its propensity to aggregation is responsible for sickle cell disease. At moderately higher than physiological pH value, this propensity is inhibited: The rate of aggregate nucleation becomes exceedingly small and solubility after polymerization increases. These order-of-magnitude effects on polymer nucleation rates and concurrent relatively modest changes of solubility after polymerization are here shown to be related to both pH-induced…
Influence of polysaccharides on wine protein aggregation.
2016
Abstract Polysaccharides are the major high-molecular weight components of wines. In contrast, proteins occur only in small amounts in wine, but contribute to haze formation. The detailed mechanism of aggregation of these proteins, especially in combination with other wine components, remains unclear. This study demonstrates the different aggregation behavior between a buffer and a model wine system by dynamic light scattering. Arabinogalactan-protein, for example, shows an increased aggregation in the model wine system, while in the buffer system a reducing effect is observed. Thus, we could show the importance to examine the behavior of wine additives under conditions close to reality, in…