Search results for "Stability."
showing 10 items of 3015 documents
Thermodynamic versus Conformational Metastability in Fibril-Forming Lysozyme Solutions
2012
The role of intermolecular interaction in fibril-forming protein solutions and its relation with molecular conformation is a crucial aspect for the control and inhibition of amyloid structures. Here, we study the fibril formation and the protein-protein interactions of lysozyme at acidic pH and low ionic strength. The amyloid formation occurs after a long lag time and is preceded by the formation of oligomers, which seems to be off-pathway with respect to fibrillation. By measuring the osmotic isothermal compressibility and the collective diffusion coefficient of lysozyme in solution, we observe that the monomeric solution is kept in a thermodynamically metastable state by strong electrosta…
Thioflavin T Hydroxylation at Basic pH and Its Effect on Amyloid Fibril Detection
2008
The fluorescent dye thioflavin T (ThT) is commonly used for in situ amyloid fibril detection. In this work, we focused on the spectroscopic properties and chemical stability of ThT in aqueous solution as a function of pH, temperature, and dye concentration. A reversible hydroxylation process occurs in alkaline solutions, which was characterized using a combination of UV-vis absorption spectroscopy, proton NMR, and density functional theory (DFT). On the basis of these studies, we propose a chemical structure for the hydroxylated form. Finally, by means of fluorescence spectroscopy, ThT hydroxylation effects on in situ amyloid detection have been investigated, providing new insights on the e…
Polysorbate 80 controls Morphology, structure and stability of human insulin Amyloid-Like spherulites
2022
AbstractAmyloid protein aggregates are not only associated with neurodegenerative diseases and may also occur as unwanted by-products in protein-based therapeutics. Surfactants are often employed to stabilize protein formulations and reduce the risk of aggregation. However, surfactants alter protein-protein interactions and may thus modulate the physicochemical characteristics of any aggregates formed. Human insulin aggregation was induced at low pH in the presence of varying concentrations of the surfactant polysorbate 80. Various spectroscopic and imaging methods were used to study the aggregation kinetics, as well as structure and morphology of the formed aggregates. Molecular dynamics s…
Corrigendum to “Polysorbate 80 controls Morphology, structure and stability of human insulin Amyloid-Like spherulites” [J. Colloid Interface Sci. 606…
2023
o-Phthalaldehyde–N-acetylcysteine polyamine derivatives: formation and stability in solution and in C18 supports
2001
A comparative study of different derivatization procedures has been performed in order to improve the stability of the reaction products o-phthalaldehyde-N-acetylcysteine (OPA-NAC) polyamines. Procedures such as solution derivatization, solution derivatization followed by retention on a packing support, derivatization on different packing supports and on-column derivatization, have been optimized and compared. The degradation rate constant (k) of the derivative was dependent on the procedure used and on the analyte. For the spermine (the most unstable isoindol tested) k was 8 +/- 2 x 10(-2) min(-1) in solution versus 7.7 +/- 1.1 x 10(-4) min(-1) on the (C18) solid support. The results obtai…
An investigation of the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in authentic urine samples.
2004
Preanalytical stability of a drug and its major metabolites is an important consideration in pharmacokinetic studies or whenever the analyte pattern is used to estimate drug habits. Firstly, the stability of free and glucuronidated 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THCCOOH, THCCOOglu) in authentic urine samples was investigated. Random urine samples of cannabis users (n = 38) were stored at -20, 4, and 20 degrees C up to 15 days and up to 5 days at 40 degrees C, and alterations of the analyte pattern during storage were followed by liquid chromatography-tandem mass spectrometry. Secondly, the influence of pH (range 5.0-8.0) on the stability of the analytes was studied us…
Understanding the role of Ti-rich domains in the stabilization of gold nanoparticles on mesoporous silica-based catalysts
2018
3 Tablae, 14 Figures.-- Supplementary material.-- © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Informatīvā paneļa "InfoDesk" izstrāde
2015
Darbā ir aprakstīts slīdrādes rīka „InfoDesk” funkcionalitātes paplašināšana, atkļūdojot un papildinot to. „InfoDesk” nodrošina slaidu veidošanu, konfigurējamību un slīdrādi uz Android ierīcēm ar API līmeni 14 vai augstāk. Pirms kvalifikācijas darbā aprakstītajām izmaiņām „InfoDesk” spēja izveidot slaidus, tos atskaņot, kā arī konfigurēt tos, bet katrā no šīm darbībām programma varēja pātraukt darboties. „InfoDesk” klāt pievienotā funkcionalitātē ietilpst plašāka slaidā pievienoto elementu kontrole, saglabāšana uz ārējas atmiņas ierīces, labāka atmiņas lietošana, vispārēja programmatūras stabilitāte. Sistēma realizēta Java programmēšanas valodā, izstrādes vidēs Eclipse un Android Studio.
Dynamics of thick discs around Schwarzschild-de Sitter black holes
2003
We consider the effects of a cosmological constant on the dynamics of constant angular momentum discs orbiting Schwarzschild-de Sitter black holes. The motivation behind this study is to investigate whether the presence of a radial force contrasting the black hole's gravitational attraction can influence the occurrence of the runaway instability, a robust feature of the dynamics of constant angular momentum tori in Schwarzschild and Kerr spacetimes. In addition to the inner cusp near the black hole horizon through which matter can accrete onto the black hole, in fact, a positive cosmological constant introduces also an outer cusp through which matter can leave the torus without accreting on…
Polyfunctional recognition of pyridinedicarboxylate anions with macrocyclic polyamine receptors containing heteroaromatic groups.
2008
The interaction of the biologically relevant anions deriving from the six pyridinedicarboxylic acids (H2PDC) with two macrocyclic receptors containing a pentamine chain and a bipyridine (1) or a phenanthroline (2) moiety, as well as with the aliphatic analogue [21]aneN7 (3), was studied by means of spectroscopic methods (UV-vis, NMR) and potentiometric titrations affording the stability constants of the adducts formed. All three receptors form stable complexes with the substrates thanks to the formation of several salt bridges and hydrogen bond contacts, as observed in the crystal structure of the H8[3(2,6-PDC)4] x H2O x 0.5 EtOH solid compound. Additional pi-stacking interactions between t…