Search results for "dynamic"
showing 10 items of 12329 documents
Aminoquinolines: Fluorescent sensors to DNA – A minor groove probe. Experimental and in silico studies
2023
An aminoquinoline (AQ4) was developed and proven to be a new and efficient DNA minor groove fluorescent probe. The specificity for DNA minor groove was attested by comparing it with well-established DNA probes such as Hoechst stain, acridine orange, and ethidium bromide. AQ4 was similar to the Hoechst stain, a classic minor groove probe, and opposite to acridine orange and ethidium bromide, the typical intercalating probes. An advantage of AQ4 to the Hoechst stain was the higher fluorescent signal-to-noise ratio (+DNA/-DNA). The interaction with DNA leads to an exclusive fluorescent band centered at 590 nm. The red-shifted fluorescent band is associated with a new absorption band (490 nm), …
Micelles of the chiral biocompatible surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB): molecular dynamics …
2017
Rationale The study of self-assembly process of surfactant molecules in gas phase is of actually interest for several theoretical and technological reasons related to their possible exploitation as drug carriers, protein shields and cleaning agents in gas phase. Methods Stability and fragmentation patterns of singly and multiply charged (either positively or negatively) aggregates of the surfactant (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl) dimethyl ammonium bromide (DMEB) in gas phase have been studied by ion mobility mass spectrometry and tandem mass spectrometry. Molecular dynamics (MD) simulations of positively and negatively singly and multiply charged DMEB aggregates have been …
Optical gain, spontaneous and stimulated emission of surface plasmon polaritons in confined plasmonic waveguide
2010
International audience; We develop a theoretical model to compute the local density of states in a confined plasmonic waveguide. Based on this model, we derive a simple formula with a clear physical interpretation for the lifetime modification of emitters embedded in the waveguide. The gain distribution within the active medium is then computed following the formalism developed in a recent work [Phys. Rev. B 78, 161401 (2008)], by taking rigorously into account the pump irradiance and emitters lifetime modifications in the system. We finally apply this formalism to describe gain–assisted propagation in a dielectric–loaded surface plasmon polariton waveguide.
(E)-2-Cyano-3-(5′-piperidin-1-yl-2,2′-bithien-5-yl)acrylic Acid: A Fluorescent Probe for Detecting Prefibrillar Oligomers
2013
The synthesis of (E)-2-cyano-3-(5′-piperidin-1-yl-2,2′-bithien-5-yl)acrylic acid, a novel amyloid aggregation fluorescent probe, is reported. This new probe is able to monitor soluble oligomeric aggregates after 24 h, at which time Thioflavin T emission, commonly used to monitor amyloid fibril formation, remains unchanged. Atomic force microscopy, native polyacrylamide gel electrophoresis, and dynamic light scattering confirm that the earlier stages of aggregation are prefibrillar oligomeric species not possessing the amyloid structure. This new molecular scaffold expands the toolbox of fluorescent probes for the identification of prefibrillar oligomers, which is needed in studies aimed at …
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…
The Boson Peak of Amyloid Fibrils: Probing the Softness of Protein Aggregates by Inelastic Neutron Scattering
2014
Proteins and polypeptides are characterized by low-frequency vibrations in the terahertz regime responsible for the so-called "boson peak". The shape and position of this peak are related to the mechanical properties of peptide chains. Amyloid fibrils are ordered macromolecular assemblies, spontaneously formed in nature, characterized by unique biological and nanomechanical properties. In this work, we investigate the effects of the amyloid state and its polymorphism on the boson peak. We used inelastic neutron scattering to probe low-frequency vibrations of the glucagon polypeptide in the native state and in two different amyloid morphologies in both dry and hydrated sample states. The dat…
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…
The popularization of plate tectonics: presenting the concepts of dynamics and time
1996
There have been many attempts to describe and represent the theory of plate tectonics to laypeople. In the context of a study conducted at the request of a museum, we have tried to determine how the concepts of both geological time and the movements of the plates have been reformulated. After having systematically studied in detail publications aimed at more or less educated readers, we have selected a corpus of twelve articles from nine different magazines or journals. Among the different means of expression used by the popularizers, rhetorical figures constitute a significant resource. Procedures based on analogy (metaphor, comparison, analogical reasoning) were brought together in a sing…
Effects of power resistance training program with elastic bands on body composition, muscle strength and physical function in older women
2020
The aim of this study was to investigate the effects of a power-strength resistance program with elastic bands on body composition, physical function, and muscle strength in older women. For such purpose, a randomized controlled trial with a pre-post-intervention design was conducted. Thus, 58 healthy, physically independent, sedentary women, aged 65-85 years, were randomly allocated to the intervention (n = 28) or control group (n = 30). Measurements of body composition (total mass, total fat mass, total skeletal-muscle mass, and body fat percentage), isokinetic muscle strength of knee flexors and extensors (at 60º/second and 180º/second), and physical performance (flexibility, agility/dyn…
Apparent content curves: description and analytical applications. Resolution of binary mixtures
1992
The apparent content curves and their analytical applications are described. Basing on these curves a mathematical method, which permits the identification of the interfering component present in a binary mixture as well as the determination of the contents of both constituents, is proposed. The existence of considerable interaction coefficients is not an impediment for its application. Besides, the analyte contents in the mixture can be obtained without the use of standard interference solutions. The proposed procedure is applied to the analysis of mixtures of dyes with overlapping absorption spectra.