Search results for "Fluorescence lifetime"
showing 10 items of 17 documents
Phasor-FLIM analysis of Thioflavin T self-quenching in Concanavalin amyloid fibrils
2020
The formation of amyloid structures has traditionally been related to human neurodegenerative pathologies and, in recent years, the interest in these highly stable nanostructures was extended to biomaterial sciences. A common method to monitor amyloid growth is the analysis of Thioflavin T fluorescence. The use of this highly selective dye, diffused worldwide, allows mechanistic studies of supramolecular assemblies also giving back important insight on the structure of these aggregates. Here we present experimental evidence of self-quenching effect of Thioflavin T in presence of amyloid fibrils. A significant reduction of fluorescence lifetime of this dye which is not related to the propert…
Multispectral fluorescence sensitivity to acidic and polyphenolic changes in Chardonnay wines – The case study of malolactic fermentation
2022
International audience; In this study, stationary and time-resolvedfluorescence signatures, were statistically and chemometrically analyzed among three typologies of Chardonnay wines (A, B and C) with the objectives to evaluate their sensitivity to acidic and polyphenolic changes. For that purpose, a dataset was built using Excitation Emission Matrices of fluorescence (N = 103) decomposed by a Parallel Factor Analysis (PARAFAC), andfluorescence decays (N = 22), mathematically fitted, using the conventional exponential modeling and the phasor plot representation. Wine PARAFAC component C4 coupledwith its phasor plot g and s values enable the description of malolactic fermentation (MLF) occur…
Neuronal activity and secreted amyloid β lead to altered amyloid β precursor protein and presenilin 1 interactions.
2013
Deposition of amyloid β (Aβ) containing plaques in the brain is one of the neuropathological hallmarks of Alzheimer's disease (AD). It has been suggested that modulation of neuronal activity may alter Aβ production in the brain. We postulate that these changes in Aβ production are due to changes in the rate-limiting step of Aβ generation, APP cleavage by γ-secretase. By combining biochemical approaches with fluorescence lifetime imaging microscopy, we found that neuronal inhibition decreases endogenous APP and PS1 interactions, which correlates with reduced Aβ production. By contrast, neuronal activation had a two-phase effect: it initially enhanced APP-PS1 interaction leading to increased …
Blue autofluorescence in protein aggregates “lighted on” by UV induced oxidation
2019
Oxidation of amino acid side chains in protein structure can be induced by UV irradiation leading to critical changes in molecular structure possibly modifying protein stability and bioactivity. Here we show, by using a combination of multiple spectroscopic techniques and Fluorescence Lifetime Imaging, that UV-light exposure induces irreversible oxidation processes in Ubiquitin structure. In particular, the growth of a new autofluorescence peak in the blue region is detected, that we attribute to tyrosine oxidation products. Blue autofluorescence intensity is found to progressively increase also during aggregation processes leading to the formation of aggregates of non-amyloid nature. Signi…
Study of Bacillus subtilis spore's : characterication of stuctures implied in its resistance
2013
The bacterial spore is a multilayer microbial form which is extremely resistant to environmental perturbations. This resistance is especially due to its unique structure which is particularly compact and weakly permeable. This work aims to identify and characterize the spore structures involved in these properties. Overall investigation methods, such as NMR and fluorescence anisotropy, have shown that the cortex of Bacillus subtilis spores is modified by temperature for level similar to that of the activation of germination. This will result in changes to the access to the inner membrane. A tool at the spore’s scale, the fluorescence lifetime imaging microscopy (FLIM) in conjunction with th…
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…
Fluorescence and spin properties of defects in single digit nanodiamonds
2009
International audience; This article reports stable photoluminescence and high-contrast optically detected electron spin resonance (ODESR) from single nitrogen-vacancy (NV) defect centers created within ultrasmall, disperse nanodiamonds of radius less than 4 nm. Unexpectedly, the efficiency for the production of NV fluorescent defects by electron irradiation is found to be independent of the size of the nanocrystals. Fluorescence lifetime imaging shows lifetimes with a mean value of around 17 ns, only slightly longer than the bulk value of the defects. After proper surface cleaning, the dephasing times of the electron spin resonance in the nanocrystals approach values of some microseconds, …
Development of multidimensional spectroscopic and microscopic techniques to facilitate the monitoring of native fluorescence of biomolecules.
2022
There is a need for the development of rapid and reliable characterization tools for biological media. The objective of this thesis is to develop a method based on the acquisition of excitation-emission matrices of fluorescence (EEMF) coupled with the use of fluorescence lifetime measurement in spectroscopy and microscopy (FLIM). These techniques have great potential due to their speed, low sample volume required for analysis, non-destructive sample analysis, and low cost. This project focused on two biological media of great interest to the food industry: wine and bacterial spores. On one hand, we have a beverage representing a large world market, and on the other hand, a food contaminant …
Direct investigation of viscosity of an atypical inner membrane of Bacillus spores: A molecular rotor/FLIM study
2013
Abstract We utilize the fluorescent molecular rotor Bodipy-C12 to investigate the viscoelastic properties of hydrophobic layers of bacterial spores Bacillus subtilis. The molecular rotor shows a marked increase in fluorescence lifetime, from 0.3 to 4 ns, upon viscosity increase from 1 to 1500 cP and can be incorporated into the hydrophobic layers within the spores from dormant state through to germination. We use fluorescence lifetime imaging microscopy to visualize the viscosity inside different compartments of the bacterial spore in order to investigate the inner membrane and relate its compaction to the extreme resistance observed during exposure of spores to toxic chemicals. We demonstr…
On the Effect of Downscaling in Inkjet Printed Life-Inspired Compartments
2019
The fabrication of size-scalable liquid compartments is a topic of fundamental importance in synthetic biology, aiming to mimic the structures and the functions of cellular compartments. Here, inkjet printing is demonstrated as a customizable approach to fabricate aqueous compartments at different size regimes (from nanoliter to femtoliter scale) revealing the crucial role of size in governing the emerging of new properties. At first, inkjet printing is shown to produce homogenous aqueous compartments stabilized by oil-confinement with mild surfactants down to the hundreds of picoliter scale [1]. Raster Image Correlation Spectroscopy allows to monitor few intermolecular events by the involv…