Search results for "FLIM"

Direct observation of alpha-lactalbumin, adsorption and incorporation into lipid membrane and formation of lipid/protein hybrid structures

2019

The interaction between proteins and membranes is of great interest in biomedical and biotechnological research for its implication in many functional and dysfunctional processes. We present an experimental study on the interaction between model membranes and alpha-lactalbumin (alpha-La). alpha-La is widely studied for both its biological function and its anti-tumoral properties. We use advanced fluorescence microscopy and spectroscopy techniques to characterize alpha-La-membrane mechanisms of interaction and alpha-La-induced modifications of membranes when insertion of partially disordered regions of protein chains in the lipid bilayer is favored. Moreover, using fluorescence lifetime imag…

Ionic liquid crystals based on viologen dimers: tuning the mesomorphism by varying the conformational freedom of the ionic layer

2016

ABSTRACTWe investigated the liquid crystal behaviour of newly synthesised bistriflimide salts of symmetric viologen dimers. A smectic A phase was observed for intermediate spacer lengths and for relatively long lateral alkyl chains. The systems were characterised by thermal analysis, polarised optical microscopy, X-ray scattering and solid-state NMR. An intermediate ordered smectic phase was also exhibited by the compounds (except for systems with very short lateral chains) consisting of molten layers of alkyl chains and partially ordered ionic layers. These results, relating to the mesomorphic behaviour of viologen salts, are qualitatively compared to those of the more common imidazolium s…

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…

Thermal behaviour and electrochemical properties of bis(trifluoromethanesulfonyl)amide and dodecatungstosilicate viologen dimers

2012

We report the synthesis and characterization of dimeric viologen salts (1',1''-(alkane-1,n-diyl)bis(1-ethyl-4,4'-bipyridinium) with n = 4-10) with bis(trifluoromethanesulfonyl)amide (bistriflimide, Tf(2)N(-)) as a counteranion. For n = 4, 5 and 6, and for the nonylviologen cation (1,1'-dinonyl-4,4'-bipyridinium) we also prepared salts with the totally inorganic dodecatungstosilicate anion, SiW(12)O(40)(4-), featuring a poly-charged surface and nanosized dimensions. The materials have been characterized by means of calorimetric techniques, X-ray diffraction and solid state NMR and a comparison is made with analogous monomeric viologen salts exhibiting smectic mesophases. A strong odd-even ef…

Roflumilast improves corticosteroid resistance COPD bronchial epithelial cells stimulated with toll like receptor 3 agonist

2015

Chronic obstructive pulmonary disease (COPD) is characterised by chronic pulmonary inflammation punctuated by periods of viral exacerbations. Recent evidence suggests that the combination of roflumilast with corticosteroids may improve the compromised anti-inflammatory properties of corticosteroids in COPD. We analyzed differential and combination anti-inflammatory effects of dexamethasone and roflumilast N-oxide in human bronchial epithelial cells (HBECs) stimulated with viral toll like receptor (TLR) agonists. Lung tissue and HBECs were isolated from healthy (n = 15), smokers (n = 12) and smokers with COPD (15). TLR3 expression was measured in lung tissue and in HBECs. IL-8 secretion was …

UV-induced modifications in collagen fibers molecular structure: a fluorescence spectroscopy and microscopy study

2021

Phasor FLIM analysis of Thioflavin T fluorescence in protein amyloid aggregates: Mapping molecular interactions.

Thioflavin T (ThT) is a worldwide used dye to monitor protein aggregation as it stains with a certain specificity amyloid structures. The interactions between ThT and its hosts are largely studied suggesting that fluorescence properties of this dye critically depend both on the environment rigidity, electrostatic and hydrophobic properties as well as on molecular details binding site structure. Here FLIM and phasor approach analysis are used to exploit ThT amyloid interactions and, in turn, to address polymorphism and structural heterogeneity of amyloid species mapping aggregate-to-aggregate structural differences and revealing details of molecular architecture within the same aggregate.

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…

Simultaneous Separation of Antioxidants and Carbohydrates From Food Wastes Using Aqueous Biphasic Systems Formed by Cholinium-Derived Ionic Liquids

2019

project CICECO-Aveiro Institute of Materials, UID/CTM/50011/2019. Associate Laboratory for Green Chemistry-LAQV, FCT Ref. UID/QUI/50006/2019. POCI-01-0145-FEDER-016403. Investigator FCT project IF/00621/2015. Programa Mais Centro under project CENTRO-07-ST24-FEDER-002008. COMPETE: PEst-C/SAU/UI0709/2011. The food industry produces significant amounts of waste, many of them rich in valuable compounds that could be recovered and reused in the framework of circular economy. The development of sustainable and cost-effective technologies to recover these value added compounds will contribute to a significant decrease of the environmental footprint and economic burden of this industry sector. Acc…

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 …