Search results for " Biophysics"
showing 10 items of 136 documents
Quantification of propagating and standing surface acoustic waves by stroboscopic X-ray photoemission electron microscopy.
2018
The quantification of surface acoustic waves (SAWs) in LiNbO3 piezoelectric crystals by stroboscopic X-ray photoemission electron microscopy (XPEEM), with a temporal smearing below 80 ps and a spatial resolution below 100 nm, is reported. The contrast mechanism is the varying piezoelectric surface potential associated with the SAW phase. Thus, kinetic energy spectra of photoemitted secondary electrons measure directly the SAW electrical amplitude and allow for the quantification of the associated strain. The stroboscopic imaging combined with a deliberate detuning allows resolving and quantifying the respective standing and propagating components of SAWs from a superposition of waves. Furth…
Vanillin cell sensor
2007
Our project for iGEM 2006 consisted of designing a cellular vanillin biosensor. We used an EnvZ -E. coli strain as a chassis, and constructed two different devices: a sensor and an actuator, assembled using OmpR-P as a standardised mediator. The sensor device contained a computation- ally designed vanillin receptor and a synthetic two-component signal transduction protein (Trz). The receptor protein was based on a ribose-binding protein as scaffold. The Trz was built by fusion of the periplasmic and transmembrane domains of a Trg protein with an EnvZ kinase domain. When the receptor complex binds Trg, an allosteric motion is propagated to the cyto- plasmic EnvZ kinase domain, resulting in a…
RNA Nanostructure Molecular Imaging
2020
Atomic force and transmission electron microscopies (AFM/TEM) are powerful tools to analyze RNA-based nanostructures. While cryo-TEM analysis allows the determination of near-atomic resolution structures of large RNA complexes, this chapter intends to present how RNA nanostructures can be analyzed at room temperature on surfaces. Indeed, TEM and AFM analyses permit the conformation of a large population of individual molecular structures to be observed, providing a statistical basis for the variability of these nanostructures within the population. Nevertheless, if double-stranded DNA molecular imaging has been described extensively, only a few investigations of single-stranded DNA and RNA …
Electrochemical modifications of proteins: disulfide bonds reduction
2002
International audience; Electrochemical reduction of lysozyme disulfide bonds was achieved at pH between 10 and 11.Below pH 10, no disulfide bond cleavage was observed. At pH higher than 12, the cleavage of disulfide bonds is essentially due to hydrolysis. The addition of denaturant considerably enhanced the performance of the electrochemical device.
1H, 13C, and 15N NMR chemical shift assignment of the complex formed by the first EPEC EspF repeat and N-WASP GTPase binding domain
2021
AbstractLEE-encoded effector EspF (EspF) is an effector protein part of enteropathogenic Escherichia coli’s (EPEC’s) arsenal for intestinal infection. This intrinsically disordered protein contains three highly conserved repeats which together compose over half of the protein’s complete amino acid sequence. EPEC uses EspF to hijack host proteins in order to promote infection. In the attack EspF is translocated, together with other effector proteins, to host cell via type III secretion system. Inside host EspF stimulates actin polymerization by interacting with Neural Wiskott-Aldrich syndrome protein (N-WASP), a regulator in actin polymerization machinery. It is presumed that EspF acts by di…
Colorimetric quantitation of trace amounts of sodium lauryl sulfate in the presence of nucleic acids and proteins
1992
A fast and sensitive procedure for the colorimetric detection of sodium lauryl sulfate (SDS) is presented. The assay is based upon the formation of a chloroform-extractable ion pair between lauryl sulfate and methylene blue that is quantified spectrophotometrically with an estimated detection limit of 150 ng of SDS. The method is suitable for the monitoring of contaminating traces of SDS in protein or nucleic acid samples that have the potential to interfere with enzymatic manipulations such as proteolytic digest, restriction analysis, or reverse transcription. Since the procedure is extremely simple and no special equipment is required it is accessible to every researcher concerned with SD…
A subset of flavaglines inhibits KRAS nanoclustering and activation.
2020
The RAS oncogenes are frequently mutated in human cancers and among the three isoforms (KRAS, HRAS and NRAS), KRAS is the most frequently mutated oncogene. Here, we demonstrate that a subset of flavaglines, a class of natural anti-tumour drugs and chemical ligands of prohibitins, inhibit RAS GTP loading and oncogene activation in cells at nanomolar concentrations. Treatment with rocaglamide, the first discovered flavagline, inhibited the nanoclustering of KRAS, but not HRAS and NRAS, at specific phospholipid-enriched plasma membrane domains. We further demonstrate that plasma membrane-associated prohibitins directly interact with KRAS, phosphatidylserine and phosphatidic acid, and these int…
A qualitative model of the HIV vital cycle
1992
Qualitative modelling is a recent artificial intelligence approach to physical system modelling. This approach has been successfully applied in several fields. On the basis of an analysis and qualitative modelling of cell growth, we reckon that a qualitative model of the vital cycle of HIV can be proposed, including the phases in which HIV can be attacked. The actions of antiviral drugs can also be qualitatively modelled, provided their action mechanism is known, even only in a broad sense.
Effects of photodynamic therapy in periodontal treatment: A randomized, controlled clinical trial
2017
Aim To evaluate the effects of photodynamic therapy (PDT) in the nonsurgical treatment of chronic periodontitis. Materials and methods A randomized, single-blind, controlled, parallel-group clinical trial was performed. Sixty patients were enrolled: 20 healthy controls and 40 patients with periodontitis. The 40 patients were randomized for scaling and root planing (SRP) or SRP+PDT. Periodontal (plaque index, probing depth, clinical recession, clinical attachment level, bleeding on probing, and gingival crevicular fluid volume, corresponding to 381 vs 428 critical sites), microbiological (Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema dentico…
Fracture Mechanics of Collagen Fibrils: Influence of Natural Cross-Links
2013
AbstractTendons are important load-bearing structures, which are frequently injured in both sports and work. Type I collagen fibrils are the primary components of tendons and carry most of the mechanical loads experienced by the tissue, however, knowledge of how load is transmitted between and within fibrils is limited. The presence of covalent enzymatic cross-links between collagen molecules is an important factor that has been shown to influence mechanical behavior of the tendons. To improve our understanding of how molecular bonds translate into tendon mechanics, we used an atomic force microscopy technique to measure the mechanical behavior of individual collagen fibrils loaded to failu…