Search results for "Biophysic"

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…

Shell palaeoproteomics: first application of peptide mass fingerprinting for the rapid identification of mollusc shells in archaeology.

2020

10 pages; International audience; Molluscs were one of the most widely-used natural resources in the past, and their shells are abundant among archaeological findings. However, our knowledge of the variety of shells that were circulating in prehistoric times (and thus their socio-economic and cultural value) is scarce due to the difficulty of achieving taxonomic determination of fragmented and/or worked remains. This study aims to obtain molecular barcodes based on peptide mass fingerprints (PMFs) of intracrystalline proteins, in order to obtain shell identification. Palaeoproteomic applications on shells are challenging, due to low concentration of molluscan proteins and an incomplete unde…

2019

The effects of ionotropic γ-aminobutyric acid receptor (GABA-A, GABAA) activation depends critically on the Cl−-gradient across neuronal membranes. Previous studies demonstrated that the intracellular Cl−-concentration ([Cl−]i) is not stable but shows a considerable amount of activity-dependent plasticity. To characterize how membrane properties and different molecules that are directly or indirectly involved in GABAergic synaptic transmission affect GABA-induced [Cl−]i changes, we performed compartmental modeling in the NEURON environment. These simulations demonstrate that GABA-induced [Cl−]i changes decrease at higher membrane resistance, revealing a sigmoidal dependency between both par…

FRET biosensor allows spatio-temporal observation of shear stress-induced polar RhoGDIα activation

2018

Rho GDP-dissociation inhibitor α (RhoGDIα) is a known negative regulator of the Rho family that shuts off GDP/GTP cycling and cytoplasm/membrane translocation to regulate cell migration. However, to our knowledge, no reports are available that focus on how the RhoGDIα-Rho GTPases complex is activated by laminar flow through exploring the activation of RhoGDIα itself. Here, we constructed a new biosensor using fluorescence resonance energy transfer (FRET) technology to measure the spatio-temporal activation of RhoGDIα in its binding with Rho GTPases in living HeLa cells. Using this biosensor, we find that the dissociation of the RhoGDIα-Rho GTPases complex is increased by shear stress, and i…

Photoactivatable Adhesive Ligands for Light-Guided Neuronal Growth

2018

Neuro-regeneration after trauma requires growth and reconnection of neurons to reestablish information flow in particular directions across the damaged tissue. To support this process, biomaterials for nerve tissue regeneration need to provide spatial information to adhesion receptors on the cell membrane and to provide directionality to growing neurites. Here, photoactivatable adhesive peptides based on the CASIKVAVSADR laminin peptidomimetic are presented and applied to spatiotemporal control of neuronal growth to biomaterials in vitro. The introduction of a photoremovable group [6-nitroveratryl (NVOC), 3-(4,5-dimethoxy-2-nitrophenyl)butan-2-yl (DMNPB), or 2,2′-((3′-(1-hydroxypropan-2-yl)…

Bioactive potential of silica coatings and its effect on the adhesion of proteins to titanium implants

2018

There is an ever-increasing need to develop dental implants with ideal characteristics to achieve specific and desired biological response in the scope of improve the healing process post-implantation. Following that premise, enhancing and optimizing titanium implants through superficial treatments, like silica sol-gel hybrid coatings, are regarded as a route of future research in this area. These coatings change the physicochemical properties of the implant, ultimately affecting its biological characteristics. Sandblasted acid-etched titanium (SAE-Ti) and a silica hybrid sol-gel coating (35M35G30T) applied onto the Ti substrate were examined. The results of in vitro and in vivo tests and t…

Identification of a classic nuclear localization signal at the N terminus that regulates the subcellular localization of Rbfox2 isoforms during diffe…

2016

Nuclear localization of the alternative splicing factor Rbfox2 is achieved by a C-terminal nuclear localization signal (NLS) which can be excluded from some Rbfox2 isoforms by alternative splicing. While this predicts nuclear and cytoplasmic localization, Rbfox2 is exclusively nuclear in some cell types. Here, we identify a second NLS in the N terminus of Rbfox2 isoform 1A that is not included in Rbfox2 isoform 1F. Rbfox2 1A isoforms lacking the C-terminal NLS are nuclear, whereas equivalent 1F isoforms are cytoplasmic. A shift in Rbfox2 expression toward cytoplasmic 1F isoforms occurs during epithelial to mesenchymal transition (EMT) and could be important in regulating the activity and fu…

The MDS and EVI1 complex locus (MECOM) isoforms regulate their own transcription and have different roles in the transformation of hematopoietic stem…

2016

Transcriptional activation of the EVI1 oncogene (3q26) leads to aggressive forms of human acute myeloid leukemia (AML). However, the mechanism of EVI1-mediated leukemogenesis has not been fully elucidated. Previously, by characterizing the EVI1 promoter, we have shown that RUNX1 and ELK1 directly regulate EVI1 transcription. Intriguingly, bioinformatic analysis of the EVI1 promoter region identified the presence of several EVI1 potential binding sites. Thus, we hypothesized that EVI1 could bind to these sites regulating its own transcription. In this study, we show that there is a functional interaction between EVI1 and its promoter, and that the different EVI1 isoforms (EVI1-145kDa, EVI1-Δ…

2020

Phytochrome proteins control the growth, reproduction, and photosynthesis of plants, fungi, and bacteria. Light is detected by a bilin cofactor, but it remains elusive how this leads to activation of the protein through structural changes. We present serial femtosecond X-ray crystallographic data of the chromophore-binding domains of a bacterial phytochrome at delay times of 1 ps and 10 ps after photoexcitation. The data reveal a twist of the D-ring, which leads to partial detachment of the chromophore from the protein. Unexpectedly, the conserved so-called pyrrole water is photodissociated from the chromophore, concomitant with movement of the A-ring and a key signaling aspartate. The chan…

Stability of Alkyl Chain-Mediated Lipid Anchoring in Liposomal Membranes

2020

Lipid exchange among biological membranes, lipoprotein particles, micelles, and liposomes is an important yet underrated phenomenon with repercussions throughout the life sciences. The premature loss of lipid molecules from liposomal formulations severely impacts therapeutic applications of the latter and thus limits the type of lipids and lipid conjugates available for fine-tuning liposomal properties. While cholesterol derivatives, with their irregular lipophilic surface shape, are known to readily undergo lipid exchange and interconvert, e.g., with serum, the situation is unclear for lipids with regular, linear-shaped alkyl chains. This study compares the propensity of fluorescence-label…