49 research outputs found
Soft Nanotechnology â from Colloid Physics to Nanostructured Functional Materials
We demonstrate how we can tune the size, shape, surface functionality and properties of nanoparticles and use them as ideal model systems for fundamental investigations as well as for materials applications. In particular we describe ways to create functionalized core-shell particles
with various degree of anisotropy and interesting magnetic properties. We show how we can use these particles in order to study the equilibrium and non-equilibrium phase behavior of colloidal suspensions with different interaction potentials and summarize our current understanding of the phenomenon
of dynamical arrest, i.e. gel and glass formation. While different nanoparticles are vital for fundamental studies of various aspects of soft condensed matter, they also offer fascinating possibilities in materials science. We will demonstrate this with the example of nanocomposites
made through an in situ polymerization reaction
Spatiotemporal density patterns of the pest predator Rhynchium haemorrhoidale (F.) along a land-use gradient in cacao agroforestry systems
Caractérisation des fonctions des modifications post-traductionnelles de PCNA à l'aide d'un nouvel outil génétique
PCNA is an essential protein that is involved in many cellular mechanisms and has many post-translational modifications (PTMs). The functions of some PTMs, still remain unknown. In order to study the function of these PTMs, we have developed a new genetic tool allowing, in cellulo, the substitution of endogenous PCNA protein with a mutated version of the protein named complementation version. The technique involves cotransfection of the cells in culture with two types of plasmids. A first plasmid allows invalidation of the endogenous PCNA gene in transfected cells by the CRISPR-Cas9 system. The second plasmid, named complementation plasmid allows the expression of a mutated form of PCNA. In the whole bank of tested mutants, two PCNA mutants were found to be lethal (D122A and E124A). We have demonstrated that these two sites are involved in the initiation of an ubiquitin-dependent protein degradation CRL4Cdt2 pathway essential for the proteolysis of a protein cocktail (cdt1, p21, set8) during the S phase. We demonstrated that PCNA mutant cells (D122A and E124A) accumulate p21 protein. This lack of degradation of p21 then causes re-replication events leading ultimately to the mutant cells death.PCNA est une protĂ©ine essentielle qui intervient dans de nombreux mĂ©canismes cellulaires et qui possĂšde de nombreuses modifications post-traductionnelles (MPTs) dont les fonctions de certaines, restent encore inconnues. Afin dâĂ©tudier la fonction de ces MPTs, nous avons dĂ©veloppĂ© un nouvel outil gĂ©nĂ©tique permettant in cellulo, de substituer la protĂ©ine endogĂšne PCNA par une version mutĂ©e de la protĂ©ine appelĂ©e version de complĂ©mentation. La technique consiste Ă cotransfecter des cellules en culture avec deux types de plasmides. Un premier plasmide permet lâinvalidation du gĂšne de PCNA endogĂšne dans les cellules transfectĂ©es par le systĂšme CRISPR-Cas9. Le deuxiĂšme plasmide dit de complĂ©mentation permet lâexpression dâune forme mutĂ©e de PCNA. Sur lâensemble dâune banque de mutants testĂ©s, deux mutants de PCNA se sont avĂ©rĂ©s ĂȘtre lĂ©taux (D122A et E124A). Nous avons dĂ©montrĂ© que ces deux sites sont impliquĂ©s dans lâinitiation dâune voie de dĂ©gradation ubiquitine dĂ©pendante CRL4Cdt2 essentielle pour la mise en place de la protĂ©olyse dâun cocktail de protĂ©ines (cdt1, p21, set8) durant la phase S. Nous avons dĂ©montrĂ© que les cellules mutantes pour PCNA (D122A et E124A) accumulent la protĂ©ine p21. Ce dĂ©faut de dĂ©gradation de p21 provoque alors des Ă©vĂšnements de re-rĂ©plication menant Ă terme Ă la mort des cellules mutantes
Characterization of PCNAâs post-translational modification functions using a new genetic tool
PCNA est une protĂ©ine essentielle qui intervient dans de nombreux mĂ©canismes cellulaires et qui possĂšde de nombreuses modifications post-traductionnelles (MPTs) dont les fonctions de certaines, restent encore inconnues. Afin dâĂ©tudier la fonction de ces MPTs, nous avons dĂ©veloppĂ© un nouvel outil gĂ©nĂ©tique permettant in cellulo, de substituer la protĂ©ine endogĂšne PCNA par une version mutĂ©e de la protĂ©ine appelĂ©e version de complĂ©mentation. La technique consiste Ă cotransfecter des cellules en culture avec deux types de plasmides. Un premier plasmide permet lâinvalidation du gĂšne de PCNA endogĂšne dans les cellules transfectĂ©es par le systĂšme CRISPR-Cas9. Le deuxiĂšme plasmide dit de complĂ©mentation permet lâexpression dâune forme mutĂ©e de PCNA. Sur lâensemble dâune banque de mutants testĂ©s, deux mutants de PCNA se sont avĂ©rĂ©s ĂȘtre lĂ©taux (D122A et E124A). Nous avons dĂ©montrĂ© que ces deux sites sont impliquĂ©s dans lâinitiation dâune voie de dĂ©gradation ubiquitine dĂ©pendante CRL4Cdt2 essentielle pour la mise en place de la protĂ©olyse dâun cocktail de protĂ©ines (cdt1, p21, set8) durant la phase S. Nous avons dĂ©montrĂ© que les cellules mutantes pour PCNA (D122A et E124A) accumulent la protĂ©ine p21. Ce dĂ©faut de dĂ©gradation de p21 provoque alors des Ă©vĂšnements de re-rĂ©plication menant Ă terme Ă la mort des cellules mutantes.PCNA is an essential protein that is involved in many cellular mechanisms and has many post-translational modifications (PTMs). The functions of some PTMs, still remain unknown. In order to study the function of these PTMs, we have developed a new genetic tool allowing, in cellulo, the substitution of endogenous PCNA protein with a mutated version of the protein named complementation version. The technique involves cotransfection of the cells in culture with two types of plasmids. A first plasmid allows invalidation of the endogenous PCNA gene in transfected cells by the CRISPR-Cas9 system. The second plasmid, named complementation plasmid allows the expression of a mutated form of PCNA. In the whole bank of tested mutants, two PCNA mutants were found to be lethal (D122A and E124A). We have demonstrated that these two sites are involved in the initiation of an ubiquitin-dependent protein degradation CRL4Cdt2 pathway essential for the proteolysis of a protein cocktail (cdt1, p21, set8) during the S phase. We demonstrated that PCNA mutant cells (D122A and E124A) accumulate p21 protein. This lack of degradation of p21 then causes re-replication events leading ultimately to the mutant cells death
Characterization of PCNAâs post-translational modification functions using a new genetic tool
PCNA est une protĂ©ine essentielle qui intervient dans de nombreux mĂ©canismes cellulaires et qui possĂšde de nombreuses modifications post-traductionnelles (MPTs) dont les fonctions de certaines, restent encore inconnues. Afin dâĂ©tudier la fonction de ces MPTs, nous avons dĂ©veloppĂ© un nouvel outil gĂ©nĂ©tique permettant in cellulo, de substituer la protĂ©ine endogĂšne PCNA par une version mutĂ©e de la protĂ©ine appelĂ©e version de complĂ©mentation. La technique consiste Ă cotransfecter des cellules en culture avec deux types de plasmides. Un premier plasmide permet lâinvalidation du gĂšne de PCNA endogĂšne dans les cellules transfectĂ©es par le systĂšme CRISPR-Cas9. Le deuxiĂšme plasmide dit de complĂ©mentation permet lâexpression dâune forme mutĂ©e de PCNA. Sur lâensemble dâune banque de mutants testĂ©s, deux mutants de PCNA se sont avĂ©rĂ©s ĂȘtre lĂ©taux (D122A et E124A). Nous avons dĂ©montrĂ© que ces deux sites sont impliquĂ©s dans lâinitiation dâune voie de dĂ©gradation ubiquitine dĂ©pendante CRL4Cdt2 essentielle pour la mise en place de la protĂ©olyse dâun cocktail de protĂ©ines (cdt1, p21, set8) durant la phase S. Nous avons dĂ©montrĂ© que les cellules mutantes pour PCNA (D122A et E124A) accumulent la protĂ©ine p21. Ce dĂ©faut de dĂ©gradation de p21 provoque alors des Ă©vĂšnements de re-rĂ©plication menant Ă terme Ă la mort des cellules mutantes.PCNA is an essential protein that is involved in many cellular mechanisms and has many post-translational modifications (PTMs). The functions of some PTMs, still remain unknown. In order to study the function of these PTMs, we have developed a new genetic tool allowing, in cellulo, the substitution of endogenous PCNA protein with a mutated version of the protein named complementation version. The technique involves cotransfection of the cells in culture with two types of plasmids. A first plasmid allows invalidation of the endogenous PCNA gene in transfected cells by the CRISPR-Cas9 system. The second plasmid, named complementation plasmid allows the expression of a mutated form of PCNA. In the whole bank of tested mutants, two PCNA mutants were found to be lethal (D122A and E124A). We have demonstrated that these two sites are involved in the initiation of an ubiquitin-dependent protein degradation CRL4Cdt2 pathway essential for the proteolysis of a protein cocktail (cdt1, p21, set8) during the S phase. We demonstrated that PCNA mutant cells (D122A and E124A) accumulate p21 protein. This lack of degradation of p21 then causes re-replication events leading ultimately to the mutant cells death
Thermoresponsive hybrid microgel particles with intrinsic optical and magnetic anisotropy
We describe the synthesis of thermoresponsive, magnetic, optically anisotropic and orientable colloidal particles based on poly(N-isopropylacrylamide) hybrid microgels (PNIPAMs) with an embedded ellipsoidal hematite (α-FeâOâ) core. Our ability to orient the particles with a magnetic field is demonstrated by small angle X-ray scattering and by optical polarization microscopy
Magnetic orientation of soft particles in a jammed solid
Densely packed atoms, molecules, or small particles can get trapped in a jammed state thereby avoiding crystallization. The resulting amorphous structures display complex, spatially heterogeneous, trapping potentials in stark contrast to the uniform case of a crystal. Here we study active and passive rotational motion in a jammed colloidal dispersion of particles consisting of an anti-ferromagnetic core and a thermo-sensitive microgel soft shell. We determine the order parameter as a function of volume fraction from optical birefringence measurements. A simple model allows us to discriminate the orientation and relaxation of different subsets of particles according to their elastic trapping state
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A general method to label metal oxide particles with fluorescent dyes using aryldiazonium salts
Different metal oxide particles are dye labeled by a novel and versatile approach based on aryldiazonium salt chemistry. For dye labeling the particles, the simplicity of aryldiazonium salts to be grafted onto metallic or metal oxide surface is advantageous. The salt is used as a linking agent for attaching the fluorescent molecules