The spinning process of spiders can modulate the mechanical properties of their silk fibers. It i... more The spinning process of spiders can modulate the mechanical properties of their silk fibers. It is therefore of primary importance to understand what are the key elements of the spider spinning process to develop efficient industrial spinning processes. We have exhaustively investigated the native conformation of major ampullate silk (MaS) proteins by comparing the content of the major ampullate gland of Nephila clavipes, solubilized MaS (SolMaS) fibers and the recombinant proteins rMaSpI and rMaSpII using (1) H solution NMR spectroscopy. The results indicate that the protein secondary structure is basically identical for the recombinant protein rMaSpI, SolMaS proteins, and the proteins in the dope, and corresponds to a disordered protein rich in 3(1) -helices. The data also show that glycine proton chemical shifts of rMaSpI and SolMaS are affected by pH, but that this change is not due to a modification of the secondary structure. Using a combination of NMR and dynamic light scattering, we have found that the spectral alteration of glycine is concomitant to a modification of the hydrodynamical diameter of recombinant and solubilized MaS. This led us to suggest new potential roles for the pH acidification in the spinning process of MaS proteins.
ABSTRACT X-ray diffraction (XRD) complemented by Raman spectroscopy analyses of synthetic organic... more ABSTRACT X-ray diffraction (XRD) complemented by Raman spectroscopy analyses of synthetic organic pigments in powder samples, layered paint systems, and commercial artists' paints bound in acrylic, alkyd, and oil media are presented. The potential and limitations of the techniques to identify and characterize mixtures of these pigments, along with inorganic extenders, in works of art are exemplified and discussed. Stratified model paint systems that mimic the layering structure typically found in modern paintings are used to evaluate the effect of the muXRD experimental parameters, as well as extenders or fillers commonly found in modern artists' paint formulations, on the quality of the patterns recorded in microsamples of paint. XRD is demonstrated for the first time to be an effective tool for the specific identification of synthetic organic pigment mixtures and fillers in acrylic and alkyd bound artists' paints, while the identification of these pigments by XRD in oil bound paints appears problematic. Detailed crystallographic information provided by XRD is shown to be complementary to molecular information provided by Raman analysis. The combined use of these techniques allows for more frequent unambiguous compound identification than would be possible using one technique alone.
The spinning process of spiders can modulate the mechanical properties of their silk fibers. It i... more The spinning process of spiders can modulate the mechanical properties of their silk fibers. It is therefore of primary importance to understand what are the key elements of the spider spinning process to develop efficient industrial spinning processes. We have exhaustively investigated the native conformation of major ampullate silk (MaS) proteins by comparing the content of the major ampullate gland of Nephila clavipes, solubilized MaS (SolMaS) fibers and the recombinant proteins rMaSpI and rMaSpII using (1) H solution NMR spectroscopy. The results indicate that the protein secondary structure is basically identical for the recombinant protein rMaSpI, SolMaS proteins, and the proteins in the dope, and corresponds to a disordered protein rich in 3(1) -helices. The data also show that glycine proton chemical shifts of rMaSpI and SolMaS are affected by pH, but that this change is not due to a modification of the secondary structure. Using a combination of NMR and dynamic light scattering, we have found that the spectral alteration of glycine is concomitant to a modification of the hydrodynamical diameter of recombinant and solubilized MaS. This led us to suggest new potential roles for the pH acidification in the spinning process of MaS proteins.
ABSTRACT X-ray diffraction (XRD) complemented by Raman spectroscopy analyses of synthetic organic... more ABSTRACT X-ray diffraction (XRD) complemented by Raman spectroscopy analyses of synthetic organic pigments in powder samples, layered paint systems, and commercial artists' paints bound in acrylic, alkyd, and oil media are presented. The potential and limitations of the techniques to identify and characterize mixtures of these pigments, along with inorganic extenders, in works of art are exemplified and discussed. Stratified model paint systems that mimic the layering structure typically found in modern paintings are used to evaluate the effect of the muXRD experimental parameters, as well as extenders or fillers commonly found in modern artists' paint formulations, on the quality of the patterns recorded in microsamples of paint. XRD is demonstrated for the first time to be an effective tool for the specific identification of synthetic organic pigment mixtures and fillers in acrylic and alkyd bound artists' paints, while the identification of these pigments by XRD in oil bound paints appears problematic. Detailed crystallographic information provided by XRD is shown to be complementary to molecular information provided by Raman analysis. The combined use of these techniques allows for more frequent unambiguous compound identification than would be possible using one technique alone.
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Papers by Fabien Pottier