Electronic Circular Dichroism Spectroscopy of Proteins

Circular dichroism (CD) is an important spectroscopic technique that enables the characterization of protein secondary and tertiary structure. Proteins can undergo changes in their structure when they participate in processes, for example, ligand binding. CD, therefore, can be used to monitor secondary and tertiary structural changes when a protein (receptor) binds to a drug molecule (ligand).This review describes experimental studies of protein CD and theoretical and computational methods that compute spectra from structure or structure from spectra. CD is a technique that can be used to complement X-ray, NMR, and ultraviolet-visible (UV-vis) experiments on biomolecules and proteins, all of which can be assisted by molecular modeling, which has the capability of computing CD from first principles. A combination of experimental CD and molecular modeling has the capacity to greatly enhance future multi-disciplinary research to expand our knowledge of the structure, function, and dynamics of proteins

Epitaxial Growth of Boron Carbide on 4H-SiC

In this work, the successful heteroepitaxial growth of boron carbide (B x C) on 4HSiC(0001) 4{\textdegree} off substrate using chemical vapor deposition (CVD) is reported. Towards this end, a two-step procedure was developed, involving the 4H-SiC substrate boridation under BCl 3 precursor at 1200{\textdegree}C, followed by conventional CVD under BCl 3 + C 3 H 8 at 1600{\textdegree}C. Such a procedure allowed obtaining reproducibly monocrystalline (0001) oriented films of B x C with a step flow morphology at a growth rate of 1.9 $\mu$m/h. Without the boridation step, the layers are systematically polycrystalline. The study of the epitaxial growth mechanism shows that a monocrystalline B x C layer is formed after boridation but covered with a B-and Si-containing amorphous layer. Upon heating up to 1600{\textdegree}C, under pure H 2 atmosphere, the amorphous layer was converted into epitaxial B x C and transient surface SiB x and Si crystallites. These crystallites disappear upon CVD growth

Financialisation of strategies, risk transfer, liquidity, property and control (In French)

The financialisation of strategies, as mentioned in the introduction, may be correlated with the dominant link between investment and funding. The principle of selection no longer seems to focus essentially on investment funding methods, but on investments themselves, according to a financial profitability criterion. The first part of the text deals with the question of “risk transfer”. The second part examines financialisation from the point of view of the principle of liquidity by emphasizing the importance of the assessment which markets exercise on the firms’ financial performance, but also on their industrial. The question of the link between property and control is dealt with in the third part of the text. It is explored in two phases: the link between structure and property rights on the one hand; the link between governance structure and resource allocation on the other hand. The general conclusion suggests placing the financial capital issue between science and magic. The conclusion is organized in two phases: the first phase means to emphasize three transverse dimensions of the financialisation process; the second phase proposes to put that process into a sequence going from the production of representations to the production of norms, to the question of the financialised firm’s model.Financialisation, risks, evaluation, liquidity, control, governance, external growth, representations, (business) models, (accounting) standards

Time-resolved synchrotron radiation circular dichroism spectroscopy

Ultraviolet (UV) synchrotron radiation circular dichroism (SRCD) spectroscopy has made an important contribution to the determination and understanding of the structure of bio-molecules. In this thesis work, we demonstrate an innovative approach that we term time-resolved SRCD (tr SRCD), overcoming limitations of current broadband UV SRCD setups, which could enable access to ultrafast (down to nanoseconds) time scales. The tr-SRCD setup takes advantage of the natural polarisation of the synchrotron radiation emitted by a bending magnet to record broadband UV CD faster than any current SRCD setup, improving the acquisition speed from 10 mHz to 130 Hz and the accessible temporal resolution by several orders of magnitude. I propose several acquisition protocols that use the two different configurations of the the tr-SRCD setup. They would allow one to follow dynamics occurring on a time range spanning from tens of nanoseconds to minutes. I present results on camphorsulfonic acid (CSA) that allowed us to validate our methodology and also to assess the performance of the tr-SRCD setup. I illustrate the potential of the new approach for biological applications by following the concentration changes of isomers of the FK-11-X peptide after photoisomerisation. I point out the limitations of this approach and I propose an alternative method that should limit them. I present the results of our first tests that use this method and we compare them with standard SRCD and tr-SRCD spectra. I dedicate the last part of this thesis to a complementary study of the FK-11-X peptide via the both theoretical and experimental approaches. I present some molecular dynamics simulations and show that using the combination of experimental data acquired with the tr-SRCD setup coupled to first principles calculations of CD could facilitate the determination of transient structures between two stable conformations

Time-resolved synchrotron radiation circular dichroism spectroscopy

Ultraviolet (UV) synchrotron radiation circular dichroism (SRCD) spectroscopy has made an important contribution to the determination and understanding of the structure of bio-molecules. In this thesis work, we demonstrate an innovative approach that we term time-resolved SRCD (tr SRCD), overcoming limitations of current broadband UV SRCD setups, which could enable access to ultrafast (down to nanoseconds) time scales. The tr-SRCD setup takes advantage of the natural polarisation of the synchrotron radiation emitted by a bending magnet to record broadband UV CD faster than any current SRCD setup, improving the acquisition speed from 10 mHz to 130 Hz and the accessible temporal resolution by several orders of magnitude. I propose several acquisition protocols that use the two different configurations of the the tr-SRCD setup. They would allow one to follow dynamics occurring on a time range spanning from tens of nanoseconds to minutes. I present results on camphorsulfonic acid (CSA) that allowed us to validate our methodology and also to assess the performance of the tr-SRCD setup. I illustrate the potential of the new approach for biological applications by following the concentration changes of isomers of the FK-11-X peptide after photoisomerisation. I point out the limitations of this approach and I propose an alternative method that should limit them. I present the results of our first tests that use this method and we compare them with standard SRCD and tr-SRCD spectra. I dedicate the last part of this thesis to a complementary study of the FK-11-X peptide via the both theoretical and experimental approaches. I present some molecular dynamics simulations and show that using the combination of experimental data acquired with the tr-SRCD setup coupled to first principles calculations of CD could facilitate the determination of transient structures between two stable conformations

L'âge géochronologique de la diorite de Saint-Quay-Portrieux (Côtes du Nord). Ses conséquences sur le Briovérien de la baie de Saint-Brieuc

Séance du 28 août 1972National audiencepas de résum

La financiarisation des stratégies : transferts de risque, liquidité, propriété et contrôle

Document de travail - Cahier du GRETh

La financiarisation des stratégies : transferts de risque, liquidité, propriété et contrôle

Document de travail - Cahier du GRETh

ROLE OF ORGANIC MATTER IN COPPER MOBILITY IN A POLYMICTIC LAKE FOLLOWING COPPER SULFATE TREATMENT (COURTILLE LAKE, FRANCE)

International audienceLake Courtille is a shallow eutrophic polymictic lake treated with copper sulphate for four years. Water column monitoring and laboratory experiments have shown that dissolved copper (CuD) behaviour correlates well with Dissolved Organic Carbon (DOC). Sequential extraction indicates that a significant fraction of the sediment-borne Cu is associated with the organic fraction (50% to 88% of total copper). This fraction of copper could be released into the water column depending on environmental conditions. Laboratory resuspension experiments have shown that significant short term release of Cu was not possible under circumneutral pH and the oxygenated conditions of the lake (less than 3% of the total copper sediment was released). Nevertheless over the long term, a fraction of the copper bound to the sediment could be released depending on the organic matter mineralization which could explain the presence of copper in the water column one year after the last copper addition