Windowed R-PDLF recoupling: A flexible and reliable tool to characterize molecular dynamics

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In situ follow-up of hybrid alginate–silicate microbeads formation by linear rheology

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Order−Disorder in the Super-Sodalite Zn 3 Al 6 (PO 4 ) 12 , 4 t ren , 17H 2 O (MIL-74): A Combined XRD−NMR Assessment

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Structure and dynamics of guest molecules confined in a mesoporous silica matrix: Complementary NMR and PDF characterisation

International audienceWe present an experimental approach to study the structure and dynamics of molecular functional complexes in porous host matrices. Combining the results of Solid-State NMR and pair distribution function analysis based on total X-ray scattering data the structural arrangement and dynamical behaviour of Na-2[Fe(CN)(5)NO]center dot 2H(2)O (SNP) embedded in amorphous SiO2 matrix is investigated. We show that the SNP complexes are embedded as isolated complexes within the SiO2 pores and propose a structural model for the cation and anion arrangement. Additionally the NMR results demonstrate the rotational dynamics of the SNP complexes

Syntheses of 13C2-labelled 11Z-retinals

To enable solid-state NMR investigations of the rhodopsin chromophore and its photointermediates, a series of 11Z-retinal isotopomers have been synthesised containing pairs of adjacent 13C labels at C9/C10, C10/C11 or C11/C12, respectively. The C9 labelled carbon atom was introduced through the Heck reaction of a 13C-labelled Weinreb acrylamide derivative, and the label at the C12 position derived from a 13C-containing ethoxy Bestmann–Ohira reagent. The 13C labels at C10 and C11 were introduced through the reaction of ?-ionone with labelled triethyl phosphonoacetat

Chemical Heterogeneities within the Disordered Mineral domains of Aragonite Platelets in nacre from the European Abalone Haliotis tuberculata

International audienceSince the observation in 2005 of a disordered mineral layer at the surface of aragonite platelets in abalone Haliotis laevigata nacre, the model of the organo–mineral interface in such biomineralized tissue has been challenged. As a direct interaction between the aragonite crystalline core and the organic matrix is no longer appropriate to describe such interface, a structural description of the disordered mineral domains at the atomic level is a key for a comprehensive view of nacre ultrastructure. Here, we use European abalone Haliotis tuberculata as a model to investigate aragonite nacre through high-resolution transmission electron microscopy (HR-TEM) and multinuclear solid state nuclear magnetic resonance (ssNMR). The presence of a disordered domain around aragonite crystals is shown through HR-TEM observations similarly to H. laevigata. The structure and the ionic composition of the disordered mineral environments of H. tuberculata nacre are investigated through 1H, 13C, 43Ca, and 23Na ssNMR. Interestingly, we demonstrate that the disordered mineral domains in nacre seem to be heterogeneous in terms of structure and chemical composition and do not match with amorphous calcium carbonate stricto sensu. At least three different carbonates species are evidenced, including CO32– and HCO3– present in the same mineral domain and closely associated with rigid H2O molecules. The local disorder around these ions is found to be inhomogeneous as some CO32– possess an aragonitic environment and are rather ordered (according to the position and line width of their 13C resonance) whereas, in opposition, the chemical environment around HCO3– is highly distributed. The analysis of potential cations as counterions revealed the presence of disordered Ca2+ and the presence of Na+ closely associated with HCO3–. On the basis of these structural data, we propose an atomic-level model for the disordered domains in abalone (H.tuberculata) nacre where the protonation level of carbonate ions, the proportion of sodium ions and the local disorder are increasing from the inner to the outer part of disordered domains. These results give an unprecedented structural view at the atomic scale of such disordered mineral domains in nacre aragonite tablets

Tuning the competition between photoisomerization and photothermy in biomimetic cyclocurcumin analogues

We report the synthesis and photophysical characterization of biomimetic D-A-D’ cyclocurcumin derivatives, which can potentially be used in light activated chemotherapy. Particularly we highlight that both the donor (D) and acceptor (A) groups significantly influence the photophysical response of the chromophore inducing strong bathochromic shift with D/A strength increase and notable fluorescence quantum yield enhancement with donor strength increase. More important, the nature of the acceptor group (oxo or malonitrile) dramatically modifies the outcome in non-radiative deactivation channels. Indeed, while compounds functionalized with an oxo-moiety undergo ethylenic E→Z photoisomerization, the one bearing a malonitrile group leads exclusively to other non-adiabatic internal conversion channels which much favor photothermal conversion as no isomerization of the ethylenic double bond being observed. The tuning of the photophysical properties and the alteration of isomerization vs. photothermal conversion is rationalized through the analysis of the potential energy surfaces along the most relevant degrees of freedom and shows a competitive pathway over malonitrile rotation. Our results offer novel perspective in oxygen-independent light activated chemotherapy and in the control of photochemical processes in biomimetic chromophores

Water dynamics in a mesoporous bioactive glass studied by NMR relaxometry

International audienceWater confined in a new class of mesoporous bioactive glasses (MBGs) has been studied by NMR relaxometry technique.Two CaO-SiO2-P2O5 materials have been compared: both have the same chemical composition but they have been made withdifferent methods – standard or microfluidic techniques -, inducing different textural properties (surface areas, porous volume,mesoporous arrangement).NMR is known for being particularly well suited for studying fluids embedded in mesostructured porous materials because, inaddition of being non-invasive and relatively fast, it allows the characterization of molecules dynamics. In this study, we used NMRrelaxometry, which consists in measuring spin relaxation times as a function of the measurement frequency (or equivalently of thestatic magnetic field B0), in order to determine the dynamics of water molecules embedded in the MBGs. The low field domain(10kHz-10MHz proton Larmor frequency) was investigated with measurements done with a fast field-cycling relaxometer, and the socalleddispersion curves (longitudinal relaxation rate as a function of the measurement frequency) were analyzed in order to haveadditional insights on the motion of confined water.The frequency dependence of the proton relaxation rate in MBGs was first studied by comparing the relaxation dispersion detected inHOD (residual proton of heavy water) with that in H2O, the proton low-frequency relaxation is thus shown to be mainly due tointramolecular dipolar interactions. Secondly, dispersion curves were recorded as a function of the filling degree and analyzed in theframe of the two-phase fast exchange model: tiny differences in the dynamical behavior of the water inside the two bioglasses(exchange timescale, hydration layers) could be evidenced