The effect of water dynamics on conformation changes of albumin in pre-denaturation state:photon correlation spectroscopy and simulation

Water is essential for protein three-dimensional structure, conformational dynamics, and activity. Human serum albumin (HSA) is one of major blood plasma proteins, and its functioning is fundamentally determined by the dynamics of surrounding water. The goal of this study is to link the conformational dynamics of albumin to the thermal motions in water taking place in the physiological temperature range. We report the results of photon correlation spectroscopy and molecular dynamics simulations of HSA in aqueous solution. The experimental data processing produced the temperature dependence of the HSA hydrodynamic radius and its zeta potential. Molecular dynamics reproduced the results of experiments and revealed changes in the secondary structure caused by the destruction of hydrogen bonds in the macromolecule's globule

Eu3+ coordination in an organic/inorganic hybrid matrix with methyl end-capped short polyether chains

Fourier Transform mid-infrared (FT-IR), Fourier Transform Raman (FT-Raman) and photoluminescence spectroscopies and Two-Dimensional (2D) Correlation Spectroscopic Analysis were employed to examine the anionic and cationic local environments in mono-urethanesils doped with europium triflate (Eu(CF 3-SO3)3). The hybrid host framework of these materials is composed of a siliceous backbone bonded through urethane linkages to CH3-terminated polymer chains containing about 7 OCH 2CH2 units. Samples with ∞ ≥ n (composition) ≥5 (where n = OCH2CH2/Eu3+) were studied. In terms of ionic association, the level of complexity of these xerogels is very high. In all the compounds the triflate ions exist "free", weakly coordinated and forming cross-link separated ion pairs. At 20 ≥ n ≥ 5, in addition to all these species contact ion pairs occur. In agreement with these conclusions, photoluminescence establishes the presence of three distinct cation local sites (Eu3+/O=C(urethane cross-links), Eu3+/O-C- C(polyether chains) and weakly coordinated Eu3+/CF3SO 3- ionic pairs)

Effect of Li+ co-doping on structural and luminescence properties of Mn4+ activated magnesium titanate films

International audienceThe effect of Li+ co-doping on crystal phase formation and photoluminescence (PL) of Mn4+ activated magnesium titanate films produced by a solid state reaction method at different temperatures (800–1200 °C) has been investigated by using X-ray diffraction (XRD), diffuse reflectance and PL spectroscopy. The chemical composition of sintered films was estimated by energy dispersive X-ray spectroscopy. The concentration of Mn impurity estimated by Electron spin resonance was about 5 × 1016 cm−3. The XRD study of the annealed films revealed several magnesium titanate crystal phases, such as Mg2TiO4, MgTiO3 and MgTi2O5. The contribution of each phase depended strongly on the annealing temperature and the presence of Li+ additive. Furthermore, Li+ co-doping facilitated the formation of both MgTiO3 and Mg2TiO4 phases, especially at lower annealing temperatures. The PL spectra showed two bands centered at 660 and 710 nm and ascribed to the $^{2}E$ → ${^4}$A$_{2}$ spin-forbidden transition of the Mn4+ ion in the Mg2TiO4 and MgTiO3, respectively. In Li co-doped films, the integrated intensity of Mn4+ luminescence was found several times stronger compared to Li-undoped films that was ascribed mainly to flux effect of lithium