When are Two Waters Worse Than One? Doubling the Hydration Number of a Gd–DTPA Derivative Decreases Relaxivity

The synthesis of a novel ligand, based on N-methyl-diethylenetriaminetetraacetate and containing a diphenylcyclohexyl serum albumin binding group (L1) is described and the coordination chemistry and biophysical properties of its Gd(III) complex Gd-L1 are reported. The Gd(III) complex of the diethylenetriaminepentaacetate analogue of the ligand described here (L2) is the MRI contrast agent MS-325. The effect of converting an acetate to a methyl group on metal-ligand stability, hydration number, water-exchange rate, relaxivity, and binding to the protein human serum albumin (HSA) is explored. The complex Gd-L1 has two coordinated water molecules in solution, that is, [Gd(L1)(H2O)2]2- as shown by D-band proton ENDOR spectroscopy and implied by 1H and 17O NMR relaxation rate measurements. The Gd-H(water) distance of the coordinated waters was found to be identical to that found for Gd-L2, 3.08 A. Loss of the acetate group destabilizes the Gd(III) complex by 1.7 log units (log K(ML) = 20.34) relative to the complex with L2. The affinity of Gd-L1 for HSA is essentially the same as that of Gd-L2. The water-exchange rate of the two coordinated waters on Gd-L1 (k(ex) = 4.4x10(5) s(-1)) is slowed by an order of magnitude relative to Gd-L2. As a result of this slow water-exchange rate, the observed proton relaxivity of Gd-L1 is much lower in a solution of HSA under physiological conditions (r1(obs) = 22.0 mM(-1) s(-1) for 0.1 mM Gd-L1 in 0.67 mM HSA, HEPES buffer, pH 7.4, 35 degrees C at 20 MHz) than that of Gd-L2 (r1(obs) = 41.5 mM(-1) s(-1)) measured under the same conditions. Despite having two exchangeable water molecules, slow water exchange limits the potential efficacy of Gd-L1 as an MRI contrast agent.     

Spin-orbit coupling and anisotropy of spin splitting in quantum dots

In lateral quantum dots, the combined effect of both Dresselhaus and Bychkov-Rashba spin-orbit coupling is equivalent to an effective magnetic field +/- B(SO) which has the opposite sign for s(z)= +/- 1/2 spin electrons. When the external magnetic field is perpendicular to the planar structure, the field B(SO) generates an additional splitting for electron states as compared to the spin splitting in the in-plane field orientation. The anisotropy of spin splitting has been measured and then analyzed in terms of spin-orbit coupling in several AlGaAs/GaAs quantum dots by means of resonant tunneling spectroscopy. From the measured values and sign of the anisotropy we are able to determine the dominating spin-orbit coupling mechanism.     

UN sustainable development goals: How can sustainable/green chemistry contribute? Green chemistry as a source of sustainable innovations in the cosmetic industry

Sustainable innovation is a key-objective for our Group that has recently integrated the principles of sustainable development into all stages of a product's life cycle, from its design to consumer use. The following ambitious commitment: 100% of its products should bring an environmental (or social benefit) by 2020, will be reached, in particular, by integrating and giving a constant privilege to renewable raw materials -or ingredients-that originate from sustainable resources that fully comply with the green chemistry rules. In this short review, integration of Green Chemistry principles by our Group, strategies to identify new performing ingredients through sustainable chemistry as well as illustrative examples of innovative raw materials will be presented. With regard to the crucial respect of the environment of our planet, sustainable chemistry has become an indispensable turning point for industrial groups highly devoted to innovation.     

Highly ordered periodic array of metallic nanodots fabricated through template‐assisted nanopatterning and its use for surface‐enhanced Raman scattering spectroscopy of flexible crystalline‐silicon nanomembranes

We report on the fabrication of highly uniform periodic arrays of metallic nanodots formed on glass substrates through a facile anodic aluminum oxide template‐assisted process and their use in selective surface‐enhanced Raman scattering spectroscopy to probe the structural properties of flexible crystalline‐silicon nanomembranes deposited on polymer substrates. A 14‐fold enhancement in Raman scattering was observed from the thin flexible silicon membranes deposited on polyethylene terephthalate substrates, which were used to probe the internal strains in the silicon nanomembrane as a function of the bending radius. Copyright © 2011 John Wiley & Sons, Ltd.     

Human Elastin‐Based Recombinant Biopolymers Improve Mesenchymal Stem Cell Differentiation

Elastin‐based polypeptides are a class of smart biopolymers representing an important model in the design of biomaterials. The combination of biomimetic materials with cells that have great plasticity provides a promising strategy for the realization of highly engineered cell‐based constructs for regenerative medicine and tissue repair applications. Two recombinant biopolymers inspired by human elastin are assessed as coating agents to prepare biomimetic surfaces for cell culture. These substrates are assayed for hBM MSC culture. The coated surfaces are also characterized with AFM to evaluate the topographical features of the deposited biopolymers. The results suggest that the elastin‐derived biomimetic surfaces play a stimulatory role on osteogenic differentiation of MSCs.

     

Dynamics of nuclear spins appearing in transport measurements of an inter-edge spin diode in tilted magnetic fields

In a wide range of magnetic fields nonlinear transport between spin polarized edge channels is studied. The observed hysteresis of the I–V characteristic is attributed to the dynamic nuclear spin polarization due to the electronic spin-flip processes. We find extremely long nuclear spin relaxation times in the regime where the hyperfine interaction with electrons is switched off.