The Strong Influence of Structure Polymorphism on the Conductivity of Peptide Fibrils

Peptide fibril nanostructures have been advocated as components of future biotechnology and nanotechnology devices. However, the ability to exploit the fibril functionality for applications, such as catalysis or electron transfer, depends on the formation of well‐defined architectures. Fibrils made of peptides substituted with aromatic groups are described presenting efficient electron delocalization. Peptide self‐assembly under various conditions produced polymorphic fibril products presenting distinctly different conductivities. This process is driven by a collective set of hydrogen bonding, electrostatic, and π‐stacking interactions, and as a result it can be directed towards formation of a distinct polymorph by using the medium to enhance specific interactions rather than the others. This method facilitates the detailed characterization of different polymorphs, and allows specific conditions to be established that lead to the polymorph with the highest conductivity.     

Paramagnetic DOSY: An Accurate Tool for the Analysis of the Supramolecular Interactions between Lanthanide Complexes and Proteins

Diffusion ordered NMR is implemented to determine accurately the mobility of paramagnetic tris‐dipicolinate lanthanide complexes that are versatile probes of protein structure. It is shown that diffusion coefficient ratios can be measured with an accuracy of 1 % using a standard BPPLED pulse sequence, which allows for observing significant, though weak, variations when different species are interacting with the paramagnetic compound. We demonstrate that this approach is complementary to classical chemical shift titration experiments, and that it can be applied successfully to probe the supramolecular dynamic interactions between lanthanide complexes and small molecules on the one hand, or to determine rapidly their affinity for a targeted protein.     

On the measurements of particles by imaging methods: Theoretical and Experimental Aspects

Imaging techniques in particle sizing have always been important. Nevertheless, owing to the progress in CCD cameras, these techniques have found new potential which strongly depends on the capability to describe the image formation. Based on a combination of the generalized Lorenz-Mie theory and the diffraction theory, the image characteristics are described, taking into account the beam size, particle location, direction of observation and collecting optics characteristics. In the case of forward detection, a finite coherence is introduced and the results are compared with those obtained by a convolution approach, with the point spread function assumed to be Gaussian. Then some experimental results are displayed which underline the improvement achieved in particle size measurement.     

Steric effects ih the reaction of di(bromomagnesio)alkanes with carboxylic esters

Largely different product distributions were observed on the action of various carboxylic esters with 1,4-di(bromomagnesio)butane and its homologue 1,5-di(bromomagnesio)pentane. The much larger yields of reduction product with the latter are the evidence for the structural geometric requirements for the annelation step.     

New estimates for the parameters of the modified oscillator potential of the rare earth nuclei

We present estimates of the (κ, μ)-modified oscillator potential parameters fitted to the experimental levels using a new set of equilibrium deformations (ε ₂,ε ₄) of rare earth nuclei obtained from the shell correction method including a simple consistency condition. The single particle levels evaluated with the new parameters (κ, μ) presented here are in good agreement with the empirical level order.