Acetylation of a heterocyclic enaminonitrile: Unambiguous structural assignment using NMR methods

Using a combination of nmr techniques, the structure of the acetylation product of methyl 3-[2-amino-3-cyano-9-methoxy-4H-5,6-dihydronaphtho[1,2-b]pyran-4-yl] benzoate 2b has been shown to be the N-acetyl derivative 5a , rather than the rearranged 2-acetoxydihydropyridine 6a.     

Detection of vacancy clustering by combined PAC and lattice location measurements

The formation of impurity-vacancy agglomerates starting with the trapping of monovacancies was studied using a combination of three complementary techniques applied to the system InCu: Perturbed -angular correlation, ion channeling and channeling of conversion electrons. This results in an almost complete picture of the first stage of vacancy agglomeration at In impurities in Cu.This work was supported by the Bundesminister für Forschung und Technologie.     

Analysis methods for identifying coordinated movements during ligand unbinding

Molecular dynamics simulations have been applied to unbind biological ligands from their receptors [1–5]. Conformation changes are observed in the biomolecules during unbinding, but there exists no systematic method to detect these conformation changes. In this work, we have used `essential dynamics' (ED) [6–7] and projection to latent structures (PLS) [8] to investigate the conformation changes of the bovine serum retinol-binding protein when retinol unbinds from its receptor site. The results of these analyses characterise a large proportion of the movements that occur during unbinding. We find that the loop regions of retinol-binding protein exhibit the largest movements during unbinding. The sudden changes in unbinding speed during the unbinding process appear not to be caused by sudden changes in protein structure.     

Interaction between a partially fluorinated alkyl sulfate and gelatin in aqueous solution

The interaction of a partially fluorinated alkyl sulfate, sodium 1H,1H,2H,2H-perfluorooctyl sulfate (C6F13CH2CH2OSO3Na), with the polyampholyte gelatin has been examined in aqueous solution using surface tension and small-angle neutron scattering (SANS). The 19F chemical shift of each fluorine environment in the surfactant is unaltered by the addition of gelatin, indicating that there is no contact between the gelatin and the fluorocarbon core of the micelle. The chemical shift of the two methylene groups closest to the headgroup is altered when gelatin is present, disclosing the location of the polymer. The critical micelle concentration (cmc) of the surfactant, cmc = 17+/-1 mM, corresponds to an effective alkyl chain (CnH2n+1) length of n = 11. In the presence of gelatin, the cmc is substantially reduced as expected, cmc(1) = 4+/-1 mM, which is also consistent with an effective alkyl chain length of n = 11. In the presence of the fluorosurfactant, the monotonic decay of the SANS from the gelatin-only system is replaced by a substantial peak at an intermediate Q value mirroring the micellar interaction. At low ionic strengths, the gelatin/micelle complex can be described by an ellipsoid. At higher ionic strengths, the electrostatic interaction between the micelles is screened and the peak in the gelatin scattering disappears. The correlation length describing the network structure decreases with increasing SDS concentration as the bound micelles promote a collapse of the network.     

A shield for reducing the thermal signal from heating holders during in situ energy-dispersive X-ray spectroscopy analysis.

This article describes a simple shield that can be placed on typical commercial heating holders to reduce the thermal signal during heating to reasonable levels for in situ energy-dispersive X-ray spectroscopy analysis. The improved temperature capability provided by the shield is demonstrated by initial compositional analysis results obtained across a solid-liquid interface on Al-Si-Cu-Mg alloy powder particles. Considerations in the design of and improvement for the shield are discussed.