Über den Nachweis von Palladium mit Violursäure

Zusammenfassung Eine Fällungsreaktion von Palladiumsalz mit Violursäure in saurer Lösung wird als Nachweismöglichkeit für das Element neben Platin, Rhodium und Gold herangezogen. Die Untersuchung der Palladiumverbindung zeigt, daß das Metall mit zwei Violursäureresten verknüpft ist.

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Summary A precipitation reaction of palladium salt with violuric acid in acid solution is used to detect this element in the presence of platinum, rhodium, and gold. The study of the palladium compound showed that the metal is bound to two violuric acid radicals.

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Résumé Mise en évidence de la possibilité d'identifier le palladium en solution acide, en présence de platine, de rhodium et d'or par une réaction de précipitation du sel de palladium par l'acide violurique. L'étude de la combinaison palladiée montre que le métal est lié à deux restes violuriques.

     

Molecular constants for NSCl and NSF

The complete infrared spectrum of gaseous NSCl, including the hitherto unobserved ν₃, is reported. A set of force constants for gaseous NSCl consistent with a number of pieces of independent data such as the isotopic shifts (¹⁴N³²S³⁵Cl, ¹⁵N³²S³⁵Cl, ¹⁴N³²S³⁷Cl, ¹⁵N³²S³⁷Cl, ¹⁴N³⁴S³⁵Cl and ¹⁵N³⁴S³⁵Cl), centrifugal distortion constants (¹⁴N³²S³⁵Cl), and the inertia defect (¹⁴N³²S³⁵Cl) has been computed. Also, the force field of NSF has been redetermined using the vibrational frequencies and the centrifugal distortion constants.     

Stability Enhancement of a Dimeric HER2-Specific Affibody Molecule through Sortase A-Catalyzed Head-to-Tail Cyclization

Natural backbone-cyclized proteins have an increased thermostability and resistance towards proteases, characteristics that have sparked interest in head-to-tail cyclization as a method to stability-enhance proteins used in diagnostics and therapeutic applications, for example. In this proof-of principle study, we have produced and investigated a head-to-tail cyclized and HER2-specific Z_HER2:342 Affibody dimer. The sortase A-mediated cyclization reaction is highly efficient (>95%) under optimized conditions, and renders a cyclic Z_HER3:342-dimer with an apparent melting temperature, T_m, of 68 °C, which is 3 °C higher than that of its linear counterpart. Circular dichroism spectra of the linear and cyclic dimers looked very similar in the far-UV range, both before and after thermal unfolding to 90 °C, which suggests that cyclization does not negatively impact the helicity or folding of the cyclic protein. The cyclic dimer had an apparent sub-nanomolar affinity (K_d ~750 pM) to the HER2-receptor, which is a ~150-fold reduction in affinity relative to the linear dimer (K_d ~5 pM), but the anti-HER2 Affibody dimer remained a high-affinity binder even after cyclization. No apparent difference in proteolytic stability was detected in an endopeptidase degradation assay for the cyclic and linear dimers. In contrast, in an exopeptidase degradation assay, the linear dimer was shown to be completely degraded after 5 min, while the cyclic dimer showed no detectable degradation even after 60 min. We further demonstrate that a site-specifically DyLight 594-labeled cyclic dimer shows specific binding to HER2-overexpressing cells. Taken together, the results presented here demonstrate that head-to-tail cyclization can be an effective strategy to increase the stability of an Affibody dimer.     

Gold(I)-catalysed iodoalkoxylation of allenes

Gold(I)-catalysed intermolecular iodoalkoxylation of allenes occurs in a regioselective and stereoselective manner to produce versatile iodo-tert-allyllic ether products. The products can be further elaborated through cross-couplings to yield highly substituted tert-allylic ethers.     

Environmental analysis of higher brominated diphenyl ethers and decabromodiphenyl ethane

Methods for environmental analysis of higher brominated diphenyl ethers (PBDEs), in particular decabromodiphenyl ether (BDE209), and the recently discovered environmental contaminant decabromodiphenyl ethane (deBDethane) are reviewed. The extensive literature on analysis of BDE209 has identified several critical issues, including contamination of the sample, degradation of the analyte during sample preparation and GC analysis, and the selection of appropriate detection methods and surrogate standards. The limited experience with the analysis of deBDethane suggests that there are many commonalities with BDE209. The experience garnered from the analysis of BDE209 over the last 15 years will greatly facilitate progress in the analysis of deBDethane.     

Synthesis and Conformation of 3,6‐Connected Cyclohexadiene Chains

3,6‐Connected cyclohexadienes as precursors for polyphenylenes are synthesized and characterized by mass spectrometry and NMR spectroscopy. Pure fractions of trimers, hexamers, and nonamers are collected after separation of the product mixture by recycling GPC. The anticipated formation of rigid linear structures, due to the trans‐configuration of the monomeric units, is supported by density functional theory and experimentally confirmed by dynamic light scattering from dilute solution at low scattering angles. The obtained translational diffusion coefficients are represented by rigid rod‐like or prolate ellipsoid‐like molecular shapes. The measurements of diffusion coefficients reveal a length‐dependent ratio of 1:2:3 between the three oligomers, which directly correlates to the expected length extension from trimer to nonamer.

     

Dialumenes – aryl vs. silyl stabilisation for small molecule activation and catalysis

Main group multiple bonds have proven their ability to act as transition metal mimics in the last few decades. However, catalytic application of these species is still in its infancy. Herein we report the second neutral NHC-stabilised dialumene species by use of a supporting aryl ligand (3). Different to the trans-planar silyl-substituted dialumene (3Si), compound 3 features a trans-bent and twisted geometry. The differences between the two dialumenes are explored computationally (using B3LYP-D3/6-311G(d)) as well as experimentally. A high influence of the ligand''s steric demand on the structural motif is revealed, giving rise to enhanced reactivity of 3 enabled by a higher flexibility in addition to different polarisation of the aluminium centres. As such, facile activation of dihydrogen is now achievable. The influence of ligand choice is further implicated in two different catalytic reactions; not only is the aryl-stabilised dialumene more catalytically active but the resulting product distributions also differ, thus indicating the likelihood of alternate mechanisms simply through a change of supporting ligand.

Ligand controlled reactivity: a trans-bent and twisted geometry enables dihydrogen activation and enhanced catalytic activity for NHC-stabilised dialumenes.