Ultrafast Single-Scan 2D NMR Spectroscopic Detection of a PHIP-Hyperpolarized Protease Inhibitor

Two-dimensional NMR spectroscopy is one of the most important spectroscopic tools for the investigation of biological macromolecules. However, due to the low sensitivity of NMR spectroscopy, it takes usually from several minutes to many hours to record such spectra. Here, the possibility of detecting a bioactive derivative of the sunflower trypsin inhibitor-1 (SFTI-1), a tetradecapeptide, by combining parahydrogen-induced polarization (PHIP) and ultrafast 2D NMR spectroscopy is shown. The PHIP activity of the inhibitor was achieved by labeling with O-propargyl-l -tyrosine. In 1D PHIP experiments a signal enhancement of a factor of approximately 1200 compared to standard NMR was found. This enhancement permits measurement of 2D NMR correlation spectra of low-concentrated SFTI-1 in less than 10 seconds, employing ultrafast single-scan 2D NMR detection. As experimental examples PHIP-assisted ultrafast single-scan TOCSY spectra of SFTI-1 are shown.     

Towards a black‐box for biological EXAFS data analysis. II. Automatic BioXAS Refinement and Analysis (ABRA)

In biological systems, X‐ray absorption spectroscopy (XAS) can determine structural details of metal binding sites with high resolution. Here a method enabling an automated analysis of the corresponding EXAFS data is presented, utilizing in addition to least‐squares refinement the prior knowledge about structural details and important fit parameters. A metal binding motif is characterized by the type of donor atoms and their bond lengths. These fit results are compared by bond valance sum analysis and target distances with established structures of metal binding sites. Other parameters such as the Debye–Waller factor and shift of the Fermi energy provide further insights into the quality of a fit. The introduction of mathematical criteria, their combination and calibration allows an automated analysis of XAS data as demonstrated for a number of examples. This presents a starting point for future applications to all kinds of systems studied by XAS and allows the algorithm to be transferred to data analysis in other fields.     

New Cyclic and Polycyclic Ring Systems Containing Group 14 (Si,Ge, Sn) and 16 (S,Se, Te) Elements

The reactions of Me₂MCl₂ (M = Si, Ge, Sn), Si₂Me₄Cl₂, Si₂Me₂Cl₃, Si₂Me₂Cl₄ and CH₂(SiCl₂Me)₂, and suitable mixtures thereof, with H₂S / NEt₃ and Li₂E (E = Se, Te) have been investigated and lead to a variety of new group 14 chalcogenide systems.     

1,2- and 1,3-diphosphetanes from alkylidenephosphines

Abstract

Alkyl- or arylbis(trimethylsilyl)phosphines as well as tris(trimethylsilyl)phosphine and the corresponding arsines react with acyl chlorides to give [1-(trimethylsiloxy)alkylidene]phosphines 1 and -arsines 2; most of their 2,2-dimethylpropylidene derivatives are thermally stable at room temperature. With the same class of phosphines as starting compounds and carbon disulfide [bis(trimethylsilylsulfano)methylidene]phosphines 3 are formed, whereas [(dialkylamino)methylidene]-4 and [diarylmethylidene]phosphines 5 or the corresponding arsines 6 and 7 can be obtained from acyl amides or ketones.¹     

The possible discovery of neutron activation in 1910

One-hundred-two years ago, on 21 April 1910, the Austrian chemist Carl Auer von Welsbach published a short comment on a fundamental discovery he had made in the field of nuclear sciences. He reported that “jonium” (²³⁰Th) was able to induce radioactivity in other materials if stored in contact with the ionium sample. He was well aware that this observation was “not quite in agreement with current theories”, because, as a basic principle, a radioactive substance cannot activate an inactive substance. Since he could not remove any superficial contamination, he concluded that the previously inactive materials had become radioactive themselves. Auer von Welsbach predicted that this observation “might be of importance for the mysterious field of radioactivity research”. In fact, we believe that in this experiment he incidentally discovered neutron activation and the production of artificial radionuclides (24 years before I. Curie and F. Joliot) or even induced nuclear fission. The neutron source in his experiments is yet unknown and shall be identified in this project. The neutrons could have been produced from nuclear reactions with impurities of beryllium in the sample. Auer von Welsbach may even have observed nuclear fission 29 years before O. Hahn, F. Straßmann, L. Meitner and O. R. Frisch. In any case, he may have noticed the effects of neutron radiation—22 years before its discovery by J. Chadwick. The main aim of this interdisciplinary project (of which preliminary results are presented herein) is to repeat the 1910-experiment and to identify the source of the neutrons. It will be equally important to investigate the historical reasons and circumstances why Auer’s report remained mostly uncommented in the scientific community. The hypothetical consequences are worth discussion: Auer’s publication could have started the “nuclear age” much earlier than it finally began, with all the consequences for mankind.     

Selective switching of individual multipole resonances in single dielectric nanoparticles

Following Mie theory, nanoparticles made of a high‐refractive‐index dielectric, such as silicon, exhibit a resonator‐like behavior and very rich resonance spectra. Which electric or magnetic particle mode is excited depends on the wavelength, the refractive‐index contrast relative to the environment, and the geometry of the nanoparticle itself. In addition, the spatial structure of the impinging light field plays a major role in the excitation of the nanoparticle resonances. Here, it is shown that, by tailoring the excitation field, individual multipole resonances can be selectively addressed while suppressing the excitation of other particle modes. This enables a detailed study of selected individual resonances without interference by the other modes.