Identifying Exchangeable Protons in a 1D NMR Spectrum by Spatially Selective Exchange-Editing

The front cover artwork is provided by Markus Rotzinger at the University of Graz, Austria. The front cover picture illustrates the way the 1D exchange-editing NMR method makes exchanging protons visible by sign alteration. The depicted spectrum of D-glucose shows all exchanging signals inverted, thus allowing a fast qualitative determination, potentially in a single scan. Read the full text of the Research Article at 10.1002/cphc.202300713.

Identifying Exchangeable Protons in a 1D NMR Spectrum by Spatially Selective Exchange-Editing

Signals undergoing chemical or conformational exchange in one-dimensional NMR spectra are often identified by deuterium exchange. In order to obtain quantitative information about the dynamic processes involved, one frequently used method is EXchange SpectroscopY (EXSY). To detect all exchange processes, the EXSY experiment requires the acquisition of time-consuming two-dimensional spectra. Here we report a faster alternative, an experiment which uses spatial encoding to extract similar information in a 1D exchange-edited experiment. Thereby, all protons are observed at once, but in different slices of the detection volume. The experiment can be carried out in a single scan to identify exchanging sites in a 1D spectrum by changes in signal intensity indicating exchange processes. If the exchanging partner, for example water is in molar excess the exchange-editing method easily identifies mobile protons by negative signals in the 1D 1H NMR spectrum.

Vibrio cholerae's ToxRS bile sensing system

The seventh pandemic of the diarrheal cholera disease, which began in 1960, is caused by the Gram-negative bacterium Vibrio cholerae. Its environmental persistence provoking recurring sudden outbreaks is enabled by V. cholerae's rapid adaption to changing environments involving sensory proteins like ToxR and ToxS. Located at the inner membrane, ToxR and ToxS react to environmental stimuli like bile acid, thereby inducing survival strategies for example bile resistance and virulence regulation. The presented crystal structure of the sensory domains of ToxR and ToxS in combination with multiple bile acid interaction studies, reveals that a bile binding pocket of ToxS is only properly folded upon binding to ToxR. Our data proposes an interdependent functionality between ToxR transcriptional activity and ToxS sensory function. These findings support the previously suggested link between ToxRS and VtrAC-like co-component systems. Besides VtrAC, ToxRS is now the only experimentally determined structure within this recently defined superfamily, further emphasizing its significance. In-depth analysis of the ToxRS complex reveals its remarkable conservation across various Vibrio species, underlining the significance of conserved residues in the ToxS barrel and the more diverse ToxR sensory domain. Unravelling the intricate mechanisms governing ToxRS's environmental sensing capabilities, provides a promising tool for disruption of this vital interaction, ultimately inhibiting Vibrio's survival and virulence. Our findings hold far-reaching implications for all Vibrio strains that rely on the ToxRS system as a shared sensory cornerstone for adapting to their surroundings.

Synthesis and Properties of Branched Hydrogenated Nonasilanes and Decasilanes

Branched higher silicon hydrides Si _nH_{2 n+2} with n > 6 were recently found to be excellent precursors for the liquid phase deposition of silicon films. Herein we report the gram-scale synthesis of the novel nona- and decasilanes (H₃Si)₃Si(SiH₂) _nSi(SiH₃)₃ (2: n = 1, 5: n = 2) from (H₃Si)₃SiLi and Cl(SiPh₂) _nCl by a combined salt elimination/dephenylation/hydrogenation approach. Structure elucidation of the target molecules was performed by NMR spectroscopy and X-ray crystallography. 2 and 5 are nonpyrophoric and exhibit a bathochromically shifted UV absorption compared to neopentasilane and the structurally related octasilane (H₃Si)₃SiSi(SiH₃)₃. TG-MS analysis elucidated increased decomposition temperatures and decreased ceramic yields for branched hydrosilanes relative to cyclopentasilane. Otherwise, very similar thermal properties were observed for hydrosilane oligomers with linear and branched structures.

Epidurale Fehllage eines Psoaskompartmentkatheters

Due to total knee replacement, a 67-year-old female patient had received a combination of general anesthesia and continuous psoas compartment block. An epidural block was detected postoperatively. An X-ray after the injection of contrast medium showed a typical epidurography with the catheter tip projecting into the epidural space. After drawing back the catheter, another X-ray showed a correct placement of the catheter and a typical spreading of the contrast medium and the catheter could be used for pain relief. In retrospect, it turned out that the catheter had been placed too far over the tip of the stimulation needle. The recommendations of different authors on this problem vary and are actually quite contradictive. We would recommend not to place the catheter further than 5 cm over the tip of the needle. After the first injection the quality of monitoring should correspond with that of an epidural anesthesia. In doubtful cases an injection of contrast medium and an X-ray can be performed.

[Electric nerve stimulation in relation to impulse strength. A quantitative study of the distance of the electrode point to the nerve]

In the present study the difference of the distances of the tip of the needle to the nerve at similar current intensities but different pulse widths (100 microseconds vs. 1000 microseconds) were determined by means of 20 blockades of the sciatic nerve using the transgluteal approach of Labat. Comparable current intensities at different pulse widths (100 microseconds vs. 1000 microseconds) were compared in the same way, using the same position of the needle. At a pulse width of 100 microseconds and a current intensity of 0.30 mA, the tip of the needle is on an average of 5.0 mm closer to the nerve than with a pulse width of 1000 microseconds and a comparable current intensity of 0.28 mA (difference statistically highly significant; p < 0.005). The comparison of the current intensities at different pulse widths at the same needle-position shows that the difference of the current intensities becomes lower when approaching the nerve. At the most distant point measured in this study, a current intensity of 0.94 mA at 100 microseconds corresponds to an aquivalent current of 0.30 mA at 1000 microseconds (difference 0.64 mA); after an approach of 5.0 mm to the sciatic nerve, this difference is significantly lower (0.30 mA at 100 microseconds, 0.11 mA at 1000 microseconds, difference 0.18 mA; p < 0.01). This means that the control of peripheral nerve stimulation is superior at a pulse width of 100 microseconds because a similar distance corresponds to a greater difference of the current. The success rate of the blockade was 95% at a current of 0.30 mA at 100 microseconds. Nerve lesions or other complications have not been seen. In conclusion, safe and successful nerve blocks in patients without polyneuropathia using the peripheral nerve stimulation seems to be obtained at a current intensity of about 0.30 mA at a pulse width of 100 microseconds.