A new solid-phase system for immunoassays

The development of a new solid-phase separation system based on silane polymers is described. A T3 radioimmunoassay (RIA) was optimized using coated tubes with polymer coatings containing hydrophilic surface aldehyde groups for antibody coupling and a T4 RIA developed on the basis of surface anilino group containing particles using a suspension method. Both RIAs offer very good performances and show the variable usability of the new separation system

X ray screening identifies active site and allosteric inhibitors of SARS CoV 2 main protease

The coronavirus disease COVID 19 caused by SARS CoV 2 is creating tremendous human suffering. To date, no effective drug is available to directly treat the disease. In a search for a drug against COVID 19, we have performed a high throughput x ray crystallographic screen of two repurposing drug libraries against the SARS CoV 2 main protease Mpro , which is essential for viral replication. In contrast to commonly applied x ray fragment screening experiments with molecules of low complexity, our screen tested already approved drugs and drugs in clinical trials. From the three dimensional protein structures, we identified 37 compounds that bind to Mpro. In subsequent cell based viral reduction assays, one peptidomimetic and six nonpeptidic compounds showed antiviral activity at nontoxic concentrations. We identified two allosteric binding sites representing attractive targets for drug development against SARS CoV

Stabilisierte biochemische Suspensionspraeparate

Stabilisierte biochemische Suspensionspraeparate enthalten in einem waessrigen Medium suspendierte Teilchen eines funktionelle Gruppen aufweisenden Kieselsaeureheteropolykondensats, an dessen funktionelle Gruppen biochemische Materialien, wie Antigene, Antikoerper, Hormone, Aminosaeuren, Haptene, Proteine oder Enzyme, kovalent gebunden sind. Die Suspensionspraeparate eignen sich insbesondere als Trennmittel in immunchemischen Verfahren, wie Radio-, Enzym- oder Fluoreszenzimmunoassays

Structure of the Cyanobacterial Phytochrome 2 Photosensor Implies a Tryptophan Switch for Phytochrome Signaling.

Phytochromes are highly versatile photoreceptors, which occur ubiquitously in plants as well as in many light-responsive microorganisms. Here, photosynthetic cyanobacteria utilize up to three different phytochrome architectures, where only the plant-like and the single-domain cyanobacteriochromes are structurally characterized so far. Cph2 represents a third group in Synechocystis species and affects their capability of phototaxis by controlling c-di-GMP synthesis and degradation. The 2.6-Å crystal structure of its red/far-red responsive photosensory module in the P(r) state reveals a tandem-GAF bidomain that lacks the figure-of-eight knot of the plant/cph1 subfamily. Its covalently attached phycocyanobilin chromophore adopts a highly tilted ZZZssa conformation with a novel set of interactions between its propionates and the GAF1 domain. The tongue-like protrusion from the GAF2 domain interacts with the GAF1-bound chromophore via its conserved PRXSF, WXE, and W(G/A)G motifs. Mutagenesis showed that the integrity of the tongue is indispensable for P(r) → P(fr) photoconversion and involves a swap of the motifs' tryptophans within the tongue-GAF1 interface. This “Trp switch” is supposed to be a crucial element for the photochromicity of all multidomain phytochromes

Self-adjusting file (SAF) separation in clinical use: A preliminary survey among experienced SAF users regarding prevalence and retrieval methods

Context: The self-adjusting file (SAFs) is reported to be resistant to file separation in laboratory tests. No information is currently available regarding SAF separation during clinical use. Aim: To conduct preliminary clinical survey among experienced SAF users in order to establish the prevalence of SAF separation during clinical use and to study how were such cases treated. Materials and Methods: A questionnaire was sent to experienced SAF users to make inquiries regarding incidence of SAF separation and how were such events treated. Only responses from operators who had used 50 SAFs or more were included in the present study. Fisher's exact test was used to compare file separation occurrence. Results: A total of 2517 SAFs had been used by these operators, and 15 cases of file separation were reported (0.6%). Twelve of these 15 separated files could be retrieved within a few minutes using Hedstrm files, with no additional dentine removal required. In the three cases in which the separated files could not be retrieved, the separated file segment was successfully bypassed. Conclusions: The SAF might separate during clinical use, but the incidence of such an event was low. In most such cases, the separated file segment was easily and quickly retrieved without additional removal of dentin

Deamidation of the human eye lens protein γS-crystallin accelerates oxidative aging

Cataract, a clouding of the eye lens from protein precipitation, affects millions of people every year. The lens proteins, the crystallins, show extensive post-translational modifications (PTMs) in cataractous lenses. The most common PTMs, deamidation and oxidation, promote crystallin aggregation; however, it is not clear precisely how these PTMs contribute to crystallin insolubilization. Here, we report six crystal structures of the lens protein γS-crystallin (γS): one of the wild-type and five of deamidated γS variants, from three to nine deamidation sites, after sample aging. The deamidation mutations do not change the overall fold of γS; however, increasing deamidation leads to accelerated disulfide-bond formation. Addition of deamidated sites progressively destabilized protein structure, and the deamidated variants display an increased propensity for aggregation. These results suggest that the deamidated variants are useful as models for accelerated aging; the structural changes observed provide support for redox activity of γS-crystallin in the lens

Tracking the route of molecular oxygen in O 2 tolerant membrane bound [NiFe] hydrogenase

Significance Tracking the route of substrates, intermediates, and inhibitors in proteins is fundamental in understanding their specific function. However, following the route of gases like molecular oxygen within enzymes has always been challenging. In protein X-ray crystallography, gases can be mimicked using krypton or xenon (with a higher electron count); however, these have a different physical behavior compared to true substrates/inhibitors. In our crystal structure of the O 2 -tolerant membrane-bound [NiFe] hydrogenase (MBH) from Ralstonia eutropha , we were able to show the direct path of molecular oxygen between the enzyme exterior and the active site with the “soak-and-freeze” derivatization method. This technique might be useful to detect O 2 traveling routes in many other enzymes. </jats:p