Towards an identification of chemically different flavin radicals by means of theirg-tensor

Theg-tensors of two chemically different flavin mononucleotide (FMN) radicals, one of which is covalently bound via N(5) of its 7,8-dimethyl isoalloxazine moiety, and the other one non-covalently bound to mutant LOV domains of the blue-light receptor phototropin, LOV1 C57M and LOV2 C450A, respectively, have been determined by very high microwave frequency and high magnetic field electron paramagnetic resonance (EPR) performed at 360 GHz and 12.8 T. Due to the high spectral resolution of the frozen-solution continuous-wave EPR spectra, the anisotropy of theg-tensors could be fully resolved. By least-squares fittings of spectral simulations to expermental data, the principal values ofg have been established:g _X=2.00554(5),g _Y=2.00391(5), andg _Z=2.00247(7) for the N(5)-alkyl-chain-linked FMN radical in LOV1 C57M-675, andg _X=2.00427(5),g _Y=2.00360(5), andg _Z=2.00220(7) for the noncovalently bound FMN radical in LOV2 C450A-605. By a comparison of these values to the ones from the flavin adenine dinucleotide radicals in two photolyases, the radical in LOV2 C450A-605 could be clearly identified as a neutral FMN radical, FMNH. In contrast, LOV1 C57M-675 exhibits significantly shifted principal components ofg, the differences being caused by spin-orbit coupling of the nearby sulfur from the reactive methionine residue, and the modified chemical structure due to the covalent attachment at N(5) of the radical to the apoprotein. The results clearly show the potential of using theg-tensor as probe of the global electronic and chemical structure of protein-bound flavin radicals.     

A Versatile and Practical Synthesis of 1,1‐Diacetates from Aldehydes Catalyzed by Cyanuric Chloride

Structurally diverse aldehydes are successfully converted into 1,1‐diacetates with acetic anhydride using cyanuric chloride as a mild, convenient and inexpensive catalyst under solvent‐free conditions. The noteworthy features of the present system are shorter reaction times, and mild and solvent‐free conditions. Furthermore, it offers chemoselective protection of aldehydes.     

Photoelectron spectroscopic investigation of transformation of trifluoroacetate precursors into superconducting YBa2Cu3O7−δ films

X-ray photoelectron spectroscopy (XPS) has been used to investigate the evolution of surface chemistry of YBa₂Cu₃O_7−δ (Y123) films prepared by the metalorganic deposition (MOD) process using trifluoroacetate (TFA) precursors. Detailed XPS core-level spectra obtained from the samples quenched from various points during the calcining and firing stages have been reported for the first time and are used to identify surface species. The XPS data show evidence of formation of intermediate phases such as Y-O-F, BaF₂, and CuO during the calcining process, which are the decomposition products of yttrium, barium, and copper trifluoroacetates, respectively. The TFA precursors are completely decomposed at the end of calcination. The change of binding energies for Y 3d_5/2, Ba 3d_5/2, and O 1s during the firing process indicates that Y123 starts to form at 800 °C after 0.5 h firing. Based on the experimental results, an alternative mechanism of the chemical evolution from precursor to final film in the TFA-MOD process is proposed.     

Die Änderung des Brechungsindex bei der Koagulation von Mangandioxyd-Sol. Nachweis eines „Stufeneffektes“ bei der Änderung

Zusammenfassung Es wurden die ?nderungen der Lichtbrechung bei der Koagulation von Mangandioxyd-Sol durch HCl-, Li₂SO₄-, NaCl-, KCl-, NH₄Cl-, BaCl₂-, AlCl₃-, Ce(NO₃)₄ und Th(NO₃)₄-L?sungen untersucht. Die tats?chliche ?nderung des Brechungsindexμ w?hrend des Verlaufs der Koagulation h?ngt von der spezifischen Beschaffenheit des Koagulators und seiner Konzentration ab. Es zeigte sich, da? dieμ-Zeit-Kurve in allen untersuchten F?llen unstetig oder stufenartig verlief. Dieser Stufeneffekt wird besonders deutlich bei langsamen Koagulationen. übersetzt von A. Siehr (Leipzig).     

Intermolecular Forces of Sugars in Water

Apparent molar volume and viscosities of fructose, glucose, mannose, and sucrose have been measured in dilute aqueous solution, concentration range 0.028–0.336 M at 293 K. The viscosity coefficient B and A were calculated from the viscosity data using the Jones-Dole equation for all the studied sugars. The data were also analysed for Stauarding equation. The structure making behavior was obtained for all the sugars. A modified Jone-Dole equation was proposed by using ratio of mole fractions of solute and solvent in place of concentrations of solute.     

Rapid label-free visual assay for the detection and quantification of viral RNA using peptide nucleic acid (PNA) and gold nanoparticles (AuNPs)

A rapid label-free visual assay for the detection of viral RNA using peptide nucleic acid (PNA) probes and gold nanoparticles (AuNPs) is presented in this study. Diagnosis is a crucial step for the molecular surveillance of diseases, and a rapid visual test with high specificity could play a vital role in the management of viral diseases. In this assay, the specific agglomerative behavior of PNA with gold nanoparticles was manipulated by its complementation with viral RNA. The assay was able to detect 5–10 ng of viral RNA from various biological samples, such as allantoic fluids, cell culture fluids and vaccines, in 100 μl of test solution. The developed assay was more sensitive than a hemagglutination (HA) test, a routine platform test for the detection of Newcastle disease virus (NDV), and the developed assay was able to visually detect NDV with as little as 0.25 HA units of virus. In terms of the specificity, the test could discriminate single nucleotide differences in the target RNA and hence could provide visual viral genotyping/pathotyping. This observation was confirmed by pathotyping different known isolates of NDV. Further, the PNA-induced colorimetric changes in the presence of the target RNA at different RNA to PNA ratios yielded a standard curve with a linear coefficient of R² = 0.990, which was comparable to the value of R² = 0.995 from real-time PCR experiments with the same viral RNA. Therefore, the viral RNA in a given samples could be quantified using a simple visual spectrophotometer available in any clinical laboratory. This assay may find application in diagnostic assays for other RNA viruses, which are well known to undergo mutations, thus presenting challenges for their molecular surveillance, genotyping and quantification.     

Wavelet based spectrum processing for reduction of counting duration for quantitative estimation of ultra-trace activity in environmental matrices

A simple wavelet transformation based pre-processing method is employed to minimize the duration of counting for gamma spectrometric measurements of samples from environmental matrices. Among the various forms of analyzing wavelets, a suitable one is chosen for this purpose. Measurements with 55 different counting durations were subjected to the wavelet based processing and results were compared with long duration counting time measurements of ⁴⁰K, ¹³⁷Cs, radionuclide from ²³⁸U series (²¹⁴Bi, ²¹⁴Pb) and ²³²Th series (²²⁸Ac, ²¹²Bi, ²¹²Pb, ²⁰⁸Tl). It is observed that with a proper choice of the wavelet function a tenfold reduction in counting duration can be achieved with errors <5 %.     

First iodocyclization reaction of allene–thioureas: an efficient approach to bicyclic β-lactams

The regioselective iodocyclization reaction of allene–thioureas is described, for the first time, for the synthesis of bicyclic β-lactams. The substitution at the allenyl part heavily influenced the iodocyclization reaction. The iodocyclization reaction of the unsubstituted allene–thioureas afforded six-membered 3-thia-1-dethiacephems whereas, the substituted allene–thiourea afforded seven-membered thiazepines along with five-membered isopenams.