The electrochemical behavior of some podands at a benzo[c]cinnoline modified glassy carbon electrode

This paper describes the grafting of benzo[c]cinnoline (BCC) molecules on glassy carbon (GC) electrode surface. The attachment of BCC molecules to carbon substrate is induced by the electrochemical reduction of the corresponding diazonium salt. The modification of GC with BCC diazonium salt was done in aprotic solution and proved by blocking of dopamine electron transfer. The presence of BCC at the GC surface was characterized by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). On modified surface, the electrochemical behavior of two different types of podands and the catalytic effects of the GC-BCC surface were studied. The XPS was used to monitor element characteristics of the adsorbates on the GC surface and confirm the attachment of BCC molecules to the GC surface.     

Using the OSL single-aliquot regenerative-dose protocol with quartz extracted from building materials in retrospective dosimetry

We report on the application of the single-aliquot regenerative-dose (SAR) protocol to the optically stimulated luminescence signal from quartz extracted from fired bricks and unfired mortar in retrospective dosimetry. The samples came from a radioactive materials storage facility, with ambient dose rates of about 0.1 mGy/h. A detailed dose-depth profile was analysed from one brick, and compared with dose records from area TL dosemeters. Small-aliquot dose-distributions were analysed from the mortar samples; one associated with the exposed brick, and one from a remote site exposed only to background radiation. We conclude that unfired materials have considerable potential in retrospective dosimetry.     

Competitive [4 + 2] cycloadditions in equimolar mixtures of 1‐arylphosphole oxides

Four different [4 + 2] cycloadditions were observed to take place in the equimolar mixtures of two different arylphosphole oxides 2a + 2b or 2b + 2c . In addition to the phosphole oxide dimers 3a‐a and 3b‐b , or 3b‐b and 3c‐c , the crossed cycloadducts 3a‐b and 3b‐a , or 3b‐c and 3c‐b were also formed in considerable portions. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:633–635, 2001     

Native chemical ligation of thioamide-containing peptides: development and application to the synthesis of labeled α-synuclein for misfolding studies

Thioamide modifications of the peptide backbone are used to perturb secondary structure, to inhibit proteolysis, as photoswitches, and as spectroscopic labels. Thus far, their incorporation has been confined to single peptides synthesized on solid phase. We have generated thioamides in C-terminal thioesters or N-terminal Cys fragments and examined their compatibility with native chemical ligation conditions. Most sequence variants can be coupled in good yields with either TCEP or DTT as the reductant, though some byproducts are observed with prolonged TCEP incubations. Furthermore, we find that thioamides are compatible with thiazolidine protection of an N-terminal Cys, so that multiple ligations can be used to construct larger proteins. Since the acid-lability of the thioamide prohibits on-resin thioester synthesis using Boc chemistry, we devised a method for the synthesis of thioamide peptides with a masked C-terminal thioester that is revealed in situ. Finally, we have shown that thioamidous peptides can be coupled to expressed protein fragments to generate large proteins with backbone thioamide labels by synthesizing labeled versions of the amyloid protein α-synuclein for protein folding studies. In a proof-of-principle experiment, we demonstrated that quenching of fluorescence by thioamides can be used to track conformational changes during aggregation of labeled α-synuclein.     

Leptopyrine,new alkaloid from Leptopyrum fumarioides L. (Ranunculaceae)

A new type of isoquinoline alkaloid leptopyrine was isolated from the aerial parts of Leptopyrum fumarioides L. (Ranunculaceae) of Mongolian origin. The known alkaloids protopine and thalifoline were isolated for the first time from this the species. All structures were established by physical and spectral analyses.     

Effect of mechanical activation on structural-chemical properties of phosphorites

Effect of mechanochemical activation of mono-and mid-fraction of phosphorites from the Burenkhan deposit was studied by IR and ESR spectroscopies in vibration and planetary mills. Original Russian Text ? B.G. Sukhov, D. Enkhtuyaa, Zh. Amgalan, T.I. Vakul’skaya, L.N. Novikova, Zh.G. Bazarova, B.G. Bazarov, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 6, pp. 881–886.     

Thioamides as fluorescence quenching probes: minimalist chromophores to monitor protein dynamics

Decreasing the size of spectroscopic probes can afford higher-resolution structural information from fluorescence experiments. Therefore, we have developed p-cyanophenylalanine (Cnf) and backbone thioamides as a fluorophore/quencher pair. Through the examination of a series of thiopeptides, we have determined the working distance for this pair to be 8-30 ?. We have also carried out a proof-of-principle protein-folding experiment in which a Cnf/thioamide-labeled version of villin headpiece HP35 was thermally unfolded while the Cnf/thioamide distance was monitored by fluorescence. For a given protein, thioamide substitutions could be used to track motions with a much greater number of measurements than for current fluorescence probes, providing a dense array of data with which to model conformational changes.     

Influence of organic dyes on the thermal,mechanical, and optical properties of l-arginine trifluoroacetate (LATF) single crystals

Bulk single crystals of pure and organic dyes (rhodamine, amaranth, and methyl orange) admixture l-arginine trifluoroacetate were grown by slow evaporation technique. The cell parameters and crystallinity of pure and dyes-mixed LATF were confirmed by powder X-ray diffraction analysis. Thermal analysis (TG/DTA, DSC) reveals the purity of the sample and no decomposition is observed up to melting point. In the TG trace of pure LATF, methyl orange: LATF, amaranth: LATF and rhodamine: LATF it is observed that the crystals were thermally stable up to 488, 485, 483, and 484.14 K, respectively. The crystals are further characterized using UV–Vis analysis, microhardness analysis, and EDAX analysis. By plotting log P versus log d, the value of the work hardening coefficient "n" was found to be 1.95, 0.52, 0.8, and 0.88 for pure, methyl orange, amaranth, and rhodamine dyes-doped LATF grown crystals, respectively. Second harmonic generation efficiency of pure and dye admixture LATF crystals was measured using Kurtz and Perry powder test, the efficiency of methyl orange, amaranth, and rhodamine dyes-doped LATF crystal is 2.7, 2.6, and 2.07 times greater than KDP, where as the efficiency of LATF pure is 2.5 times greater than that of KDP.