Mono(dinitrogen) and carbon monoxide adducts of bis(cyclopentadienyl) titanium sandwiches

The silyl-substituted titanocene complex, (eta5-C5Me4SiMe2Ph)2Ti, coordinates dinitrogen upon cooling to -35 degrees C to yield an unprecedented example of a mono(dinitrogen) complex of a substituted bis(cyclopentadienyl) titanium compound, (eta5-C5Me4SiMe2Ph)2Ti(N2). Analogous monocarbonyl derivatives, (eta5-C5Me4R)2Ti(CO) (R = SiMe3, SiMe2Ph, CHMe2), have been prepared by mixing the dicarbonyl compounds with the corresponding sandwiches. Both (eta5-C5Me4SiMe2Ph)2Ti(N2) and (eta5-C5Me4SiMe2Ph)2Ti(CO) have been characterized by X-ray diffraction, and mixed N2-CO titanocene complexes have also been observed by in situ IR spectroscopy.     

Infrared absorption and electron paramagnetic resonance studies of vinyl radical in noble-gas matrices

Vinyl radicals produced by annealing-induced reaction of mobilized hydrogen atoms with acetylene molecules in solid noble-gas matrices (Ar, Kr, and Xe) were characterized by Fourier transform infrared and electron paramagnetic resonance (EPR) spectroscopies. The hydrogen atoms were generated from acetylene by UV photolysis or fast electron irradiation. Two vibrational modes of the vinyl radical (nu7 and nu5) were assigned in IR absorption studies. The assignment is based on data for various isotopic substitutions (D and 13C) and confirmed by comparison with the EPR measurements and density-functional theory calculations. The data on the nu7 mode is in agreement with previous experimental and theoretical results whereas the nu5 frequency agrees well with the computational data but conflicts with the gas-phase IR emission results.     

Electronic and ionic transports for negative charge carriers in smectic liquid crystalline photoconductor

We have investigated negative charge carrier transport in the smectic mesophases of the 2-phenylnaphthalene derivative, 6-(4'-octylphenyl)-2-dodecyloxynaphthalene (8-PNP-O12), using the time-of-flight (TOF) method. We revealed that the negative charge carrier transport in its smectic mesophases had two different mechanisms, i.e., electronic and ionic conductions: we observed two transits of the carriers in both the smectic A (SmA) and smectic B (SmB) phases and demonstrated their origins by dilution experiments with a hydrocarbon (n-dodecane); the fast transit was attributed to the electronic transport of electrons and the slow one to the ionic transport of negative ions. Furthermore, it was clarified that the ionic transport was caused by small amounts of chemical impurities ionized by trapping photogenerated electrons in 8-PNP-O12 in addition to photoinduced autoionization of the impurities. Furthermore, we determined the trapping lifetimes for electrons to be 140 and 24 mus for the SmA and SmB phases, respectively. The experimental results suggest the coexistence of two distinctive transport channels for these charge carriers in the smectic mesophases.     

Retention Behavior of New Oral Antidiabetic Drugs in Reversed-Phase Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - The thin-layer chromatographic behavior of three of the newest oral antidiabetic agents, pioglitazone, rosiglitazone, and...     

Alterations of ciliate phosducin phosphorylation in Blepharisma japonicum cells

We have previously reported that motile photophobic response in ciliate Blepharisma japonicum correlates with dephosphorylation of a cytosolic 28 kDa phosphoprotein (PP28) exhibiting properties similar to those of phosducin. Here we demonstrate in in vivo phosphorylation assay that the light-elicited dephosphorylation of the PP28 is significantly modified by cell incubation with substances known to modulate protein phosphatase and kinase activities. Immunoblot analyses showed that incubation of ciliates with okadaic acid and calyculin A, potent inhibitors of type 1 or 2A protein phosphatases, distinctly increased phosphorylation of PP28 in dark-adapted cells and markedly weakened dephosphorylation of the ciliate phosducin following cell illumination. An enhancement of PP28 phosphorylation was also observed in dark-adapted ciliates exposed to 8-Br-cAMP and 8-Br-cGMP, slowly hydrolysable cyclic nucleotide analogs and 3-isobutyryl-1-methylxanthine (IBMX), a non-specific cyclic nucleotide phosphodiesterase (PDEs) inhibitor. Only slight changes in light-evoked dephosphorylation levels of PP28 were observed in cells treated with the cyclic nucleotide analogs and IBMX. Incubation of ciliates with H 89 or KT 5823, highly selective inhibitor of cAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG), respectively, decreased PP28 phosphorylation levels in dark-adapted cells, whereas the extent of light-evoked dephosphorylation of the phosphoprotein was only slightly influenced. Cell treatment with higher Ca2+ concentration together with ionophore A23187 in culture medium resulted in marked increase in PP28 phosphorylation levels, while quite an opposite effect was observed in cells exposed to Ca2+ chelators, EGTA or BAPTA/AM as well as calmodulin antagonists, such as trifluoperazine (TFP), W-7 or calmidazolium. Light-dependent dephosphorylation was not considerably affected by these treatments. The experimental findings presented here suggest that an endogenous light-dependent protein kinase-phosphatase system may be engaged in the alteration of phosducin phosphorylation in ciliate B. japonicum thereby to modulate the cell motile photophobic behavior.     

Videodensitometric HPTLC Determination of Fleroxacin,Sparfloxacin, and Cinoxacin in Tablets

JPC – Journal of Planar Chromatography – Modern TLC - A new, simple, accurate, and rapid high-performance thin-layer chromatographic method has been developed for the determination of...     

Analysis of the normal modes of molecules with D3h symmetry: Infrared spectra of monomeric s-triazine and cyanuric acid

Normal modes of s-triazine and cyanuric acid were calculated at the DFT(B3LYP)/6-311++G(d,p) level. These modes were analyzed in terms of potential energy distribution (PED), computed using a specially designed set of symmetry coordinates. The normal-mode analysis was described in detail and the PED matrix definition used in the calculations was provided. Particular attention has been devoted to the degenerate vibrations. The experimental infrared spectra of s-triazine and cyanuric acid isolated in low-temperature Ar matrices have been recorded and interpreted by comparison with the theoretically predicted normal modes. In the spectrum of matrix-isolated s-triazine, the IR bands originating from ¹³C and ¹⁵N isotopologues with one of the ring atoms substituted by a rare isotope were detected. These bands were identified thanks to the excellent agreement between the experimentally observed and theoretically predicted isotope shifts.     

T2 relaxation measurement with solvent suppression and implications to solvent suppression in general

A number of suppression pulse sequences including Excitation Sculpting and WATERGATE were incorporated into the standard Carr‐Purcell‐Meiboom‐Gill (CPMG) program for T₂ measurement and experimentally evaluated. The chosen suppression schemes were of varying complexity encompassing pulse program elements, such as presaturation, gradients, and selective pulses, which are typically utilized for solvent suppression. The quality of the spectral data and the accuracy of T₂ measurements of the investigated suppression schemes were evaluated using three aqueous samples with increasing proton content in the water solvent, i.e. by volume 100% D₂O, 80/20% D₂O/H₂O, and 20/80% D₂O/H₂O. For signals removed from the water signal, the T₂ values were generally very consistent between all pulse sequences tested. T₂ measurements can be unreliable for signals too close to the water signal such that they are significantly suppressed as well. Their intensity may actually grow initially through cross relaxation that transfers magnetization back to the solute signal. In turn, this relaxation phenomenon can be exploited to improve the spectral quality of conventional solvent suppression schemes. In favorable cases, even signals that are completely masked by the water signal can be recovered by adding a carefully chosen number of spin echoes with optimized evolution time to conventional water suppression pulse programs, such as Excitation Sculpting or WATERGATE. Copyright © 2009 John Wiley & Sons, Ltd.     

Temporal cleaning of a high-energy fiber-based ultrafast laser using cross-polarized wave generation

We report the use of cross-polarized wave generation to perform both pulse shortening and temporal cleaning of a high-energy ytterbium-doped fiber-based femtosecond laser system. The nonlinear processes allow both a highly efficient nonlinear conversion of 20% and a large compression ratio of 3.5, with inherently improved coherent and incoherent contrasts. This results in the generation of 37 μJ, 115 fs pulses at a repetition rate of 100 kHz with high temporal quality.