MicroGISAXS of Langmuir–Blodgett protein films: effect of temperature on long‐range order

The grazing‐incidence small‐angle X‐ray scattering technique has been used here with a microfocus beamline (µGISAXS) to study the effect of temperature on the protein reorganization taking place in a Langmuir–Schaefer multilayered enzyme film. The study appears quite reproducible in the two enzymes being utilized, penicillin G acylase and urease. In‐plane and out‐of‐plane cuts are used to account for the changes in the film thickness and distance between structures taking place by the process of heating up to 423 K and cooling to room‐temperature. The out‐of‐plane cut suggests that the structures are getting closer and are becoming more organized owing to the heating affect. Merging of layers is likely to occur during the heating and cooling process, leading to a loss of correlation between the interfaces of the layers and to the establishment of long‐range order. The dramatic increase in long‐range order in the Langmuir–Blodgett multilayered enzyme films after heating and cooling, made here apparent by grazing‐incidence small‐angle X‐ray scattering using a microbeam, could in the future open the way to avoiding the bottleneck of protein crystallization for protein structure determination.     

Determination of gatifloxacin and ornidazole in tablet dosage forms by high-performance thin-layer chromatography.

A simple and sensitive high-performance thin-layer chromatography (HPTLC) method has been developed for the quantitative estimation of gatifloxacin and ornidazole in its combined dosage forms. Gatifloxacin and ornidazole were chromatographed on silica Gel 60 F(254) TLC plate using n-butanol:methanol:ammonia (6 M) (8:1:1.5 v/v) as the mobile phase and scanned at 302 nm using a Camag TLC Scanner 3. The R(f) value of gatifloxacin and ornidazole was found to be 0.21 +/- 0.02 and 0.76 +/- 0.04, respectively. The linearity of gatifloxacin and ornidazole were in the range of 100 - 500 ng/spot and 250 - 1250 ng/spot, respectively. The limit of detection was found to be 40 ng/spot for gatifloxacin and 100 ng/spot for ornidazole. The proposed method was applied for the determination of gatifloxacin and ornidazole in combined dosage forms.     

Phenothiazine-pyridyl chalcone: an easily accessible colorimetric and fluorimetric ‘on-off’ dual sensing probe for Cu

Phenothiazine-pyridyl chalcone, a new internal charge transfer (ICT) probe, has been designed that allows naked eye detection and a reversible, ratiometric ‘on-off’ sensing capability for biologically and environmentally significant Cu²⁺ in CH₃OH-H₂O (4:1 v/v) under buffered conditions. The association constants determined using spectrophotometric and the fluorimetric techniques follow the order Cu²⁺ > Ni²⁺ > Co²⁺ > Zn²⁺ > Cd²⁺ > Mg²⁺ ≈ Ba²⁺ ≈ Ca²⁺ ≈ K⁺≈ Na⁺ ≈ Li⁺.     

Surface sensitive probe of the morphological and structural aspects of CdSe core-shell nanoparticles

The promising technological applications of colloids of CdSe nanoparticles in solid state devices is hampered due to issues related to their stoichiometry, agglomeration effects and core-shell relationship. Due to the short inelastic mean free path of core-level electrons, X-ray photoelectron spectroscopy is the most reliable method for analysis at the nanometer depth scale, and in conjunction with layer by layer ion beam erosion it can provide valuable information regarding distribution of elements along the depth of the sample. In this work, we address the issue of synthesis of CdSe nanoparticles and probing them by XPS and conventional techniques such as like transmission electron microscopy (TEM) and X-ray diffraction (XRD). Cd/Se input precursor ratio is varied to form colloidal TOP/TOPO capped CdSe nanoparticles. An optimum input precursor ratio is determined where stoichiometric yield, efficiently capped smallest sized (∼5 nm) CdSe nanoparticles with superior optical, structural and morphological properties are obtained. Electron diffraction and deconvolution of XPS-core-levels enables the identification of the different compositional regimes of CdSe nanocrystallites. For non-optimal precursor ratios, the presence of Cd- and Se-related oxides are observed. This multi-technique approach has enabled us to pictorially model the compositional, structural and morphological aspects of TOP/TOPO capped CdSe nanoparticles.     

Electron paramagnetic resonance study of Cu2+-doped ammonium iodide single crystals

Room-temperature (≈ 300 K) EPR studies of Cu²⁺-doped in NH₄I single crystals are reported. The Cu²⁺ ion is found to substitute for NH₄⁺ and get associated with a second or fourth neighbour cation vacancy. The spectra for the two distinct types of centres have been analysed and the parameters presented.     

Paramagnetic resonance of Gd3+ in Sm (NO3)3. 6H2O single crystals

The paramagnetic resonance of Gd³⁺ in Sm(NO₃)₃.6H₂O single crystals, grown from solution, is studied at room temperature. A seven line spectrum for H//Z as well as for H//X corresponding to ΔM=±1 transitions are observed. The spin Hamiltonian analysis is presented.     

Analytical Quality-by-Design Approach for the Stability Study of Thiocolchicoside by Eco-Friendly Chromatographic Method

JPC – Journal of Planar Chromatography – Modern TLC - A robust and eco-friendly stability-indicating high-performance thin-layer chromatography (HPTLC) method was developed for the...     

Single-Pot Synthesis of Spiroannulated Dihydrofurans by Iodine–Ammonium Acetate–Mediated Reaction of Dimedone with Aldehydes

Iodine–ammonium acetate–mediated annealation of dimedone with aldehydes led to facile formation of spirodihydrofuran in good yields through tandem Knoevenagel–Michael iodonation and cyclodehydroiodonation reactions in a single pot.