Investigation of nematic order by coherent neutron scattering

The mathematical relationship between the orientational order parameters and the coherent neutron scattering cross section for a nematic liquid crystal is given. For deuterated para-azoxyanisole the single-molecule part of the cross section is evaluated within the meanfield approximation and combined with experimental results to give information about molecular orientational order in terms of P ₂, P ₄ and P ₆. Both P ₂ and P ₄ are found necessary for describing the molecular order. Discrepancies between experimental and theoretical results are interpreted as possibly reflecting the inadequacy of the meanfield theory of Maier and Saupe.     

Simple and Sensitive High-Performance Liquid Chromatographic Method for Determination of Transdermally Applied Flurbiprofen in Rat Plasma and Excised Skin Samples

A simple reversed-phase HPLC method has been developed for determination of flurbiprofen in rat plasma, excised skin extract, and transdermal patch formulations. The mobile phase was methanol–1% (v/v) phosphoric acid in water, 80:20 (v/v), at a flow rate of 0.5 mL min^-1; ibuprofen was used as internal standard. Flurbiprofen and ibuprofen was detected by UV absorption at 254 nm and 220 nm, respectively. The limit of quantitation was 0.1 µg mL^-1. The response was linearly dependent on concentration in the range 0.1–10 µg mL^-1, and accuracy and reproducibility were good. At these concentrations intraday and interday assay variability were below 8%. Recovery of flurbiprofen was greater than 94% over the linear range of calibration plot.     

3-Nitroso-4-hydroxy-5,6-benzocoumarin as a specific reagent for the detection of cobalt

Microchimica Acta - The complexation of 3-nitroso-4-hydroxy-5,6-benzocoumarin with cobalt is used to detect cobalt in presence of various common ions. The spot test has been successfully used for...     

Neutral strange particle correlations in 360 GeV/cpp interactions

Production properties and correlations forK _s ⁰ K _s ⁰ ,K _s ⁰ Λ,K _s ⁰ ¯Λ and Λ¯Λ systems in 360 GeV/cpp interactions are presented. All rapidity gap distributions are observed to peak at Δy=0 and the azimuthal angular distributions between the two particles are consistent with being flat. Experimental results are compared with the quark fusion and Lund models of particle production.     

Chemoenzymatic route to macrocyclic hybrid peptide/polyketide-like molecules

Hybrid peptide-polyketides are a class of medically and biologically important natural products characterized by stereochemical and functional diversity. In their biosynthesis, hybrids are often macrocyclized to achieve rigid structures that populate bioactive conformations. We herein present a chemoenzymatic strategy to access the stereochemical and functional diversity found in macrocyclic hybrid natural products in a manner amenable to efficient library synthesis. Our method makes use of small building blocks in the form of Fmoc-protected epsilon-amino acids containing embedded polyketide functionality. The building block approach allows for combinatorial synthesis of linear molecules that can be activated as soluble thioesters or tethered to a solid-phase resin. We demonstrate that these linear molecules are substrates for macrocyclization by a tolerant catalyst, TycC TE, derived from a nonribosomal peptide synthetase. The method should allow for access to diverse structures with hybrid peptide-polyketide character that can be screened for improved or novel activities.     

Stability indicating high-performance thin-layer chromatographic determination of gatifloxacin as bulk drug and from polymeric nanoparticles

A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method for determination of gatifloxacin both as a bulk drug and from polymeric nanoparticles was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed thin-layer chromatography (TLC) aluminium plates precoated with silica gel 60F-254 as the stationary phase and the mobile phase consisted of n-propanol-methanol-concentrated ammonia solution (25%) (5:1:0.9, v/v/v). This solvent system was found to give compact spots for gatifloxacin (R_f value of 0.60 ± 0.02). Densitometric analysis of gatifloxacin was carried out in the absorbance mode at 292 nm. The linear regression analysis data for the calibration plots showed good linear relationship with r = 0.9953 with respect to peak area in the concentration range of 400-1200 ng spot⁻¹. The mean value (±S.D.) of slope and intercept were 9.66 ± 0.05 and 956.33 ± 27.67, respectively. The method was validated for precision, accuracy, ruggedness and recovery. The limits of detection and quantitation were 2.73 and 8.27 ng spot⁻¹, respectively. Gatifloxacin was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. The drug undergoes degradation under acidic and basic conditions and upon wet and dry heat treatment. The degraded products were well separated from the pure drug. The statistical analysis proves that the developed method for quantification of gatifloxacin as bulk drug and from polymeric nanoparticles is reproducible and selective. As the method could effectively separate the drug from its degradation products, it can be employed as stability-indicating one.     

Hydrogen bonding of formo- and thioformohydroxamic acid with methanethiol and methaneselenol as amino acid side chain groups

Hydrogen (H-) bonding ability of most stable keto and enol tautomers of formo- and thioformohydroxamic acids has been investigated by optimizing their 1:1 aggregates with MeSH and MeSeH as model molecules for sulfur and selenium containing amino acid side chains. Although enol is the most stable conformer of thioformohydroxamic acid, yet the most stable aggregate in both hydroxamic acids (HAs) being formed with keto conformer suggests that H-bonding can influence specific conformational dominance. In the aggregates, HAs preferably act as H-bond donor and S/Se of MeSH and MeSeH act as H-bond acceptor. The S···H and Se···H H-bonds although disfavored by electrostatics yet are favored by significant charge transfer. H-bonding preference and strength of interaction of HAs with MeSH and MeSeH is remarkably similar but markedly different from MeOH. AIM and NBO analysis have been employed to understand the role of electron delocalization, bond polarizations, charge transfer etc. as contributors to stabilization energy.