Synthesis of functionalized and fused furans and pyrans from the Morita–Baylis–Hillman acetates of nitroalkenes

The Morita–Baylis–Hillman (MBH) acetates derived from nitroalkenes and ethyl glyoxylate have been transformed in one pot at room temperature to highly fused and functionalized furans and pyrans in good to excellent yield. The reaction involves a cascade Michael–oxa-Michael addition of β-dicarbonyl compounds to the MBH acetates in the presence of an amine base such as DABCO. An unusual switching of selectivity in the oxa-Michael addition from 5-exo-trig to 6-endo-trig was observed when the β-dicarbonyl compound was changed from acyclic or six-membered ring cyclic to five-membered ring cyclic system.     

Synthesis and studies of covalently linked meso-furyl boron-dipyrromethene-ferrocene conjugates

Four meso-furyl BODIPY-ferrocene conjugates 1–4 in which one or more ferrocene groups were connected directly to BODIPY core or meso-furyl group were synthesized by coupling of appropriate bromo meso-furyl BODIPYs with α-ethynylferrocene under mild Pd(0) coupling conditions. The compounds were characterized by HR-MS mass, NMR, absorption, electrochemistry and fluorescence techniques. The absorption studies of compounds 1–4 showed charge transfer band in addition to BODIPY absorption bands indicating that the BODIPY and ferrocene moieties interact within the conjugates. On the other hand, the charge transfer band is absent in meso-phenyl BODIPY-ferrocene conjugate due to the orthogonal arrangement of ferrocene appended meso-phenyl group with BODIPY core which prevents the interaction between the two moieties. The electrochemical studies showed strong oxidation due to ferrocene moiety and reduction due to meso-furyl BODIPY unit. The compounds 3 and 4 which contain two and three ferrocenyl groups respectively were oxidized at the same potential with two and three electrons involved in the redox process. The compounds 1–4 are weakly fluorescent due to electron transfer from ferrocene unit to BODIPY unit. However, the fluorescence can be restored by oxidizing the ferrocene to ferrocenium ion which prevents the electron transfer between the two moieties. The computational studies support the experimental results.     

Peptide peak intensities enhanced by cysteine modifiers and MALDI TOF MS

Two cysteine‐specific modifiers we reported previously, N‐ethyl maleimide (NEM) and iodoacetanilide (IAA), have been applied to the labeling of cysteine residues of peptides for the purpose of examining the enhancement of ionization efficiencies in combination with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI TOF MS). The peak intensities of the peptides as a result of modification with these modifiers were compared with the peak intensities of peptides modified with a commercially available cysteine‐specific modifier, iodoacetamide (IA). Our experiments show significant enhancement in the peak intensities of three cysteine‐containing synthetic peptides modified with IAA compared to those modified with IA. The results showed a 4.5–6‐fold increase as a result of modification with IAA compared to modification with IA. Furthermore, it was found that IAA modification also significantly enhanced the peak intensities of many peptides of a commercially available proteins, bovine serum albumin (BSA), compared to those modified with IA. This significant enhancement helped identify a greater number of peptides of these proteins, leading to a higher sequence coverage with greater confidence scores in identification of proteins with the use of IAA. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermally Conducting Partially Ionized Plasma in a Variable Magnetic Field

An infinitely extending homogenous partially ionized plasma endowed with several physical mechanisms and permeated by a variable magnetic field is considered. The combined effect of these parameters, namely, Hall currents, finite conductivity, ion viscosity, collision with neutrals and thermal conductivity on the gravitational instability of the plasma is studied. It is found that the several mechanisms play different physical roles in the perturbed problem. Jeans' Criterion is analyzed in the framework of Tsallis' statistics for possible modifications due to the presence of nonextensive effects. A simple generalization of the Jeans' criterion is obtained and the standard values are obtained in the limiting case q = 1, q being the nonextensive parameter. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis of cis bis-β-lactams via Staudinger cycloaddition reaction using C2-symmetric 1,2-diamines

An efficient stereoselective synthesis of bis-β-lactams via cycloaddition reaction (Staudinger reaction) of ketenes with bisimines derived from C₂-symmetric 1, 2-diamines is described. The reaction provided diastereomeric mixture of meso and C₂-symmetric cis-bis-β-lactams with higher selectivity for meso-bis-β-lactams.     

Measurements of electron density, temperature and photoionization cross sections of the excited states of neon in a discharge plasma

In the present work emission and absorption spectroscopy have been used to determine the plasma parameters of neon in a hollow cathode discharge lamp. The excitation temperature is determined using the intensity ratio method and Boltzmann's plot method whereas the electron density is determined from the Stark broadening of the spectral lines. The behavior of the optogalvanic signal as a function of laser energy has been studied for three transitions from the 2p⁵3s [1/2]₂ metastable state following ΔJ=ΔK=0, ±1 dipole selection rules. The saturation technique has been used to measure the photoionization cross section from three intermediate states 2p⁵3p′ [1/2]_1, 2p⁵3p′ [3/2]₂ and 2p⁵3p [5/2]₃ up to the 2p^{5 2}P_1/2 ionization threshold.     

Development and validation of a selective online dissolution method for rosiglitazone maleate

A new specific, accurate, precise, and reproducible selective online dissolution method for rosiglitazone maleate is developed and validated for the dissolution of rosiglitazone maleate in pharmaceutical formulations. The rationale of the method is based on the direct measurement of the absorbance of the analyte in the buffer medium at 242 nm using buffer as blank. Dissolution is achieved on a dissolution test apparatus consisting of photo diode array spectrophotometer, peristaltic pump, and temperature controller, using 0.01N HCl and 0.05M potassium chloride as the dissolution medium. The proposed method is developed, optimized, and validated in terms of linearity, reproducibility, accuracy, and selectivity for the dissolution of rosiglitazone maleate in pharmaceutical formulations. The method is found to be linear in the range of 1 to 14 microg/mL of rosiglitazone maleate with a correlation coefficient of 0.999. The dissolution studies of rosiglitazone maleate tablets obtained by the proposed method are in good agreement with those by high-performance liquid chromatography.     

Comparative study of 110mAg(I) removal from aqueous media by humic substances

Journal of Radioanalytical and Nuclear Chemistry - In this study, humic substances—dry cowdung powder and humic acid were used for the removal of precious metal ion Ag(I) from aqueous...     

pH‐Independent Recognition of the dG ⋅ dC Base Pair in Triplex DNA: 9‐Deazaguanine N7‐(2′‐Deoxyribonucleoside) and Halogenated Derivatives Replacing Protonated dC

Triplex-forming oligonucleotides (TFOs) containing 9-deazaguanine N⁷-(2′-deoxyribonucleoside) 1a and halogenated derivatives 1b,c were synthesized employing solid-phase oligonucleotide synthesis. For that purpose, the phosphoramidite building blocks 5a – c and 8a – c were synthesized. Multiple incorporations of 1a – c in place of dC were performed within TFOs, which involved the sequence of five consecutive 1a – c ⋅ dG ⋅ dC triplets as well as of three alternating 1a – c ⋅ dG ⋅ dC and dT ⋅ dA ⋅ dT triplets. These TFOs were designed to bind in a parallel orientation to the target duplex. Triplex forming properties of these oligonucleotides containing 1a – c in the presence of Na⁺ and Mg²⁺ were studied by UV/melting-curve analysis and confirmed by circular-dichroism (CD) spectroscopy. The oligonucleotides containing 1a in the place of dC formed stable triplexes at physiological pH in the case of sequence of five consecutive 1a ⋅ dG ⋅ dC triplets as well as three alternating 1a – c ⋅ dG ⋅ dC and dT ⋅ dA ⋅ dT triplets. The replacement of 1a by 9-halogenated derivatives 1b,c further enhanced the stability of DNA triplexes. Nucleosides 1a – c also stabilized duplex DNA.     

Investigation of the interaction between trazodone hydrochloride and bovine serum albumin

In this paper, the binding of trazodone hydrochloride (TZH) to bovine serum albumin (BSA) was investigated by spectroscopic (fluorescence, spectrophotometry and circular dichroism) techniques under simulative physiological conditions. A strong fluorescence quenching reaction of TZH to BSA was observed and the quenching mechanism was suggested as dynamic quenching according to the Stern-Volmer equation. The binding constants of TZH with BSA at 288, 302 and 309 K were calculated as (1.56±0.003)×10⁴, (2.31±0.002)×10⁴ and (5.44±0.004)×10⁴ M⁻¹, respectively. The thermodynamic parameters, ΔH⁰ and ΔS⁰ were obtained to be 39.86±0.008 kJ mol⁻¹ and 217.89±0.011 J mol⁻¹ K⁻¹, respectively, which indicated the presence of hydrophobic forces between TZH and BSA. The spectral results observed showed that the binding of TZH to BSA induced conformational changes in BSA. Based on the Förster's theory of non-radiation energy transfer, the binding average distance, r between donor (BSA) and acceptor (TZH) was found to be 2.4 nm. The effect of common ions on binding of TZH to BSA was also examined.