Inductive effect for the phase stability in hydrogen bonded liquid crystals,x-(p/m)BA:9OBAs

A new series of hydrogen bonded liquid crystal (HBLC) complexes, made up with substituted benzoic acids (BAs) and nonyloxy benzoic acid, viz., x-(p/m)BA:9OBAs are reported for x = F, Cl, Br and –CH₃ substituted at para (p) or meta (m) positions of BA moiety. Proton nuclear magnetic resonance (¹H-NMR) spectrum confirms the HBLC complex. Infra red (IR) spectrum confirms linear, double and complementary type of hydrogen bonding (HB) between x-(p/m)BAs and 9OBA. The liquid crystal (LC) phases are characterised by polarisation optical microscopy (POM) and differential scanning calorimetry (DSC) techniques. x-(p/m)BA:9OBA exhibit N, C and G LC phase variance. HB induces tilted phases and enhances LC phase stability. The influence of configuration, size, electronegativity, electron directing capacity and inductive nature of substituent (x) is investigated for the stability of LC phases. An overview of the LC phase data indicates predominant ‘negative inductive effect’ in HBLCs with electron withdrawing substituents. Inductive effect operates effectively for para substitutions. Results are discussed in the wake of reports in other HBLCs.     

Influence of hydrogen bonding on phase abundance in ferroelectric liquid crystals

The synthesis and characterization of five hydrogen-bonded ferroelectric liquid crystal complexes (HBFLCs) prepared from mesogenic p-n-alkoxy benzoic acids and non-mesogenic propionic/butyric acids with different chiral centres are reported. Complementary intermolecular hydrogen bonding is confirmed through IR study. HBFLCs are found to exhibit chiral nematic (N*), smectic C* (SmC*) and smectic G* (monotropic) phases in their cooling profiles during polarizing thermal microscopy and differential scanning calorimetry. Phase coexistence regions are observed above the IN* transition. The chiral nematic to smectic C* transition is found to be of first order. The temperature variation of spontaneous polarization exhibited by these HBFLC complexes in their SmC* phase is presented. The effect of non-covalent interaction imparted by the soft hydrogen bonding in these LC complexes on enhanced or induced thermal stability of tilted LC phases is discussed.     

Potential constants and mean amplitudes of vibrations of N-methyl acetamide

A normal co-ordinate treatment based on general quadratic forcefield has been applied to N-methyl acetamide molecule. In these calculations, the structure parameters of N-methyl acetamide, as given recently by Katzet al., and the Raman and infra-red data obtained by the authors are used and the potential constants have been obtained. The potential energy distribution among the various symmetry co-ordinates of each normal vibration and the mean amplitudes of vibrations have been calculated.     

Insights on Aggregation of Hen Egg-White Lysozyme from Raman Spectroscopy and MD Simulations

Protein misfolding and aggregation play a significant role in several neurodegenerative diseases. In the present work, the spontaneous aggregation of hen egg-white lysozyme (HEWL) in an alkaline pH 12.2 at an ambient temperature was studied to obtain molecular insights. The time-dependent changes in spectral peaks indicated the formation of β sheets and their effects on the backbone and amino acids during the aggregation process. Introducing iodoacetamide revealed the crucial role of intermolecular disulphide bonds amidst monomers in the aggregation process. These findings were corroborated by Molecular Dynamics (MD) simulations and protein-docking studies. MD simulations helped establish and visualize the unfolding of the proteins when exposed to an alkaline pH. Protein docking revealed a preferential dimer formation between the HEWL monomers at pH 12.2 compared with the neutral pH. The combination of Raman spectroscopy and MD simulations is a powerful tool to study protein aggregation mechanisms.     

Vibrational spectra and normal vibrations of acetanilide and N-deuterated acetanilide

The Raman and infra-red spectra of acetanilide and N-methylacetamide and of their N-deuterated compounds have been recorded. The vibrational frequencies of acetanilide have been assigned and the nature of the Amide I, II and III bands in acetanilide and N-methylacetamide has been investigated by the study of the changes in the frequencies of these bands in the spectra of their deuterated compounds. Acetanilide and deuterated acetanilide molecules have been subjected to normal co-ordinate treatment and the mixing up of the skeletal frequencies arising out of the in-plane vibrations has been determined. These results indicate that as in secondary amides, the amide II and amide III bands in acetanilide are due to the combined contribution ofδ (NH) andν (C-N) vibrations, but the contribution ofν (C-N) to the amide II band is less in acetanilide and deuterated acetanilide than in cases of N-methylacetamide and deuterated N-methylacetamide.     

Bioanalysis of tolvaptan,a novel AVP‐V2 receptor antagonist in human plasma by a novel LC‐ESI‐MS/MS method: a pharmacokinetic application in healthy South Indian male subjects

A simple, rapid and sensitive liquid chromatography/electrospray ionization tandem mass spectrometry (LC‐ESI‐MS/MS) assay method is proposed for the determination of tolvaptan in human plasma samples using tolvaptan d₇ as internal standard (IS). Analyte and the IS were extracted from 100 μL of human plasma via simple liquid–liquid extraction. The chromatographic separation was achieved on a C₁₈ column using a mixture of methanol and 0.1% formic acid buffer (80:20, v/v) as the mobile phase at a flow rate of 1.0 mL/min. The calibration curve obtained was linear (r² ≥ 0.99) over the concentration range of 0.05–501 ng/mL. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. The intra‐day and inter‐day precision (coefficient of variation) and accuracy results in three validation batches across five concentration levels were well within the acceptance limits. A run time of 2.0 min for each sample made it possible to analyze more samples in a short time, thus increasing the productivity. The proposed method was successfully applied to a pharmacokinetic study of 15 mg and 60 mg tolvaptan tablet formulation in healthy South Indian male subjects under fasting condition. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis, spectral characterization and biological activities of Mn(II) and Co(II) complexes with benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone

Mn(II) and Co(II) complexes of benzyloxybenzaldehyde-4-phenyl-3-thiosemicarbazone have been synthesized and characterized by the investigations of electronic and EPR spectra and X-ray diffraction. Based on the spectral studies, an octahedral geometry is assigned for the Mn(II) and Co(II) complexes. X-ray powder diffraction studies reveal that Mn(II) and Co(II) complexes have triclinic crystal lattices. The unit cell parameters of the Mn(II) complex are a=11.0469 ?, b=6.2096 ?, c=7.4145 ?, α=90.646°, β=95.127°, γ=104.776°, V=489.7 ?(3) and those of Co(II) complex are a=9.3236 ?, b=10.2410 ?, c=7.8326 ?, α=90.694°, β=99.694°, γ=100.476°, V=724.2 ?(3). When the free ligand and its metal complexes are subjected to antibacterial activity, the metal complexes are proved to be more active than the ligand. However with regard to in vitro antioxidant activity, the ligand exhibits greater antioxidant activity than its metal(II) complexes.     

Writing low-loss waveguides in borosilicate (BK7) glass with a low-repetition-rate femtosecond laser

Borosilicate glass (BK7) is a widely-used material in integrated optics devices and in the optical communications industry. We report on laser-written waveguiding in BK7 glass using a low-repetition-rate (1 kHz) laser producing 40 fs pulses of 800 nm light. A 500 μm slit is used to write structures 100 μm below the glass surface. These waveguides show strong guidance at 635 nm, with an index contrast of 3 × 10^− 4 and a propagation loss of ~ 0.5 dB/cm. We measured the change in refractive index for a range of writing conditions as quantified in terms of energy dose; there is an energy dose window (> 0.6 μJ μm^− 3 and < 1.5 μJ μm^− 3) within which the written structures show guidance.