The role of molecular shape in bilayer elasticity and phase behavior

A previously developed molecular level model for lipid bilayers [G. Brannigan and F. L. H. Brown, J. Chem. Phys. 120, 1059 (2004)] is extended to allow for variations in lipid length and simulations under constant surface tension conditions. The dependence of membrane elasticity on bilayer thickness is obtained by adjusting lipid length at constant temperature and surface tension. Additionally, bilayer fluidity at various lipid lengths is quantified by analysis of a length versus temperature phase diagram at vanishing tension. Regions of solid, gel-like (hexatic) and fluid bilayer behavior are established by identification of phase boundaries. The main melting transition is found to be density driven; the melting temperature scales inversely with lipid length since thermal expansion increases with lipid aspect ratio.     

Glabridin,a Stable Flavonoid of Glycyrrhiza glabra: HPTLC Analysis of the Traditional Formulation

JPC – Journal of Planar Chromatography – Modern TLC - A novel HPTLC method has been developed for the estimation of glabridin in Licorice rhizome and its Unani polyherbal formulation...     

Effect of hydrophobic and hydrophilic additives on sol–gel transition and release behavior of timolol maleate from polycaprolactone-based hydrogel

The objective of this work was to delineate the effect of hydrophilic and hydrophobic polymeric additives on sol–gel transition and release profile of timolol maleate (TM) from poly (ethylene glycol)–poly (ε-caprolactone)–poly (ethylene glycol) (PEG–PCL–PEG)-based thermosensitive hydrogel. Polycaprolactone (hydrophobic additive) and polyvinyl alcohol (PVA) (hydrophilic additive) reduced critical gel concentration of PEG–PCL–PEG triblock polymer. The effect of PCL on sol–gel transition was more pronounced than PVA. However, with PCL no statistically significant difference in release profile was observed. The effect of PVA on release profile was more pronounced, which reduced the cumulative percentage release of TM from 86.4 ± 0.8% to 73.7 ± 1.8% over 316 h. Moreover, cytotoxicity of the hydrogel was also investigated utilizing rabbit primary corneal epithelial culture cells. No significant cytotoxicity of hydrogel alone or in presence of additives was observed. So, polymeric additive strategy serves as a valuable tool for optimizing TM release kinetics from PEG–PCL–PEG hydrogel matrix.     

A study of resveratrol-copper complexes by electrospray ionization mass spectrometry and density functional theory calculations

Resveratrol is a polyphenolic compound found in plants and human foods which has shown biological activities including chemoprevention, acting through a mechanism which involves the reduction of Cu(II) species. By electrospray ionization (ESI) mass spectrometry we have produced and detected the resveratrol-copper complexes [Resv+Cu](+), [Resv+Cu+H(2)O](+) and [2Resv+Cu](+) by using a resveratrol/CuSO(4) solution in CH(3)CN/H(2)O. The most stable structures of the detected complexes have been calculated at the B3LYP/6-311G(d) level of theory. Resveratrol interacts with the copper ion through nucleophilic carbon atoms on the aromatic ring and the alkenyl group. The fact that only singly charged ions were observed implies that Cu(II) is reduced to Cu(I) in the ESI process. For investigating the structure-reactivity correlation, we have carried out a similar study on the synthetic analogue dihydroresveratrol (DHResv). For the latter only the [DHResv+Cu](+) complex has been detected.     

Adhesion and stress of magnesium oxide thin films: Effect of thickness, oxidation temperature and duration

Nanoscale magnesium oxide thin films have been deposited on glass substrate by thermal oxidation (in air) of vacuum evaporated magnesium films. X-ray diffraction (XRD) showed orientation along (2 0 0) and (2 2 0) directions. The mechanical properties of the MgO thin films were found to be the function of thickness (300, 450 and 600 nm), oxidation temperature (573, 623 and 673 K) and oxidation duration (90 and 180 min). As oxidation temperature and oxidation duration increases, adhesion and intrinsic stress were found to increase. Intrinsic stress decreased whereas adhesion increased due to increase in thin film thickness. The value of intrinsic stress was in range 28.902-73.212 (×10⁷ N/m²) and that of adhesion was 12.1-27.4 (×10⁴ N/m²) for the thin film of thickness 300 nm.     

Novel pentablock copolymer (PLA–PCL–PEG–PCL–PLA)-based nanoparticles for controlled drug delivery: effect of copolymer compositions on the crystallinity of copolymers and in vitro drug release profile from nanoparticles

The purpose of this investigation was to design novel pentablock copolymers (polylactide–polycaprolactone–polyethylene glycol–polycaprolactone–polylactide) (PLA–PCL–PEG–PCL–PLA) to prepare nanoparticle formulations which provide continuous delivery of steroids over a longer duration with minimal burst effect. Another purpose was to evaluate the effect of poly(l-lactide) (PLLA) and poly(d,l-lactide) (PDLLA) incorporation on crystallinity of pentablock copolymers and in vitro release profile of triamcinolone acetonide (selected as model drug) from nanoparticles. PLA–PCL–PEG–PCL–PLA copolymers with different block ratio of PCL/PLA segment were synthesized. Release of triamcinolone acetonide from nanoparticles was significantly affected by crystallinity of the copolymers. Burst release of triamcinolone acetonide from nanoparticles was significantly minimized with incorporation of proper ratio of PDLLA in the existing triblock (PCL–PEG–PCL) copolymer. Moreover, pentablock copolymer-based nanoparticles exhibited continuous release of triamcinolone acetonide. Pentablock copolymer-based nanoparticles can be utilized to achieve continuous near–zero-order delivery of corticosteroids from nanoparticles without any burst effect.     

Intramolecular Cyclization of Carbonate and Thiocarbonate Derivatives of myo‐Inositol in the Solid State: Implications for Acyl Group Transfer Reactions in Molecular Crystals

Racemic 4‐O‐phenoxycarbonyl and 4‐O‐phenoxythiocarbonyl derivatives of myo‐inositol orthoformate undergo thermal intramolecular cyclization in the solid state to yield the corresponding 4,6‐bridged carbonates and thiocarbonates, respectively. The thermal cyclization also occurs in the solution and molten states, but less efficiently, suggesting that these cyclization reactions are aided by molecular pre‐organization, although not strictly topochemically controlled. Crystal structures of two carbonates and a thiocarbonate clearly revealed that the relative orientation of the electrophile and the nucleophile in the crystal lattice facilitates the intramolecular cyclization reaction and forbids the intermolecular reaction. The correlation observed between the chemical reactivity and the non‐covalent interactions in the crystal of the reactants provides a way to estimate the chemical stability of analogous molecules in the solid state.     

Nanostructured microspheres of silver @ zinc oxide: an excellent impeder of bacterial growth and biofilm

Au@TiO₂ core–shell hollow nanoparticles were prepared by a simple hydrothermal method without surfactants or templates. The core–shell structure materials were characterized by transmission electron microscopy, X-ray powder diffraction, scanning electron microscopy, and specific surface area of the test (BET). The catalytic activity was tested in a stainless reactor with a fixed bed and connected with a gas chromatograph. The results show that the microstructure, crystallography, and morphology were correlated with the hydrothermal reaction time and temperature, and the properties of the solvent. The crystallinity degree of TiO₂ and the particle size increased with the reaction time and temperature. Particles with different morphologies can be obtained when using different solvents. The size of microsphere can be controlled easily by changing the amount of TiF₄. This material exhibited the complete CO conversion temperature to be about 130 °C and no deactivation was observed after 1,000 min reaction.     

Identification of Molecular Crystals Capable of Undergoing an Acyl‐Transfer Reaction Based on Intermolecular Interactions in the Crystal Lattice

Investigation of the intermolecular acyl‐transfer reactivity in molecular crystals of myo‐inositol orthoester derivatives and its correlation with crystal structures enabled us to identify the essential parameters to support efficient acyl‐transfer reactions in crystals: 1) the favorable geometry of the nucleophile (? OH) and the electrophile (C?O) and 2) the molecular assembly, reinforced by C? H???π interactions, which supports a domino‐type reaction in crystals. These parameters were used to identify another reactive crystal through a data‐mining study of the Cambridge Structural Database. A 2:1 co‐crystal of 2,3‐naphthalene diol and its di‐p‐methylbenzoate was selected as a potentially reactive crystal and its reactivity was tested by heating the co‐crystals in the presence of solid sodium carbonate. A facile intermolecular p‐toluoyl group transfer was observed as predicted. The successful identification of reactive crystals opens up a new method for the detection of molecular crystals capable of exhibiting acyl‐transfer reactivity.     

Room-Temperature Ionic Liquid–DMSO Promoted and Improved One-Pot Synthesis of 5,6-Diaryl-1,2,4-triazines

An improved and rapid one-pot synthesis of 5,6-diarylsubstituted-1,2,4-triazines in a mixture of room-temperature ionic liquid 1,3-dibutylimidazolium bromide [Bbim]⁺Br^? and dimethylsulfoxide (DMSO) is described without the need for any added catalyst. Different polar aprotic solvents were screened along with ionic liquids and a synergistic effect with DMSO has been found. The predominance of one regioisomer over the other has also been studied with varying reaction temperatures. The one-pot methodology leading to excellent isolated yields in short span of time is achieved by simple workup procedure. The ionic liquid was efficiently recovered and reused three times without the loss of catalysis. All the compounds were characterized by infrared, NMR, mass spectrometry, and elemental analysis.