Characterization of gelatin nanofibers electrospun using ethanol/formic acid/water as a solvent

Gelatin nanofibers were prepared via electrospinning using aqueous solutions of formic acid and ethanol as the solvent instead of cytotoxic solvents. The resulting mat was further crosslinked with glutaraldehyde (GTA). The influence of the storing time on the viscosity and gel point of the solution was investigated. The gelatin nanofibers were examined using a field emission scanning electron microscope (FESEM) for the fiber size and morphology. The lowest diameter of gelatin fiber (85 nm, without beads) was achieved when the gelatin concentration was 20 wt% and electrospinning was conducted with a voltage of 20 kV over a distance of 10 cm at ambient temperature. The results from differential scanning calorimetry (DSC) showed that the softening temperature of gelatin nanofibers crosslinked with GTA was elevated. In addition, GTA‐crosslinked gelatin nanofibers exhibited cell compatibility for mouse mesangial cells (CRL 1927). Copyright © 2008 John Wiley & Sons, Ltd.     

An algorithm to determine a dipole current in a sphere

Suppose a spherical conductor has a single dipole. If it is assumed that the direction of current is perpendicular to the location of dipole, then we prove that the dipole can be obtained as an exact form from the induced magnetic field and provide an easy algorithm to locate the dipole from the samples of a magnetic field outside the sphere without using any series approximation. A numerical implementation is also presented. Copyright © 2006 John Wiley & Sons, Ltd.     

A “plug and play” polymer through biocomplementary hydrogen bonding

This article describes a DNA‐like polymer that exhibits the ability to self‐assemble through hydrogen bonding. We synthesized poly[1‐(4‐vinylbenzyl)thymine] (PVBT) and 9‐hexadecyladenine (A‐C16) through an atom transfer radical polymerization (ATRP) and alkylation, respectively. Biocomplementary PVBT/A‐C16 hierarchical supramolecular complexes formed in dilute DMSO solution through nucleobase recognition, that is, hydrogen bonding interactions between the thymine (T) groups of PVBT and the adenine (A) group of A‐C16; evidence for this molecular recognition was also gained from dynamic light scattering studies. ¹H NMR titration studies in CDCl₃ showed that T–A complexes formed rapidly on the NMR time scale with high association constants (up to 534 M^?1). Moreover, FTIR spectroscopic, differential scanning calorimetry, wide‐angle X‐ray diffraction, and small‐angle X‐ray scattering analyses provided further details into the nature of the self‐assembly of these systems. In the bulk state, these complexes self‐assemble into well‐ordered lamellar structures; the changing d‐spacing distance (ranging from 4.98 to 2.32 nm) at different A‐C16 loadings reveals that the molecular structures of the PVBT/A‐C16 complexes are readily tailored. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6416–6424, 2008     

Efficient initiators for the ring‐opening polymerization of L‐lactide: Synthesis and characterization of NNO‐tridentate Schiff‐base zinc complexes

A series of efficient catalysts, based on zinc alkoxides coordinated with NNO‐tridentate Schiff‐base ligands (L¹H‐L⁶H), for ring opening polymerization of L ‐lactide have been prepared. The reactions of diethyl zinc (ZnEt₂) with L¹H‐L⁶H yielded [(μ‐L)ZnEt]₂ ( 1a–6a ), respectively. Further reaction of compounds 1a–6a with benzyl alcohol (BnOH) produced the corresponding compounds of [LZn(μ‐OBn)]₂ ( 1b–6b), respectively. X‐ray crystal structural studies reveal that all of these compounds 1a–6a are dimeric bridging through the phenolato oxygen atoms of the Schiff‐base ligand. However, the molecular structures of 1b–6b show a dimeric character bridging through the benzylalkoxy oxygen atoms. Ring‐opening polymerization of L ‐lactide, initiated by 1b–6b , proceeds rapidly with good molecular weight control and yields polymer with a very narrow molecular weight distribution. Experimental results show that the substituents on the imine carbon of the NNO‐ligand affect the reactivity of zinc complexes dramatically. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6466–6476, 2008     

catena‐Poly­[[bis­(thio­cyanato‐N)lead(II)]‐μ‐1,2‐bis(4‐pyridyl)ethane‐N:N′]

In the title coordination polymer, [Pb(NCS)₂(C₁₂H₁₂N₂)], the coordination geometry about the Pb^II atom is a distorted octahedron, composed of two N atoms from bpe ligands [bpe is 1,2‐bis(4‐pyridyl)ethane], two other N atoms from NCS^? groups and two neighbouring S atoms through short contacts. The trans‐bpe ligands act as bridges between two Pb^II centres resulting in the formation of a linear chain. The terminal S atoms of the NCS^? ligands make short contacts with the Pb^II atom of neighbouring chains to form an infinite two‐dimensional polymeric structure.     

Synthesis of gold nanocomposite via chemisorption of gold nanoparticles with poly(p‐methylstyrene) containing multiple bonding groups on the chain side

Styrenic nanocomposite containing gold nanoparticles (AuNPs) has been synthesized by anchoring polymer molecules containing multiple functional groups onto the gold surface. p‐Methylstyrene was first anionically polymerized and the resulting polymer was chlorinated with sodium hypochlorite in the presence of a phase transfer catalyst. The chlorinated poly(p‐methylstyrene) was next reacted with methylthiomethyllithium, which had been prepared via a metalation reaction of dimethyl sulfide with n‐butyllithium, to form a styrenic polymer containing thioether groups on the sides of the molecule. These thioether groups on the chain sides afforded more chemisorption sites per molecule to AuNPs. The nanocomposite was analyzed using NMR, TEM, UV‐VIS, TGA, and XPS. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4710–4720, 2005     

An efficient and accurate non‐hydrostatic model with embedded Boussinesq‐type like equations for surface wave modeling

A novel approach that embeds the Boussinesq‐type like equations into an implicit non‐hydrostatic model (NHM) is developed. Instead of using an integration approach, Boussinesq‐type like equations with a reference velocity under a virtual grid system are introduced to analytically obtain an analytical form of pressure distribution at the top layer. To determine the size of vertical layers in the model, a top‐layer control technique is proposed and the reference location is employed to optimize linear wave dispersion property. The efficiency and accuracy of this NHM with Boussinesq‐type like equations (NHM‐BTE) are critically examined through four free‐surface wave examples. Overall model results show that NHM‐BTE using only two vertical layers is capable of accurately simulating highly dispersive wave motion and wave transformation over irregular bathymetry. Copyright © 2008 John Wiley & Sons, Ltd.     

Biaryl scaffold-focused virtual screening for anti-aggregatory and neuroprotective effects in Alzheimer’s disease

Background

Alzheimer’s disease (AD) is a primary cause of dementia in ageing population affecting more than 35 million people around the globe. It is a chronic neurodegenerative disease caused by defected folding and aggregation of amyloid beta (Aβ) protein. Aβ is formed by the cleavage of membrane embedded amyloid precursor protein (APP) by using enzyme ‘transmembrane aspartyl protease, β-secretase’. Inhibition of β-secretase is a viable strategy to prevent neurotoxicity in AD. Another strategy in the treatment of AD is inhibition of acetylcholinesterase. This inhibition reduces the degradation of acetylcholine and temporarily restores the cholinergic function of neurons and improves cognitive function. Monoamine oxidase and higher glutamate levels are also found to be linked with Aβ peptide related oxidative stress. Oxidative stress leads to reduced activity of glutamate synthase resulting in significantly higher level of glutamate in brain. The aim of this study is to perform in silico screening of a virtual library of biaryl scaffold containing compounds potentially used for the treatment of AD. Screening was done against the primary targets of AD therapeutics, acetylcholinesterase, β-secretase (BACE1), Monoamine oxidases (MAO) and N-Methyl-D-aspartate (NMDA) receptor. Compounds were screened for their inhibitory potential by employing molecular docking approach using AutoDock vina. Binding energy scores were embodied in the heatmap to display varies strengths of interactions of the ligands targeting AD.

Results

Several ligands showed notable interaction with at least two targets, but the strong interaction with all the targets is shown by very few ligands. The pharmacokinetics of the interacting ligands was also predicted. The interacting ligands have good drug-likeness and brain availability essential for drugs with intracranial targets.

Conclusion

These results suggest that biaryl scaffold may be pliable to drug development for neuroprotection in AD and that the synthesis of further analogues to optimize these properties should be considered.

     

Computer simulation to investigate absorption of energies of arrayed disk‐like nanoiron particles under magnetic fields

In this research, we focus on the studying of absorbed energies of materials under an external magnetic field frequency of 0.5 GHz. This wave corresponds to microwave irradiation. The absorbent materials were arrayed disk‐like iron particles with dimension on the nanometer scale and magnetic responses of the particles were simulated by solving the Landau–Lifshitz–Gilbert equation. The external fields were applied from various directions and energies of absorption of the system were calculated. The maximum absorbed energies were found when the field was 135° ± 30° along the X‐axis or the Y‐axis. The current simulation demonstrated that the direction of applied field results in different absorption energies of the system.