Synthesis of novel pyrimidine nucleoside analogues owning multiple bases/sugars and their glycosidase inhibitory activity

A series of novel nucleoside analogues having dual bases (pyrimidine and triazole) and sugars have been synthesized by CuAAC reaction of azido sugars with propynylated pyrimidines. These compounds were evaluated for their in vitro α-glucosidase inhibitory activity. In this series, compounds 4b, 4d, 8a, 8b, 8c, 8e, 8g, 8h, and 8i exhibited very good inhibition of α-glucosidase enzyme. Nucleoside analogues 8a, 4b, 8h, and 8c displayed 47.4%, 41.8%, 39.4%, and 34.6% inhibition, respectively, comparable to the standard drug acarbose (53.4%).     

Direct Synthesis of Hexagonal NaGdF4 Nanocrystals from a Single‐Source Precursor: Upconverting NaGdF4:Yb3+,Tm3+ and Its Composites with TiO2 for Near‐IR‐Driven Photocatalysis

A novel single‐source precursor NaGd(TFA)₄(diglyme) (TFA=trifluoroacetate) was synthesized, characterized thoroughly, and used to obtain the hexagonal phase of NaGdF₄ nanoparticles as an efficient matrix for lanthanide‐doped upconverting nanocrystals (NCs) that convert near‐infrared radiation into shorter‐wavelength UV/visible light. These NCs were then used to prepare well‐characterized TiO₂@NaGdF₄:Yb³⁺,Tm³⁺ nanocomposites to extend the absorption range of the TiO₂ photocatalyst from the UV to the IR region. While the visible/near IR part of the photoluminescent spectra remains almost unaffected by the presence of TiO₂, the UV part is strongly quenched due to the absorption of TiO₂ above its gap at approximately 380 nm by energy transfer or FRET. Preliminary results on the photocatalytic activity of the above obtained nanocomposites are presented.     

Polymers from Renewable Resources. Xiv. Interpenetrating Polymer Networks Derived from Castor Oil—Isophorone Diisocyanate-Polyacrylamide: Thermal,Scanning Electron Microscopy,and Xrd Studies

Abstract

A large number of castor oil based polyurethanes were prepared using various diisocyanates such as isophorone diisocyanate varying the NCO/OH ratio. All the polyurethanes were reacted with acrylamide and methacrylamide using ethylene glycol dimethacrylate as crosslinker and benzoyl peroxide as initiator. Thermogravimetric analysis of the polymers were followed using computer analysis method for assigning the kinetic mechanism. The degradation steps have been discussed in the light of kinetic parameters. The SEM of some of the IPNs has been studied and the morphology has been examined. The samples were subjected to wide angle X-ray diffraction analysis. Ruland and Vonk method was used to calculate the degree of crystallinity (X_cr).     

Ethylene-vinyl acetate (EVA)/polycaprolactone (PCL)–Fe3O4 composites

In this study, we investigate the effect of nano sized Fe₃O₄ nanoparticles on the mechanical and thermal properties of EVA/PCL–Fe₃O₄ composites. Composites were prepared using the melt mixing technique on a Rheomex mixer coupled to a single screw extruder. The fine dispersion of nano-Fe₃O₄ aggregates in the polymer matrices led to a significant improvement in the crystallinity, thermal and mechanical properties of EVA/PCL–Fe₃O₄ nanocomposites compared to that of native polymers due to improved interface bonding between the filler and the polymer matrix. Techniques such as scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Instron for mechanical properties were used to characterize nanocomposites samples. The results obtained from this investigation demonstrated that composite materials could be promising raw materials in industry.     

Spin Filtering Along Chiral Polymers

Spin‐dependent conduction and polarization in chiral polymers were studied for polymers organized as self‐assembled monolayers with conduction along the polymer backbone, namely, along its longer axis. Large spin polarization and magnetoresistance effects were observed, showing a clear dependence on the secondary structure of the polymer. The results indicate that the spin polarization process does not include spin flipping and hence it results from backscattering probabilities for the two spin states.     

Fabrication of 3D polymeric photonic arrays and related applications

This review article describes the state-of-art methodologies, mainly self-assembly routes, which are in practice to fabricate photonic crystals (PCs) for advanced applications. The self-assembly of colloidal building blocks is an effective, affordable, and tunable approach to fabricate varieties of photonic materials of desired shapes and surface areas. Because of easy fabrication and controlled performance factors, PCs emerged as a potential platform for designing and developing optical devices with desired features such as photonic bandgap, high reflectance/transmittance, low loss, and lasing in the visible range of wavelengths. To develop next-generation optoelectronics and optical system, significant efforts are being made to explore novel and cost-effective fabrication methods to design and develop 3D-PCs platform, which is covered in this mini-review. The challenges, potential alternatives, and prospects of self-assembled 3D PCs are also discussed in this review.     

Thermodynamic stability of RECl3·xH2O (RE = Ce,Pr) determined by dynamic transpiration technique

Journal of Thermal Analysis and Calorimetry - In the present study, decomposition mechanism of CeCl3·xH2O(s) and PrCl3·xH2O(s) was investigated using thermogravimetry, differential...     

Insights into Molecular Assembly of ACCase Heteromeric Complex in Chlorella variabilis—A Homology Modelling, Docking and Molecular Dynamic Simulation Study

Acetyl-CoA carboxylase (ACCase), a biotin-dependent enzyme that catalyses the first committed step of fatty acid biosynthesis, is considered as a potential target for improving lipid accumulation in oleaginous feedstocks, including microalgae. ACCase is composed of three distinct conserved domains, and understanding the structural details of each catalytic domain assumes great significance to gain insights into the molecular basis of the complex formation and mechanism of biotin transport. In the absence of a crystal structure for any single heteromeric ACCase till date, here we report the first heteromeric association model of ACCase from an oleaginous green microalga, Chlorella variabilis, using a combination of homology modelling, docking and molecular dynamic simulations. The binding site of the docked biotin carboxylase (BC) and carboxyltransferase (CT) were predicted to be contiguous but distinct in biotin carboxyl carrier protein (BCCP) molecule. Simulation studies revealed considerable flexibility for the BC and CT domains in the BCCP-bound forms, thus indicating the adaptive behaviour of BCCP. Further, principal component analysis revealed that in the presence of BCCP, the BC and CT domains exhibited an open-state conformation via the outward clockwise rotation of the binding helices. These conformational changes might be responsible for binding of BCCP domain and its translocation to the respective active sites. Various rearrangements of inter-domain hydrogen bonds (H-bonds) contributed to conformational changes in the structures. H-bond interactions between the interacting residue pairs involving Glu201BCCP/Arg255BC and Asp224BCCP/Gln228CT were found to be essential for the intermolecular assembly. The present findings are consistent with previous biochemical studies.     

Nanoporous alumina (γ- and α-phase) gel cast thick film for the development of trace moisture sensor

In this study, erbia (Er₂O₃)-doped Bi₂O₃ ceramics were prepared from sol–gel derived nanocrystalline powders. The morphological properties were investigated by scanning electron microscopy. X-ray diffraction (XRD) analysis was carried out in order to characterize the phase and crystal structure of the powder samples. Temperature dependent electrical properties were determined by thermogravimetry/differential thermal analyzer (TG/DTA) and 4-point probe techniques. The stable fluorite face centered cubic δ-type phase was observed at room temperature from the XRD result, which was supported by the DTA and temperature dependent electrical conductivity measurements. Electrical conductivity results indicate that there is a transition approximately at 650 °C, which can be attributed to an order–disorder transition (ODT). The activation energy values obtained from the Arrhenius approach for heating and cooling process were presented. Two regimes, corresponding to high temperature region (HTR) and low temperature region (LTR), were observed. As a result of morphological changes during the ODT, the electrical conductivity modifies and the activation energies are different for studied sample at HTR and LTR.