DFT study of acceleration of electrocyclization in photochromes under radical cationic conditions: Comparison with recent experimental data

Radical cation formation is proposed for the rapid cyclization of 1, 2-bis[5-phenyl-2-methylthien-3-yl]cyclopentene and oligothiophene functionalized dimethyldihydropyrenes (DMDHP). Density functional theory calculations have been performed to rationalize the effect of a radical cation on the activation barrier of different classes of electrocyclic photochromes (DHP, dithienylethene, dihydroazulene and fulgide). For exact comparative analysis, the activation barrier of neutral (singlet) analogues at the same level of theory are also calculated. In addition, the concerted nature and aromaticity of transition states were investigated with the help of synchronicity (Sy.) and nuclear independent chemical shift values NICS(0) calculations, respectively, for both the radical cation and neutral systems. In case of the radical cation, thermal return of CPD to DHP, the activation barrier is very low (ΔH = 3.13 kcal mol^?1, ΔG = 4.01 kcal mol^?1) as compared to the neutral analogue (ΔH = 20.6 kcal mol^?1, ΔG = 20.98 kcal mol^?1), which is consistent with experimental observations. Similarly for dithenylethenes, radical cation formation has a large impact on the activation barrier (ΔH = 19.44 kcal mol^?1, ΔG = 22.29 kcal mol^?1). However, radical cation formation has almost negligible impact on the activation barrier of VHF-DHA and fulgide isomerization. The significant difference has been observed for synchronicity and NICS(0) values of all types of photochromes under radical cation conditions as compared to the neutral system.     

Chemical and structural characterization of α-N-acetylgalactosaminidase I and II from starfish, <Emphasis Type="Italic">asterina amurensis</Emphasis>

Background

The marine invertebrate starfish was found to contain a novel α-N-acetylgalactosaminidase, α-GalNAcase II, which catalyzes removal of terminal α-N-acetylgalactosamine (α-GalNAc), in addition to a typical α-N-acetylgalactosaminidase, α-GalNAcase I, which catalyzes removal of terminal α-N-acetylgalactosamine (α-GalNAc) and, to a lesser extent, galactose. The interrelationship between α-GalNAcase I and α-GalNAcase II and the molecular basis of their differences in substrate specificity remain unknown.

Results

Chemical and structural comparisons between α-GalNAcase I and II using immunostaining, N-terminal amino acid sequencing and peptide analysis showed high homology to each other and also to other glycoside hydrolase family (GHF) 27 members. The amino acid sequence of peptides showed conserved residues at the active site as seen in typical α-GalNAcase. Some substitutions of conserved amino acid residues were found in α-GalNAcase II that were located near catalytic site. Among them G171 and A173, in place of C171 and W173, respectively in α-GalNAcase were identified to be responsible for lacking intrinsic α-galactosidase activity of α-GalNAcase II. Chemical modifications supported the presence of serine, aspartate and tryptophan as active site residues. Two tryptophan residues (W16 and W173) were involved in α-galactosidase activity, and one (W16) of them was involved in α-GalNAcase activity.

Conclusions

The results suggested that α-GalNAcase I and II are closely related with respect to primary and higher order structure and that their structural differences are responsible for difference in substrate specificities.

     

Improved antibacterial activity of HAP garlanded PLGA ultrafine fibers incorporated with CuO: synthesis and characterization

Well-organized nanocrystalline hydroxyapatite nanoparticles garlanded poly(dl-lactide-co-glycolide) (PLGA) ultrafine fibers with efficient antibacterial properties are of great interest in the development of new products. In the present study, hydroxyapatite doped PLGA ultrafine fibers incorporated with copper oxide nanocrystals were fabricated via two step methodology. Primarily; copper oxide nanocrystals were synthesized using wet chemical method. Then the as-synthesized nanocrystals were used for the preparation of composite fibers using electrospinning technique. The properties of pure and composite ultrafine fibers were characterized using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, and electron probe mapping analysis. The in vitro antimicrobial activity of synthesized pure and hydroxyapatite doped PLGA ultrafine fibers was investigated against model organism Escherichia coli (gram negative) using optical density method and morphological damage was observed by TEM. Ultrafine fibers with average diameter ranges from 1.0 to 1.2 μm were obtained. Uniform distribution of hydroxyapatite was observed. Admirable antimicrobial activity against E. coli was achieved which could be attributed by the synergy between hydroxyapatite and copper oxide. In contrast to pristine PLGA, lower concentrations of hydroxyapatite–copper oxide doped PLGA nanocomposite were needed to strongly inhibit the growth of E. coli. Our results report successful preparation of hydroxyapatite–copper oxide based novel nanocomposite. The developed hybrid nanocomposite possess exceptionally good antibacterial activity against E. coli due to the synergistic effect of hydroxyapatite and copper oxide. The antimicrobial nanocomposite can be utilized for a range of bio-functional purposes such as a good candidate for water purification, antibiofouling, wound dressings and bone tissue engineering etc.     

7β-(3-Ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z Notonipetranone Attenuates Neuropathic Pain by Suppressing Oxidative Stress,Inflammatory and Pro-Apoptotic Protein Expressions

7β-(3-Ethyl-cis-crotonoyloxy)-1α-(2-methylbutyryloxy)-3,14-dehydro-Z-notonipetranone (ECN), a sesquiterpenoid obtained from a natural source has proved to be effective in minimizing various side effects associated with opioids and nonsteroidal anti-inflammatory drugs. The current study focused on investigating the effects of ECN on neuropathic pain induced by partial sciatic nerve ligation (PSNL) by mainly focusing on oxidative stress, inflammatory and apoptotic proteins expression in mice. ECN (1 and 10 mg/kg, i.p.), was administered once daily for 11 days, starting from the third day after surgery. ECN post-treatment was found to reduce hyperalgesia and allodynia in a dose-dependent manner. ECN remarkably reversed the histopathological abnormalities associated with oxidative stress, apoptosis and inflammation. Furthermore, ECN prevented the suppression of antioxidants (glutathione, glutathione-S-transferase, catalase, superoxide dismutase, NF-E2-related factor-2 (Nrf2), hemeoxygenase-1 and NAD(P)H: quinone oxidoreductase) by PSNL. Moreover, pro-inflammatory cytokines (tumor necrotic factor-alpha, interleukin 1 beta, interleukin 6, cyclooxygenase-2 and inducible nitric oxide synthase) expression was reduced by ECN administration. Treatment with ECN was successful in reducing the caspase-3 level consistent with the observed modulation of pro-apoptotic proteins. Additionally, ECN showed a protective effect on the lipid content of myelin sheath as evident from FTIR spectroscopy which showed the shift of lipid component bands to higher values. Thus, the anti-neuropathic potential of ECN might be due to the inhibition of oxidative stress, inflammatory mediators and pro-apoptotic proteins.     

Effect of Currently Available Nanoparticle Synthesis Routes on Their Biocompatibility with Fibroblast Cell Lines

Nanotechnology has acquired significance in dental applications, but its safety regarding human health is still questionable due to the chemicals utilized during various synthesis procedures. Titanium nanoparticles were produced by three novel routes, including Bacillus subtilis, Cassia fistula and hydrothermal heating, and then characterized for shape, phase state, size, surface roughness, elemental composition, texture and morphology by SEM, TEM, XRD, AFM, DRS, DLS and FTIR. These novel titanium nanoparticles were tested for cytotoxicity through the MTT assay. L929 mouse fibroblast cells were used to test the cytotoxicity of the prepared titanium nanoparticles. Cell suspension of 10% DMEM with 1 × 10⁴ cells was seeded in a 96-well plate and incubated. Titanium nanoparticles were used in a 1 mg/mL concentration. Control (water) and titanium nanoparticles stock solutions were prepared with 28 microliters of MTT dye and poured into each well, incubated at 37 °C for 2 h. Readings were recorded on day 1, day 15, day 31, day 41 and day 51. The results concluded that titanium nanoparticles produced by Bacillus subtilis remained non-cytotoxic because cell viability was >90%. Titanium nanoparticles produced by Cassia fistula revealed mild cytotoxicity on day 1, day 15 and day 31 because cell viability was 60–90%, while moderate cytotoxicity was found at day 41 and day 51, as cell viability was 30–60%. Titanium nanoparticles produced by hydrothermal heating depicted mild cytotoxicity on day 1 and day 15; moderate cytotoxicity on day 31; and severe cytotoxicity on day 41 and day 51 because cell viability was less than 30% (p < 0.001). The current study concluded that novel titanium nanoparticles prepared by Bacillus subtilis were the safest, more sustainable and most biocompatible for future restorative nano-dentistry purposes.     

Mercury meniscus on solid silver amalgam electrode as a sensitive electrochemical sensor for tetrachlorvinphos

The in-house prepared mercury meniscus modified solid silver amalgam electrode (m-AgSAE) was successfully applied for the detection of organophosphate pesticide tetrachlorvinphos in pH 7 buffer solution. The electrochemical performance of m-AgSAE for the reduction of tetrachlorvinphos was evaluated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV), respectively. The surface morphology of solid silver electrode (AgE), as-amalgamated solid silver amalgam electrode (AgSAE), and polished solid silver amalgam electrode (p-AgSAE) was examined by field emission scanning electron microscopy (FESEM). Among the applied techniques, DPV and SWV analysis showed a remarkable increase in the reduction peak current and provided a simple, fast, and sensitive method for the determination of tetrachlorvinphos. The electrochemical impedance spectroscopy (EIS) was used to correlate the electrocatalytic activity of AgSAE, p-AgSAE and m-AgSAE with their interfacial charge transport capabilities. Under the optimized experimental conditions, the DPV and SWV responses were linear over the 1–9 μM and 10–50 μM concentration ranges with a detection limit of 0.06 μM for DPV and 0.04 for SWV. The estimation of tetrachlorvinphos in the ground and waste water samples with the proposed method was in good agreement with that of the added amount. The proposed electrochemical method not only extends the application of non-toxic m-AgSAE, but also offers new possibilities for fast and sensitive analysis of tetrachlorvinphos and its structural analogs in environmental samples.     

Mode matching analysis for wave scattering in triple and pentafurcated spaced ducts

We present solutions to both trifurcated and pentafurcated spaced waveguides using the mode matching (or eigenfunction expansion) method. While the trifurcated problem with mean fluid flow has been solved previously using the Wiener–Hopf technique, we solve this problem to validate and demonstrate our method. We then show how we can easily generalize the method to the pentafurcated problem that has not been solved previously. We observe that mode matching method is easier to derive and generalize than the Wiener–Hopf technique. We also investigate the numerical solution in detail for various geometries to model practical exhaust systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Marrusidins A and B,New Epimeric Labdane Diterpenes from Marrubium anisodon

Marrusidins A ( 1 ) and B ( 2 ), two new labdane‐type diterpenes, were isolated from the CHCl₃‐soluble subfraction of Marrubium anisodon, along with polyodonine. Their structures were assigned with the aid of ¹H‐ and ¹³C‐NMR spectra and by COSY, HMQC, NOESY, and HMBC experiments.     

Identification of the representative crack length evolution in a multi-level interface model for quasi-brittle masonry

It is proposed here to identify the law of crack length evolution with a small number of parameters governing a recently presented model (Rekik and Lebon, submitted for publication) describing the interface behavior in damaged masonry. Studies on non-confined medium- and large-sized masonry structures have shown that it is necessary to obtain a linear increasing crack in the post-peak part of the “stress–strain or –displacement” diagram. In confined masonry structures showing softening and sliding parts, the results obtained with this crack evolution failed to match the experimental data. The crack lengths identified in the post-peak part at several points on the experimental “stress–displacement” diagram show that the representative crack length is a bilinear or trilinear function describing the increase in the crack length with respect to the decrease in the shear stress. Numerical studies on medium- and large-sized masonry structures consisting of the same materials subjected to various loads were performed to determine the ultimate crack length, and the results are relatively insensitive to the size of the masonry and the type of the load applied. The numerical local fields determined in the elementary and full-scale structures investigated were used to test the validity of the present model at the local scale, as well as to obtain an additional unilateral condition in the case of compressed masonry structures in order to prevent overlapping between the masonry components.     

STUDIES OF MIXED LIGAND COMPLEXES FROM DIALKYLDITHIOPHOSPHATE AND THIOSEMICARBAZIDE OR THIOSEMICARBAZONES WITH NICKEL(II)

The complexes [Ni{(RO)₂PS₂}₂Tsc], [Ni{(RO)₂PS₂}₂ApTsc], and [Ni{(RO)₂PS₂}FurTsc.2H₂O] where R = methyl (Me), ethyl (Et) or propyl (Prop); Tsc = thiosemicarbazide, ApTsc = 2-acetylpyridine-thiosemicarbazone, and FurTsc = furfuraldhydethiosemicarbazone have been synthesized and characterized by elemental analysis, conductance measurements, and spectral studies (IR, UV-Vis, and mass). Thermal studies of the complexes have been carried out using TG and DTG techniques. An octahedral structure has been proposed for all types of the complexes. A representative types of the complexes are tested against various pathogenic bacteria and fungi. The [Ni{(EtO)₂PS₂}₂ApTsc] shows a high degree of activity against bacteria and fungi; this may be attributed to the pyridyl ring of the 2-acetylpyridinethiosemicarbazone ligand.