Antioxidant and antibacterial activities of bark extracts from Commiphora berryi and Commiphora caudata

This study investigates the in vitro antioxidant and antimicrobial activities of eight extracts obtained from the dried barks of Commiphora berryi and Commiphora caudata (Burseraceae). The radical scavenging activity was assessed by 1,1-diphenyl-2-picryl hydrazyl (DPPH) and nitric oxide assays. The methanolic extracts of C. berryi and C. caudata showed significant DPPH radical scavenging activity, with IC?? values of 26.92 and 21.16?μg?mL?1, respectively, and low radical scavenging activity against the nitric oxide assay. The antimicrobial activity of the plants was tested against the Gram-positive and Gram-negative bacteria. The ethyl acetate, chloroform and petroleum ether extracts of C. berryi showed good antibacterial activity against Pseudomonas aeruginosa, with a minimum inhibitory concentration (MIC) of 0.26?mg?mL?1, whereas the ethyl acetate and methanol extracts of C. caudata showed moderate antimicrobial activity with an MIC of more than 2.0?mg?mL?1 against P. aeruginosa compared to the petroleum ether and chloroform extracts, which showed an MIC of 1.1?mg?mL?1. The methanolic extracts of C. berryi and C. caudata also showed moderate cytotoxic activity against a human mammary carcinoma cell line (MCF-7), with values IC?? of 82.6 and 88.4?μg?mL?1, respectively.     

Biomolecular hybrid of a conducting polymer with DNA: morphology, structure, and doping behavior

A poly(o-methoxyaniline) (POMA)/DNA [weight fraction of DNA (W(DNA)) = 0.45] hybrid was prepared by mixing their solutions in sterilized double distilled water. The solution turned green upon aging for a longer time, and the doping of POMA by DNA was complete after about 15 d of aging. The doping was confirmed from the UV-vis spectra where the 599 nm peak of POMA(EB) disappeared and a new peak for a pi to localized polaron band-transition appeared. With increasing aging time the new peak gradually shifted from 674 nm at 3 h to 820 nm at 15 d of mixing and thereafter it remained constant. The absence of a free carrier tail in the UV-vis spectra indicated a coiled structure of POMA in the complex. Circular dichroism spectra of the hybrid solution indicated that the DNA conformation (double helical structure) remained unchanged in the hybrid. The SEM micrograph of the freeze-dried hybrid showed a needle-like morphology of the DNA dispersed in a polymer matrix and it was completely different from the fibrillar network morphology of pure DNA in the solid state. The TEM micrograph indicated a homogeneous dispersion of DNA fibrils in the POMA matrix. The melting temperature of the POMA-DNA hybrid showed an increase compared to that of pure DNA by 5 degrees C, probably caused by an electrostatic interaction between the DNA anion and the POMA radical cation generated in the doping process. WAXS investigations revealed that the DNA crystal structure remained unchanged in the hybrid whereas the POMA crystal structure might be lost. An FT-IR study suggested that interaction occurred between the phosphoric acid group of DNA and a nitrogen atom of POMA through proton transfer from the OH group of the former. A schematic model of the POMA-DNA complex randomly anchoring POMA chains with the DNA molecule was proposed. The dc conductivity of the POMA-DNA complex was found to be ca. 10(-7) S . cm(-1). Hence, this work describes a procedure for making a DNA-conducting polymer hybrid without changing the conformation and structure of DNA. [Diagram: see text]     

Formation of linkage isomers via the substitution of halides by selenocyanate in ruthenium(III) complexes

Summary Substitution of the halide ion of [Ru(NH₃)₅X]²⁺ (X=Cl^– or Br^–) by SeCN^– was monitored spectrophotometrically between 45 and 60° C in aqueous medium. The pseudo-first order rate constants were evaluated by Guggenheim's procedure, which shows linearity for 2–3 half-lives. The rate increases linearly with [SeCN^–] and all the plots have a positive intercept on the rate axis. The SeCN^–-independent path represents aquation and the SeCN^–-dependent path represents anation of the aqua complex with simultaneous formation of two isomeric (the N bonded and the Se bonded) products. The formation of the isomeric products is entropy controlled.     

Intrinsic Dimension Estimation-Based Feature Selection and Multinomial Logistic Regression for Classification of Bearing Faults Using Compressively Sampled Vibration Signals

As failures of rolling bearings lead to major failures in rotating machines, recent vibration-based rolling bearing fault diagnosis techniques are focused on obtaining useful fault features from the huge collection of raw data. However, too many features reduce the classification accuracy and increase the computation time. This paper proposes an effective feature selection technique based on intrinsic dimension estimation of compressively sampled vibration signals. First, compressive sampling (CS) is used to get compressed measurements from the collected raw vibration signals. Then, a global dimension estimator, the geodesic minimal spanning tree (GMST), is employed to compute the minimal number of features needed to represent efficiently the compressively sampled signals. Finally, a feature selection process, combining the stochastic proximity embedding (SPE) and the neighbourhood component analysis (NCA), is used to select fewer features for bearing fault diagnosis. With regression analysis-based predictive modelling technique and the multinomial logistic regression (MLR) classifier, the selected features are assessed in two case studies of rolling bearings vibration signals under different working loads. The experimental results demonstrate that the proposed method can successfully select fewer features, with which the MLR-based trained model achieves high classification accuracy and significantly reduced computation times compared to published research.     

Regioselective synthesis of functionalized [1,6]-naphthyridines by KF/basic alumina as a recyclable catalyst and a brief study of their photophysical properties

An efficient, one-pot, solvent-free, regioselective synthesis of functionalized [1,6]-naphthyridines was explored by a heterogeneous catalyst via a three-component multicomponent reaction (MCR). KF/basic alumina–catalyzed double heteroannulation of aryl alkyl ketones, malononitrile, and alkyl amines generates the compounds with high appendage diversity combinatorially via Knoevenagel condensation followed by Michael addition and cyclization pathway. Short reaction time, high yield, simple reaction technique, and recoverability and reusability of the catalyst without compromising the yield and purity of the compounds are the salient features of this methodology. Additionally, these compounds exhibit promising photophysical properties.     

Structural hierarchy in melt-processed poly(3-hexyl thiophene)-montmorillonite clay nanocomposites: novel physical, mechanical, optical, and conductivity properties

Poly(3-hexyl thiophene) (P3HT) organically modified montmorillonite (om-MMT) polymer nanocomposites (PNCs) are prepared in the melt-cooled state. Hierarchical structures up to third order, namely, side chain mesomorph formation followed by the interchain lamellar structure of P3HT and finally its intercalation within the clay tactoids are observed. The structures are supported by transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS) experiments. The TGA curves show two-stage degradation corresponding to those of the side chain and main chain of P3HT, and both temperatures decrease with an increase in clay concentration in the PNCs. The melting points of PNCs have increased by 2-3 degrees C higher than that of P3HT. The glass-transition temperature (Tg) and beta-transition temperature (Tbeta), measured by DMA, increase with an increase in clay concentration. The storage modulus (G) of PNCs has also increased more dramatically than that of P3HT. The UV-vis spectra of the PNCs show a blue shift in the pi-pi* absorption peak of the conjugated chain, but the photoluminescence spectra showed a red shift with an increase in the clay concentration. The quantum yield of the photoluminescence process also increases in the melt-cooled PNCs, and this is in sharp contrast to that of solvent cast PNCs where photoluminescence quenching was observed. Fibrillar network structure of the solvent cast PNCs promotes energy transfer of the charge carriers, but its absence in the melt-cooled films inhibits such energy transfer, increasing the quantum yield. The room-temperature dc conductivity of the PNCs decreased by an order compared to that of P3HT in both the doped and undoped states. The I-V characteristic curve shows semiconducting behavior, and it slowly transforms into insulator with increasing clay concentration.     

Palladium-catalyzed regioselective oxidative amination of alkenes: an efficient route to the synthesis of pyrrolocoumarin and pyrroloquinolone derivatives

Palladium-catalyzed IBX-induced intramolecular oxidative amination of alkenes has been utilized for the synthesis of pyrrolocoumarin and pyrroloquinolone derivatives in excellent yields in a short reaction time.     

Magnetic field effect corroborated with docking study to explore photoinduced electron transfer in drug-protein interaction

Conventional spectroscopic tools such as absorption, fluorescence, and circular dichroism spectroscopy used in the study of photoinduced drug-protein interactions can yield useful information about ground-state and excited-state phenomena. However, photoinduced electron transfer (PET) may be a possible phenomenon in the drug-protein interaction, which may go unnoticed if only conventional spectroscopic observations are taken into account. Laser flash photolysis coupled with an external magnetic field can be utilized to confirm the occurrence of PET and authenticate the spin states of the radicals/radical ions formed. In the study of interaction of the model protein human serum albumin (HSA) with acridine derivatives, acridine yellow (AY) and proflavin (PF(+)), conventional spectroscopic tools along with docking study have been used to decipher the binding mechanism, and laser flash photolysis technique with an associated magnetic field (MF) has been used to explore PET. The results of fluorescence study indicate that fluorescence resonance energy transfer takes place from the protein to the acridine-based drugs. Docking study unveils the crucial role of Ser 232 residue of HSA in explaining the differential behavior of the two drugs towards the model protein. Laser flash photolysis experiments help to identify the radicals/radical ions formed in the due course of PET (PF(?), AY(?-), TrpH(?+), Trp(?)), and the application of an external MF has been used to characterize their initial spin-state. Owing to its distance dependence, MF effect gives an idea about the proximity of the radicals/radical ions during interaction in the system and also helps to elucidate the reaction mechanisms. A prominent MF effect is observed in homogeneous buffer medium owing to the pseudoconfinement of the radicals/radical ions provided by the complex structure of the protein.     

Characterization of the tryptophan residues of human placental ribonuclease inhibitor and its complex with bovine pancreatic ribonuclease A by steady-state and time-resolved emission spectroscopy

Human placental ribonuclease inhibitor (hRI) containing six tryptophan (Trp) residues located at positions 19, 261, 263, 318, 375, and 438 and its complex with RNase A have been studied using steady-state and time-resolved fluorescence (298 K) as well as low-temperature phosphorescence (77 K). Two Trp residues in wild-type hRI and also in the protein-protein complex with RNase A are resolved optically. The accessible surface area values of Trp residues in the wild-type hRI and its complex and consideration of inter-Trp energy transfer in the wild-type hRI reveal that one of the Trp residues is Trp19, which is located in a hydrophobic buried region. The other Trp residue is tentatively assigned as Trp375 based on experimental results on wild-type hRI and its complex. This residue in the wild-type hRI is more or less solvent exposed. Both the Trp residues are perturbed slightly on complex formation. Trp19 moves slightly toward a more hydrophobic region, and the environment of Trp375 becomes less solvent exposed. The complex formation also results in a more heterogeneous environment for both the optically resolved Trp residues.