Physicochemical characteristics of the Lasiococca comberi Haines seeds

Physicochemical characteristics and fatty acid composition of Lasiococca comberi Haines (Euphorbiaceae), an endangered forest tree species, were determined for the first time. The oil, protein, crude fibre and carbohydrate contents in seeds were 41.5, 13.8, 22.2 and 11.6%, respectively. The refractive index, pH, specific gravity, saponification value, iodine value, peroxide value and p-anisidine value of seed oil were 1.4781, 6.4, 0.9, 178.4 mg KOH/g, 196 g I₂/100 g of oil, 5.1 mEq O₂/kg and 188.4, respectively. The predominant fatty acids were linolenic acid (65.3%), oleic acid (13.8%), linoleic acid (7.1%) and palmitic acid (5.3%). HPLC analysis revealed the presence of α-tocopherol (13.2 mg/100 g) and γ-tocopherol (6.3 mg/100 g) as the major tocopherols. The results indicated that L. comberi seed oil can be classified as drying oil having possible applications in different industries and as an important dietary source of omega-3 fatty acids.     

Silicon–oxygen bonding on diphenylsilane through palladium(II)‐catalysed reactions

The reactions of phenols with diphenylsilane are catalysed by palladium(II) catalysts such as Pd(TMEDA)Cl₂ (TMEDA = tetramethylethylenediamine), Pd(DEED)Cl₂ (DEED = N,N′‐diethylethylenediamine), Pd(TEEDA)Cl₂ (TEEDA = N,N′‐tetraethylethylenediamine) or PdCl₂ to form hydrated silanols with molecular formula Ph₂Si(OR)OH·nH₂O (when R = C₆H₅, n = 3; when R = p‐CH₃C₆H₄ or o‐CH₃C₆H₄, n = 1). The reaction of hydroquinone with diphenylsilane in the presence of catalytic amounts of Pd(TMEDA)Cl₂ forms an Si–O‐bonded hydrated aggregate of composition [(C₆H₅)₂Si(OC₆H₄O).0.5H₂0] _n. p‐Benzoquinone reacted with diphenylsilane in the presence of a catalytic amount of Pd(TMEDA)Cl₂ and the reaction proceeded via a multiple pathway involving quinhydrone as an intermediate charge‐transfer complex which reacted further with diphenylsilane to give a linear siloxane. Copyright ­© 2000 John Wiley & Sons, Ltd.     

Rapid Discrimination of Bacterial Drug Resistivity by Array-Based Cross-Validation Using 2D MoS2

The precise discrimination of microbes based on family, class and drug resistivity is essential for the early diagnosis of infectious diseases. Information about the type and strength of drug resistivity can help the analyst to prescribe a suitable antibiotic at the proper dosage to completely eradicate microbes without giving them a chance to gain further resistance. Herein, we propose a sensor array based on the use of cationic two-dimensional MoS₂ units and green fluorescence protein as building blocks. Cationic surfaces of receptors with various functionality were suitable for tunable interaction with anionic surfaces of microbes. The array successfully discriminates six different bacterial strains. The versatile ability of the receptors to bind with the wild-type as well as the corresponding ampicillin-resistant strain contributed significantly to rapid detection with high sensitivity. The optimized array was able to classify five different types and three different extents of drug-resistant variants of Escherichia coli by using bacteria cells and lysates. Finally, we have introduced the cross identification method using both bacteria cells and lysates and we found a great enhancement of detection in sensitivity and accuracy. This is the first report of this approach, which can be extended to many other methods for better accuracy in array-based detection.     

Molecular dynamics simulation of HIV-protease with polarizable and non-polarizable force fields

The effect of polarization in biomolecular force field is investigated by performing Molecular Dynamics (MD) simulation of HIV-protease by using two AMBER force fields, namely ff99 (non-polarizable) and ff02 (polarizable). The results of simulation show that the overall structural fluctuation of HIV-protease is reduced in the polarizable simulation. Comparison with the NMR order parameters with the calculated values shows that although some residues are less flexible in the ff02 simulation, the dynamics of two β-hairpins (flaps), the most flexible part of the protein, is relatively insensitive to the effect of polarization. The flap-active site distance, a measure of flap opening, is distinctly more in the non-polarizable simulation. The water count and radial distribution functions are investigated near a representative residue of three types — charged, polar and hydrophobic. Both water count and radial distribution function differ significantly near the charged residue (catalytic Asp25) between the force fields. However, the water movement is similar near the polar (Ser37) and hydrophobic (Ile85) residues. The preliminary results of this investigation show that polarization is likely to influence both global and specific local motions of protein and solvent.      

Nanosecond folding dynamics of a three-stranded beta-sheet

We studied conformational stability and folding kinetics of a three-stranded beta-sheet containing two rigid turns. Static infrared measurements indicate that this beta-sheet undergoes a broad but cooperative thermal unfolding transition with a midpoint at approximately 53 degrees C. Interestingly, time-resolved infrared experiments show that its relaxation kinetics in response to a temperature-jump (T-jump) occur on the nanosecond time scale (e.g., the relaxation time is approximately 140 ns at 35.0 degrees C), thereby suggesting that the conformational relaxation encounters only a small free energy barrier or even proceeds in a downhill manner. Further Langevin dynamics simulations suggest that the observed T-jump relaxation kinetics could be modeled by a conformational diffusion process along a single-well free energy profile, which allowed us to determine the effective diffusion constant and also the roughness of the folding energy landscape.     

Photophysics of two structurally similar dyes containing substituted amino as donor and carbonyl as acceptor groups

The present work entails a comparative photophysical study of two structurally similar donor–acceptor dyes. In one of the dyes (DN2) twisting about C–N bond is permissible, while twisting is strategically restricted in the other (N2). Optical responses of both the dyes have been monitored in pure and mixed binary solvents comprising of mainly aprotic+protic systems. Results indicate that the nature of emitting states in protic and aprotic microenvironments is different for the two dyes. In aprotic media the solvated dye molecule is the emitting species while emission mainly takes place, supposedly, from the dye-solvent hydrogen bonded complex in protic media. The parallel behaviour of the two dyes indicates that twisting about C–N bond in the excited state is not an important photophysical process. Further, the effect of addition of strong acid to the dye solution and the corresponding existence of equilibrium between two tautomeric forms for both the dye has been studied.     

Ball remotality in Banach spaces

In this paper, we continue our study of ball remotality of subspaces of Banach spaces. In particular, we study the problem in classical sequence spaces c₀, c, ?₁ and ?_∞; and also ball remotality of a Banach space in its bidual.     

Surfactant-free thermal decomposition route to phase pure tricobalt tetraoxide nanoparticles from cobalt(II)-tartrate complex

Tricobalt tetraoxide nanoparticles have been successfully synthesized following a ‘bottom-up’ approach by surfactant-free thermal decomposition of cobalt(II)-tartrate complex obtained by a modified sol–gel route. The synthesized complex was characterized by Fourier transform infrared (FT-IR) spectroscopy, elemental and thermogravimetric-differential thermal analysis (TG–DTA). The nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman studies. The powder XRD pattern furnished evidence for a face-centered cubic structure of Co₃O₄. With the rise in calcination temperature from 400 through 500 to 600 °C, the average crystallite sizes of Co₃O₄ were found to increase from 28 through 36 to 46 nm. The TEM image revealed a faceted morphology of the as-synthesized Co₃O₄ nanoparticles. The high-resolution TEM image indicated the interplanar separation to be 0.28 nm which corresponds to the (220) plane in face-centered cubic Co₃O₄. The electron diffraction (ED) pattern showed single-crystalline nature of the synthesized nanoparticles. Raman spectrum showed four characteristic peaks of Co₃O₄ which further confirmed the phasic purity of the material.     

Orientation of a TICT probe trapped in the peripheral confined water created by ionic surfactant envelope around silver nanoparticles

Ionic surfactants are known to aggregate around the surface of a nanoparticle as a single layer in premicellar and a double layer in micellar concentrations. This motif of arrangement indicates the development of a layer of confined water of lower polarity than bulk water around the surface of the nanoparticle. We have demonstrated the behavior of a twisted intramolecular charge transfer (TICT) probe, trans-2-[4-(dimethylamino)styryl]benzothiazole (DMASBT), in the confined aqueous layer developed at the surface of spherical silver nanoparticles (Ag NPs) at and above the critical micellar concentrations (CMC) of a cationic and an anionic surfactant, namely, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS). It is observed that the presence of charged surfactant head groups affects DMASBT differentially in the ground and the excited states. In presence of CTAB, DMASBT turns over in the excited state and interacts with the Ag NP surface, whereas in SDS the probe remains in its original orientation during the interaction. Steady-state and time-resolved fluorescence spectral studies provide enough evidence for orientation of the TICT probe in the peripheral water of Ag NP created by the surfactants. The results were confirmed by steady-state anisotropy measurements. The data show the difference between the properties of the confined peripheral water and the bulk aqueous environment. The TICT probe, DMASBT, is proved to be an excellent marker for the phenomenon.     

Microwave promoted improved regioselective synthesis of 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones by radical cyclisation

In this work, two new effective methodologies have been adopted for the preparation of 5-(2′-bromobenzyloxy)pyrimidine-2,4-diones 6(a–k). In the first methodology, 5-hydroxy uracils 4(a–f) were alkylated with 2-bromobenzyl bromide 5a or 2-bromo-5-methoxy benzyl bromide 5b under phase transfer catalysis condition using lithium hydroxide/tetrabutyl ammonium bromide in N,N-dimethylformamide at 45 °C, and in the second method, the microwave irradiation (MWI) protocol has been exploited by mixing 5-hydroxy uracils 4(a–f) with 30 % excess of 2-bromobenzyl bromide 5a or 2-bromo-5-methoxy benzyl bromide 5b. A catalytic amount of TBAB and potassium carbonate was added and irradiated in an open Erlenmeyer flask in a microwave oven for 3–12 min. The tributyltin hydride-mediated radical cyclisation of 6(a–k) was carried out under MWI to generate 1H,3H,6H[2]benzopyrano[4,3-d]pyrimidine-2,4-diones 7(a–k) in 80–89 % yield, and the reaction time was shortened compared to the previously reported conventional radical cyclisation method.