Synthesis of 3,4‐Fused γ‐Lactone‐γ‐Lactam Bicyclic Moieties as Multifunctional Synthons for Bioactive Molecules

A short approach for the synthesis of 3,4‐fused γ‐lactone‐γ‐lactam bicyclic systems ( 1 ) in diastereomeric mixtures from chiral D ‐alanine methyl ester hydrochloride is described. The key step towards lactonisation is the reduction of the carbonyl ketone of the 5R‐configured 3,5‐dimethylpyrrolidine‐2,4‐dione diastereomers ( 8 ) via sodium borohydride in the presence of hydrochloric acid. With the presence of ethyl acetyl functionality at C3‐position, ester hydrolysis of 8 occurred concomitantly with keto reduction leading to lactonisation and eventually affording the anticipated (3S,4S,5R), (3R,4R,5R), (3R,4S,5R) and (3S,4R,5R) bicyclic moieties. The formation of the fused systems was confirmed by mass spectroscopy (MS) and nuclear magnetic resonance (NMR) analyses.     

Polystyrene/mesoporous diatomite composites by in situ simultaneous reverse and normal initiation technique for atom transfer radical polymerization

Mesoporous diatomite platelets were employed to synthesize different polystyrene/diatomite composites by in situ polymerization of styrene via simultaneous reverse and normal techniques of atom transfer radical polymerization. Furrier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning and transmission electron microscopy, gas and size exclusion chromatography were used to examine characteristics of polymer and composite. Addition of 3 wt% pristine mesoporous diatomite leads to increase of conversion from 79 to 93%, while control over molecular weight characteristics become worse.     

Intramolecular hydrogen bonding in derivatives of 3‐amino‐propenethial

Intramolecular H‐bonds existing for derivatives of 3‐amino‐propenethial have been studied using the B3LYP/6‐311++G** level of theory. The nature of these interactions, known as resonance assisted hydrogen bonds, has been discussed. The topological properties of the electron density distributions for N—H—S intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules. Correlations between the H‐bond strength and topological parameters have been also studied. Furthermore, we obtained the exact value of the intramolecular hydrogen bond energies by the related rotamers method. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

One-pot synthesis of 2-amino-3-cyano-4-arylsubstituted tetrahydrobenzo[<Emphasis Type="Italic">b</Emphasis>]pyrans catalysed by silica gel-supported polyphosphoric acid (PPA-SiO<Subscript>2</Subscript>) as an efficient and reusable catalyst

A convenient method for the synthesis of tetrahydrobenzo[b]pyrans by a one-pot three-component cyclocondensation of dimedone, aryl aldehydes, and malononitrile in water using silica gel-supported polyphosphoric acid (PPA-SiO₂) as an efficient and reusable catalyst is described. The present methodology offers several advantages, such as a simple procedure with ease of handling, short reaction time, high yields, and the absence of any volatile and hazardous organic solvents.     

Three-dimensional Brownian diffusion of rod-like macromolecules in the presence of randomly distributed spherical obstacles: molecular dynamics simulation

Brownian diffusion of rod-like polymers in the presence of randomly distributed spherical obstacles is studied using molecular dynamics simulations. It is observed that dependence of the reduced diffusion coefficient of these macromolecules on the available volume fraction can be described reasonably by a power law function. Despite the case of obstructed diffusion of flexible polymers in which reduced diffusion coefficient has a weak dependence on the polymer length, this dependence is noticeably strong in the case of rod-like polymers. Diffusion of these macromolecules in the presence of obstacles is observed that is anomalous at short time scales and normal at long times. Duration time of the anomalous diffusion regime is found that increases very rapidly with increasing both the polymer length and the obstructed volume fraction. Dynamics of diffusion of these polymers is observed that crosses over from Rouse to reptation type with increasing the density of obstacles.     

Radiological dose assessment of naturally occurring radioactive materials in concrete building materials

Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg^?1 respectively. The annual radiation dose rates (μSv year^?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers.     

99mTc-ceftriaxone, as a targeting radiopharmaceutical for scintigraphic imaging of infectious foci due to Staphylococcus aureus in mouse model

^99mTc-labeled antibiotics have opened an exciting field of research in infectious diseases diagnosis. Direct labeling of ceftriaxone with ^99mTc was carried out using the various amounts of ceftriaxone and SnCl₂·2H₂O at different pH and incubation time intervals to find the highest radiochemistry efficiency with high stability at room temperature and human blood serum. ITLC-SG and HPLC were performed to measure the radiochemical purity of the conjugate. The binding study showed 45 % specific binding to Staphylococcus aureus. The biodistribution study and scintigraphic imaging showed the localization of ^99mTc-ceftriaxone at the site of infection in comparison with normal and inflamed muscles with high sensitivity and specificity in mouse model. The results showed that ^99mTc-ceftriaxone is a promising candidate as a targeting radiopharmaceutical for Staphylococcal infection imaging in humans which needs further investigations.     

Substituent effect on structure,electron density,and intramolecular hydrogen bonding in nitroso‐oxime methane

Density functional calculations with Beck's three‐parameter hybrid method using the correlation functional of Lee, Yang, and Parr (B3LYP) were carried out for investigation of the intramolecular hydrogen bond strength in Nitroso‐oxime methane and its derivatives. Also, vibrational frequencies for them were calculated at the same level of theory. The π‐electron delocalization parameter (Q) and as a geometrical indicator of a local aromaticity, the geometry‐based harmonic oscillator measure of aromaticity index has been applied. Additionally, the linear correlation coefficients between substituent constants and selected parameters in R position have calculated. The obtained results show that the hydrogen bond strength is mainly governed by the resonance variations inside the chelate ring induced by the substituent groups. The topological properties of the electron density distributions for O? H ··· O intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules (AIM). Correlations between the H‐bond strength and topological parameters have been also studied. The electron density (ρ) and Laplacian (?²ρ) properties, estimated by AIM calculations, show that O ··· H bond have low ρ and negative (?²ρ) values (consistent with covalent character of the HBs), whereas O? H bond have positive (?²ρ) Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by quantum theory of natural bond orbital (NBO) methods fairly support the ab initio results. Natural population analysis data, the electron density, and Laplacian properties as well as υ(O? H) and γ(O? H) were further used for estimation of the hydrogen bonding interactions and the forces driving their formation. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Biochemical Characterization of Thermostable and Detergent-Tolerant β-Agarase,PdAgaC, from Persicobacter sp. CCB-QB2

Applied Biochemistry and Biotechnology - Persicobacter sp. CCB-QB2 belonging to the family Flammeovirga is an agarolytic bacterium and exhibits a diauxic growth in the presence of tryptone and...