On-line sample cleanup and enrichment chromatographic technique for the determination of ambroxol in human serum

A sensitive and efficient on-line clean up and pre-concentration method has been developed using column-switching technique and protein-coated μ-Bondapak CN silica pre-column for quantification of ambroxol (AM) in human serum. The method is performed by direct injection of serum sample onto a protein-coated μ-Bondapak CN silica pre-column, where AM is pre-concentrated and retained, while proteins and very polar constituents are washed to waste using a phosphate buffer saline (pH 7.4). The retained analyte on the pre-column is directed onto a C(18) analytical column for separation, with a mobile phase consisting of a mixture of methanol and distilled deionized water (containing 1% triethylamine adjusted to pH 3.5 with ortho-phosphoric acid) in the ratio of 50:50 (v/v). Detection is performed at 254 nm. The calibration curve is linear over the concentration range of 12-120 ng/mL (r(2) = 0.9995). The recovery, selectivity, linearity, precision, and accuracy of the method are convenient for pharmacokinetic studies or routine assays.     

Fast fluorescence switching within hydrophilic supramolecular assemblies

We designed a supramolecular strategy to modulate fluorescence in water under optical control. It is based on the entrapment of fluorophore-photochrome dyads within the hydrophobic interior of an amphiphilic polymer. The polymeric envelope around the dyads protects them from the aqueous environment, while imposing hydrophilic character on the overall supramolecular construct. In the resulting assemblies, the photochromic component can be operated reversibly on a microsecond timescale under the influence of ultraviolet stimulations. In turn, the reversible transformations control the emission intensity of the adjacent fluorophore. As a result, the fluorescence of such nanostructured constructs can be photomodulated for hundreds of cycles in water with microsecond switching speeds. Thus, our protocol for fast fluorescence switching in aqueous solutions can eventually lead to the realization of functional probes for the investigation of biological samples.     

99mTc–meropenem as a potential SPECT imaging probe for tumor hypoxia

Meropenem was successfully radiolabeled with ^99mTc in high labeling yield (92 ± 2%) and stability (~6 h). ^99mTc–meropenem showed high accumulation in tumor hypoxic tissue (4.193% injected dose/g organ). ^99mTc–meropenem showed high ability to differentiate the tumor tissue from inflamed or infected tissues in different mice models as its T/NT ratio ~4 in case of tumor mice model while T/NT ratio ~1 in case of inflamed mice model. So, ^99mTc–meropenem showed high selectivity in comparison with FDG-PET and ^99mTc-nitroimidazole analogues. Thus, ^99mTc–meropenem could be used as a selective potential imaging agent for diagnosis of tumor hypoxia.     

Oil Palm Empty Fruit Bunch as Alternative Substrate for Acetone–Butanol–Ethanol Production by <Emphasis Type="Italic">Clostridium butyricum</Emphasis> EB6

Acetone–butanol–ethanol (ABE) production from renewable resources has been widely reported. In this study, Clostridium butyricum EB6 was employed for ABE fermentation using fermentable sugar derived from treated oil palm empty fruit bunch (OPEFB). A higher amount of ABE (2.61 g/l) was produced in a fermentation using treated OPEFB as the substrate when compared to a glucose based medium that produced 0.24 g/l at pH 5.5. ABE production was increased to 3.47 g/l with a yield of 0.24 g/g at pH 6.0. The fermentation using limited nitrogen concentration of 3 g/l improved the ABE yield by 64%. The study showed that OPEFB has the potential to be applied for renewable ABE production by C. butyricum EB6.     

Effects of hydrolysis conditions on the morphology,crystallinity, and thermal stability of cellulose nanocrystals extracted from kenaf bast fibers

Cellulose nanocrystals (CNC) were first isolated from kenaf bast fibers and then characterized. The raw fibers were subjected to alkali treatment and bleaching treatment and subsequent hydrolysis with sulfuric acid. The influence of the reaction time on the morphology, crystallinity, and thermal stability of CNC was investigated. Fourier transform infrared spectroscopy showed that lignin and hemicellulose were almost entirely removed during the alkali and bleaching treatments. The morphology and dimensions of the fibers and acid-released CNC were characterized by field emission scanning electron microscopy and transmission electron microscopy. X-Ray diffraction analysis revealed that the crystallinity first increases upon hydrolysis and then decreases after long durations of hydrolysis. The optimal extraction time was found to be around 40 min during hydrolysis at 45 °C with 65% sulfuric acid. The thermal stability was found to decrease as the hydrolysis time increased. The electrophoretic mobility of the CNC suspensions was measured using the zeta potential, and it ranged from −8.7 to −95.3 mV.     

Experimental and theoretical study of the reaction of the ethynyl radical with nitrous oxide, C2H + N2O

We investigated the rate constants and reaction mechanism of the gas phase reaction between the ethynyl radical and nitrous oxide (C(2)H + N(2)O) using both experimental methods and electronic structure calculations. A pulsed-laser photolysis/chemiluminescence technique was used to determine the absolute rate coefficient over the temperature range 570 K to 836 K. In this experimental temperature range, the measured temperature dependence of the overall rate constants can be expressed as: k(T) (C(2)H + N(2)O) = 2.93 × 10(-11) exp((-4000 ± 1100) K/T) cm(3) s(-1) (95% statistical confidence). Portions of the C(2)H + N(2)O potential energy surface (PES), containing low-energy pathways, were constructed using the composite G3B3 method. A multi-step reaction route leading to the products HCCO + N(2) is clearly preferred. The high selectivity between product channels favouring N(2) formation occurs very early. The pathway corresponds to the addition of the terminal C atom of C(2)H to the terminal N atom of N(2)O. Refined calculations using the coupled-cluster theory whose electronic energies were extrapolated to the complete basis set limit CCSD(T)/CBS led to an energy barrier of 6.0 kcal mol(-1) for the entrance channel. The overall rate constant was also determined by application of transition-state theory and Rice-Ramsperger-Kassel-Marcus (RRKM) statistical analyses to the PES. The computed rate constants have similar temperature dependence to the experimental values, though were somewhat lower.     

β‐Enaminonitriles in Heterocyclic Synthesis: Synthesis of New 1,4‐Dihydropyridine,Tetrahydropyridine, Nicotinonitrile and Aminopyrazole Derivatives

A series of new pyridine, dihydropyridine, tetrahydropyridine, nicotinonitrile and pyrazole derivatives with expected biological activity were prepared through the reactions of 3‐aminopent‐2‐enenitrile 1 with some electrophilic reagents, nucleophilic reagents, and aryl diazonium salts. The newly synthesized compounds were characterized by IR, ¹H‐NMR, ¹³C‐NMR and mass spectral studies.     

Molecular Interactions in Binary Mixtures of Benzene with 1-Alkanols(C5,C7,C8) at 35℃:An Ultrasonic Study

Densities and ultrasonic speeds have been measured in binary mixtures of benzene with 1‐pentanol, 1‐heptanol and 1‐octanol, and in the pure components, as a function of composition at 35 °C. The isentropic compressibility, intermolecular free length, relative association, acoustic impedance, isothermal compressibility, thermal expansion coefficient, deviations in isentropic compressibility, excess free length, excess volume, deviations in ultrasonic speed, excess acoustic impedance, apparent molar compressibility, apparent molar volume, partial molar volume of 1‐alkanol in benzene have been calculated from the experimental data of densities and ultrasonic speeds. The variation of these parameters with composition indicates weak interaction between the component molecules and this interaction decreases in the order: 1‐pentanol > l‐heptanol> 1‐octanol. Further, theoretical values of ultrasonic speeds were evaluated using free length theory, collision factor theory, Nomoto's relation and Van Dæl‐Vangeel ideal mixing relation. The relative merits of these theories and relations were discussed for these systems.     

Efficient synthesis of 16-28 membered macrocyclic crown amides via ring closing metathesis

Ring closing metathesis of suitable diamides containing 1,ω-dienes led to efficient synthetic approaches towards macrocylic polyoxadiamides 1-18 with 16-28 membered ring sizes in good to excellent yields using Grubbs' catalyst.     

N-aryl pyrazoles: DFT calculations of CH acidity and deprotonative metallation using a combination of lithium and zinc amides

A series of N-aryl and N-heteroaryl pyrazoles have been deproto-metallated using a 2,2,6,6-tetramethylpiperidino-based mixed lithium-zinc combination. Mono-, di-, and tri-iodides have been obtained after subsequent trapping with iodine, depending on the substrate and on the quantity of base used. The results have been discussed in the light of the CH acidities of the substrates, determined both in the gas phase and in THF solution using the DFT B3LYP method.