Monte Carlo and molecular dynamics simulations of methane in potassium montmorillonite clay hydrates at elevated pressures and temperatures

The structure and dynamics of methane in hydrated potassium montmorillonite clay have been studied under conditions encountered in sedimentary basin and compared to those of hydrated sodium montmorillonite clay using computer simulation techniques. The simulated systems contain two molecular layers of water and followed gradients of 150 bar km(-1) and 30 K km(-1) up to a maximum burial depth of 6 km. Methane particle is coordinated to about 19 oxygen atoms, with 6 of these coming from the clay surface oxygen. Potassium ions tend to move away from the center towards the clay surface, in contrast to the behavior observed with the hydrated sodium form. The clay surface affinity for methane was found to be higher in the hydrated K-form. Methane diffusion in the two-layer hydrated K-montmorillonite increases from 0.39 x 10(-9) m2 s(-1) at 280 K to 3.27 x 10(-9) m2 s(-1) at 460 K compared to 0.36 x 10(-9) m2 s(-1) at 280 K to 4.26 x 10(-9) m2 s(-1) at 460 K in Na-montmorillonite hydrate. The distributions of the potassium ions were found to vary in the hydrates when compared to those of sodium form. Water molecules were also found to be very mobile in the potassium clay hydrates compared to sodium clay hydrates.     

Some approaches to the synthesis of fluorinated alcohols and esters. II. Use of F-alkyl iodides for the synthesis of F-alkyl alkanols

Free radical addition of an F-alkyl iodide (R_FI) to an alkenol or ester, followed by appropriate reduction is an efficient method for preparing the corresponding F-alkyl-alkanols of the homologous series, R_F(CH₂)_n?OH. When n = 2,4 or higher, the two steps take place smoothly. The 1,2,3-substituted systems R_FCH₂CHYCH₂Z, however, are susceptible to surprising difficulties. Reduction of R_FCH₂CHICH₂ON to R_F(CH₂)₃OH by hydrogen and catalyst (strong base acid acceptor), can be done either in one step or $\text{via}$ R_FCHCHCH₂OH; however, dehydrohalogenation may also give the epoxide, and reduction in this case leads to the secondary alcohol, R_FCH₂CH(CH₃)OH. By contrast, reduction of R_FCH₂CHICH₂OAc by tributyltin hydride or with hydrogen over palladium (diethylamine acid acceptor) goes smoothly. Zinc and acid reduction of R_FCH₂CHICH₂OAc gives elimination to R_FCH₂CHCH₂; even R_FCHCICH₂OH gives R_FCHCCH₂ besides R_FCHCHCH₂OH. R_FCHCICH₂CH₂OH, however, with zinc and acid is reduced cleanly to R_FCHCHCH₂CH₂OH.     

Synthesis and Application of Disperse Dyes Based on 2-Aminothiazole Derivatives

A series of novel monoazo disperse dyes based on 2-amino-5-nitro-4-(p-nitrophenyl)thiazole were prepared using various N,N-dialkylaniline derivatives as the coupling components. The spectral properties in the IR and visible range of the dyes were investigated. The dyeing performance of these dyes was assessed on nylon fabric. These dyes were found to give a wide range of color shades from reddish brown to indigo with excellent brightness, levelness, and depth on nylon fabric. The dyed fabric showed fairly good light fastness, good to excellent fastness to wash and perspiration, and excellent fastness to sublimation. The dyebath exhaustion and fixation of the dyes on nylon were found to be very good and acceptable.     

Composite polymer electrolyte membranes comprising P(VDF‐co‐CTFE)‐g‐PSSA graft copolymer and zeolite for fuel cell applications

Hybrid organic/inorganic composite polymer electrolyte membranes based on a poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) grafted membrane and varying concentrations of zeolite were investigated for application in proton exchange membrane fuel cells (PEMFC). A proton conducting comb copolymer consisting of poly(vinylidene fluoride‐co‐chlorotrifluoroethylene) backbone and poly(styrene sulfonic acid) (PSSA) side chains, i.e. P(VDF‐co‐CTFE)‐g‐PSSA (graft copolymer) with 47 wt% of PSSA was synthesized using atom transfer radical polymerization (ATRP) and solution blended with zeolite. Upon incorporation of zeolite, the symmetric stretching band of both SO group (1169 cm^?1) and the ? OH group (3426 cm^?1) shifted to lower wavenumbers. The shift in these FT‐IR spectra suggests that the zeolite particles strongly interact with the sulfonic acid groups of PSSA chains. When the weight percent of zeolite 5A is above 7%, the proton conductivity at room temperature was reduced to 0.011 S/cm. The water uptake of the composite membranes decreased from 234 to 125% with an increase of the zeolite 5A weight percent to 10 wt%. The decrease in water uptake is likely a result of the decrease in the number of available water absorption sites because of the hydrogen bonding interactions between the zeolite particles and the graft copolymer matrix. This behavior is successfully investigated by scanning electron microscopy (SEM). The results of thermal gravimetric analysis (TGA) also showed that all the membranes were stable up to 300°C. Copyright © 2009 John Wiley & Sons, Ltd.     

Separation of a BMS drug candidate and acyl glucuronide from seven glucuronide positional isomers in rat plasma via high-performance liquid chromatography with tandem mass spectrometric detection

A high-performance liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for the determination of a BMS drug candidate and its acyl glucuronide (1-O-beta glucuronide) in rat plasma. A 50-microL aliquot of each plasma sample was fortified with acetonitrile containing the internal standard to precipitate proteins and extract the analytes of interest. After mixing and centrifugation, the supernatant from each sample was transferred to a 96-well plate and injected into an LC/MS/MS system. Chromatographic separation was achieved isocratically on a Phenomenex Luna C(18), 3 mm x 150 mm, 3 microm column. The mobile phase contained 0.075% formic acid in 70:30 (v/v) acetonitrile/water. Under the optimized chromatographic conditions, the BMS drug candidate and its acyl glucuronide were separated from its seven glucuronide positional isomers within 10 min. Resolution of the parent from all glucuronides and acyl glucuronide from its positional isomers was critical to avoid their interference with quantitation of parent or acyl glucuronide. Detection was by positive ion electrospray MS/MS on a Sciex API 4000. The standard curve, which ranged from 5 to 5000 ng/mL, was fitted to a 1/x(2) weighted quadratic regression model for both the BMS drug candidate and its acyl glucuronide. Whole blood and plasma stability experiments were conducted to establish the sample collection, storage, and processing conditions. The validation results demonstrated that this method was rugged and repeatable. The same methodology has also been used in mouse and human plasma for the determination of the BMS drug candidate and its acyl glucuronide.     

Fluorescence Investigation of the Binding of Model PDT Drugs to Nonionic and Zwitterionic Surfactants

The binding of two model photodynamic therapy drugs, chlorin p ₆ and purpurin 18, with surfactants has been studied using steady-state and time-resolved fluorescence techniques. The surfactants used are amphiphilic nonionic surfactant (Tween 80 and Tween 40) and zwitterionic surfactant (HAPS). These have applications in drug delivery. The studies have been performed at pH 7 and 5 for chlorin p ₆ and at pH 7 for purpurin 18. The binding constants have been estimated from the change in fluorescence parameters and have been compared with those for Cremophor EL and human serum albumin. Chlorin p ₆ is found to bind to the surfactants to a greater extent at pH 5 than at pH 7. The same ionic species of chlorin p ₆ is found to exist at the maximum concentrations of the surfactants.     

Reversal in solvatochromism in some novel styrylpyridinium dyes having a hydrophobic cleft

The influence of solvent polarity on the electronic transition of four different N-hexadecyl styrylpyridinium dyes has been investigated in 15 solvents. The E(T)(30) scale has been used to propose a quantitative approach towards the relative stability of the electronic ground and excited state species. The extents of contribution of dipolar aprotic solvents towards the solvation of the excited species have been determined to be 42-48% for some of the dyes. Instead of a steady solvatochromism, all the dyes suffer a reversal in solvatochromism. The transitions of the solvatochromism, referred to as solvatochromic switches, are found to be at E(T)(30) values of approximately 50 for methyl and N,N-dimethylamino substituted dyes while at 37.6 for hydroxyl substituted dye and approximately 45 for 4-(1-methyl-2-phenylethenyl) pyridinium dye. A reversal in the trend of solvent effect in the later dye corresponding to 4-(4-methyl styryl)pyridinium dye has been attributed to an analogy of series and parallel electron flow.     

Synthesis and characterization of polyaniline nanoparticles in the presence of magnetic field and samarium chloride

A new and economical method of preparing polyaniline (PANI) nanoparticles will be introduced in this article. Compared with conventional methods, this method is much more simple and convenient. Scanning electron microscope (SEM) shows that the diameter of particles are between 30 and 50 nm, which is in good agreement with the results of a transmission electron microscope (TEM). Polyaniline/SmCl₃/Bp, polyaniline/SmCl₃ and polyaniline/HCl were prepared in a solution containing 1.0 mol dm⁻³ aniline, 1.0 mol dm⁻³ HCl with and without 0.5 mol dm⁻³ SmCl₃, in the presence and in the absence of a magnetic field, respectively. Their conductivity, UV-vis spectra, FTIR spectra, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were investigated. Changes in UV-vis and FTIR spectra indicate a strong interaction between Samarium ions (SmCl₃) and polyaniline chains. The conductivity of PANI depends on magnetization and concentration of Sm³⁺. Polyaniline/SmCl₃/Bp has the higher degree of crystallinity than that of polyaniline/HCl.     

Structure of the human telomere in K+ solution: an intramolecular (3 + 1) G-quadruplex scaffold

We present the intramolecular G-quadruplex structure of human telomeric DNA in physiologically relevant K(+) solution. This G-quadruplex, whose (3 + 1) topology differs from folds reported previously in Na(+) solution and in a K(+)-containing crystal, involves the following: one anti.syn.syn.syn and two syn.anti.anti.anti G-tetrads; one double-chain reversal and two edgewise loops; three G-tracts oriented in one direction and the fourth in the opposite direction. The topological characteristics of this (3 + 1) G-quadruplex scaffold should provide a unique platform for structure-based anticancer drug design targeted to human telomeric DNA.     

Carbon nanotube amplification strategies for highly sensitive immunodetection of cancer biomarkers

We describe herein the combination of electrochemical immunosensors using single-wall carbon nanotube (SWNT) forest platforms with multi-label secondary antibody-nanotube bioconjugates for highly sensitive detection of a cancer biomarker in serum and tissue lysates. Greatly amplified sensitivity was attained by using bioconjugates featuring horseradish peroxidase (HRP) labels and secondary antibodies (Ab(2)) linked to carbon nanotubes (CNT) at high HRP/Ab(2) ratio. This approach provided a detection limit of 4 pg mL(-)(1) (100 amol mL(-)(1)), for prostate specific antigen (PSA) in 10 microL of undiluted calf serum, a mass detection limit of 40 fg. Accurate detection of PSA in human serum samples was demonstrated by comparison to standard ELISA assays. PSA was quantitatively measured in prostate tissue samples for which PSA could not be differentiated by the gold standard immunohistochemical staining method. These easily fabricated SWNT immunosensors show excellent promise for clinical screening of cancer biomarkers and point-of-care diagnostics.