Pressure‐assisted tryptic digestion using a syringe

A simple and effective digestion method was developed using a syringe. A 3 mL syringe was used to apply a pressure of 6 atm to expedite tryptic digestion. Application of a pressure of 6 atm during digestion resulted in better digestion efficiency than digestion under atmospheric pressure. The protein peaks in the matrix‐assisted laser desorption/ionization mass spectra of three model proteins (cytochrome c, horse heart myoglobin, and bovine serum albumin (BSA)) completely disappeared within 30 min at 37°C under a pressure of 6 atm, with greater numbers of peptides observed in 30 min pressure‐assisted digestion than in overnight atmospheric pressure digestion. This is mostly due to the miscleaved peptides. Similar sequence coverages were obtained for 30 min pressure‐assisted digestion and overnight atmospheric pressure digestion of the three model proteins (92% vs. 88% for cytochrome c, 100% vs. 97% for horse heart myoglobin, and 53% vs. 53% for BSA). Copyright © 2010 John Wiley & Sons, Ltd.     

Electrically assisted capillary liquid chromatography using a silica monolithic column

A silica monolithic capillary column was linked to an open capillary of the same internal diameter via a Teflon sleeve to form a duplex column to investigate the combination of chromatography and electrophoresis in the mode of electrically assisted capillary liquid chromatography (eCLC). Using a commercial CE instrument with an 8.5 cm long, 100 μm i.d. reversed phase silica monolithic section and a window 1.5 cm beyond the end of this in a 21.5 cm open section, a minimum plate height of 9 μm was obtained in capillary liquid chromatography (CLC) mode at a low driving pressure of 50 psi. In eCLC mode, high speed and high resolution separations of acidic and basic compounds were achieved with selectivity tuning based on the flexible combination of pressure (0–100 psi) and voltage. Taking advantage of the excellent permeability of silica monolithic columns, use of a step flow gradient enabled elution of compounds with different charge state.     

Chirality induction in a cation-driven assembly using a crowned metalloporphyrin

15-Crown-5-appended metalloporphyrin causes a K(+)-driven self-organization to bind a bifunctional guest ditopically, thereby allowing the circular dichroism (CD) detection of chirality induced in the ensemble when chiral amines are employed as the guest; the chiroptical properties are discussed.     

Characteristics of reference electrodes using a polymer gate ISFET

A new type of ISFET with a Parylene gate as a site-free and ion-blocked membrane has been proposed for a reference electrode. The reference ISFET should be insensitive to the variation of ion concentrations of all ions or a specific ion in the electrolyte and should have a constant gate surface potential. In this paper, the operation of this reference ISFET is analysed by the site binding model and the conditions required to make the gate surface potential constant are examined. In general, the surface potential of an electrolyte-insulator-semiconductor (EIS) system is determined by two factors, i.e., the available surface site density of the insulator and the total charge density of the semiconductor, and it can be made constant by controlling the total charge density of the semiconductor. The preliminary experimental results on the electrolyte-Parylene-Si diode and ISFET are in good agreement with the theoretical calculations and suggest that a reference ISFET could be realized by using the Parylene gate.     

Characterization of polyolefin melts using the polymer reference interaction site model integral equation theory with a single‐site united atom model

A general approach, based on the polymer reference interaction site model (PRISM) integral equation theory, suitable for characterizing arbitrarily complex polyolefin melts is described. We tested the method by calculating the melt structures of linear polyethylene (PE) and isotactic polypropylene (iPP) and the spinodal decomposition temperatures for PE/iPP blends. The computational expense of the PRISM calculation was reduced with a single‐site united atom model in which the polyolefin CH, CH₂, and CH₃ groups were approximated as chemically equivalent sites with spherically symmetric energetic interactions. The site–site interactions were defined by a potential function comprising a hard core with an attractive Lennard–Jones term. These energetic parameters were optimized with a central composite design strategy that enabled a simultaneous fit of experimental melt density and structure factor data. Values were obtained for PE and iPP individually and for common universal parameters that could potentially be used for all polyolefins. The rotational isomeric state–metropolis Monte Carlo (RMMC) technique was used to generate sets of conformers at specified temperatures covering the melt‐temperature range of the polymers. The characteristic ratio was used to assess the quality of the conformers and the RMMC method. Values of 9.68 for PE and 9.27 for iPP were obtained. The single‐chain structure factors calculated by the RMMC method were used to calculate the total structure factor for each melt. These were validated against published X‐ray diffraction results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1803–1814, 2001     

Embossing of organic thin films using a surfactant assisted lift-off technique

A simple technique for patterning organic materials using a surfactant assisted lift-off method is proposed. Thin films of various organic materials are prepared, and areas in contact with a surfactant coated poly(dimethylsiloxane) (PDMS) stamp are selectively removed. The general applicability of this technique is shown for materials containing nitrate, amine, and carboxylic acid functional groups. This technique provides a new methodology for fabricating patterns with vertical dimensions ranging from 30 nm up to 3 μm on organic thin films with specific functional groups.     

Formation of cellulose acetate membranes using a supercritical fluid assisted process

Microporous cellulose acetate membranes have been prepared from polymer–acetone solutions using a supercritical fluid phase inversion process in which CO₂ acts as the non-solvent. Series of experiments were performed at various polymer concentrations, temperatures and pressures. The structure of the resulting membranes was analysed using scanning electron microscopy. We operated with polymer concentrations ranging between 5 and 40% (w/w) in acetone obtaining different pore dimensions and membrane structures. Increasing the percentage of polymer in the solution, the structure of the membranes changed from beads-like structure to cellular structure. Polymer concentration also influenced the mean diameter of the pores that ranged from 2 to 50 μm for polymer concentrations from 40 to 5% (w/w). We also tested membrane formation pressures between 100 and 200 bar and at temperature between 45 and 65 °C. Pressure influences the change in membrane structure from cellular to beads-like, whereas temperature has a minor influence on pore size: both the effects can be partially related to CO₂ density. Cellulose acetate membrane formation mechanisms have also been discussed.     

Flexible generation of gradient electrospinning nanofibers using a microfluidic assisted approach

The nanofiber surface modified with physical or chemical gradients is very useful in a wide range of areas including tissue engineering, regenerative medicine, drug screening, and biomaterial chemistry. In this work, we presented a novel and straightforward microfluidic assisted approach to produce electrospinning nanofibers containing gradients in different compositions, nanoparticles and biomolecule concentrations. The series of gradient nanofibers were mainly produced by using a two inlet microfluidic device in combination with an electrospinning nozzle on a 3-D controllable platform, which exhibited different functions and properties. The controlled nanofibers with incorporated biomolecule gradient were used for guiding the spatial differentiation in mesenchymal stem cells (MSCs). This established approach is very simple, and flexible to operate, which might find enormous potential for biology and tissue engineering applications.     

Absolute free-energy calculations of liquids using a harmonic reference state

Absolute free-energy methods provide a potential solution to the overlap problem in free-energy calculations. In this paper, we report an extension of the previously published confinement method (J. Phys. Chem. B 2006, 110, 17212-20) to fluid simulations. Absolute free energies of liquid argon and liquid water are obtained accurately and compared with results from thermodynamic integration. The method works by transforming the liquid state into a harmonic, solid reference state. This is achieved using a special restraint potential that allows molecules to change their restraint position during the simulation, which circumvents the need for the molecules to sample the full extent of their translational freedom. The absolute free energy of the completely restrained reference state is obtained from a normal mode calculation. Because of the generic reference state used, the method is applicable to nonhomogeneous, diffusive systems and could provide an alternative method in situations in which solute annihilation fails due to the size of the solute. Potential applications include calculation of solvation energies of large molecules and free energies of peptide conformational changes in explicit solvent.     

Calibration of a 2D-CDB spectrometer using a reference 133Ba source

A procedure for calibrating a FAST-ComTec 2D-CDB spectrometer using a ¹³³Ba source is presented. The energy calibration consisted of acquiring two-dimensional (2D) spectra by measuring simultaneously with two HPGe detectors the 356 and 511 keV peaks. As the ¹³³Ba source only emits one photon per decay, the Ba contribution to the 2D spectra was built up by taking two successive and uncorrelated events, i.e. one from each detector (pseudo-coincidence technique). The FWHM of the spectrometer was estimated from the E₁=E₂ diagonal of the spectra.     

Polymer support assisted selective functionalization of azoles using a palladium-catalyzed coupling reaction

Regioselective palladium-catalyzed monoarylation of azoles was achieved using iodobenzoate immobilized on an insoluble polymer support. The positional selectivity for the coupling reaction was dramatically influenced by the presence of CuI. No diarylation was observed in either case. Unsymmetrical diarylation was also obtained with the polymer support using sequential coupling reactions.     

Nanorod shape separation using surfactant assisted self-assembly

High quality single size nanorods can be separated from polydisperse samples using surfactant-assisted nanorod self-assembly.     

Analysis of all-rac-alpha-tocopheryl acetate and retinyl palmitate in medical foods using a zero control reference material (ZRM) as a method development tool

A liquid chromatographic method is described for analysis of all- rac-alpha-tocopheryl acetate and retinyl palmitate in medical food. The vitamins are extracted in isopropyl alcohol and hexane-ethyl acetate without saponification and quantitated by normal-phase chromatography with fluorescence detection. All rac-alpha-tocopheryl acetate and retinyl palmitate are chromatographed isocratically with a mobile phase of 0.5% (v/v) and 0.125% (v/v) isopropyl alcohol in hexane, respectively. Recovery studies performed on a medical food zero control reference material (ZRM) fortified with the analytes averaged 99.7% (n = 25) for retinyl palmitate and 101% (n = 25) for all- rac-alpha-tocopheryl acetate. Coefficients of variation were 0.87-2.63% for retinyl palmitate and 1.42-3.20% for all-rac-alpha-tocopheryl acetate. The method provides a rapid, specific, and easily controlled assay for analysis of vitamin A and vitamin E in medical foods. Use of chlorinated solvents is avoided.     

Neural network model predictive control of a styrene polymerization plant: online testing using an electronic worksheet

The batch styrene polymerization process presents transient and nonlinear temperature behavior. In this work, manual control and open loop experiments were carried out in order to build a process knowledge database. Initially, a cascade feedback control loop was implemented by manipulating the thyristor unit of the electrical heater in the thermal fluid tank. Aiming at the MPC development, algebraic equations of a neural network and its adjusted parameters were implemented in an electronic worksheet. Every five seconds, the worksheet was updated with measurements (reactor temperature, thermal fluid temperature and thyristor position) by means of the OLE for the Process Control protocol (OPC). The one-step-ahead temperature prediction was then employed in the objective function of the worksheet solver which used Visual Basic Applications programming. The manipulated variable action was then calculated and sent to the process. A hybrid controller (cascade feedback and MPC) outperformed the pure strategies since the time-integral performance indexes, IAE and ITAE, were reduced by around 22 % and 32 %, respectively. Methodology for the Model Predictive Control presented in this study was considered feasible because the solver of Microsoft Office Excel (2007) is very friendly, easy to understand and ready to implement using VBA.     

High asymmetric induction using a diastereomeric mixture of axially dissymmetric ligands

We have reported that our new axially dissymmetric ligand with two chiral centers, (R_a)-2,2′-bis[(R)-1H-1-hydroxyperfluorooctyl]biphenyl ((R_a)-(R)₂-1c, or tentatively called as (R_a)-(R)₂-PFCAB-7), worked as a good asymmetric inducer for the reaction of benzaldehyde with diethylzinc. Now, a mixture of (R_a)-(R)₂- and (S_a)-(R)₂-PFCAB-7 even in 1:4 ratio (−60% de) was found to give nearly the same asymmetric induction as pure (R_a)-(R)₂-PFCAB-7 of the corresponding molar percents. This result suggests that both isomers do not form complex and that (R_a)-(R)₂-PFCAB-7 accelerates the reaction and induces high asymmetry, while (S_a)-(R)₂-1c does not accelerate the reaction significantly and does not induce asymmetry at all. This ligand of low ee, (R_a)-(R)₂-PFCAB-7 of 20% ee, did not show appreciable asymmetric amplification, suggesting no formation of heterochiral complex.     

Optical induction - IV : Optical induction by using homogeneous catalyst

Better optical induction during Michael addition has been achieved by using new homogeneous catalysts based on quinine and quinidine.     

The possibility of using beef tallow biodiesel as a viscosity reference material

This study analyses the possibility of using beef tallow biodiesel transesterified with ethanol, provided by Universidade Federal Fluminense, as a viscosity reference material for biodiesels. The quantity viscosity was measured with capillary viscometers, according to Brazilian standards, in a temperature range between 20 °C and 40 °C for characterisation, and at 40 °C for homogeneity, in short-term stability (90 days) and long-term stability (450 days). Thirty-nine samples were stored, 9 at 45 °C, 6 at 4 °C and 24 at 20 °C. The behaviour of viscosity is analysed considering the estimated uncertainty of measurements for characterisation, homogeneity and stability. The reason to study a transesterified biofuel with ethanol lies in the fact that it is easy to produce this fluid from sugarcane in Brazil.     

Quality control and reference materials in speciation analysis

This contribution describes the need and some strategies for a rigid quality control in speciation analysis. Firstly, the term “chemical speciation” is defined and differentiated from experimental concepts now called “operationally defined speciation” or “functionally defined speciation”. The need for quality control in speciation is given by the big number of sources of errors during sampling, sample preparation, separation and detection. Errors such as stability problems, contaminations or losses, spectral interferences etc. are discussed. On the other hand, several concepts for problem solutions are described. One of these solutions is the use of certified reference materials (CRM). Unfortunately, species-certified CRM are only available for few matrices and few elements, e.g. mercury in fish or sediments, lead in solutions and urban dust etc. Therefore special quality control strategies are necessary for each part of the analytical speciation procedure. Several examples of such procedures are given and discussed. Received: 25 July 1998 / Accepted: 8 August 1998     

一混沌模型系综模拟研究

用随机模拟方法研究了化学混沌模型的介观动力学。对该混沌模型的系综模拟发现,在这种不稳定运动中存在强烈的内部涨落,然而由于混沌运动整体上的稳定性,使得系综中的代表点被限制在混沌吸引子上,并且单个代表点形成的随机轨道很好地保持了确定性混沌吸引子的基本特征。     

A basic measurement model for reference material preparation

The basic model $ x_{\text{CRM}} = x_{\text{char}} + \delta x_{\text{bb}} + \delta x_{\text{sts}} + \delta x_{\text{lts}} $ in the ISO Guide 35 for the evaluation of uncertainty is reviewed. In the basic model, the authors of the Guide assume that the homogeneity and stability studies are designed in such a way that the values of the error terms are zero, but their uncertainties are not. Based on their assumption, it is shown that the basic model in the Guide requires output quantity x _CRM to be employed as input quantities to define ??x _bb, ??x _sts, and ??x _lts, which results in circular reasoning on the value of CRM. In order to revise the basic model in the Guide, a proposed basic model Y?=?X is derived from the general model Y?=?X(1?+?b??T) in the Guide as the special case of T?=?0. The uncertainty evaluation for the proposed model is discussed. It is shown that it is not necessary to evaluate the uncertainty due to the between-bottle inhomogeneity u _bb separately, when a single method is employed in the characterization. The u _bb is shown to be one of the uncertainty components of the certified value x _char, because x _char is the mean value of at least 10 bottles.