Isolation and purification of the bioactive carotenoid zeaxanthin from the microalga Microcystis aeruginosa by high-speed counter-current chromatography

High-speed counter-current chromatography was successfully applied for the first time to the isolation and purification of the bioactive carotenoid zeaxanthin from the cyanobacterium Microcystis aeruginosa. The crude zeaxanthin was obtained by extraction with organic solvents after the microalgal sample had been saponified. Preparative high-speed counter-current chromatography with a two-phase solvent system composed of n-hexane-ethyl acetate-ethanol-water (8:2:7:3, v/v/v/v) was successfully performed yielding zeaxanthin at 96.2% purity from 150 mg of the crude extract in a one-step separation. The recovery of zeaxanthin was 91.4%. This was also the first report that zeaxanthin was successfully separated and purified from microalgae.     

Analysis of monoclonal antibody by a novel CE‐UV/MALDI‐MS interface

mAbs are highly complex proteins that present a wide range of microheterogeneity that requires multiple analytical methods for full structure assessment and quality control. As a consequence, the characterization of mAbs on different levels is particularly product‐ and time‐consuming. CE‐MS couplings, especially to MALDI, appear really attractive methods for the characterization of biological samples. In this work, we report the last instrumental development and performance of the first totally automated off‐line CE‐UV/MALDI‐MS/MS. This interface is based on the removal of the original UV cell of the CE apparatus, modification of the spotting device geometry, and creation of an integrated delivery matrix system. The performance of the method was evaluated with separation of five intact proteins and a tryptic digest mixture of nine proteins. Intact protein application shows the acquisition of electropherograms with high resolution and high repeatability. In the peptide mapping approach, a total number of 154 unique identified peptides were characterized using MS/MS spectra corresponding to average sequence coverage of 64.1%. Comparison with NanoLC/MALDI‐MS/MS showed complementarity at the peptide level with an increase of 42% when using CE/MALDI‐MS coupling. Finally, this work represents the first analysis of intact mAb charge variants by CZE using an MS detection. Moreover, using a peptide mapping approach CE‐UV/MALDI‐MS/MS fragmentation allowed 100% sequence coverage of the light chain and 92% of the heavy chain, and the separation of four major glycosylated peptides and their structural characterization.     

Photodissociation of high molecular weight peptides and proteins in a two-stage linear time-of-flight mass spectrometer

A two-stage linear time-of-flight mass spectrometer is used to investigate the requirements for performance of laser photodissociation of peptide and protein ions. Results are presented that demonstrate that desorption and dissociation laser pulses can be synchronized to irradiate ions that travel at high velocities down the drift tube of a time-of-flight mass spectrometer. For example, 193-nm photodissociation of bovine insulin and doubly charged lysozyme is demonstrated, and laser power studies suggest that dissociation is initiated by the absorption of a single 193-nm photon. These results are encouraging because they suggest that laser photodissociation of high molecular weight proteins can lead to fragmentation on time scales compatible with time-of-flight mass spectrometry.     

Experimental investigation of discharge characteristics in enhanced glow discharge plasma immersion ion implantation

In enhanced glow discharge plasma immersion ion implantation (EGD-PIII) that involves a small pointed anode and large area tabular cathode, the high negative substrate bias not only acts as the plasma producer but also supplies the implantation voltage. Consequently, an electric field is created to focus the electrons and the electron focusing field in turn enhances the glow discharge process. In this work, the discharge characteristics of EGD-PIII are investigated experimentally. The discharge initiation and extinction characteristics during pulsed biasing are discussed. The duration of the post pulse-off plasma is explained from the viewpoint of particle motion and experimentally verified by employing an auxiliary disk. Our experiments show that a dual-pulse method may be utilized to determine the remnant plasma.     

Optical and structural characteristics of yttrium doped ZnO films using sol–gel technology

Yttrium-doped ZnO gel was spin-coated on the SiO₂/Si substrate. The as-prepared ZnO:Y (YZO) thin films then underwent a rapid thermal annealing (RTA) process conducted at various temperatures. The structural and photoluminescence characteristics of the YZO films were discussed thereafter. Our results indicated that the grain size of YZO thin films being treated with various annealing temperatures became smaller as compared to the ones without being doped with yttrium. Furthermore, unlike other ZnO films, the grains of YZO thin films appeared to separate from one another rather than aggregating together as both types of the films were annealed under the same environment. The photoluminescence characteristic measured showed that the UV emission was the only radiation obtained. However, the UV emission intensity of YZO thin film was much stronger than that of the ZnO thin film after annealing them with the same condition. It was also found that the intensity increased with an increase in the annealing temperature, which was caused by the exciton generated and the texture surface of the YZO thin film.     

Ratiometric fluorescent Zn chemosensor constructed by appending a pair of carboxamidoquinoline on 1,2-diaminocyclohexane scaffold

By appending a pair of carboxamidoquinoline pendants onto 1,2-diaminocyclohexane scaffold via N-alkylation, multifunctionalized ACAQ was designed and synthesized as a water soluble fluorescent ratiometric chemosensor for Zn²⁺. In 50% aqueous methanol buffer pH 7.4 solution, upon excitation at 316 nm, ACAQ (5 μM) displayed a selective ratiometric fluorescence changes with a shift from 410 to 490 nm in response to the interaction with Zn²⁺. After binding with 1 equiv of Zn²⁺, ACAQ exhibited a 12-fold enhancement in I₄₉₀/I₄₁₀ characterized by a clear isoemissive point at 440 nm. The metal sensor binding mode was established by Job’s plot and the combined fluorescence and ¹H NMR spectroscopic method. The selectivity of the probe toward biological relevant cations and transition metal ions was proven to be good. In addition, the interference caused by Cu²⁺ and Cd²⁺ in the quantitation of Zn²⁺ can be completely eliminated by the use of diethyldithiocarbamate as the screening agent. Exploitation of ACAQ as the sensing probe, ratiometric determination of Zn²⁺ with the limit of detection (LOD) at 28.3 nm can be realized. In addition, the unique responsive properties of the probe toward Fe³⁺ and Zn²⁺ were used to construct a fluorescent switch. The membrane permeability of ACAQ to living cells and bio-imaging of Zn²⁺ were demonstrated.     

Double-imprinted polymer based on cross-linked poly(vinylimidazole–trimethylolpropane trimethacrylate) in solid phase extraction for determination of lead from wastewater samples by UV–vis spectrophotometry

The monitoring of the heavy metal pollution in wastewater is increasingly becoming a crucial global issue since they tend to accumulate in food chains and can cause many biological abnormalities. In this work, it was developed a novel lead ion-imprinted polymer (IIP) using sodium dodecyl sulphate (SDS) as a second template to be used as adsorbent in solid phase extraction (SPE) for determination of lead from wastewater samples by UV–vis spectrophotometry. The polymer called IIP–SDS was synthesised by a double-imprinting process with lead (template) and SDS (template). IIP–SDS was characterised by infrared spectroscopy Fourier transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. IIP–SDS showed good recovery for lead (around 82.0%), while the IIP (only lead as template) was 72.2% and non-IIP was 44.9%. Thus, the double-imprinting process for the preconcentration of Pb²⁺ proved to be a more adequate methodology than IIP with a single template. The optimised parameters of sample preparation were washing solvent (2.0 mL of tetrahydrofuran), type and volume of eluent (5 mL of 1 mol L^?1 hydrochloric acid), sample amount (30 mL of water spiked with 10.0 µg mL^?1), amount of IIP–SDS (400 mg) and sample pH (pH = 4.5). Linearity ranged from 10 to 125 µg L^?1 with r > 0.992. The limit of detection and quantification were 6.3 and 10 µg L^?1, respectively. The precision (relative standard deviation, %) and accuracy (relative error, %) were lower than 15%. Finally, IIP–SDS may be an alternative and effective adsorbent for SPE procedures in monitoring of wastewater samples.     

Liquid chromatography/mass spectrometry for metabonomics investigation of the biochemical effects induced by aristolochic acid in rats: the use of information-dependent acquisition for biomarker identification

The toxic effects of oral administrations of nephrotoxic and carcinogenic aristolochic acid (AA) to male Sprague-Dawley rats were investigated by using high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. Analysis of the urine and plasma samples revealed distinct changes in the biochemical patterns in the AA-dosed rats. After peak finding and alignment, principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) were used for multivariate data analysis. Potential biomarkers were studied by high-resolution mass spectrometry (MS) and tandem mass spectrometry (MS/MS) analyses. The MS/MS spectra of all endogenous metabolites satisfying the pre-defined criteria were acquired in a single information-dependent acquisition (IDA) analysis, demonstrating that IDA was an efficient approach for structural elucidation in metabonomic studies. Citric acid and a glucuronide-containing metabolite were observed as potential biomarkers in rat urine. A significant increase in plasma creatinine concentration was also observed in the AA-dosed rats, which indicated that AA induced an adverse effect on the renal clearance function.     

Thermo-mechanical method for the determination of the fractal dimension of fat crystal networks

The physical properties of a fat are determined by its thermal history, processing conditions, chemical composition, polymorphism and spatial distribution of mass. The mass fractal dimension of a fat crystal network can be determined from the slope of the log–log plot of the storage modulus (G′) versus the solid fat content (SFC). Different SFCs were obtained by melting the fat, diluting it to different extents in liquid oil, and crystallizing the blends under specific conditions. One of the major drawbacks of this method is the inability of characterizing the native structure of an already crystallized fat. In the thermo-mechanical method developed in this study, SFC is changed via temperature variations instead. At each temperature, the G′ and SFC were measured and the fractal dimension calculated as described above. The thermomechanical method proved to be a simpler and more reliable estimator of the fractal dimension of a fat crystal network than the dilution method.     

Droplet Microfluidic Optimisation Using Micropipette Characterisation of Bio-Instructive Polymeric Surfactants

Droplet microfluidics can produce highly tailored microparticles whilst retaining monodispersity. However, these systems often require lengthy optimisation, commonly based on a trial-and-error approach, particularly when using bio-instructive, polymeric surfactants. Here, micropipette manipulation methods were used to optimise the concentration of bespoke polymeric surfactants to produce biodegradable (poly(d,l-lactic acid) (PDLLA)) microparticles with unique, bio-instructive surface chemistries. The effect of these three-dimensional surfactants on the interfacial tension of the system was analysed. It was determined that to provide adequate stabilisation, a low level (0.1% (w/v)) of poly(vinyl acetate-co-alcohol) (PVA) was required. Optimisation of the PVA concentration was informed by micropipette manipulation. As a result, successful, monodisperse particles were produced that maintained the desired bio-instructive surface chemistry.