Extraction and preconcentration of manganese(II) from biological fluids (water, milk and blood serum) using supported liquid membrane and membrane probe methods

A supported liquid membrane (SLM) technique was investigated to extract and preconcentrate Mn(II) from water, milk and blood serum. Di-2-ethylhexyl phosphoric acid (DEHPA) with kerosene as diluent was used as a carrier in the membrane to transport Mn(II) from the donor side to acceptor side. The membrane was modified with tri-n-octylphosphine oxide (TOPO) to increase its polarity. Various parameters were investigated to optimise the extraction efficiency: pH of the donor and acceptor phase, dilution factor, donor flow rate. Scanning electron microscope images of the membranes revealed that some matrix compounds were deposited on the surface, thus limiting the extraction process. The optimum conditions found were: pH 3 in the donor phase, 0.2 M nitric acid in the acceptor phase, donor flow rate between 1.0 and 0.3 ml min⁻¹, 15% (w/v) DEPHA and 10% TOPO in kerosene as a carrier in membrane, and dilution factors of 20 times for blood serum and 30 times for milk. The extraction efficiencies were found to be low but constant and highly reproducible showing, strong dependence on sample matrix. The new SLM extraction probe was developed and optimised for Mn(II) extraction. Compared to traditional SLM configurations, this is the simplest configuration. The use of stirring allows the same sample to be extracted many times giving higher extraction efficiency and to minimise the sample size. Adsorptive stripping voltammetry (AdSV) was applied to measure Mn(II) concentration. The optimised method was used to determine the concentration of Mn(II) in water, milk and blood serum samples.     

气体分离膜成膜技术及成膜机理的研究进展

介绍了气体分离膜的发展历史，从７０年代初期反渗透膜干燥技术获得气体分离膜，８０年代出现的“阻力型”“复合型”到９０年代发明的致密皮层非对称气体分离膜，着重介绍了成膜液相转化过程中发生微相分离的成膜机理，最后，提出现行成膜技术的不足及成膜机理的研究方向。     

Design and application of a post-column extraction system compatible with miniaturized liquid chromatography

An on-line, post-column, extraction system suitable for use with miniaturized HPLC (0.7–1 mm i.d. columns) is described. The system consists of a 30° angle segmenting tee, a PTFE extraction coil of variable length and a membrane phase separator. The internal volume of the phase separator is less than 1 l. The total variance contribution of the system is between 1 and 6 sec².The determination of the anti-cancer drugs VP 16 and VM 26 in urine by means of reversed-phase HPLC and fluorescence detection, using both on-column preconcentration and the present miniaturized post-column extraction system is presented as an application.     

Polystyrene-type Uniform Porous Microsphere Enables High Resolution and Low-Pressure Chromatography of Natural Products – A Case Study with Icariin Purification

An efficient low-pressure preparative chromatography for purification of icariin from crude extract has been developed by employing a novel uniform porous microsphere, named PST, as packing material. A comparison was made between the PST medium and a commercially available silica-based C₁₈ medium on their column chromatographic performance. The PST column demonstrated a higher resolution and better selectivity than the C₁₈ column. Crude extract of 20% icariin can be purified to 90.0% with the recovery of 99.9% and column loadability of 2.5 mg·mL^–1 medium on the PST column under the optimized condition. After crystallization the purity of icariin can reach more than 98% with a total recovery of 93%. The product structure was determined by means of UV, IR, MS and NMR.Acknowledgements This work was supported by the National Natural Science Foundation of China under Contract No. 20125616 and 20136020.     

Thylakoid membrane at altered metabolic state: challenging the forgotten realms of the proteome

Analysis of the membrane integral proteome is mainly dependent on the ability of protein separation. Blue-native polyacrylamide gel electrophoresis (BN-PAGE) is a technique capable of efficient membrane protein separation, so far mainly applied to the mitochondrial oxidative phosphorylation machinery. Applying BN-PAGE to the thylakoid membranes after mild solubilization with digitonin we succeeded in displaying the response of the green algae Chlamydomonas reinhardtii to altered culture conditions. In addition, by peptide mass fingerprinting and matrix assisted laser desorption/ionization-mass spectrometry (MALDI-MS) extremely hydrophobic subunits of the photosystem complexes with 5-11 transmembrane helices were identified, which could not be accessed by in-gel digestion in previous studies.     

Molecular iodine selective membrane for iodate determination in salt samples: chemical amplification and preconcentration

A molecular iodine selective membrane has been used for preconcentration of I₂ generated in situ by iodometric reaction of with excess I⁻ in acidic medium (pH 1–2). This iodometric reaction amplifies the iodine content six times resulting in enhancement of analytical response ranging from three times for molecular methods to six times for elemental methods. The chemical conditions of this iodometric reaction were optimized for quantitative generation and subsequent sorption of I₂ in the membrane samples (96 ± 3%). The homogeneous transparent membrane was prepared by immobilizing I₂-complexing polyvinylpyrrolidone (PVP) in the plasticized cellulose triacetate matrix. Four different analytical methods were examined for quantitative determination of in iodized salt samples by preconcentrating it as I₂ in the membrane matrix. These methods were: (1) spectrophotometry of the PVP-I₂ complex formed in the membrane matrix, (2) a radiotracer method using I⁻ tagged with ¹³¹I radiotracer, (3) instrumental neutron activation analysis (INAA), and (4) energy-dispersive X-ray fluorescence (EDXRF) analysis. The contents thus determined in the iodized salt samples by the membrane-based radiotracer method were compared with the total iodine determined in salt samples by epithermal instrumental neutron activation analysis (EINAA). The membrane-based method for iodate determination in salt samples has advantages over conventional analytical methods, for example preconcentration and chemical amplification, and is free from interference from anions. Figure A molecular iodine selective membrane was used for the quantitative preconcentration of I₂ generated in situ by iodometric reaction of with excess I^aˆ’ in acidic medium, which amplifies iodine content six times     

Applicability of nanofiltration and reverse osmosis for the treatment of wastewater of different origin

Membrane separations are finding greater use in wastewater treatment because of their efficiency. In order to prove the effectiveness of membrane filtration an applicability study is carried out. Nanofiltration and reverse osmosis membranes are tested under quite different conditions to reduce the chemical oxygen demands (COD) of wastewaters to meet the Council Directive 76/464/EEC release limit. Two kinds of real wastewaters were selected for the investigation. The wastewaters represent extreme different circumstances since the difference between their COD is two orders of magnitude. All of the membranes tested can be applied either to the treatment of wastewater of high COD (pharmaceutical wastewater) or wastewater of low COD (dumpsite leachate), since the different conditions do not change the membrane characteristics. The experimental data show that none of the membranes can decrease the COD to the release limit in one step. However, if two-stage filtrations (nanofiltration followed by reverse osmosis) are accomplished for both of the wastewaters, a total COD reduction of 94% can be achieved. With the application of the two-stage filtration the COD of the wastewater of low COD can be decreased below the release limit but in case of wastewater of the high COD further treatment will be required.      

Polymer nanocomposite membranes and their application for flow catalysis and photocatalytic degradation of organic pollutants

The modern world essentially needs a chemical industry that can operate with reduced production costs, and produce high-quality products with low environmental impact. The polymer nanocomposite-based flow catalytic membrane reactor where the reaction and separation can be amalgamated in one unit is considered as one of the new alternative solutions to solve these problems. In this review, we have discussed state-of-the-art flow-through catalytic reactors based on polymer nanocomposite membranes. The unique advantages of flow catalysis include uninterrupted operation, good recyclability, and reaction product without contamination that leads to simple purification. Various catalytic model reactions such as coupling, hydrogenation, esterification in the flow system are presented. We have also presented an overview of methods adopted for preparing such nanocomposite membranes. In the last section, a discussion has been made on the recent advances on polymer-based nanocomposite membranes for the degradation and separation of organic pollutants.     

ActTRANS: Functional classification in active transport proteins based on transfer learning and contextual representations

MotivationPrimary and secondary active transport are two types of active transport that involve using energy to move the substances. Active transport mechanisms do use proteins to assist in transport and play essential roles to regulate the traffic of ions or small molecules across a cell membrane against the concentration gradient. In this study, the two main types of proteins involved in such transport are classified from transmembrane transport proteins. We propose a Support Vector Machine (SVM) with contextualized word embeddings from Bidirectional Encoder Representations from Transformers (BERT) to represent protein sequences. BERT is a powerful model in transfer learning, a deep learning language representation model developed by Google and one of the highest performing pre-trained model for Natural Language Processing (NLP) tasks. The idea of transfer learning with pre-trained model from BERT is applied to extract fixed feature vectors from the hidden layers and learn contextual relations between amino acids in the protein sequence. Therefore, the contextualized word representations of proteins are introduced to effectively model complex structures of amino acids in the sequence and the variations of these amino acids in the context. By generating context information, we capture multiple meanings for the same amino acid to reveal the importance of specific residues in the protein sequence.ResultsThe performance of the proposed method is evaluated using five-fold cross-validation and independent test. The proposed method achieves an accuracy of 85.44 %, 88.74 % and 92.84 % for Class-1, Class-2, and Class-3, respectively. Experimental results show that this approach can outperform from other feature extraction methods using context information, effectively classify two types of active transport and improve the overall performance.     

Pyrimidinetrione-imidazoles as a Unique Structural Type of Potential Agents towards Candida Albicans: Design,Synthesis and Biological Evaluation

Substantial morbidity and mortality of fungal infections have aroused concerns all over the world, and common Candida spp. currently bring about severe systemic infections. A series of pyrimidinetrione-imidazole conjugates as potentially antifungal agents were developed. Bioassays manifested that 4-fluobenzyl pyrimidinetrione imidazole 5 f exerted favorable inhibition towards C. albicans (MIC=0.002 mM), being 6.5 folds more active than clinical antifungal drug fluconazole (MIC=0.013 mM). Preliminary mechanism research indicated that compound 5 f could not only depolarize membrane potential but also permeabilize the membrane of C. albicans. Molecular docking was operated to simulate the interaction mode between molecule 5 f and CYP51. In addition, hybrid 5 f might form 5 f -DNA supramolecular complex via intercalating into DNA. The interference of membrane and DNA might contribute to its fungicidal capacity with no obvious tendency to induce the resistance against C. albicans. Conjugate 5 f endowed good blood compatibility as well as low cytotoxicity towards HeLa and HEK-293T cells.