Synthesis of New Aza-crown Ethers Containing Pyridine Ring and their Liquid Membrane Transport of Alkali Cations

Five new aza-crown ethers have been prepared by the condensation of 2,6-bis[(2-formylphenyl)oxymethyl] pyridine with different diamino compounds in hot methanol, the bis-Schiff bases without isolation were reduced with NaBH4 to afford the corresponding aza-crown ethers. The liquid membrane transport or alkali cations using the five new macrocycles as the ion-carriers was also studied.

Liquid Membrane Transport Behavior of Functional Substituted Crown Ethers for Amino Acids

Three functional substituted crown ethers were synthesized as liquid membrane transport carriers for amino acids. The result obtained shows that this kind of ditopic ligands can transport sodium salt of amino acids in good rate value especially the one with two pyridinyl groups as binding site outside the macrocycle.

Electrifying Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) for focalized heating in oxygen transport membranes

Industry decarbonization requires the development of highly efficient and flexible technologies relying on renewable energy resources,especially biomass and solar/wind electricity.In the case of pure oxygen production,oxygen transport membranes(OTMs)appear as an alternative technology for the cryogenic distillation of air,the industrially-established process of producing oxygen.Moreover,OTMs could provide oxygen from different sources(air,water,CO_(2),etc.),and they are more flexible in adapting to current processes,producing oxygen at 700^(-1)000℃.Furthermore,OTMs can be integrated into catalytic membrane reactors,providing new pathways for different processes.The first part of this study was focused on electrification on a traditional OTM material(Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)),imposing different electric currents/voltages along a capillary membrane.Thanks to the emerging Joule effect,the membrane-surface temperature and the associated O_(2) permeation flux could be adjusted.Here,the OTM is electrically and locally heated and reaches 900℃on the surface,whereas the surrounding of the membrane was maintained at 650℃.The O_(2)permeation flux reached for the electrified membranes was~3.7 NmL min^(-1)cm^(-2),corresponding to the flux obtained with an OTM non-electrified at 900℃.The influence of depositing a porous Ce_(0.8)Tb_(0.2)O_(2-δ) catalytic/protective layer on the outer membrane surface revealed that lower surface temperatures(830℃)were detected at the same imposed electric power.Finally,the electrification concept was demonstrated in a catalytic membrane reactor(CMR)where the oxidative dehydrogenation of ethane(ODHE)was carried out.ODHE reaction is very sensitive to temperature,and here,we demonstrate an improvement of the ethylene yield by reaching moderate temperatures in the reaction chamber while the O_(2) injection into the reaction can be easily fine-tuned.

Synthesis of Bis-substituted Calix[4]arenes and Mechanism of Substituents Effect on K^+ and Hg^(2+) Ions Transports through Liquid Membrane

New calix[4]arene derivatives containing nitro,amino and benzoyl in the upper and lower rims of molecule were successfully synthesized.Their effectiveness towards K+ and Hg2+ across bubbling liquid membrane(BLM) was examined.For K+ ion transfer,preserving phenolic hydroxyl in the lower rim of calix[4]arene could enhance its transport ability.When benzoyl replaced phenolic hydroxyl,the transport would fall off,because benzoyl caused steric hindrance on the K+ transfer.The study also revealed that the group having the electron-withdrawing conjugative effect on phenolic hydroxyl,-NO2 in the upper rim of calix[4]arene,made transport ability of calix[4]arene fall off.On the contrary,-NH2 that had electron-repulsive conjugative effect enhanced the transport ability of the compound.For Hg2+ ion,only -NH2 in the upper rim of calix[4]arenes had high affinity for it and contributed to Hg2+ transfer.Transport amount of Hg2+ ion increased with increasing calix[4]arene5 concentration and ΔpH in BLM.

Synthesis and Crystal Structure of A New Armed-tetraazacrown Ether and Its Liquid Membrane Transport of Alkali Metal Cations

A new tetra-N-substituted tetraazacrown ether derivative, 4,7,13,16-tetra(2-cyanobenzyl)-1,10-dioxa-4,7,13,16-tetraazacyclooctadecane, C 44H 48N 8O 2, has been synthesized and structurally characterized. It crystallizes in the monoclinic system, space group P2 1/c with a=1.1176(3) nm, b=2.1906(7) nm, c=0.8430(3) nm, V=2.0132(10) nm 3, β=102.740(5)°, Z=4, D c=1.189 g/cm 3, final R 1=0.0460, wR 2=0.0803. The liquid membrane transports of alkali metal cations using the new macrocycle as the ion-carrier were also studied. Compared with some macrocyclic ligands, our newly synthesized ligand showed a good selectivity ratio for Na +/Li +.

Plant Membrane Transport Research in the Post-genomic Era

Membrane transport processes are indispensable for many aspects of plant physiology including mineral nutrition,solute storage,cell metabolism,cell signaling,osmoregulation,cell growth,and stress responses.Completion of genome sequencing in diverse plant species and the development of multiple genomic tools have marked a new era in understanding plant membrane transport at the mechanistic level.Genes coding for a galaxy of pumps,channels,and carriers that facilitate various membrane transport processes have been identified while multiple approaches are developed to dissect the physiological roles as well as to define the transport capacities of these transport systems.Furthermore,signaling networks dictating the membrane transport processes are established to fully understand the regulatory mechanisms.Here,we review recent research progress in the discovery and characterization of the components in plant membrane transport that take advantage of plant genomic resources and other experimental tools.We also provide our perspectives for future studies in the field.

Polyvinylamine-Based Facilitated Transport Membranes for Post-Combustion CO_(2) Capture:Challenges and Perspectives from Materials to Processes

Carbon dioxide(CO_(2))capture by gas-separation membranes has become increasingly attractive due to its high energy efficiency,relatively low cost,and environmental impact.Polyvinylamine(PVAm)-based facilitated transport(FT)membranes were developed in the last decade for CO_(2) capture.This work discusses the challenges of applying PVAm-based FT membranes from materials to processes for postcombustion CO_(2) capture in power plants and cement factories.Experiences learned from a pilot demonstration system can be used to guide the design of other membranes for CO_(2) capture.The importance of module and process design is emphasized in the achievement of a high-performance membrane system.Moreover,the results from process simulation and cost estimation indicate that a three-stage membrane system is feasible for achieving a high CO_(2) purity of 95 vol%.The specific CO_(2) capture cost was found to significantly depend on the required CO_(2) capture ratio,and a moderate CO_(2) capture ratio of 50%presented a cost of 63.7USD per tonne CO_(2) captured.Thus,FT membrane systems were found to be more competitive for partial CO_(2) capture.

Molecular mechanisms of salinity tolerance in rice

Salinity is one of the major abiotic stresses which impose constraints to plant growth and production.Rice(Oryza sativa L.)is one of the most important staple food crops and a model monocot plant.Its production is expanding into regions that are affected by soil salinity,requiring cultivars more tolerant to saline conditions.Understanding the molecular mechanisms of such tolerance could lay a foundation for varietal improvement of salt tolerance in rice.In spite of extensive studies exploring the mechanism of salt tolerance,there has been limited progress in breeding for increased salinity tolerance.In this review,we summarize the information about the major molecular mechanisms underlying salinity tolerance in rice and further discuss the limitations in breeding for salinity tolerance.We show that numerous gene families and interaction networks are involved in the regulation of rice responses to salinity,prompting a need for a comprehensive functional analysis.We also show that most studies are based on whole-plant level analyses with only a few reports focused on tissue-and/or cell-specific gene expression.More details of salt-responsive channel and transporter activities at tissue-and cell-specific level still need to be documented before these traits can be incorporated into elite rice germplasm.Thus,future studies should focus on diversity of available genetic resources and,particular,wild rice relatives,to reincorporate salinity tolerance traits lost during domestication.

Fluid and Osmotic Pressure Balance and Volume Stabilization in Cells Dedicated to Professor Karl Stark Pister for his 95th birthday

A fundamental problem for cells with their fragile membranes is the control of their volume.The primordial solution to this problem is the active transport of ions across the cell membrane to modulate the intracellular osmotic pressure.In this work,a theoretical model of the cellular pump-leak mechanism is proposed within the general framework of linear nonequilibrium thermodynamics.The model is expressed with phenomenological equations that describe passive and active ionic transport across cell membranes,supplemented by an equation for the membrane potential that accounts for the electrogenicity of the ionic pumps.For active ionic transport,the model predicts that the intracellular fluid pressure will be balanced by the osmotic pressure and a new pressure component that arises from the active ionic fluxes.A model for the pump-leak mechanism in an idealized human cell is introduced to demonstrate the applicability of the proposed theory.

Evaluation of La_(0.7)Ca_(0.3)Cr_(0.95)Zn_(0.05)O_(3-δ)-Gd_(0.1)Ce_(0.9)O_(2-δ) Dual-phase Material and its Potential Application in Oxygen Transport Membrane

In this work, a dual-phase material consisting Gd0.1Ce0.9O2-δ （GDC, 60 wt%） was synthesized. of La0.7Ca0.3Cr0.95Zn0.05O3-δ （LCCZ, 40 wt%） and Properties including phase structure, sintering behavior, electrical conductivity and oxygen permeability for LCCZ-GDC were evaluated. The results show that dense LCCZ-GDC dual-phase disks were obtained at the sintering temperature of 1250, 1300, 1350 and 1400 ℃ by tape casting and high temperature sintering method. The grain sizes of both GDC and LCCZ grew up with the increasing of sintering temperature. The average grain size of GDC was about 0.5, 0.8, 1.4, 1.8 μm while the average grain size of LCCZ was about 0.8, 1.5, 1.8 and 2 pm after sintering at 1250, 1300, 1350 and 1400℃, respectively. Oxygen flux of LCCZ-GDC decreased with the increase of sintering temperature from 1250 to 1400 ℃. The oxygen flux of LCCZ-GDC sintered at 1250 ℃ reached 0.079 mL/min/cm2 at 975℃ with a membrane thickness of 800 μm. Dual-phase material of LCCZ-GDC will be a promising oxygen transport membrane material for its low sintering temperature and good microstructure.

System integration of China's first PEMFC locomotive

In the face of growing environmental pollution, developing a fuel-cell-driven shunting locomotive is a great challenge in China for environmental protection and energy saving, which combines the environmental advantages of an electric locomotive with the lower infrastructure costs of a diesel-electric locomotive. In this paper, the investigation status and the development trend of the fuel-cell-driven shunting locomotive were introduced. Through innovation of the power system using fuel cells, an experiment prototype of a fuel-cell shunting locomotive was developed, which would reduce the effects on the environment of the existing locomotives. This was the first locomotive to use a proton exchange membrane fuel-cell （PEMFC） power plant in China. From October 2012, we started to test the fuel-cell power plant and further test runs on the test rail-line in Chengdu, Sichuan. The achieved encouraging results can provide fundamental data for the modification of the current individual fuel cell locomotives or further development of the fuel-cell hybrid ones in China.

Transport and selectivity of indium through polymer inclusion membrane in hydrochloric acid medium

In the present paper, a polymer inclusion membrane （PIM） containing polyvinyl chloride （PVC）, and bis-（2-ethylhexyl） phosphate （D2EHPA） which was used as extracting agent was used for the recovery of In（Ⅲ） ions in hydrochloric acid medium. The effects of carrier concentration, feed phase pH, strip phase HCI concentration, temperature on the transport, and the membrane＇s stability and thickness were examined. And the conditions for the selective separation of In（Ⅲ） and CU（Ⅱ） were optimized. The results showed that the transport of In（Ⅲ） across PIM was consistent with the first order kinetics equation, and also it was controlled by both the diffusion of the metal complex in the membrane and the chemical reaction at the interface of the boundary layers. The transport flux （J0） was inversely proportional to the membrane thickness, however, the transport stability improved as the membrane thickness increased. The transport flux of In（Ⅲ） and CU（Ⅱ） was decreased by excessive acidity of feed phase and high concentration of Cl^- . The selectivity separation coefficient of In（Ⅲ）/Cu（Ⅱ） was up to 34.33 when the original concentration of both In（Ⅲ） and Cu（Ⅱ） was 80 mg· L^ -1 as well as the pH of the feed phase and the concentration of Cl^- in the adjusting context were 0.6 and 0.5 mol· L^-1, respectively. Within the range of pH = 1-3, the separation selectivity of In（Ⅲ）/Cu（Ⅱ） reached the peak in the case when the Cl^- concentration was 0.7 mol·L^ -1.

The effect of humidity on the CO_2/N_2 separation performance of copolymers based on hard polyimide segments and soft polyether chains:Experimental and modeling

In this work, we studied two copolymers formed by segments of a rubbery polyether（PPO or PEO） and of a glassy polyimide（BPDA-ODA or BKDA-ODA） suitable for gas separation and CO2 capture. Firstly, we assessed the absorption of water vapor in the materials, as a function of relative humidity（R.H.）, finding that the humidity uptake of the copolymers lies between that of the corresponding pure homopolymers values.Furthermore, we studied the effect of humidity on CO2 and N2 permeability, as well as on CO2/N2 selectivity, up to R.H. of 75%. The permeability decreases with increasing humidity, while the ideal selectivity remains approximately constant in the entire range of water activity investigated. The humidity-induced decrease of permeability in the copolymers is much smaller than the one observed in polyimides such as Matrimid? confirming the positive effect of the polyether phase on the membrane performance.Finally, we modeled the humidity-induced decrease of gas solubility, diffusivity and, consequently, permeability, using a suitable approach that considers the free volume theory for diffusion and LF model for solubility. Such model allows estimating the extent of competition that the gases undergo with water during sorption in the membranes, as a function of the relative humidity, as well as the expected reduction of free volume by means of water molecules occupation and consequent reduction of diffusivity.

Theoretical investigations of transport properties of organic solvents in cation-functionalized graphene oxide membranes： Implications for drug delivery

We perform detailed quantum chemical calculations to elucidate the origin and mechanism of the selective permeability of alkali and alkaline earth cation- decorated graphene oxide （M-GO） membranes to organic solvents. The results show that the selectivity is associated mainly with the transport properties of solvents in the membranes, which depends on two regions of the flow path： the sp3 C-O matrix of the GO sheets and the cation at the center of the hexagon rather than the sp~ region. According to the delocalization of ~ states in sp2 regions, we propose a design guide for high-quality M-GO membranes. The solvent-cation interaction essentially causes directional transport of molecules in the M-GO membranes under the transmembrane pressure, indicating a site-to-site mech- anism. The solvent-sp3 C-O matrix interaction may inhibit molecular transport between two fixed cations by consuming energy. The competition between energy consumption by the solvent-cation interaction and energy expenditure by the solvent-sp3 C-O matrix interaction leads to various transport properties of solvents and thus allows for the selective permeability of the M-GO membranes. Findings from the study are helpful for the future design of multifunctional M-GO macro-membranes as cost-effective solution nanofilters in chemical, biological, and medical applications

Diverse Functional Roles of Monosaccharide Transporters and their Homologs in Vascular Plants： A Physiological Perspective

Vascular plants contain two gene families that encode monosaccharide transporter proteins. The classical monosaccharide transporter（-like） gene superfamily is large and functionally diverse, while the recently identified SWEET transporter family is smaller and, thus far, only found to transport glucose. These transporters play essential roles at many levels, ranging from organelles to the whole plant. Many family members are essential for cellular homeostasis and reproductive success. Although most transporters do not directly participate in long-distance transport, their indirect roles greatly impact carbon allocation and transport flux to the heterotrophic tissues of the plant. Functional characterization of some members from both gene families has revealed their diverse roles in carbohydrate partitioning, phloem function, resource allocation, plant defense, and sugar signaling. This review highlights the broad impacts and implications of monosaccharide transport by describing some of the functional roles of the monosaccharide transporter（-like） superfamily and the SWEET transporter family.

Molecular rotors as a class of generally highly active ion transporters

We describe here a class of unconventional ion transporters,molecular rotors that transport ions through a rotating function rather than via traditional carrier or channel mechanisms.Mimicking macroscopic rotors,these molecular rotors consist of three modularly tunable components,i.e.,a membrane-anchoring stator,a crown ether-containing rotator for ion binding and transport,and a triple bond-based axle that allows the rotator to freely rotate around the stator in the lipid membrane.Lipid bilayer experiments reveal the generally high ability of all molecular rotors in promoting the highly efficient transmembrane K^(+)flux(EC50 values=0.49-1.37 mol%relative to lipid).While molecular rotors differing only in the ion-binding unit exhibit similar ion transport activities,those differing in the rotator’s length display activity differences by up to 174%.

Molecular Tetrahedrons as Selective and Efficient Ion Transporters via a Two-Station Swing-Relay Mechanism

The traditional approach to utilizing an ion-relay mechanism for ion transport requires three or more ion-relay stations.Herein,we describe a novel strategy,incorporating a swing action to realize a minimal ion-relay mechanism via only two relay stations.This swing-relay mechanism was achieved using a class of crown ether-appended,long-armed molecular tetrahedrons(MTs).These MTs comprise ion-relaying crown units attached to a rigid tetrahedral core via flexible alkyl linkers,which act as the mobile arms and endow the crown units with great mobility to swing.

Highly active artificial potassium channels having record-high K^(+)/Na^(+) selectivity of 20.1

Replicating extraordinarily high membrane transport selectivity of protein channels in artificial channel is a challenging task.In this work,we demonstrate that a strategic application of steric code-based social self-sorting offers a novel means to enhance ion transport selectivities of artificial ion channels,alongside with boosted ion transport activities.More specifically,two types of mutually compatible sterically bulky groups(benzo-crown ether and tert-butyl group)were appended onto a monopeptide-based scaffold,which can order the bulky groups onto the same side of a one-dimensionally aligned H-bonded structure.Strong steric repulsions among the same type of bulky groups(either benzo-crown ethers or tert-butyl groups),which are forced into proximity by H-bonds,favor the formation of hetero-oligomeric ensem-bles that carry an alternative arrangement of sterically compatible benzo-crown ethers and tert-butyl groups,rather than homo-oligomeric ensembles containing a single type of either benzo-crown ethers or tert-butyl groups.Coupled with side chain tuning,this social self-sorting strategy delivers highly ac-tive hetero-oligomeric K+-selective ion channel(5F12-BF12)_(n),displaying the highest K+/Na+selectivity of 20.1 among artificial potassium channels and an excellent ECso value of 0.50μmol/L(0.62 mo1%relative to lipids)in terms of single channel concentration.

Amino Acid Export in Plants： A Missing Link in Nitrogen Cycling

The export of nutrients from source organs to parts of the body where they are required （e.g. sink organs） is a fundamental biological process. Export of amino acids, one of the most abundant nitrogen species in plant long-distance transport tissues （i.e. xylem and phloem）, is an essential process for the proper distribution of nitrogen in the plant. Phys- iological studies have detected the presence of multiple amino acid export systems in plant cell membranes. Yet, surpris- ingly little is known about the molecular identity of amino acid exporters, partially due to the technical difficulties hampering the identification of exporter proteins. In this short review, we will summarize our current knowledge about amino acid export systems in plants. Several studies have described plant amino acid transporters capable of bi-directional, facilitative transport, reminiscent of activities identified by earlier physiological studies. Moreover, recent expansion in the number of available amino acid transporter sequences have revealed evolutionary relationships between amino acid exporters from other organisms with a number of uncharacterized plant proteins, some of which might also function as amino acid exporters. In addition, genes that may regulate export of amino acids have been discovered. Studies of these putative transporter and regulator proteins may help in understanding the elusive molecular mechanisms of amino acid export in plants.

K^+ retention in leaf mesophyll, an overlooked component of salinity tolerance mechanism:A case study for barley

Plant salinity tolerance is a physiologically complex trait, with numerous mechanisms contributing to it. In this work, we show that the ability of leaf mesophyll to retain K＋ represents an important and essentially overlooked component of a salinity tolerance mechanism. The strong positive correlation between mesophyll K＋ retention ability under saline conditions （quantified by the magnitude of NaCl-induced K＋ efflux from mesophyll） and the overall salinity tolerance （relative fresh weight and/or survival or damage under salinity stress） was found while screening 46 barley （Hordeum vulgare L.） genotypes contrasting in their salinity tolerance. Genotypes with intrinsically higher leaf K＋ content under control conditions were found to possess better K＋ retention ability under salinity and, hence, overall higher tolerance. Contrary to previous reports for barley roots, K＋ retention in mesophyll was not associated with an increased H＋-pumping in tolerant varieties but instead correlated negatively with this trait. These findings are explained by the fact that increased H＋ extrusion may be needed to charge balance the activity and provide the driving force for the high affinity HAK/KUP K＋ transporters required to restore cytosolic K＋ homeostasis in salt-sensitive genotypes.