Bulk Membrane Transport Research Articles

Gene Transcription in End Stage Ankle Osteoarthritis Differs Markedly From Knee Arthritis and Non- Arthritic Ankles

Category: Ankle Arthritis; Arthroscopy; Basic Sciences/Biologics; Trauma Introduction/Purpose: Post-traumatic Osteoarthritis (OA) of the ankle is a debilitating condition that impacts millions of people. However, little is known about the genetic and epigenetic risk factors for progression to OA following injury. In order to better understand these factors, a thorough knowledge of the molecular signature in ankle OA relative to non-arthritic ankles is critical. The objective of this study was to perform RNA-sequencing of ankle joint synovial samples from OA and non-OA ankles to better characterize the synovial transcriptome. We compared synovial gene expression patterns in patients with end-stage OA with ankle synovium from non-OA ankles to investigate the unique biological pathways altered in ankle OA. Methods: Patients undergoing total ankle arthroplasty or ankle arthrodesis for end stage OA and patients undergoing ankle arthroscopic surgery for non-arthritic conditions (negative control), were consented for participation. Patients with immune disorders or inflammatory arthropathies were excluded. Patient demographics and medical history were collected. Synovial samples were harvested during surgery and RNA was isolated. Bulk 150 bp, paired-end RNA seq was performed using the Illumina NovaSeq6000 platform. Differential expression was determined using the edgeR (v3.16.5) package for R, after adjustment using a scaling normalization factor and P-values were corrected using the Benjamini Hochberg method. Similarities between samples were determined using Spearman Correlation and degree of similarity was visualized considering the first three Principal Components. Gene Ontology terms were identified to classify gene properties. Results: A total of 8 synovial samples from total ankle OA and 24 synovial samples from ankle non-OA were available for analysis. We found 808 genes uniquely expressed in OA synovium and another 786 different genes expressed in synovium from the control group. GO enrichment term analysis revealed an upregulation in endomembrane system organization, ubiquitin system/proteasomal degradation, and membrane transport processes including cytoskeletal, endosomal, and vacuolar in ankle OA samples compared to controls (Figure 1). These signatures differ from those previously identified in knee OA. Reactome analysis revealed pathways to those previously identified in OA of other joints, including TGF-beta signaling modulation. However, several signatures unique to ankle OA included extracellular matrix organization, integrin signaling, and AKT signaling modulation, among others. In addition, unlike in knee OA, reactome analyses of ankle OA synovium did not present with an inflammatory component associated with M1 macrophage infiltration. Conclusion: Ankle synovium in patients with end-stage ankle OA exhibit a transcriptomic signature distinct from ankle synovium collected from non-OA patients. More intriguing, we find that the ankle OA synovial transcriptome signature is distinct from previously published datasets studying synovium from patients with OA in other joints, particularly the knee. GO term and Reactome analyses identified signatures in bulk membrane transport, proteasome, matrix organization, integrin signaling, and AKT signaling, which are different from phenotypes previously reported in the knee. We conclude that development of effective disease modifying treatments for OA require attention to joint-specific biology and disease progression.

Chiral Separation of Underivatized Amino Acids by Reactive Extraction with Palladium−BINAP Complexes

In answer to the need for a more economic technology for the separation of racemates, a novel system for reactive enantioselective liquid-liquid extraction (ELLE) is introduced. Palladium (S)-BINAP complexes are employed as hosts in the separation of underivatized amino acids. The system shows the highest selectivity for the ELLE of tryptophan with metal complexes as hosts reported to date and shows a good selectivity toward a range of natural and unnatural amino acids. Furthermore, the host can be prepared in situ from commerically available compounds. Bulk-membrane transport in the form of U-tube experiments demonstrates the enantioselective and catalytic nature of the transport. The dependency of the system on parameters such as pH, organic solvent, and host-substrate ratio has been established. (31)P NMR spectroscopy has been used to confirm the preferred enantiomer in the extraction experiments. The intrinsic selectivity was deduced by determination of the association constants of the palladium complex with the tryptophan enantiomers.

Synthesis of calix[4]arene-based dipodal receptors: Competitive solvent extraction and liquid bulk membrane transport for selective recovery of Cu2+

A series of new p-tert-butylcalix[4]arene-based dipodal receptors are synthesised in high yields. The calix[4]arene units of all the receptors have been found to be present in cone conformation. To optimise the good extraction ability and high transport rate, we synthesised the receptors that differ from each other in their end groups. These receptors extract Cu2+ ion selectively from the buffered aqueous medium containing a mixture of metal ions. The receptor bearing four sp3 nitrogens has by far the greater ability to extract Cu2+ than the other receptors. All these receptors were effectively used for Cu2+ ion transport from the aqueous buffered source phase to the aqueous receiving phase.

Transport of calcium ions through a bulk membrane by use of a dynamic combinatorial library

In a bulk membrane transport experiment, a dynamic combinatorial library (DCL) has been used to transport calcium ions; the calcium ions amplify the formation of a macrocyclic carrier which results in transport.

Quantification of polarized trafficking of transferrin and comparison with bulk membrane transport in hepatic cells

Transport of the recycling marker transferrin was analysed in polarized hepatic HepG2 cells using quantitative fluorescence microscopy and mathematical modelling. A detailed map and kinetic model for transport of transferrin in hepatic cells was developed. Fluorescent transferrin was found to be transported sequentially through basolateral SE (sorting endosomes) to a SAC/ARC (subapical compartment/apical recycling compartment). DiI (di-indocarbocyanine) lipid probes of different acyl chain length (DiIC12 and DiIC16) co-localized with transferrin in basolateral SE and in the SAC/ARC. By kinetic comparison of hepatic transport of transferrin and labelled HDL (high-density lipoprotein), it is shown that transport of transferrin from SE to the SAC/ARC follows a default pathway together with HDL. Kinetic modelling of fluorescence data provides an identical half-time for SE-to-SAC/ARC transport of transferrin and fluorescent HDL (t(1/2)=4.2 min). Fluorescent transferrin was found to recycle with a half-time of t(1/2)=12.9 min from the SAC/ARC to the basolateral cell surface of HepG2 cells. In contrast with HDL, targeting of labelled transferrin from the SAC/ARC to the apical biliary canaliculus was negligible. The results indicate that transport from basolateral hepatic SE to the SAC/ARC represents a bulk flow process and that polarized sorting occurs mainly at the level of the SAC/ARC.

Effect of Solvent on Competitive Bulk Membrane Transport of Transition and Post Transition Metal Cations Using Decyl-18-crown-6

A series of competitive metal ion transport experiments have been performed. Each involved transport from an aqueous source phase across an organic membrane phase into an aqueous receiving phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), cupper(II), zinc(II), cadmium(II), silver(I) and lead(II) metal cations. The membrane phase incorporated ionophore, decyl-18-crown-6. The membrane solvents include: chloroform, dichloromethane, 1,2-dichloroethane, nitrobenzene and chloroform–nitrobenzene binary solvents. A good transport efficiency and selectivity of Pb2+ transport from aqueous solutions are observed in this investigation. The selectivity order for competitive bulk liquid membrane transport of the studied transition and post transition metal cations through chloroform is: Pb2+>Co2+>Ni2+>Ag+>Cd2+, but in the case of dichloromethane, 1,2-dichloroethane and nitrobenzene as liquid membranes, the selectivity sequences were found to be: Pb2+>Co2+>Cd2+>Cu2+>Ag+>Ni2+>Zn2+, Pb2+>Co2+>Ag+>Ni2+>Zn2+ and Pb2+>Co2+>Ni2+>Zn2+>Cd2+>Ag+, respectively. The transport rate of the metal cations in chloroform–nitrobenzene binary solvents is sensitive to the solvent composition. The transport processes were studied in absence and presence of the stearic acid and the results show that the sequence of selectivities and ion transport rates change in the presence of stearic acid.

Study of Bulk Membrane Transport of Some Heavy Metal Cations Using Three Macrocyclic Ligands Containing Oxygen and Nitrogen Heteroatoms

The transport experiments of Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ag+ and Pb2+ metal cations were carried out by dibenzo-18-crown-6 (DB18C6), dibenzyl-diaza-18-crown-6 (Dibenzyl-diaza-18C6) and di-tert-butyl-dibenzo-18-crown-6 (Di-tert-butyl-DB18C6) using chloroform (CHCl3), 1,2-dichloroethane (1,2-DCE) and nitrobenzene (NB) organic solvents as liquid membranes. The source phase contained equimolar concentration of these metal cations and the source and receiving phases being buffered at pH=5 and pH=3, respectively. The obtained results show that the selectivity and the efficiency of transport for these heavy metal cations change with the nature of the ligand and also the organic solvents, which were used as liquid membranes in these experiments. A good selectivity was observed for silver (I) ion by dibenzyl-diaza-18C6 in all membrane systems. Dibenzo-18C6 and di-tert-butyl-DB18C6 showed the highest transport efficiency for cobalt (II) ion. The effect of stearic acid on transport efficiency was also investigated and the results show that the efficiency of transport of the heavy metal cations increases in the presence of this organic acid.

Silver(i) complexation of linked 2,2′-dipyridylamine derivatives. Synthetic, solvent extraction, membrane transport and X-ray structural studies

Synthesis of the 2,2'-dipyridylamine derivatives di-2-pyridylaminomethylbenzene 1, 1,2-bis(di-2-pyridylaminomethyl)benzene 2, 1,3-bis(di-2-pyridylaminomethyl)benzene 3, 2,6-bis(di-2-pyridylaminomethyl)pyridine 4, 1,4-bis(di-2-pyridylaminomethyl)benzene 5, and 1,3,5-tris(di-2-pyridylaminomethyl)benzene 6 are reported together with the single-crystal X-ray structures of 2, 3, and 5. Reaction of individual salts of the type AgX (where X = NO(3)(-), PF(6)(-), ClO(4)(-), or BF(4)(-)) with the above ligands has led to the isolation of thirteen Ag(I) complexes, nine of which have also been characterised by X-ray diffraction. In part, the inherent flexibility of the respective ligands has resulted in the adoption of a range of coordination arrangements. A series of liquid-liquid (H(2)O/CHCl(3)) extraction experiments of Ag(I) with varying concentrations of 1-6 in the organic phase have been undertaken, with the counter ion in the aqueous phase being respectively picrate, perchlorate and nitrate. In general, extraction efficiencies for a given ionophore followed the Hofmeister order of picrate > perchlorate > nitrate; in each case the tris-dpa derivative 6 acting as the most efficient extractant of the six systems investigated. Competitive seven-metal bulk membrane transport experiments (H(2)O/CHCl(3)/H(2)O) employing the above ligands as the ionophore in the organic phase and equimolar concentrations of Co(II), Ni(II), Zn(II), Cu(II), Cd(II), Pb(II) and Ag(I) in the aqueous source phase were also undertaken, with transport occurring against a pH gradient. Under the conditions employed 1 and 5 yielded negligible transport of any of the metals present in the source phase while sole transport selectivity for Ag(I) was observed for 2-4 and 6.

Metal-Ion Recognition—Selective Bulk Membrane Transport of Silver(I) Using Thioether Donor Macrocycles as Ionophores, and X-Ray Structure of the Silver Complex of an S4-Donor Ring

Competitive metal-ion transport experiments, each involving transport from an aqueous source phase containing equimolar concentrations of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(i), and lead(II) across a chloroform membrane phase to an aqueous receiving phase have been carried out. The membrane phase incorporated an ionophore chosen from a series of thioether-containing macrocycles. For those systems that displayed transport behaviour, sole selectivity for silver(I) was observed under the conditions employed. The effect of variation in the macrocyclic sulfur atom donor set and the presence of hydrophilic ring substituents on transport efficiency is presented. An X-ray structure of the 1 : 1 silver(I) nitrate complex of a 16-membered, S4-donor macrocycle shows the presence of four crystallographically independent macrocycles displaying conformational isomerism. Each silver(I) has an approximate tetrahedral geometry, being bound to three sulfur atoms from three different macrocycles and to one nitrato ligand to yield a three-dimensional network.

Metal ion recognition. Interaction of a series of successively N-benzylated derivatives of 1,4,8,11-tetraazacyclotetradecane (cyclam) with selected transition and post-transition metal ions

The interaction of a series of N-benzylated cyclam ligand derivatives incorporating from one to four N-benzyl groups with cobalt(II), zinc(II), cadmium(II), lead(II) and silver(I) nitrates is reported; the results are compared with those obtained in a prior study involving the formation of the corresponding complexes of nickel(II) and copper(II) with this ligand series. The isolation of a selection of 1 ∶ 1 (metal ∶ ligand) complexes has been carried out and X-ray diffraction structures of five such products have been determined. In each complex the metal ion is coordinated to the N4-donor set of the cyclam ring with the latter adopting either a trans-I or a trans-V configuration; monodentate or bidentate nitrato ligands complete the respective coordination spheres. Coordination numbers range from five in a zinc(II) complex, through six in two cadmium(II) complexes, to eight in two lead(II) complexes. Competitive bulk membrane transport experiments (water/chloroform/water) have been carried out in which each of the five benzylated ligands were in turn employed as the ionophore in the chloroform phase. The respective aqueous source phases (buffered at pH 4.9) contained an equimolar mixture of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) nitrates. The aqueous receiving phase was buffered at pH 3.0. Under these conditions, high selectivity for copper(II) was observed for each of the ionophores incorporating one or two N-benzyl groups whereas no transport for any of the seven metals present in the source phase was observed for the tribenzylated derivative. In marked contrast to the above behaviour, the tetra-N-benzyl derivative yielded sole transport selectivity for silver(I) under similar conditions. 1H NMR and 13C NMR titration experiments in CD3CN–CDCl3 confirmed the 1 ∶ 1 stoichiometry of the silver(I) tetra-N-benzylcyclam complex in this solvent mixture.

Competitive bulk membrane transport and solvent extraction of transition and post transition metal ions using mixed-donor acyclic ligands as ionophores

Competitive transport experiments involving metal ion transport from an aqueous source phase across a chloroform membrane phase into an aqueous receiving phase have been carried out using a series of open-chain mixed-donor ligands as the ionophore in the organic phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II), with the source and receiving phases being buffered at pH 4.9 and 3.0, respectively. Clear transport selectivity for silver(I) was observed in all cases. This was also observed in a series of parallel solvent extraction experiments carried out under similar source and membrane phase conditions. Stability constant data confirm that all these ligands show significant affinity for silver(I) in methanol. An X-ray diffraction study of the silver(I) complex of a tripodal NS3-donor ligand from the present series is reported. This complex occurs as two crystallographically independent molecules with both forms having a 1 ∶ 1 silver ∶ ligand ratio. The metal coordination geometry of the first form is distorted tetrahedral, with three coordination sites occupied by the three sulfur atoms of the ligand and the fourth site filled by an oxygen atom of the nitrate anion. The silver ion in the second form is five-coordinate being bound to the ligand's apical nitrogen as well as to its three sulfur donors. The remaining position is again occupied by a nitrate oxygen, with the metal coordination geometry in this case best described as distorted trigonal bipyramidal.

Metal ion recognition. Selective interaction of silver(i) with tri-linked N2S2-donor macrocycles and their single-ring analogues

The interaction of four tri-linked N2S2-donor macrocyclic ligands and their single ring analogues with silver(I) has been investigated. The 3 ∶ 1 (metal ∶ ligand) stoichiometries of the silver(I) complexes of the tri-linked species in dimethyl sulfoxide-d6/CDCl3 were confirmed by means of NMR titrations involving the incremental addition of silver(I) nitrate to the respective ligands in the above solvent mixture and following the corresponding induced shifts in the 1H NMR spectrum. Solid 3 ∶ 1 (metal ∶ ligand) complexes were isolated for each of the parent (unsubstituted) tri-linked ligands. Competitive solvent extraction experiments (water/chloroform) and related bulk membrane transport (water/chloroform/water) experiments have been performed in which each of the four tri-linked ligands as well as their single ring analogues were employed as the extractant/ionophore in the chloroform phase. In both sets of experiments the respective aqueous source phases (buffered at pH 4.9) contained an equimolar mixture of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) nitrates. For membrane transport the aqueous receiving phase was buffered at pH 3. Under the conditions employed, both the solvent extraction and the bulk membrane transport experiments resulted in high extraction/transport selectivity for silver(I) relative to the other six metal ions present.

Metal ion recognition. The interaction of cobalt(ii), nickel(ii), copper(ii), zinc(ii), cadmium(ii), silver(i) and lead(ii) with N-benzylated macrocycles incorporating O2N2-, O3N2- and O2N3-donor sets

The interaction of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) with a series of mixed-donor, N-benzylated macrocyclic ligands incorporating O2N2-, O3N2- and O2N3-donor sets has been investigated. The log K values for the respective 1 ∶ 1 complexes in 95% methanol (I = 0.1 mol dm−3; Et4NClO4, 25 °C) have been determined potentiometrically and the results compared with the values obtained previously for the parent (non-benzylated) macrocyclic systems. Examples of N-benzylation of individual parent macrocycles leading to enhanced discrimination for silver(I) are presented. In the case of a dibenzylated O3N2-ring and a tribenzylated O2N3-ring, both 17-membered, high selectivity for this ion was observed relative to the other metal ions investigated. Competitive mixed-metal transport experiments across a bulk chloroform membrane have been performed using the benzylated derivatives as ionophores. For each experiment the source contained equimolar concentrations of the above metal ions and transport was performed against a pH gradient; the aqueous source and receiving phases were buffered at pH 4.9 and 3.0, respectively. In parallel to the log K results, transport selectivity for silver(I) was exhibited by the di- and tri-benzylated ligands mentioned above. The remaining ligands proved to be poor ionophores, showing no significant metal ion transport under the conditions employed. In a further study, high silver ion (transport) selectivity was maintained when the above tribenzylated ligand was incorporated as the ionophore in a polymer inclusion membrane system. Single metal and mixed (seven-metal) solvent extraction experiments employing similar aqueous source and chloroform phases to those used in the bulk membrane transport runs have also been performed for the tribenzylated ligand derivative; significant selectivity for silver was again maintained in these solvent extraction experiments. An X-ray study of [AgL]ClO4 (where L is the above-mentioned dibenzylated derivative) confirms that all donor atoms of the macrocycle coordinate to the silver ion; the latter is five-coordinate with the complex cation exhibiting a highly distorted trigonal bipyramidal geometry.

Metal-ion recognition. Competitive bulk membrane transport of transition and post transition metal ions using oxygen–nitrogen donor macrocycles as ionophores

A series of competitive metal ion transport experiments have been performed. Each involved transport from an aqueous source phase across a chloroform membrane phase into an aqueous receiving phase. The source phase contained equimolar concentrations of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), silver(I) and lead(II) while the membrane phase incorporated an ionophore chosen from a series of single-ring and double-ring macrocyclic ligands (incorporating mixed oxygen–nitrogen donor sets) together with hexadecanoic acid. The transport process was ‘driven’ by a back flux of protons, maintained by buffering the source and receiving phases at pH 4.9 and 3.0, respectively. Transport selectivity for copper(II) was observed in all cases. The results confirm that consideration of the mass balance of the metal ions present across all three transport phases is important for a fuller understanding of the nature of the discrimination process for the present systems.

Phosphoryl containing podands as carriers in plasticized membrane electrodes selective to quaternary ammonium surfactants

Open chain polyethers with phosphoryl-containing terminal groups have been studied as carriers in plasticized membrane electrodes that are selective towards cationic surfactants. Host–guest complexation has also been studied by means of batch extraction and bulk membrane transport experiments. For the various guests, the bulk membrane (chloroform) transport rate decreases in the series tetraalkyl ammonium > alkyl pyridinium > alkyl ammonium, while the series of solvent extraction efficiency is exactly opposite; an explanation for this behaviour is proposed. The performance of electrode membranes follows the series for bulk membrane transport. Among the ISE membranes of various composition, one containing the longest (seven oxygen atoms) podand, o-nitrophenyl octyl ether (plasticizer), and sodium tetraphenyl borate (anionic additive) performs the best. The slope of the electrode function equals 58.5 mV/decade, the detection limit for dodecyltrimethylammonium is 3.2 × 10-6 M. ISE response time is 5–10 s, the working pH range is 2–11 and lifetime is at least 6 months. The electrode selectivity is significantly better than that of conventional ion-association and crown ether based electrodes.

Surfactant Ion Selective Membrane Electrodes

Abstract Calix[8]arene ethers, carboxylic esters having various p-substituents and acid are synthesized and studied. In a bulk membrane transport of dodecylpyridinium the better carrier is the simplest host, calix[8]arene octamethyl ether. Inversely, it is the worst carrier for dodecyltrimethylammonium; the better here is carboxy ester with adamantyl p-substituents. Various calixarenes are successfully used in plasticized membrane ion-selective electrodes (ISE) for both above ammonium and pyridinium surfactants. Operational characteristics, potentiometric selectivity and optimal membrane compositions are reported. Typical limit of detection is at the level of nx10−6 - 1x10−5 M, response time 5-10 s, and lifetime is at least 6 months. ISE's selectivity is significantly better than that of ion-association and crown-ether based electrodes.

Chalcogenide glass chemical sensors: Relationship between ionic response, surface ion exchange and bulk membrane transport

Different factors affecting chalcogenide glass chemical sensor response are discussed. It is shown that definite relationships between composition, glass structure, chemical durability, bulk and surface ionic processes, and sensor performance exist. All these factors are connected to each other in a complicated way; therefore, further development of new sensors with improved analytical characteristics needs a detailed study of the chemical and physical properties of the glasses.

Silver ion sensors based on AgAsSeTe glasses I. Ionic sensitivity and bulk membrane transport

AgAsSeTe glasses have been used as membranes of silver ion-selective electrodes. Sensors based on ion-conducting glasses with low tellurium content display high Ag + ion sensitivity, potential stability and reproducibility. They are superior to crystalline silver-ion sensors in selectivity in the presence of interfering ions, such as mercury(II), iron(III) and copper(II) ions. Semiconducting Te-rich glasses show some features in silver ion response (super-Nernstian slope in diluted solutions, less stable potentials, etc.) that are explained by competitive redox processes at the glass/solution interface. Deterioration of the response is related both to increases in electronic conductivity and to decreases in ionic conductivity. A lack of chemical stability of the surface of Te-rich glasses can also play a certain role.

Comparison of time constants for liquid ion-exchange membrane electrode responses determined by an impedance method and an activity step method

Linear current-step perturbations and resulting membrane potential responses of liquid ion-exchange membranes have been analyzed and the numerous possible time constants examined and catalogued. Ideal activity steps at a single membrane interface produce potential—time responses similar to those resulting from current steps. The common time constants have nearly identical values. However, fewer time constants are observed for activity steps than for current steps. Slow processes at the active interface dominate and obscure short time processes. For liquid ion-exchange membranes it is concluded that an activity step on one side is not identical to a current step because processes involving bulk membrane transport and the far side of the membrane are not involved to the same extent for the two excitation modes. Two analog circuit models (one active, one passive) are proposed for the potential—time response to an activity step. Systems containing neutral carriers are not considered.