Average Separation Research Articles

Correction to "Characterizing Large-Scale Receptor Clustering on the Single Cell Level: A Comparative Plasmon Coupling and Fluorescence Superresolution Microscopy Study".

Spatial clustering of cell membrane receptors has been indicated to play a regulatory role in signal initiation, and the distribution of receptors on the cell surface may represent a potential biomarker. To realize its potential for diagnostic purposes, scalable assays capable of mapping spatial receptor heterogeneity with high throughput are needed. In this work, we use gold nanoparticle (NP) labels with an average diameter of 72.17 ± 2.16 nm as bright markers for large-scale epidermal growth factor receptor (EGFR) clustering in hyperspectral plasmon coupling microscopy and compare the obtained clustering maps with those obtained through fluorescence superresolution microscopy (direct stochastic optical reconstruction microscopy, dSTORM). Our dSTORM experiments reveal average EGFR cluster sizes of 172 ± 99 and 150 ± 90 nm for MDA-MB-468 and HeLa, respectively. The cluster sizes decrease after EGFR activation. Hyperspectral imaging of the NP labels shows that differences in the EGFR cluster sizes are accompanied by differences in the average separations between electromagnetically coupled NPs. Because of the distance dependence of plasmon coupling, changes in the average interparticle separation result in significant spectral shifts. For the experimental conditions investigated in this work, hyperspectral plasmon coupling microscopy of NP labels identified the same trends in large-scale EGFR clustering as dSTORM, but the NP imaging approach provided the information in a fraction of the time. Both dSTORM and hyperspectral plasmon coupling microscopy confirm the cortical actin network as one structural component that determines the average size of EGFR clusters.

Ferrofluid Flow and Heat Transfer From a Sphere in the Presence of Nonuniform Magnetic Fields

Abstract In this article, the effects of nonuniform magnetic fields on the hydrodynamics and heat transfer from a heated sphere to its surrounding ferrofluid flow have been investigated. Kelvin body forces originate from the nonuniformity of the applied magnetic field and can generate the vortices behind the sphere leading to a considerable change in the velocity and temperature fields. The applied magnetic field disturbs the thermal boundary layer and decreases heat-transfer resistance, leading to a significant enhancement in the heat-transfer coefficient. Variations of the local and average Nusselt number value (Nu), separation angle, recirculation length, and drag coefficient were considered to investigate the effects of magnetic field intensity, Reynolds number, and the relative magnetic permeability of the sphere. In addition, the arrangement of the coils was optimized to provide the highest heat-transfer rate. Moreover, the obtained results indicate that enhancement in Nuavg is much larger than the drag resistance penalty.

Investigation of the attapulgite hybrid carbon molecular sieving membranes for permanent gas separation

Carbon molecular sieving (CMS) membranes with enhanced separation performance were prepared from polyimide incorporated with attapulgite (ATP). The membranes were characterized by thermogravimetry, Fourier transform infrared spectroscopy, scanning electron microscope and X-ray diffraction. The effect of ATP content on the structure and property of CMS membranes was investigated. The results show that the ATP addition can improve the thermal stability of precursor membranes, and the average pore size, graphitization degree and gas separation performance of as-obtained CMS membranes. In particular, ATP exhibits a good compatibility with the matrix of CMS membranes. The incorporation of ATP significantly elevates the gas permeability of CMS membranes by 2–3 times.

Preparation of chabazite zeolite membranes by a two-stage varying-temperature hydrothermal synthesis for water-ethanol separation

Pure and thin chabazite zeolite membranes were successfully prepared on macroporous symmetrical stainless steel supports by a two-stage varying-temperature hydrothermal synthesis. The morphologies and pervaporation properties of chabazite zeolite membranes were greatly influenced by synthesis times and temperatures at each stage. XRD and SEM characterization results showed that a high temperature at the first stage could effectively avoid the formation of MER impurity phase. The optimal crystallization condition was 150 °C for 10 h at the first stage and 100 °C for 5 h at the second stage. Pervaporation results presented that the precursor gel containing a certain amount of chabazite seed crystals was beneficial to prepare high-performance chabazite zeolite membranes. Well reproducible chabazite zeolite membranes displayed an average permeation flux of 6.25 kg m−2 h−1 and an average separation factor of 1950 for a water/ethanol (10/90 wt%) mixture at 75 °C. Besides, as-synthesized membranes had a good stability for separation of a water/ethanol (30/70 wt%) mixture at 75 °C for 10 d test period, indicating that chabazite zeolite membranes had a promising dehydration application even in water-rich organic solvents.

Effects of Janus Oscillators in the Kuramoto Model with Positive and Negative Couplings

We study the effects of Janus oscillators in a system of phase oscillators in which the coupling constants take both positive and negative values. Janus oscillators may also form a cluster when the other ones are ordered and we calculate numerically the traveling speed of three clusters emerging in the system and average separations between them as well as the order parameters for three groups of oscillators, as the coupling constants and the fractions of positive and Janus oscillators are varied. An expression explaining the dependence of the traveling speed on these parameters is obtained and observed to fit well the numerical data. With the help of this, we describe how Janus oscillators affect the traveling of the clusters in the system.

Energy Conversion and Electron Acceleration in the Magnetopause Reconnection Diffusion Region

AbstractData are analyzed from a Magnetospheric Multiscale encounter with a dayside magnetopause reconnection region on 29 December 2016. The uniqueness of the event stems from the small (~7 km) average spacecraft separation and the sequential sampling of an electron diffusion region with electron crescent distributions. We quantitatively investigate the earthward acceleration of magnetosheath electrons through the in‐plane null by the polarization electric field EN that points radially outward from the magnetopause. The results compare favorably with previous plasma simulations with one important difference that the reconnection electric field (EM) extends throughout the region of strong EN so that both fields energize electrons in the same region. This acceleration is quantified here for the first time. As the spacecraft penetrate deeper into the region of enhanced EN, the magnetic reflection of lower‐energy electrons produces a thinner crescent.

The application of an aqueous two-phase system combined with ultrasonic cell disruption extraction and HPLC in the simultaneous separation and analysis of solanine and Solanum nigrum polysaccharide from Solanum nigrum unripe fruit

An aqueous two-phase system was used in conjunction with ultrasonic cell disruption to extract and separate solanine (mainly solasonine and solamargine) and Solanum nigrum polysaccharide from Solanum nigrum unripe fruit. The optimized conditions of the present study were determined by a single-factor experiment and a multifactor experiment. The concentration of ethanol was set at 60% and the duration of the ultrasonic cell disruption extraction was 50 min. In the ethanol-K2CO3 aqueous two-phase separation system, the concentration of ethanol was 36%, the concentration of K2CO3 was 0.21 mg·mL−1, and the temperature was 15 °C. The solasonine and solamargine were determined by high-performance liquid chromatography, and the Solanum nigrum polysaccharide was determined by an ultraviolet–visible spectrophotometer in accordance with the phenol–sulfuric acid method. xUnder optimized conditions, the average extraction efficiencies of solasonine, solamargine and Solanum nigrum polysaccharide were 95.86%, 95.95% and 96.95%, respectively, and the average separation efficiencies of solasonine, solamargine and Solanum nigrum polysaccharide were 2.07 mg·g−1, 2.05 mg·g−1 and 8.15 mg·g−1, respectively.

Efficient separation of tumor cells from untreated whole blood using a novel multistage hydrodynamic focusing microfluidics

Significant progress on circulating tumor cells (CTCs) has profound impact for noninvasive tumor profiling including early diagnosis, treatment monitoring, and metastasis recognition. Therefore, CTCs based liquid biopsy technology is taking a rapid growth in the field of precision oncology. The label-free approaches relied on microfluidic chip stand out from a crowd of methods that suffer from time consuming, extensive blood samples, lost target cells and labor-intensive operation. In this paper, a label-free separation microfluidic device was developed using multistage channel, which took full advantage of inertial lift force. Our strategy demonstrated CTCs were efficiently isolated from untreated human blood samples including antibody conjugation and erythrocyte lysis. This device was applied for isolating human brain malignant glioma cells that were spiked in human peripheral blood samples. The experimental condition was optimized and exhibited an average separation efficiency of ≥ 90% across cell morphological analysis, up to 84.96% purity of collected CTCs and the viability of all cells is >95%, which was better than other one-step CTCs separation methods. Furthermore, the CTCs were successfully separated from untreated clinical blood sample of cancer patient on the proposed microfluidic device. The entire experimental procedures are extremely low-cost and easy manipulation. It is believed that the proposed multistage microfluidic chip can become a promising tool for CTCs separation and early diagnosis of cancer.

Charged Nanoparticles Quench the Propulsion of Active Janus Colloids.

Active colloidal particles regularly interact with surfaces in applications ranging from microfluidics to sensing. Recent work has revealed the complex nature of these surface interactions for active particles. Herein, we summarize experiments and simulations that show the impact of charged nanoparticles on the propulsion of an active colloid near a boundary. Adding charged nanoparticles not only decreased the average separation distance of a passive colloid because of depletion attraction as expected but also decreased the apparent propulsion of a Janus colloid to near zero. Complementary agent-based simulations considering the impact of hydrodynamics for active Janus colloids were conducted in the range of separation distances inferred from experiment. These simulations showed that propulsion speed decreased monotonically with decreasing average separation distance. Although the trend found in experiments and simulations was in qualitative agreement, there was still a significant difference in the magnitude of speed reduction. The quantitative difference was attributed to the influence of charged nanoparticles on the conductivity of the active particle suspension. Follow-up experiments delineating the impact of depletion and conductivity showed that both contribute to the reduction of speed for an active Janus particle. The experimental and simulated data suggests that it is necessary to consider the synergistic effects between various mechanisms influencing interactions experienced by an active particle near a boundary.

Fiamme degassing structures and their implications for the post-emplacement temperatures and H2O contents of high-grade ignimbrites

A new process in post-emplacement ignimbrite degassing is proposed from observations of unusual structures in a high-grade ignimbrite in Sardinia. The structures consist of fiamme decorated above and below by vesicles, termed here Fiamme Degassing Structures (FDS). The relative volumes of vesicles and fiamme have a positive, linear correlation, and the ratio between the volume of vesicles above and below fiamme (asymmetry ratio) is <1 for a significant number of structures. The positive relationship between the volume of fiamme and vesicles implies that the vesicles were produced by the degassing of fiamme post-emplacement. An equal volume of vesicles would be expected above and below fiamme under simple degassing under compression, contrary to observation in many FDS. The low asymmetry ratio is, therefore, related to a secondary process; vesicle loss and capture is proposed as an explanation. A numerical model of vesicle migration within rhyolitic ignimbrites is used to show that vesicles can rise further than the average separation distance between the fiamme, allowing them to be trapped by overlying fiamme. Sufficient migration of vesicles to result in trapping, however, requires a restricted range of H2O contents and temperatures on emplacement (e.g > 1 wt% at <860 °C), explaining the rare occurrence of FDS. The H2O contents required to form these structures post-emplacement are relatively high for pyroclasts, suggesting they are indicators of unusually large supersaturation in water resulting from rapid excavation rate. These structures also illustrate that interaction of volatiles with fiamme occurs during post-emplacement degassing; FDS may act as baffles that channel volatiles into fumarole columns, slowing volatile loss.

Re-Establishment and Maintenance of Geodetic Networks in Parts of Oyo State Using Modern Techniques

Oyo state like most of the other states in the Nigeria has an old and conventional Geodetic Network. This network was established and computed using the conventional method of position determination and the science of navigation in the 1930- 1950's which is based on the 30th arc-meridian of the Clarke 1880 modified ellipsoid with its origin at L40 Minna datum. This does not satisfy the overgrowing mapping requirements of the state and as well as other Geo-related information requirements. The required data were acquired with GNSS receivers set up on each of the existing points in static mode. The reference network that was re- established consists of eight (8) primary points, covering an area of approximately ?12km?^2 with an average separation of about 7Km. The new network monuments are made of reinforced concrete, solidly cemented in the ground with metal caps (brass markers), and coordinated using the static carrier phase differential GPS measurement. Several observation sessions were conducted and processed to compute 3D coordinates for the network. Post processed data were rigorously adjusted using Least Squares and must meet the distance accuracy specifications for a first order network (1:100,000). Final coordinates are based on WGS84 frame/ ITRF 2008 datum and are within a mean accuracy of ±0. 05m. Finally, the plots of the re-established control points were presented and thus re-established a reliable first order geodetic reference network within Oyo state. Based on the findings the study recommends all geodetic networks in Nigeria should be re- established.

Presence of substrate aids lateral gate separation in LptD

Lipopolysaccharides (LPS) provide the outer membrane (OM) of Gram-negative bacteria with a strong protective barrier. The periplasm-spanning Lpt machinery is responsible for the transport of LPS molecules across the periplasm, culminating in insertion by the outer-membrane proteins LptD and LptE. In order to elucidate the mechanisms of LPS insertion by LptDE, we performed over 14 microseconds of equilibrium molecular dynamics simulations. Bilayer-dependent differences in the fluctuations and secondary structure of LptD's extracellular loops are observed for a pure DMPE membrane vs. a model of the OM. Furthermore, LptD's periplasmic N-terminal domain is highly dynamic, which may help to maintain the integrity of the periplasm-spanning complex amidst relative motion of the inner-membrane and outer-membrane anchored domains. In addition, our simulations demonstrate that binding of LPS substrate activates a switching between the associated and dissociated states of two lumenal loops at the interface between the β-barrel and the N-terminal domain as well as LptD's lateral gate on the microsecond timescale, neither of which is observed for the apo state. Placement of a substrate LPS molecule also causes an increase in the average separation of the LptD lateral gate strands and a lowering of the energetic barrier to lateral gate opening.

Aggregation of Plate-like Colloids Induced by Charged Polymer Chains: Organization at the Nanometer Scale Tuned by Polymer Charge Density.

We study the aggregation of charged plate-like colloids, Na-montmorillonite clays, in the presence of ionenes, oppositely charged polymer chains. The choice of the charged polymer allows tuning its linear charge density to match/mismatch the average charge separation on the clay surfaces. We assess the nanoscale structure of the aggregates formed by small-angle X-ray and neutron scattering. The nanoscale features of the formed clay aggregates are dominated by the presence of a stacking peak, giving clear evidence for the formation of clay tactoids, that is, a face-to-face aggregation geometry of the clay platelets. The chain charge density of ionenes influences not only the stacking repeat distance within the clay tactoids but also the extent of stacking and abundance of the tactoids. We may distinguish two regimes as a function of clay and ionene polymer charge densities (ρc and ρp, respectively). The first regime applies to ρp > ρc and ρp ≈ ρc, that is, for highly and "matching" charged chains. Under these conditions, the intercalated chains lie in a flat conformation within the tactoids, irrespective of the ionic strength (within the range studied, i.e., up to 0.05 M NaBr). For weakly charged chains, ρp < ρc, undulation of the ionene chains within the tactoid is seen. The degree of undulation increases with ionic strength due to the decreasing persistence length of the ionene chains. The extent of stacking (5-10 platelets per tactoid) is a general feature of all the systems, and its origin remains unknown. The system corresponding to the closest match in charge separations on the clay surface and on the polymer chain (ρp ≈ ρc) features the highest abundance of tactoids. This coincides with the highest macroscopic density as deduced from simple visual inspection of sediment volumes. This leads to the open question regarding the link between the density at the nanoscale and the macroscopic density and sedimentation behavior of the aggregate.

Aggregation of stable colloidal dispersion under short high-shear microfluidic conditions

We have designed and carried out intense shear-driven aggregation of charge-stabilized polystyrene nanoparticles (NPs) to big fractal clusters, in a single and a double Z-shape microchannels (SZ-MC and DZ-MC). Both the MCs have the same cross-section, but the length of DZ-MC is double of SZ-MC. It is found that when the NP dispersion repeatedly passes through each of the two MCs, the conversion of the NPs to big clusters can only reach a plateau value that is far smaller than full conversion. The plateau conversion at a given mean velocity (shear rate) is larger for the DZ-MC than for the SZ-MC, i.e., it increases as the MC length (or the residence time of one pass) increases. This surprising phenomenon can be explained upon considering that, as the conversion increases, the average NP separation distance increases, i.e., the time for the specific shear-driven bi-particle aggregation to occur increases. When the aggregation time becomes larger than the NP residence time in a MC, the NP dispersion passing through the MC does not lead to aggregation. The situation does not change if we let the NP dispersion repeatedly pass through the MC many times (i.e., by increasing the cumulative residence time), because if the residence time of one pass is not enough for the NPs to overcome the interaction energy barrier, when they come out from the MC, the intense shear force disappears and the NPs return to their original interaction state.

Carrier escape mechanism in laterally correlated InAs sub-monolayer quantum dots using temperature dependent photoluminescence

We have quantitatively investigated relative effects of photo-carrier escape mechanism upon the quenching of photoluminescence with temperature in an ensemble of embedded InAs sub-monolayer (SML) quantum dots by varying InAs SML coverage from 0.4 ML to 0.8 ML. The mutual interplay of carrier recombination and tunneling throughout the laterally coupled quantum dots for different InAs coverage have been established to determine the temperature dependent photoluminescence (TDPL) spectra. The respective characteristic life times were extracted from the individual TDPL spectra by fitting them with model carrier rate equation. The consequent enhancement of inter-dot tunnel strength with respect to the carrier recombination rate with increasing InAs coverage has been marked out to be responsible for sustainable photoluminescence efficiency at higher temperature. Enhancement of tunneling rate with increasing InAs SML coverage has been physically described as consequence of reduced average inter-dot lateral separation as estimated from grazing incidence small angle x-ray scattering (GISAXS) measurement. Moreover, we have observed the anomalous decrease of spectral linewidth with temperature which can also be described as a consequence of the tunnel induced faster inter-dot carrier transfer at higher sub-monolayer coverage. The absence of any wetting layer in SML QD resulted in speeding up of carrier transfer through inter-dot tunneling pathways with tunnel time as low as 350 ps. This is significantly faster than the conventional InAs/GaAs SK QDs with tunnel time of 1328 ps.

Exclusive Breastfeeding, 24-Hour Rooming-In, and the Importance of Women’s Informed Choices

ObjectiveTo measure the relationship between exclusive breastfeeding and 24-hour rooming-in for low-risk primiparous women with uncomplicated vaginal births at term. DesignDescriptive correlational design with a qualitative component. SettingThe Labor & Delivery and Mother/Baby units of a community hospital with more than 2,300 births annually. ParticipantsA convenience sample of 89 women. Intervention/MeasurementsParticipants completed a demographic questionnaire, the Iowa Infant Feeding Attitude Scale, which measures attitudes toward breastfeeding, and a four-item questionnaire at 2, 6, and 12 weeks postpartum to assess breastfeeding status. ResultsIowa Infant Feeding Attitude Scale scores suggest that most of the sample had positive attitudes toward breastfeeding. The average separation time for women and newborns was 3 hours 40 minutes. No statistically significant differences were found regarding maternal attitudes toward breastfeeding or mother–newborn separation during the postpartum period between newborns who were exclusively breastfeeding or formula-feeding at 12 weeks. ConclusionSuccess with exclusive breastfeeding in the immediate postpartum period is not necessarily dependent on 24-hour rooming in, and it is important for women to have the ability to make informed choices regarding newborn separation in the hospital.

Exceptionally high natal homing precision in hawksbill sea turtles to insular rookeries of the Caribbean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 620:155-171 (2019) - DOI: https://doi.org/10.3354/meps12957 Exceptionally high natal homing precision in hawksbill sea turtles to insular rookeries of the Caribbean Kathryn E. Levasseur1,2,*, Seth P. Stapleton2,3, Mykl Clovis Fuller4, Joseph M. Quattro1 1Department of Biological Sciences, University of South Carolina, Columbia, SC 29208, USA 2Jumby Bay Hawksbill Project, Jumby Bay, PO Box 243, St. John’s, Antigua, West Indies 3Department of Fisheries, Wildlife and Conservation Biology, University of Minnesota, St. Paul, MN 55108, USA 4Antigua Sea Turtle Conservation Project, Environmental Awareness Group, Long Street, St. John’s, Antigua, West Indies *Corresponding author: kathryn.levasseur@gmail.com ABSTRACT: Marine turtles migrate back to their natal region during reproduction, but the precision of this homing behavior and how the precision varies among populations and across biogeographic regions are unclear. We hypothesize that marine turtles nesting on insular landmasses navigate to their rookeries with greater precision than those nesting on continuous coastlines. We analyzed new mitochondrial and microsatellite marker data from hawksbill turtles Eretmochelys imbricata at nesting sites across Antigua and Barbuda, West Indies, to assess the scale of natal homing in the highly insular Leeward Islands. We then used published data from 15 western Atlantic rookeries to examine regional patterns of rookery structure. Mitochondrial control region data showed weak to no partitioning among nesting sites within Antigua and strong partitioning between Antigua and Barbuda, suggesting natal homing at a scale of 50 km. Microsatellite data showed weak to no partitioning between sites, indicating male-mediated gene flow. Regionally, we found stronger population structuring among rookeries of insular landmasses than among those of larger landmasses with continuous coastlines, despite shorter average rookery separation for the former. We also found a positive relationship between a rookery’s isolation index (a metric incorporating distances from larger landmasses) and its genetic divergence from proximate rookeries. These findings support our hypothesis, and we caution that insular rookeries that host marine turtles with extreme homing behavior have limited ability to colonize new nesting habitat. The unprecedented rates of development and increasing instability of present-day nesting habitat might therefore pose a greater and increasing threat to insular rookeries. KEY WORDS: Philopatry · Endangered species · Management units · Eretmochelys imbricata · Mitochondrial DNA · Microsatellites Full text in pdf format Supplementary material PreviousNextCite this article as: Levasseur KE, Stapleton SP, Fuller MC, Quattro JM (2019) Exceptionally high natal homing precision in hawksbill sea turtles to insular rookeries of the Caribbean. Mar Ecol Prog Ser 620:155-171. https://doi.org/10.3354/meps12957 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 620. Online publication date: June 18, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Essential role of treatment in hydrogen atmosphere on creation of ferromagnetic order in carbon incorporated TiO2 nanocomposite

Carbon incorporated TiO2 nanocomposite powders were synthesized by a facile thermal co-decomposition of a mixture of titanium tetrachloride (TiCl4) and sucrose (C12H22O11) as a source of carbon ions. The crystalline structures were studied by x-ray diffraction (XRD) method through the Rietveld refinement technique of analysis. It was found that the samples consist of anatase (A) and rutile (R) with a small amount of brookite (B). It was noticed that the incorporation of C ions in TiO2 lattice enhanced the A to R transformation through creation of oxygen (O)-vacancies. It was concluded that the incorporated small-size C ion-species might occupy interstitial positions in the lattice of host TiO2. Such incorporation should create O-vacancies due to the re-distribution of static charges of ions. The optical properties were investigated by the diffuse reflection spectroscopy (DRS) method. The C-ions incorporation red-shifted the optical band gap, while the hydrogenation of the samples blue-shifted the band gap according to Moss-Burstein effect. Annealing the samples in H2-atmosphere could create O-vacancies, increase carrier concentration, and toss the incorporated in the interstitial C ion-species to occupy the O-vacancies (CO). The possible creation of FM behavior due to CO ions mutual interaction depends on their average separation (RC–C) that was estimated to explain the obtained ferromagnetic (FM) results. The FM properties were observed only with hydrogenated samples that incorporated by ∼1% C. The effective magnetic moment was evaluated to be 1.24 μB/C, which was attributed to the magnetic moment of C2p in addition to some contributions to O-vacancies. This study showed the critical importance of hydrogenation processes to create FM properties in C-incorporated TiO2 nanocomposites.

Further improvement for separation of heavy rare earths by mixtures of acidic organophosphorus extractants

This work aims to improve the extraction performance of organophosphorus acid extractants (di-(2-ethylhexyl) phosphoric acid (P204), 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (P507, H2A2), di-(2-ethylhexyl) phosphinic acid (P227, H2B2) and bis (2,4,4-trimethylpentyl) phosphinic acid (Cyanex272, C272)) for the extraction of heavy rare earths (HREs) from chloride medium by simple mixed two of them and formed six mixture systems. The comparison of extraction properties for lutetium (Lu) revealed that mixture of P507 and P227 is the most effective among the six mixed systems. Under the premise of no emulsification, this system also showed lower stripping acidity, higher load and shorter equilibrium time than others. Worthwhile, a synergistic effect was found by the mixture of P507 and P227 for Lu(III) extraction. A cation exchange mechanism was determined by slope analysis method. FT-IR was adopted to characterize the structure of extracted complex. The composition of extracted complex was determined as Lu(HB2)(HA2)2. In addition, this mixture system showed high separation ability of HREs. Its average separation factor of adjacent HREs from Ho to Lu was 2.19, superior to the single P507 (1.21) or P227 (1.83) system. More importantly, the mixture of P507 and P227 system has revealed industrial application values for the separation of HREs from mixed feed solution.

Molecular Mechanisms of Membrane Curvature Sensing by a Disordered Protein.

The ability of proteins to sense membrane curvature is essential for the initiation and assembly of curved membrane structures. Established mechanisms of curvature sensing rely on proteins with specific structural features. In contrast, it has recently been discovered that intrinsically disordered proteins, which lack a defined three-dimensional fold, can also be potent sensors of membrane curvature. How can an unstructured protein sense the structure of the membrane surface? Many disordered proteins that associate with membranes have two key physical features: a high degree of conformational entropy and a high net negative charge. Binding of such proteins to membrane surfaces results simultaneously in a decrease in conformational entropy and an increase in electrostatic repulsion by anionic lipids. Here we show that each of these effects gives rise to a distinct mechanism of curvature sensing. Specifically, as the curvature of the membrane increases, the steric hindrance between the disordered protein and membrane is reduced, leading to an increase in chain entropy. At the same time, increasing membrane curvature increases the average separation between anionic amino acids and lipids, creating an electrostatic preference for curved membranes. Using quantitative imaging of membrane vesicles, our results demonstrate that long disordered amino acid chains with low net charge sense curvature predominately through the entropic mechanism. In contrast, shorter, more highly charged amino acid chains rely largely on the electrostatic mechanism. These findings provide a roadmap for predicting and testing the curvature sensitivity of the large and diverse set of disordered proteins that function at cellular membranes.