A Fluorogenic Probe for Cell Surface Phosphatidylserine Using an Intramolecular Indicator Displacement Sensing Mechanism

The detection of externalized phosphatidylserine (PS) on the cell surface is commonly used to distinguish between living, apoptotic, and necrotic cells. The tools of choice for many researchers to study apoptosis are annexin V‐fluorophore conjugates. However, the use of this 35 kDa protein is associated with several drawbacks, including temperature sensitivity, Ca²⁺ dependence, and slow binding kinetics. Herein, a fluorogenic probe for cell surface PS, P‐IID , is described, which operates by an intramolecular indicator displacement (IID) mechanism. An intramolecularly bound coumarin indicator is released in the presence of cell surface PS, leading to a fluorescence “turn‐on” response. P‐IID demonstrates superior performance when compared to annexin V, for both fluorescence imaging and flow cytometry. This allows P‐IID to be used in time‐lapse imaging of apoptosis using confocal laser scanning microscopy and demonstrates the utility of the IID mechanism in live cells.     

Immobilizing single lipid and channel molecules in artificial lipid bilayers with annexin A5

The effects of annexin A5 on the lateral diffusion of single-molecule lipids and single-molecule proteins were studied in an artificial lipid bilayer membrane. Annexin A5 is a member of the annexin superfamily, which binds preferentially to anionic phospholipids in a Ca2+-dependent manner. In this report, we were able to directly monitor single BODIPY 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE) and ryanodine receptor type 2 (RyR2) labeled with Cy5 molecules in lipid bilayers containing phosphatidylserine (PS) by using fluorescence microscopy. The diffusion coefficients were calculated at various annexin A5 concentrations. The diffusion coefficients of BODIPY-DHPE and Cy5-RyR2 in the absence of annexin A5 were 4.81 x 10(-8) cm(2)/s and 2.13 x 10(-8) cm(2)/s, respectively. In the presence of 1 microM annexin A5, the diffusion coefficients of BODIPY-DHPE and Cy5-RyR2 were 2.2 x 10(-10) cm(2)/s and 9.5 x 10(-11) cm(2)/s, respectively. Overall, 1 microM of annexin A5 was sufficient to induce a 200-fold decrease in the lateral diffusion coefficient. Additionally, we performed electrophysiological examinations and determined that annexin A5 has little effect on the function of RyR2. This means that annexin A5 can be used to immobilize RyR2 in a lipid bilayer when imaging and analyzing RyR2.     

Fluorophore-linked zinc(II)dipicolylamine coordination complexes as sensors for phosphatidylserine-containing membranes

A series of Zn²⁺-2,2′-dipicolylamine (Zn²⁺-DPA) coordination complexes with an attached NBD fluorophore are synthesized and evaluated as fluorescent sensors. The sensors do not respond to vesicles composed of zwitterionic phosphatidylcholine, but the NBD fluorescence emission is enhanced in the presence of anionic vesicles. A sensor with two Zn²⁺-DPA units and a hydrophilic tris(ethyleneoxy) linker produced a larger emission enhancement than an analogue with a butyl linker, and titration with 1:1 POPC:POPS vesicles lead to an apparent phospholipid association constant of 5.3×10⁴ M⁻¹. The sensor can detect the presence of vesicles containing as little as 5% phosphatidylserine. The sensing effect apparently requires a membrane surface because the sensors do not respond to a phosphatidylserine derivative that is monodispersed in aqueous solution.     

Bio-Inspired Polyanionic Electrolytes for Highly Stable Zinc-Ion Batteries

For zinc-ion batteries (ZIBs), the non-uniform Zn plating/stripping results in a high polarization and low Coulombic efficiency (CE), hindering the large-scale application of ZIBs. Here, inspired by biomass seaweed plants, an anionic polyelectrolyte alginate acid (SA) was used to initiate the in situ formation of the high-performance solid electrolyte interphase (SEI) layer on the Zn anode. Attribute to the anionic groups of −COO⁻, the affinity of Zn²⁺ ions to alginate acid induces a well-aligned accelerating channel for uniform plating. This SEI regulates the desolvation structure of Zn²⁺ and facilitates the formation of compact Zn (002) crystal planes. Even under high depth of discharge conditions (DOD), the SA-coated Zn anode still maintains a stable Zn stripping/plating behavior with a low potential difference (0.114 V). According to the classical nucleation theory, the nucleation energy for SA-coated Zn is 97 % less than that of bare Zn, resulting in a faster nucleation rate. The Zn||Cu cell assembled with the SA-coated electrode exhibits an outstanding average CE of 99.8 % over 1,400 cycles. The design is successfully demonstrated in pouch cells, where the SA-coated Zn exhibits capacity retention of 96.9 % compared to 59.1 % for bare Zn anode, even under the high cathode mass loading (>10 mg/cm²).     

Fluorescent biomembrane probe for ratiometric detection of apoptosis

Herein, we developed the first ratiometric fluorescent probe for apoptosis detection. This probe incorporates selectively into the outer leaflet of the cell plasma membrane and senses the loss of the plasma membrane asymmetry occurring during the early steps of apoptosis. The high specificity to the plasma membranes was achieved by introduction into the probe of a membrane anchor, composed of a zwitterionic group and a long (dodecyl) hydrophobic tail. The fluorescence reporter of this probe is 4'-(diethylamino)-3-hydroxyflavone, which exhibits excited-state intramolecular proton transfer (ESIPT), resulting in two-band emission highly sensitive to the lipid composition of the biomembranes. Fluorescence spectroscopy, flow cytometry, and microscopy measurements show that the ratio of the two emission bands of the probe changes dramatically in response to apoptosis. This response reflects the changes in the lipid composition of the outer leaflet of the cell plasma membrane because of the exposure of the anionic phospholipids from the inner leaflet at the early steps of apoptosis. Being ratiometric, the response of the new probe can be easily quantified on an absolute scale. This allows monitoring by laser scanning confocal microscopy the degree and spatial distribution of the apoptotic changes at the cell plasma membranes, a feature that can be hardly achieved with the commonly used fluorescently labeled annexin V assay.     

Triazole–containing zinc(II)dipicolylamine-functionalised peptides as highly selective pyrophosphate sensors in physiological media

A small family of linear bis[zinc(II)dipicolylamine] (bis[Zn(II)-DPA])-functionalised peptidic anion receptors has been prepared where the Zn(II)-DPA binding sites have been installed via either a reductive amination reaction or a copper(I)-catalysed azide-alkyne cycloaddition reaction. The latter reaction connects the Zn(II)-DPA binding site and the peptide backbone through a 1,2,3-triazole linkage. Subsequent anion binding studies using indicator displacement assays were conducted to elucidate the effect of the triazole linker on the anion-binding properties of these novel receptors and it was found that the triazole-containing receptors exhibited stronger affinity and slightly improved selectivity for pyrophosphate over adenosine triphosphate and adenosine diphosphate compared to the analogous receptors which did not bear the triazole linker.     

Cofactor-free detection of phosphatidylserine with cyclic peptides mimicking lactadherin

Cyclic peptides (cLacs) are designed to mimic the natural phosphatidylserine (PS) binding protein lactadherin. Unlike annexin V or its small molecule mimics, the cLac peptides selectively target PS-presenting membranes with no need for metal cofactors. We further show that a fluorophore-labeled cLac effectively stains early apoptotic cells. The small size and facile conjugation with a variety of imaging tracers make the cLac design promising for imaging cell death in vitro as well as in living organisms.     

Facilitated phosphatidylserine (PS) flip-flop and thrombin activation using a synthetic PS scramblase

A cationic steroid with a hydrogen-bonding pocket that has an affinity for anionic phospholipid headgroups was synthesized and shown to strongly promote the translocation or flip-flop of a fluorescent, C(6)NBD-labeled phosphatidylserine probe (C(6)NBD-PS) across vesicle membranes. In addition, the synthetic PS scramblase increases the levels of endogenous PS on the surface of erythrocytes as monitored by flow cytometry analysis of annexin V-FITC binding. The PS scrambling effect is enhanced when the cells are pretreated with N-ethylmaleimide (NEM), an inhibitor of the endogenous aminophospholipid flippase. The combination of NEM and synthetic PS scramblase enhances the ability of erythrocytes to promote the conversion of prothrombin to thrombin by a factor of 4. An analogous cationic steroid with a smaller binding pocket has no measurable PS translocation activity, a result that is attributed to its inability to sufficiently diminish the hydrophilicity of the multiply charged PS headgroup.     

Mononuclear Zn(II)- and Cu(II)-complexes of a hydroxynaphthalene-derived dipicolylamine: fluorescent sensing behaviours toward pyrophosphate ions

Mononuclear Zn(II)-DPA and Cu(II)-DPA complexes crafted on 2-hydroxy-6-cyanonaphthalene fluorophore selectively recognize PPi over ATP and other anions including inorganic phosphates in aqueous medium, showing turn-on type fluorescence enhancements. Coordination of a hydroxyl group of the fluorophore, directly or in alkoxy form, to the central metal ion is crucial for the sensing processes. Both the complexes elicit a fluorescence increase in a time-dependent fashion.     

Cascade-mode multiaffinity chromatography. Fractionation of human serum proteins.

The group-resolving power of cascade-mode multiaffinity column chromatography (CASMAC), was demonstrated with human serum as a model mixture. More than 99% of the serum proteins were adsorbed in the same high salt-containing buffer on a tandem column consisting of (1) immobilized Zn2+ on triscarboxymethyl diamine gel followed by (2) thiophilic (T) gel, (3) Zn2+ bound to the new tridentate chelating adsorbent dipicolylamine (DPA) agarose, (4) hexyl-thioether C6-S agarose and (5) Ni(2+)-DPA agarose. After the adsorption step the immobilized metal ion affinity gels were attached to the top of tandem columns of other adsorbents (T gel, Sephadex G-25 for desalting and Mono-Q) and the elution conditions were selected such that further group separation was achieved. High resolution, high recovery, easy manipulation and high capacity are characteristic features of the cascade process with these adsorbents. The advantage of CASMAC is particularly striking when, with a given number of adsorbents, the overall number of operations involving adsorption, desorption, washing, buffer change and substance concentration can be effectively minimized.     

A turn-on two-photon fluorescent probe for ATP and ADP

An acedan derivative containing Zn(II)-DPA has been developed as a two-photon probe for nucleoside phosphates, which shows enhanced fluorescence toward ATP and ADP at physiological pH 7.4 among other competing anions including AMP; the probe is permeable to cell membranes and thus can be directly used for two-photon imaging of ATP and ADP in live cells.     

The first solid composed of [As4V16O42(H2O)] clusters

A new polyoxovanadate [Zn2(dien)3][[Zn(dien)]2As4V16O42(H2O)] x 3H2O (1, dien = diethylenetriamine) has been hydrothermally synthesized and structurally characterized by EA, IR, TGA, magnetic measurement and single crystal X-ray diffraction. X-Ray diffraction analyses reveal that 1 exhibits the first [As4V16O42(H2O)]-containing polyoxometalate. In 1, the adjacent [As4V16O42(H2O)] clusters are linked to each other through dual mono-nuclear zinc complexes {Zn(dien)} to form one-dimensional anionic chains with isolated dinuclear zinc complexes [Zn2(dien)3] occupying the interchain regions as charge compensation. The study of the magnetic susceptibility demonstrates the presence of antiferromagnetic interaction between VIV cations in 1.     

Characterization of the early stages of programmed cell death in maize root cells by using comet assay and the combination of cell electrophoresis with annexin binding

An emerging topic in plant biology is whether plant cells display similar elements of programmed cell death (PCD) as animal cells do. We have studied cell death in maize roots exposed to cold stress by using fluorescence microscopy, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL), DNA gel electrophoresis, single cell gel electrophoresis (SCGE), cell electrophoresis, and annexin binding techniques. The results showed that cell death in maize root cells triggered by cold stress was accompanied by a subset of features characteristic of animal PCD such as nuclear condensation and fragmentation, and oligonucleosomal DNA fragmentation. In addition to DNA laddering and TUNEL positivity, a "comet" pattern indicative of DNA breakage appeared as short as after one day of treatment. The maize root cell PCD process was also accompanied by an increase in negative surface charge of the dying cells due to exposure of phosphatiolylserine (PS) from inner to outer membrane. After annexin binding, however, the enhanced electrophoretic mobility (EPM) of the dying cells decreased nearly to normal values. This result suggests that the combination between cell electrophoresis and annexin binding provides a quantitative method for monitoring PS exposure during plant PCD.     

Controlled Anionic Synthesis of Poly[2‐(3‐nitrocarbazolyl)ethyl methacrylate]

Poly[2‐(3‐nitrocarbazolyl)ethyl methacrylate] (poly(NCzMA)) with controlled molecular weight and narrow molecular weight distribution was successfully synthesized using (methyl methacryloyl)potassium (MMA) as a weak initiator in the presence of diethylzinc (Et₂Zn) in THF at –78°C. Et₂Zn acted both as an additive for the coordination with enolate anion and nitro group and as a scavenger to remove impurities. Block copolymers PMMA‐block‐poly(NCzMA)‐block‐PMMA and poly(NCzMA)‐block‐PS‐block‐poly(NCz‐MA), were also synthesized quantitatively (PMMA: poly(methyl methacrylate), PS: polystyrene). The results indicate that Et₂Zn can be used to synthesize the polymers of solid, nitro group‐containing methacrylate monomers by anionic polymerization in THF.     

磷脂酰甘油与缺钙光系统Ⅱ的相互作用

对磷脂酰甘油(PG)对缺钙光系统Ⅱ(d~C~aPSⅡ)放氧活性的影响及其作用机制进行了研究。结果表明,PG除能促进PSⅡ的放氧活性以外,还对PSⅡ系统表现出新的作用,即PG可以使PSⅡ颗粒因缺钙而受抑制的放氧活性得到恢复;外加Ca^2^+可使PG表现出对d~C~aPSⅡ放氧活性的更大促进作用,且随Ca^2^+浓度的增加,促进作用也越显著。PG的作用就在于恢复蛋白的正常结构,而PG与Ca^2^+形成的配合物可以优化这种结构而使缺钙PSⅡ颗粒的放氧活性得到增强。     

Synthesis and Crystal Structure of a New Organic-inorganic Hybrid One-dimensional Polymer： [Zn（C8H23N5）]2（Pb3I10）

1 INTRODUCTION Recently, the organic-inorganic hybrid Ⅳa groupmetal halides with low-dimensional structure haveattracted much attention of chemists and physicistsdue to their particular properties and applications.For example, they are akin to “natural quantum-well”architectures and have tunable excitonic propertiesusually governed by the inorganic substructure andorganic component[1]; they have been applied assome technologically important materials, such assemiconductor materials in …     

Polymerization of propylene sulphide by the Zn(C2H5)2-H2O catalyst system

The hydrolysis of a complex of diethyl zinc (DEZ) with propylene sulphide (PS) in PS solution has been investigated. Suitable conditions have been found for the quantitative hydrolysis of DEZ with the formation of a catalyst system containing (ZO)_n groups and ZnS bonds and effective for initiating the polymerization of PS. This polymerization was investigated and a tentative scheme for polymerization by a coordinate anionic mechanism is suggested. The structure of polypropylene sulphide (PPS) was investigated by high-resolution NMR spectroscopy and X-rays. The Zn(C₂H₅)₂—H₂O system prepared in situ is highly selective in the reactions of breaking the α-thioxide ring. Amorphous PS consists entirely of head-to-tail bonded units with equal content of iso- and syndiotactic diads. It was also shown that extremely high values of the molecular mass of PPS, the unusual dependence of [η] on conversion and the instability of polymer solutions are due to the presence of polymer aggregates formed in the polymerization of PS on complex associated active centres with a steric structure. Conditions were found for the stabilization of PS solutions containing zinc and for the purification of the polymer from traces of the catalyst system. It was shown that it is incorrect to use equations available in the literature to calculate $\text{M}$_η for PPS obtained with the DEZ—H₂O system from viscometric data without thorough purification of the polymer. Osmometry and light scattering technique were used to estimate true values of the molecular mass of polymer aggregates and of linear PPS.     

Trivalent metal-mediated gelation of novel supergiant sulfated polysaccharides extracted from <Emphasis Type="Italic">Aphanothece stagnina</Emphasis>

Anionic polysaccharide (PS) was extracted from Aphanothece stagnina biomaterials where trivalent metal ions were remarkably condensed from environmental water. Structural analyses indicated that the PS was considered to be a kind of sulfated rhamnoglucan-containing uronic acid at a composition of 23 mol% and that the total composition of anionic groups such as sulfate and carboxylate was 31 mol% to the monosaccharide residues. Since the PS was found to be a huge macromolecule with an ultra-high molecular weight (3.14 × 10⁷ g/mol), the simple calculation indicated that about 9.5 × 10⁴ anions exist on one chain of the PS. The electric conductivity of the highly anionic PS solutions indicated that the metal ions such as Ga³⁺, La³⁺, and Ca²⁺ complexed ionically with PS chains. The PS formed the gels as a result of trivalent metal complexation, but the gelation behavior of the PS was different from that of the representative metal-complexable polysaccharide, alginate, in terms of the minimum gel formation concentration and the average molecular weight between cross-linking points.     

Geometry and electronic structure of Vn(Bz)m complexes

First-principles calculations based on the generalized gradient approximation to the density functional theory are performed to explore the global geometries, ground-state spin multiplicities, relative stabilities, and energetics of neutral and anionic V(n)(Bz)(m) (n=1-3, m=1-4, with n相似文献   

Structure and Photosynthetic Mimicking of Bis(2,6-bis(benzimidazol-2-yl)pyridine)manganese(II)

Introduction　　Manganeseionsplayanimportantroleinthelight in ducedoxidationofwatertomolecularoxygeninphotosys temII (PSII)ofgreenplants.1 3Inrecentyears ,man ganesecomplexesofpolypyridineligands ,suchasbipyri dine ,1,10 phenanthrolineand 2 ,2′:6′,2″ terpyridine ,havehadconsiderableattentionasthecomplexesformedareusefulmodelsformanganese containingbimolecu lars .4 6 Therefore ,synthesisandcharacterizationofman ganeseinitsvariousoxidationstates ,withvariousligandtypesandnuclearities ,hav…