Macroscopic phase separation in high-temperature superconductors

High-temperature superconductivity is recovered by introducing extra holes to the Cu-O planes, which initially are insulating with antiferromagnetism. In this paper I present data to show the macroscopic electronic phase separation that is caused by either mobile doping or electronic instability in the overdoped region. My results clearly demonstrate that the electronic inhomogeneity is probably a general feature of high-temperature superconductors.

Quantitative ER ↔ Golgi Transport Kinetics and Protein Separation upon Golgi Exit Revealed by Vesicular Integral Membrane Protein 36 Dynamics in Live CellsV⃞

To quantitatively investigate the trafficking of the transmembrane lectin VIP36 and its relation to cargo-containing transport carriers (TCs), we analyzed a C-terminal fluorescent-protein (FP) fusion, VIP36-SP-FP. When expressed at moderate levels, VIP36-SP-FP localized to the endoplasmic reticulum, Golgi apparatus, and intermediate transport structures, and colocalized with epitope-tagged VIP36. Temperature shift and pharmacological experiments indicated VIP36-SP-FP recycled in the early secretory pathway, exhibiting trafficking representative of a class of transmembrane cargo receptors, including the closely related lectin ERGIC53. VIP36-SP-FP trafficking structures comprised tubules and globular elements, which translocated in a saltatory manner. Simultaneous visualization of anterograde secretory cargo and VIP36-SP-FP indicated that the globular structures were pre-Golgi carriers, and that VIP36-SP-FP segregated from cargo within the Golgi and was not included in post-Golgi TCs. Organelle-specific bleach experiments directly measured the exchange of VIP36-SP-FP between the Golgi and endoplasmic reticulum (ER). Fitting a two-compartment model to the recovery data predicted first order rate constants of 1.22 ± 0.44%/min for ER → Golgi, and 7.68 ± 1.94%/min for Golgi → ER transport, revealing a half-time of 113 ± 70 min for leaving the ER and 1.67 ± 0.45 min for leaving the Golgi, and accounting for the measured steady-state distribution of VIP36-SP-FP (13% Golgi/87% ER). Perturbing transport with AlF4− treatment altered VIP36-SP-GFP distribution and changed the rate constants. The parameters of the model suggest that relatively small differences in the first order rate constants, perhaps manifested in subtle differences in the tendency to enter distinct TCs, result in large differences in the steady-state localization of secretory components.

Chemical communication in scarab beetles: reciprocal behavioral agonist-antagonist activities of chiral pheromones.

A novel mechanism of reciprocal behavioral agonist-antagonist activities of enantiomeric pheromones plays a pivotal role in overcoming the signal-to-noise problem derived from the use of a single-constituent pheromone system in scarab beetles. Female Anomala osakana produce (S, Z)-5-(+)-(1-decenyl)oxacyclopentan-2-one, which is highly attractive to males; the response is completely inhibited even by 5% of its antipode. These two enantiomers have reverse roles in the Popillia japonica sex pheromone system. Chiral GC-electroantennographic detector experiments suggest that A. osakana and P. japonica have both R and S receptors that are responsible for behavioral agonist and antagonist responses.

Silver ion high pressure liquid chromatography provides unprecedented separation of sterols: application to the enzymatic formation of cholesta-5,8-dien-3 beta-ol.

We report that silver ion HPLC provides remarkable separations of C27 sterols differing only in the number or location of olefinic double bonds. This technique has been extended to LC-MS, analysis of purified components by GC, GC-MS, and 1H NMR, and to its use on a semipreparative scale. The application of this methodology for the demonstration of the catalysis, by rat liver microsomes, of the conversion of 7-dehydrocholesterol to cholesta-5,8-dien-3 beta-ol is also presented.

Genetic separation of tumor growth and hemorrhagic phenotypes in an estrogen-induced tumor.

Chronic administration of estrogen to the Fischer 344 (F344) rat induces growth of large, hemorrhagic pituitary tumors. Ten weeks of diethylstilbestrol (DES) treatment caused female F344 rat pituitaries to grow to an average of 109.2 +/- 6.3 mg (mean +/- SE) versus 11.3 +/- 1.4 mg for untreated rats, and to become highly hemorrhagic. The same DES treatment produced no significant growth (8.9 +/- 0.5 mg for treated females versus 8.7 +/- 1.1 for untreated females) or morphological changes in Brown Norway (BN) rat pituitaries. An F1 hybrid of F344 and BN exhibited significant pituitary growth after 10 weeks of DES treatment with an average mass of 26.3 +/- 0.7 mg compared with 8.6 +/- 0.9 mg for untreated rats. Surprisingly, the F1 hybrid tumors were not hemorrhagic and had hemoglobin content and outward appearance identical to that of BN. Expression of both growth and morphological changes is due to multiple genes. However, while DES-induced pituitary growth exhibited quantitative, additive inheritance, the hemorrhagic phenotype exhibited recessive, epistatic inheritance. Only 5 of the 160 F2 pituitaries exhibited the hemorrhagic phenotype; 36 of the 160 F2 pituitaries were in the F344 range of mass, but 31 of these were not hemorrhagic, indicating that the hemorrhagic phenotype is not merely a consequence of extensive growth. The hemorrhagic F2 pituitaries were all among the most massive, indicating that some of the genes regulate both phenotypes.

Separation of the transcriptional coactivator and antirepression functions of transcription factor IIA.

Human transcription factor IIA (TFIIA) is composed of three subunits (alpha, beta, and gamma). TFIIA interacts with the TATA-box binding protein and can overcome repression of transcription. TFIIA was found to be necessary for VP16-mediated transcriptional activation through a coactivator function. We have separated the coactivator and antirepression activities of TFIIA. A TFIIA lacking the alpha subunit was isolated from HeLa cells. This "mini-TFIIA" interacts with the TATA-box binding protein and can overcome repression of transcription, but it is defective in transcriptional coactivator function.

Long-time quantum simulation of the primary charge separation in bacterial photosynthesis.

Accurate quantum mechanical simulations of the primary charge transfer in photosynthetic reaction centers are reported. The process is modeled by three coupled electronic states corresponding to the photoexcited chlorophyll special pair (donor), the reduced bacteriopheophytin (acceptor), and the reduced accessory chlorophyll (bridge) that interact with a dissipative medium of protein and solvent degrees of freedom. The time evolution of the excited special pair is followed over 17 ps by using a fully quantum mechanical path integral scheme. We find that a free energy of the reduced accessory chlorophyll state approximately equal to 400 cm(-1) lower than that of the excited special pair state yields state populations in agreement with experimental results on wild-type and modified reaction centers. For this energetic configuration electron transfer is a two-step process.

Phase separation in aqueous solutions of lens gamma-crystallins: special role of gamma s.

We have studied liquid-liquid phase separation in aqueous ternary solutions of calf lens gamma-crystallin proteins. Specifically, we have examined two ternary systems containing gamma s--namely, gamma IVa with gamma s in water and gamma II with gamma s in water. For each system, the phase-separation temperatures (Tph (phi)) alpha as a function of the overall protein volume fraction phi at various fixed compositions alpha (the "cloud-point curves") were measured. For the gamma IVa, gamma s, and water ternary solution, a binodal curve composed of pairs of coexisting points, (phi I, alpha 1) and (phi II, alpha II), at a fixed temperature (20 degrees C) was also determined. We observe that on the cloud-point curve the critical point is at a higher volume fraction than the maximum phase-separation temperature point. We also find that typically the difference in composition between the coexisting phases is at least as significant as the difference in volume fraction. We show that the asymmetric shape of the cloud-point curve is a consequence of this significant composition difference. Our observation that the phase-separation temperature of the mixtures in the high volume fraction region is strongly suppressed suggests that gamma s-crystallin may play an important role in maintaining the transparency of the lens.

Kinetics of spindle pole body separation in budding yeast.

In the budding yeast Saccharomyces cerevisiae, the spindle pole body (SPB) serves as the microtubule-organizing center and is the functional analog of the centrosome of higher organisms. By expressing a fusion of a yeast SPB-associated protein to the Aequorea victoria green fluorescent protein, the movement of the SPBs in living yeast cells undergoing mitosis was observed by fluorescence microscopy. The ability to visualize SPBs in vivo has revealed previously unidentified mitotic events. During anaphase, the mitotic spindle has four sequential activities: alignment at the mother-daughter junction, fast elongation, translocation into the bud, and slow elongation. These results indicate that distinct forces act upon the spindle at different times during anaphase.

Identification of receptor ligands and receptor subtypes using antagonists in a capillary electrophoresis single-cell biosensor separation system.

A capillary electrophoresis system with single-cell biosensors as a detector has been used to separate and identify ligands in complex biological samples. The power of this procedure was significantly increased by introducing antagonists that inhibited the cellular response from selected ligand-receptor interactions. The single-cell biosensor was based on the ligand-receptor binding and G-protein-mediated signal transduction pathways in PC12 and NG108-15 cell lines. Receptor activation was measured as increases in cytosolic free calcium ion concentration by using fluorescence microscopy with the intracellular calcium ion indicator fluo-3-acetoxymethyl ester. Specifically, a mixture of bradykinin (BK) and acetylcholine (ACh) was fractionated and the components were identified by inhibiting the cellular response with icatibant (HOE 140), a selective antagonist to the BK B2 receptor subtype (B2BK), and atropine, an antagonist to muscarinic ACh receptor subtypes. Structurally related forms of BK were also identified based on inhibiting B2BK receptors. Applications of this technique include identification of endogenous BK in a lysate of human hepatocellular carcinoma cells (Hep G2) and screening for bioactivity of BK degradation products in human blood plasma. The data demonstrate that the use of antagonists with a single-cell biosensor separation system aids identification of separated components and receptor subtypes.

Pseudoscalar susceptibilities and quark condensates: chiral restoration and lattice screening masses

We derive the formal Ward identities relating pseudoscalar susceptibilities and quark condensates in three-flavor QCD, including consistently the 77-n' sector and the U-A(1) anomaly. These identities are verified in the low-energy realization provided by ChPT, both in the standard SU(3) framework for the octet case and combining the use of the SU(3) framework and the large-Nc expansion of QCD to account properly for the nonet sector and anomalous contributions. The analysis is performed including finite temperature corrections as well as the calculation of U(3) quark condensates and all pseudoscalar susceptibilities, which together with the full set of Ward identities, are new results of this work. Finally, the Ward identities are used to derive scaling relations for pseudoscalar masses which explain the behavior with temperature of lattice screening masses near chiral symmetry restoration.

Separation and fractionation of order and disorder in highly polydisperse systems

We study a polydisperse soft-spheres model for colloids by means of microcanonical Monte Carlo simulations. We consider a polydispersity as high as 24%. Although solidification occurs, neither a crystal nor an amorphous state are thermodynamically stable. A finite size scaling analysis reveals that in the thermodynamic limit: a the fluid-solid transition is rather a crystal-amorphous phase-separation, b such phase-separation is preceded by the dynamic glass transition, and c small and big particles arrange themselves in the two phases according to a complex pattern not predicted by any fractionation scenario.

Comment Letter: The NYSE and the End of the Structural Separation between Regulatory and Commercial Interests of the Exchange

The NYSE transformed into a for profit entity in 2006. As part of the approval process, the NYSE agreed to structurally separate the regulatory function from the business function. In doing so, the NYSE created NYSE Regulation, a non-profit with an independent board, to handle most regulatory matters. During the comment period, a spirited debate arose over the ability of a for profit company to carry out a regulatory mission. Some suggested that the regulatory function was incompatible with a "for profit" motive and that NYSE Regulation should be spun off. Others accepted the proposed structure but called for additional changes designed to reduce the possible influence of the public holding company over the regulatory function. In the end, the SEC approved the structure but with a number of prophylactic safeguards including the requirement that NYSE Regulation have a board consisting of all independent directors (save the CEO) and that directors from the for profit holding company could not make up a majority of the board. More recently, however, the NYSE has proposed to end the structural separation of the two functions and instead put in place a functional separation. The proposal would result in the termination of the delegation agreement between the Exchange and NYSE Regulation and the creation of both a Regulatory Oversight Committee of the Board of Directors of the Exchange and the creation of a Chief Regulatory Officer. This letter examines the history of the separation of the two functions and critiques the NYSE's proposal.

Chiral gold(I) vs chiral silver complexes as catalysts for the enantioselective synthesis of the second generation GSK-hepatitis C virus inhibitor

The synthesis of a GSK 2nd generation inhibitor of the hepatitis C virus, by enantioselective 1,3-dipolar cycloaddition between a leucine derived iminoester and tert-butyl acrylate, was studied. The comparison between silver(I) and gold(I) catalysts in this reaction was established by working with chiral phosphoramidites or with chiral BINAP. The best reaction conditions were used for the total synthesis of the hepatitis C virus inhibitor by a four step procedure affording this product in 99% ee and in 63% overall yield. The origin of the enantioselectivity of the chiral gold(I) catalyst was justified according to DFT calculations, the stabilizing coulombic interaction between the nitrogen atom of the thiazole moiety and one of the gold atoms being crucial.

Spin separation in digital ferromagnetic heterostructures

In a study of the ferromagnetic phase of a multilayer digital ferromagnetic semiconductor in the mean-field and effective-mass approximations, we find the exchange interaction to have the dominant energy scale of the problem, effectively controlling the spatial distribution of the carrier spins in the digital ferromagnetic heterostructures. In the ferromagnetic phase, the majority-spin and minority-spin carriers tend to be in different regions of the space (spin separation). Hence, the charge distribution of carriers also changes noticeably from the ferromagnetic to the paramagnetic phase. An example of a design to exploit these phenomena is given here.