Structure of cytochrome a3-Cua3 couple in cytochrome c oxidase as revealed by nitric oxide binding studies

The addition of NO to oxidized cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) causes the appearance of a high-spin heme electron paramagnetic resonance (EPR) signal due to cytochrome a3. This suggests that NO coordinates to Cu{a3}+2 and breaks the antiferromagnetic couple by forming a cytochrome a3+3-Cu{a3}+2-NO complex. The intensity of the high-spin cytochrome a3 signal depends on the method of preparation of the enzyme and maximally accounts for 58% of one heme. The effect of N3- on the cytochrome a3+3-Cu{a3}+2-NO complex is to reduce cytochrome a3 to the ferrous state, and this is followed by formation of a new complex that exhibits EPR signals characteristic of a triplet species. On the basis of optical and EPR results, a NO bridge between cytochrome a3+2 and Cu{a3}+2 is proposed-i.e., cytochrome a3+2-NO-Cu{a3}+2. The half-field transition observed at g = 4.34 in the EPR spectrum of this triplet species exhibits resolved copper hyperfine splittings with |A{}| = 0.020 cm-1, indicating that the Cu{a3}+2 in the cytochrome a3+2-NO-Cu{a3}+2 complex is similar to a type 2 copper site

Experiences in deploying metadata analysis tools for institutional repositories

Current institutional repository software provides few tools to help metadata librarians understand and analyze their collections. In this article, we compare and contrast metadata analysis tools that were developed simultaneously, but independently, at two New Zealand institutions during a period of national investment in research repositories: the Metadata Analysis Tool (MAT) at The University of Waikato, and the Kiwi Research Information Service (KRIS) at the National Library of New Zealand. The tools have many similarities: they are convenient, online, on-demand services that harvest metadata using OAI-PMH; they were developed in response to feedback from repository administrators; and they both help pinpoint specific metadata errors as well as generating summary statistics. They also have significant differences: one is a dedicated tool wheres the other is part of a wider access tool; one gives a holistic view of the metadata whereas the other looks for specific problems; one seeks patterns in the data values whereas the other checks that those values conform to metadata standards. Both tools work in a complementary manner to existing Web-based administration tools. We have observed that discovery and correction of metadata errors can be quickly achieved by switching Web browser views from the analysis tool to the repository interface, and back. We summarize the findings from both tools' deployment into a checklist of requirements for metadata analysis tools

Effect of buffer on heparin binding and sensing in competitive aqueous media

Although buffer-specific effects on molecular recognition are known in biological science, they remain rare in supramolecular chemistry. The binding between a cationic dye, Mallard Blue (MalB), and polyanionic heparin in aqueous NaCl (150 mM) is studied in three commonly-used buffers (Tris-HCl, HEPES, Phosphate, each 10 mM). Although MalB has a very similar UV-Vis spectrum in each buffer, the sensory response towards heparin was different in each case. This can be ascribed to differences in the complex formed. In Tris-HCl which has the least competitive chloride counter-anions, MalB exhibits a hypsochromic shift of 25 nm, assigned to strong binding and aggregation of the dye on heparin. In more competitive HEPES, containing a sulfonate anion, there is weaker binding and less aggregation of MalB along the heparin; the hypsochromic shift is only 15 nm. In phosphate buffer, MalB can interact quite strongly with buffer phosphate anions; although heparin binding is still observed, the hypsochromic shift associated with dye aggregation is only 5 nm. As such, specific buffer interactions with the MalB-heparin complex mediate host-guest binding and sensing. Buffer choice must be made carefully in studies of molecular recognition – we would caution against using phosphate and sulfonate containing buffers when studying electrostatic binding

Building Quality Schools for Our Children

Whether our schools are implementing an education suited only to an earlier era or they have failed the mission of education all along, their restructuring and redesign are urgently required. In addressing both utilitarian and epistemological concerns, the "variable" and "constant" aspects of education are examined, the centrality of learners as well as the process of learning and teaching are highlighted, and the need for going beyond basic literacies and introducing disciplinary thinking through in-depth studies of cultural exemplars of "zhen," "shan," and "mei" (truth, goodness, and beauty) are emphasized. Finally, the importance of building quality schools for our children on the basis of good practices and their evaluation is discussed. Key words: school restructuring; quality school; Hong Kong Currently, as Hong Kong education reform rhetoric and action intensify, many educators are struggling with the task of how best to restructure or redesign schools in pre-collegiate education to meet the needs of our society as well as to prepare our students for important challenges in the 21st century. This impetus for school restructuring or redesign may be seen a

Unconventional Planar Hall Effect in Exchange-Coupled Topological Insulator-Ferromagnetic Insulator Heterostructures

The Dirac electrons occupying the surface states (SSs) of topological insulators (TIs) have been predicted to exhibit many exciting magneto-transport phenomena. Here we report on the first experimental observation of an unconventional planar Hall effect (PHE) and an electrically gate-tunable hysteretic planar magnetoresistance (PMR) in EuS/TI heterostructures, in which EuS is a ferromagnetic insulator (FMI) with an in-plane magnetization. In such exchange-coupled FMI/TI heterostructures, we find a significant (suppressed) PHE when the in-plane magnetic field is parallel (perpendicular) to the electric current. This behavior differs from previous observations of the PHE in ferromagnets and semiconductors. Furthermore, as the thickness of the 3D TI films is reduced into the 2D limit, in which the Dirac SSs develop a hybridization gap, we find a suppression of the PHE around the charge neutral point indicating the vital role of Dirac SSs in this phenomenon. To explain our findings, we outline a symmetry argument that excludes linear-Hall mechanisms and suggest two possible non-linear Hall mechanisms that can account for all the essential qualitative features in our observations.Comment: 17 pages, 4 figures, accepted by Phys. Rev.

Electron Spin Relaxation of Cu_A and Cytochrome a in Cytochrome c Oxidase. Comparison to heme, copper, and sulfur radical complexes

The method of continuous saturation has been used to measure the electron spin relaxation parameter T_(1)T_(2) at temperatures between 10 and 50 K for a variety of S = 1/2 species including: Cu_A and cytochrome a of cytochrome c oxidase, the type 1 copper in several blue copper proteins, the type 2 copper in laccase, inorganic Cu(II) complexes, sulfur radicals, and low spin heme proteins. The temperature dependence and the magnitude of T_(1)T_(2) for all of the species examined are accounted for by assuming that the Van Vleck Raman process dominates the electron spin-lattice relaxation. Over the entire temperature range examined, the relaxation of the type 1 coppers in six to seven times faster than that of type 2 copper, inorganic copper, and sulfur radicals, in spite of the similar g-anisotropies of these species. This result may indicate that the coupling of the phonon bath to the spin center is more effective in type 1 coppers than in the other complexes studied. The relaxation of Cu_A of cytochrome oxidase exhibits an unusual temperature dependence relative to the other copper complexes studied, suggesting that the protein environment of this center is different from that of the other copper centers studied and/or that Cu_A is influenced by a magnetic dipolar interaction with another, faster-relaxing paramagnetic site in the enzyme. A comparison of the saturation characteristics of the Cu_A EPR signal in native and partially reduced CO complexes of the enzyme also suggests the existence of such an interaction. The implications of these results with respect to the disposition of the metal centers in cytochrome oxidase are discusse

Melvin Models and Diophantine Approximation

Melvin models with irrational twist parameter provide an interesting example of conformal field theories with non-compact target space, and localized states which are arbitrarily close to being delocalized. We study the torus partition sum of these models, focusing on the properties of the regularized dimension of the space of localized states. We show that its behavior is related to interesting arithmetic properties of the twist parameter $\gamma$, such as the Lyapunov exponent. Moreover, for $\gamma$ in a set of measure one the regularized dimension is in fact not a well-defined number but must be considered as a random variable in a probability distribution.Comment: 26pp. harvmac(b); v2: Some clarifications and references added. One small error corrected; v3: reference adde

Evaluation of person-level heterogeneity of treatment effects in published multiperson N-of-1 studies: systematic review and reanalysis.

OBJECTIVE:Individual patients with the same condition may respond differently to similar treatments. Our aim is to summarise the reporting of person-level heterogeneity of treatment effects (HTE) in multiperson N-of-1 studies and to examine the evidence for person-level HTE through reanalysis. STUDY DESIGN:Systematic review and reanalysis of multiperson N-of-1 studies. DATA SOURCES:Medline, Cochrane Controlled Trials, EMBASE, Web of Science and review of references through August 2017 for N-of-1 studies published in English. STUDY SELECTION:N-of-1 studies of pharmacological interventions with at least two subjects. DATA SYNTHESIS:Citation screening and data extractions were performed in duplicate. We performed statistical reanalysis testing for person-level HTE on all studies presenting person-level data. RESULTS:We identified 62 multiperson N-of-1 studies with at least two subjects. Statistical tests examining HTE were described in only 13 (21%), of which only two (3%) tested person-level HTE. Only 25 studies (40%) provided person-level data sufficient to reanalyse person-level HTE. Reanalysis using a fixed effect linear model identified statistically significant person-level HTE in 8 of the 13 studies (62%) reporting person-level treatment effects and in 8 of the 14 studies (57%) reporting person-level outcomes. CONCLUSIONS:Our analysis suggests that person-level HTE is common and often substantial. Reviewed studies had incomplete information on person-level treatment effects and their variation. Improved assessment and reporting of person-level treatment effects in multiperson N-of-1 studies are needed