Unprecedented chemical transformation: crystallographic evidence for 1,1,2,2-tetrahydroxyethane captured within an Fe6Dy3 single molecule magnet

A nonanuclear {Fe6Dy3} coordination cluster displaying SMM behaviour in which an unprecedented chemical transformation provides structural information for the existence of 1,1,2,2-tetrahydroxyethane is reported

Black Holes with Weyl Charge and Non-Riemannian Waves

A simple modification to Einstein's theory of gravity in terms of a non-Riemannian connection is examined. A new tensor-variational approach yields field equations that possess a covariance similar to the gauge covariance of electromagnetism. These equations are shown to possess solutions analogous to those found in the Einstein-Maxwell system. In particular one finds gravi-electric and gravi-magnetic charges contributing to a spherically symmetric static Reissner-Nordstr\"om metric. Such Weyl ``charges'' provide a source for the non-Riemannian torsion and metric gradient fields instead of the electromagnetic field. The theory suggests that matter may be endowed with gravitational charges that couple to gravity in a manner analogous to electromagnetic couplings in an electromagnetic field. The nature of gravitational coupling to spinor matter in this theory is also investigated and a solution exhibiting a plane-symmetric gravitational metric wave coupled via non-Riemannian waves to a propagating spinor field is presented.Comment: 18 pages Plain Tex (No Figures), Classical and Quantum Gravit

Octonionic representations of Clifford algebras and triality

The theory of representations of Clifford algebras is extended to employ the division algebra of the octonions or Cayley numbers. In particular, questions that arise from the non-associativity and non-commutativity of this division algebra are answered. Octonionic representations for Clifford algebras lead to a notion of octonionic spinors and are used to give octonionic representations of the respective orthogonal groups. Finally, the triality automorphisms are shown to exhibit a manifest \perm_3 \times SO(8) structure in this framework.Comment: 33 page

Identification of prognostic factors and risk groups in patients found to have nodal metastasis at the time of radical hysterectomy for early-stage squamous carcinoma of the cervix

In a retrospective study conducted at the University of Alabama at Birmingham, the University of Michigan, and the Mayo Clinic, 185 patients with previously untreated FIGO stage IB and IIA squamous cell carcinoma of the cervix were found to have nodal metastasis at the time of radical hysterectomy and pelvic lymphadenectomy. Of these patients, 103 received adjuvant pelvic irradiation. Cancer recurred in 76 patients; the median time to recurrence was 3.1 years. The prognostic significance of patient age, clinical stage, lesion diameter, number and location of nodal metastases, and use of adjuvant radiation therapy was determined by multivariate analysis. Only patient age (P = 0.0006), lesion diameter (P P = 0.0004) were noted to be significant factors in determining overall survival. Rates of recurrence were also related to these factors. Employment of these significant variables led to identification of four risk groups. In general, patients with small cervical lesions (diameter 4 cm) and more than two involved nodes fell into the high-risk category. All other patients were categorized into intermediate-risk groups. Ten-year survival was 92% in the low-risk group (n = 13), 70% in the low-intermediate-risk group (n = 66), 56% in the high-intermediate-risk group (n = 66), and 13% in the high-risk group (n = 20). This risk group classification identifies subgroups of early-stage cervical carcinoma patients found to have nodal metastasis at the time of radical hysterectomy that warrant appropriately selected adjuvant therapy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27695/1/0000081.pd

Human erythrocyte sugar transport is incompatible with available carrier models

GLUT1-mediated, passive D-glucose transport in human erythrocytes is asymmetric, Vmax and K(m)(app) for D-glucose uptake at 4 degrees C are 10-fold lower than Vmax and K(m)(app) for D-glucose export. Transport asymmetry is not observed for GLUT1-mediated 3-O-methylglucose transport in rat, rabbit, and avian erythrocytes and rat adipocytes where Vmax for sugar uptake and exit are identical. This suggests that transport asymmetry is either an intrinsic catalytic property of human GLUT1 or that factors present in human erythrocytes affect GLUT1-mediated sugar transport. In the present study we assess human erythrocyte sugar transport asymmetry by direct measurement of sugar transport rates and by analysis of the effects of intra- and extracellular sugars on cytochalasin B binding to the sugar export site. We also perform internal consistency tests to determine whether the measured, steady-state 3-O-methylglucose transport properties of human erythrocytes agree with those expected of two hypothetical models for protein-mediated sugar transport. The simple-carrier hypothesis describes a transporter that alternately exposes sugar import and sugar export pathways. The fixed-site carrier hypothesis describes a sugar transporter that simultaneously exposes sugar import and sugar export pathways. Steady-state 3-O-methylglucose transport in human erythrocytes at 4 degrees C is asymmetric. Vmax and K(m)(app) for sugar uptake are 10-fold lower than Vmax and K(m)(app) for sugar export. Phloretin-inhibitable cytochalasin B binding to intact red cells is unaffected by extracellular D-glucose but is competitively inhibited by intracellular D-glucose. This inhibition is reduced by 13% +/- 4% when saturating extracellular D-glucose levels are also present. Assuming transport is mediated by a simple-carrier and that cytochalasin B and intracellular D-glucose binding sites are mutually exclusive, the cytochalasin B binding data are explained only if transport is almost symmetric (Vmax exit = 1.4 Vmax entry). The cytochalasin B binding data are consistent with both symmetric and asymmetric fixed-site carriers. Analysis of 3-O-methylglucose, 2-deoxy-D-glucose, and D-glucose uptake in the presence of intracellular 3-O-methylglucose, demonstrates significant divergence in experimental and theoretical transport behaviors. We conclude either that human erythrocyte sugar transport is mediated by a carrier mechanism that is fundamentally different from those considered previously or that human erythrocyte-specific factors prevent accurate determination of GLUT1-mediated sugar translocation across the cell membrane. We suggest that GLUT1-mediated sugar transport in all cells is an intrinsically symmetric process but that intracellular sugar complexation in human red cells prevents accurate determination of transport rates

Regulation of GLUT1-mediated sugar transport by an antiport/uniport switch mechanism

Avian erythrocyte sugar transport is stimulated during anoxia and during exposure to inhibitors of oxidative phosphorylation. This stimulation results from catalytic desuppression of the cell surface glucose transporter GLUT1 [Diamond, D., and Carruthers, A. (1993) J. Biol. Chem. 268, 6437-6444]. The present study was undertaken to investigate the mechanisms of GLUT1 suppression/desuppression. Sugar uniport (sugar uptake or exit in the absence of sugar at the opposite side of the membrane) is absent in normoxic avian erythrocytes, but sugar antiport (sugar uptake coupled to sugar exit) is present. Exposure to cyanide and/or to FCCP (mitochondrial inhibitors) stimulates erythrocyte sugar uniport but not sugar antiport. K(m)(app) for 3-O-methylglucose uniport and antiport are unaffected by metabolic poisoning. Ki(app) for inhibitions of 3-O-methylglucose uniport by cytochalasin B and forskolin (sugar export site ligands) are unaffected by progressive stimulation of sugar uniport. Cyanide and FCCP stimulation of 3-O-methylglucose uniport are associated with increased AMP-activated protein kinase activity. Purified human GLUT1 is not phosphorylated by exposure to cytosol extracted from poisoned avian erythrocytes. FCCP does not stimulate GLUT1-mediated 3-O-methylglucose uptake in K562 cells but does increase K562 AMP-activated protein kinase activity. FCCP stimulation of 3-O-methylglucose uniport in resealed erythrocyte ghosts requires cytosolic ATP and/or glutathione. The nonmetabolizable ATP analog AMP-PNP cannot be substituted for ATP in this action. These results are contrasted with allosteric regulation of human erythrocyte sugar transport and suggest that avian erythrocyte sugar transport suppression results from inhibition of carrier uniport function. Uniport suppression is not mediated by interaction with cytosolic molecular species that bind to the sugar export site. The antiport to uniport switch mechanism requires ATP hydrolysis, is associated with elevated AMP-activated kinase function, and, if triggered by this kinase, is mediated by factors absent in K562 cells and downstream from the kinase

Fe-Gd Ferromagnetic Cyclic Coordination Cluster [FeIII4GdIII4(teaH)8(N3)8(H2O)] with Magnetic Anisotropy─Theory and Experiment

Schray D, Westerbeck D, Braun J, et al. Fe-Gd Ferromagnetic Cyclic Coordination Cluster [FeIII4GdIII4(teaH)8(N3)8(H2O)] with Magnetic Anisotropy─Theory and Experiment. Inorganic Chemistry . 2023;62(17):6642-6648.The synthesis, structural, and magnetic characterization of [FeIII4LnIII4(teaH)8(N3)8(H2O)] (Ln = Gd and Y) and the previously reported isostructural Dy analogue are discussed. The commonly held belief that both FeIII and GdIII can be regarded as isotropic ions is shown to be an oversimplification. This conclusion is derived from the magnetic data for the YIII analogue in terms of the zero-field splitting seen for FeIII and from the fact that the magnetic data for the new GdIII analogue can only be fit employing an additional anisotropy term for the GdIII ions. Furthermore, the Fe4Gd4 ring shows slow relaxation of magnetization. Our analysis of the experimental magnetic data employs both density functional theory as well as the finite-temperature Lanczos method which finally enables us to provide an almost perfect fit of magnetocaloric properties