High-resolution Compton spectroscopy using X-ray microcalorimeters

X-ray Compton spectroscopy is one of the few direct probes of the electron momentum distribution of bulk materials in ambient and operando environments. We report high-resolution inelastic X-ray scattering experiments with high momentum and energy transfer performed at a storage-ring-based high-energy X-ray light source facility using an X-ray microcalorimeter detector. Compton profiles were measured for lithium and cobalt oxide powders relevant to lithium-ion battery research. Spectroscopic analysis of the measured Compton profiles shows high-sensitivity to the low-Z elements and oxidation states. The lineshape analysis of the measured Compton profiles in comparison with computed Hartree-Fock profiles is limited by the resolution of the energy-resolving semiconductor detector. We have characterized an X-ray transition-edge sensor microcalorimeter detector for high-resolution Compton scattering experiments using a bending magnet source at the Advanced Photon Source (APS) with a double crystal monochromator providing monochromatic photon energies near 27.5 keV. The momentum resolution below 0.16 atomic units was measured yielding an improvement of more than a factor of 7 over a state-of-the-art silicon drift detector for the same scattering geometry. Furthermore, the lineshapes of narrow valence and broad core electron profiles of sealed lithium metal were clearly resolved using an X-ray microcalorimeter detector compared to smeared and broadened lineshapes observed when using a silicon drift detector. High-resolution Compton scattering using the energy-resolving detector shown here presents new opportunities for spatial imaging of electron momentum distributions for a wide class of materials with applications ranging from electrochemistry to condensed matter physics.Comment: The following article has been submitted to Applied Physics Letter

A genistein derivative, ITB-301, induces microtubule depolymerization and mitotic arrest in multidrug-resistant ovarian cancer

PURPOSE: To investigate the mechanistic basis of the anti-tumor effect of the compound ITB-301. METHODS: Chemical modifications of genistein have been introduced to improve its solubility and efficacy. The anti-tumor effects were tested in ovarian cancer cells using proliferation assays, cell cycle analysis, immunofluorescence, and microscopy. RESULTS: In this work, we show that a unique glycoside of genistein, ITB-301, inhibits the proliferation of SKOv3 ovarian cancer cells. We found that the 50% growth inhibitory concentration of ITB-301 in SKOv3 cells was 0.5 μM. Similar results were obtained in breast cancer, ovarian cancer, and acute myelogenous leukemia cell lines. ITB-301 induced significant time- and dose-dependent microtubule depolymerization. This depolymerization resulted in mitotic arrest and inhibited proliferation in all ovarian cancer cell lines examined including SKOv3, ES2, HeyA8, and HeyA8-MDR cells. The cytotoxic effect of ITB-301 was dependent on its induction of mitotic arrest as siRNA-mediated depletion of BUBR1 significantly reduced the cytotoxic effects of ITB-301, even at a concentration of 10 μM. Importantly, efflux-mediated drug resistance did not alter the cytotoxic effect of ITB-301 in two independent cancer cell models of drug resistance. CONCLUSION: These results identify ITB-301 as a novel anti-tubulin agent that could be used in cancers that are multidrug resistant. We propose a structural model for the binding of ITB-301 to α- and β-tubulin dimers on the basis of molecular docking simulations. This model provides a rationale for future work aimed at designing of more potent analogs

Combined effect of low-molecular-weight organic acids and creosote on phosphatase activities in sandy soil

This paper assesses the impact of creosote and low-molecular-weight organic acids (LMWOAs) on the activity of acid phosphomonoesterase, alkaline phosphomonoesterase, phosphotriesterase, and inorganic pyrophosphatase in soil. The experiment was carried out on loamy sand samples with organic carbon content of 8.71 g·kg⁻¹, with the following variable factors: dosages of creosote: 0, 0.5%, and 2.5%; type of LMWOAs: oxalic acid, tartaric acid, and citric acid in the amount of 50 mmol·kg⁻¹ of soil; days of experiment: 1, 7, 14, 28, 56, 112. Obtained results showed that contamination with creosote caused decrease in the activity of soil phosphatases. The observed effect did not always increase with increase in the dosage of the pollutant. Among the assayed phosphatases, the biggest changes were noted in the activity of phosphomonoesterases. Application of LMWOAs to contaminated soil mainly effected the inhibition of phosphatase, especially the activity of acid phosphomonoesterase. Comparison of the effects of LMWOAs showed that the citric acid was the least toxic to soil phosphatases

A concept for G protein activation by G protein-coupled receptor dimers : the transducin/rhodopsin interface

G protein-coupled receptors (GPCRs) are ubiquitous and essential in modulating virtually all physiological processes. These receptors share a similar structural design consisting of the seven-transmembrane alpha-helical segments. The active conformations of the receptors are stabilized by an agonist and couple to structurally highly conserved heterotrimeric G proteins. One of the most important unanswered questions is how GPCRs couple to their cognate G proteins. Phototransduction represents an excellent model system for understanding G protein signaling, owing to the high expression of rhodopsin in rod photoreceptors and the multidisciplinary experimental approaches used to study this GPCR. Here, we describe how a G protein (transducin) docks on to an oligomeric GPCR (rhodopsin), revealing structural details of this critical interface in the signal transduction process. This conceptual model takes into account recent structural information on the receptor and G protein, as well as oligomeric states of GPCRs

A genistein derivative, ITB-301, induces microtubule depolymerization and mitotic arrest in multidrug-resistant ovarian cancer.

PURPOSE: To investigate the mechanistic basis of the anti-tumor effect of the compound ITB-301. METHODS: Chemical modifications of genistein have been introduced to improve its solubility and efficacy. The anti-tumor effects were tested in ovarian cancer cells using proliferation assays, cell cycle analysis, immunofluorescence, and microscopy. RESULTS: In this work, we show that a unique glycoside of genistein, ITB-301, inhibits the proliferation of SKOv3 ovarian cancer cells. We found that the 50% growth inhibitory concentration of ITB-301 in SKOv3 cells was 0.5 μM. Similar results were obtained in breast cancer, ovarian cancer, and acute myelogenous leukemia cell lines. ITB-301 induced significant time- and dose-dependent microtubule depolymerization. This depolymerization resulted in mitotic arrest and inhibited proliferation in all ovarian cancer cell lines examined including SKOv3, ES2, HeyA8, and HeyA8-MDR cells. The cytotoxic effect of ITB-301 was dependent on its induction of mitotic arrest as siRNA-mediated depletion of BUBR1 significantly reduced the cytotoxic effects of ITB-301, even at a concentration of 10 μM. Importantly, efflux-mediated drug resistance did not alter the cytotoxic effect of ITB-301 in two independent cancer cell models of drug resistance. CONCLUSION: These results identify ITB-301 as a novel anti-tubulin agent that could be used in cancers that are multidrug resistant. We propose a structural model for the binding of ITB-301 to α- and β-tubulin dimers on the basis of molecular docking simulations. This model provides a rationale for future work aimed at designing of more potent analogs

Activities of Topoisomerase I in Its Complex with SRSF1

Human DNA topoisomerase I (topo I) catalyzes DNA relaxation and phosphorylates SRSF1. Whereas the structure of topo I complexed with DNA has been resolved, the structure of topo I in the complex with SRSF1 and structural determinants of topo I activities in this complex are not known. The main obstacle to resolving the structure is a contribution of unfolded domains of topo I and SRSF1 in formation of the complex. To overcome this difficulty, we employed a three-step strategy: identifying the interaction regions, modeling the complex, and validating the model with biochemical methods. The binding sites in both topo I and SRSF1 are localized in the structured regions as well as in the unfolded domains. One observes cooperation between the binding sites in topo I but not in SRSF1. Our results indicate two features of the unfolded RS domain of SRSF1 containing phosphorylated residues that are critical for the kinase activity of topo I: its spatial arrangement relative to topo I and the organization of its sequence. The efficiency of phosphorylation of SRSF1 depends on the length and flexibility of the spacer between the two RRM domains that uniquely determine an arrangement of the RS domain relative to topo I. The spacer also influences inhibition of DNA nicking, a prerequisite for DNA relaxation. To be phosphorylated, the RS domain has to include a short sequence recognized by topo I. A lack of this sequence in the mutants of SRSF1 or its spatial inaccessibility in SRSF9 makes them inadequate as topo I/kinase substrates