Pre-replication complex proteins assemble at regions of low nucleosome occupancy within the Chinese hamster dihydrofolate reductase initiation zone

Genome-scale mapping of pre-replication complex proteins has not been reported in mammalian cells. Poor enrichment of these proteins at specific sites may be due to dispersed binding, poor epitope availability or cell cycle stage-specific binding. Here, we have mapped sites of biotin-tagged ORC and MCM protein binding in G1-synchronized populations of Chinese hamster cells harboring amplified copies of the dihydrofolate reductase (DHFR) locus, using avidin-affinity purification of biotinylated chromatin followed by high-density microarray analysis across the DHFR locus. We have identified several sites of significant enrichment for both complexes distributed throughout the previously identified initiation zone. Analysis of the frequency of initiations across stretched DNA fibers from the DHFR locus confirmed a broad zone of de-localized initiation activity surrounding the sites of ORC and MCM enrichment. Mapping positions of mononucleosomal DNA empirically and computing nucleosome-positioning information in silico revealed that ORC and MCM map to regions of low measured and predicted nucleosome occupancy. Our results demonstrate that specific sites of ORC and MCM enrichment can be detected within a mammalian intitiation zone, and suggest that initiation zones may be regions of generally low nucleosome occupancy where flexible nucleosome positioning permits flexible pre-RC assembly sites

Float zone growth and anisotropic spectral properties of Nd:LaVO4 single crystals

Nd:LaVO4 single crystals were successfully grown by the floating zone method and their optical properties along each optic elasticity axis were investigated. The crystals grown at 10mm/h in air did not contain any macroscopic defects for Nd-concentrations up to 5 at%. The optic elasticity axes were determined by the conoscopic figures with a polarizing microscope. The absorption cross-section along the Z-axis was 2.6 x 10^[-20] cm2 near 800 nm and the FWHM was 20 nm. The absorption cross-sections along other directions were much the same as that along the Z-axis. The fluorescence lifetime of the 5 at%-doped crystal was approximately 80 μs. All the polarized fluorescence spectra of the Nd:LaVO4 single crystal had a broadened band around 1060 nm with FWHMs of 7-10 nm, which are wide enough to generate femtosecond order pulses

Float zone growth and spectral properties of Cr,Nd:CaYAlO4 single crystals

Cr,Nd:CaYAlO4 single crystals were grown by the floating zone method and their spectroscopic properties were investigated. Many voids were observed in the crystals grown with a stoichiometric feed rod even at a relatively low growth rate of 2.5 mm/h, while a void-free crystal was grown at the same growth rate using a feed rod the composition of which was Y-rich to Ca. These results indicate that voids were attributable to constitutional supercooling due to the segregation of main constituents caused by the difference in congruent and stoichiometric compositions. The as-grown crystals were deep red and showed strong absorption in the wavelength region of 320-600 nm. The absorption cross section for sigma-polarization at 430 nm, where Cr,Nd:YAG has the maximum absorption, is about 1160 x 10(-20) cm(2), which is 165 times as large as that of Cr,Nd:YAG. By pumping at 400 nm, which is a pad of the absorption band of Cr3+ Cr,Nd:CaYAlO4 showed fluorescence bands around 900 am and 1080 nm by Nd3+ indicating energy transfer from Cr3+ to Nd3+ in the crystal. Cr,Nd:CaYAlO4 single crystals are therefore one of the promising gain media for solar-pumped solid state laser systems

3D Printed Alginate Hydrogels with Stiffness-Gradient Structure in a Carbomer Supporting Bath by Controlled Ca²⁺ Diffusion

Manufacturing biocompatible materials with higher-order structure has great significance because they can mimic the extracellular medium of the human organism and are a novel strategy for tissue regeneration. In this study, a device with stiffness-gradient characteristics based on two biocompatible materials, alginate with presolidification and photocurable acrylamide-containing supporting bath, was designed and constructed by the 3D printing technique. The presolidification can avoid rapid diffusion of alginate in aqueous solutions, improve mechanical properties without the introduction of heterogeneous gel precursor, and endow gradient stiffness by the controlled diffusion of calcium ions. Besides, a photocurable supporting bath was combined to manufacture a device with a dual-gradient structure by a 4-step procedure, including 3D printing, removal of the inner hydrogel, solidification of alginate, and curing of the supporting bath. A cylinder-like container was manufactured as the template, and the wall of the resultant container with two types of gradient structures showed parabola-like stiffness changes (open upward), resulting from calcium ion diffusion-controlled gradient solidification and alginate diffusion-controlled gradient photocuring. Moreover, the resultant device exhibited lower cytotoxicity to both adherent and suspension cells than containers manufactured with alginate. Because of the high water uptake of the photocured supporting bath, the removal of toxic metabolic products together with cell culture medium from the container leads to better cell compatibility. This diffusion-controlled device is also applicable to other additive manufacturers with biomedical significance

Radiation resistance of Nd-doped laser crystals for space application

The radiation resistance of Nd-doped laser crystals was measured using a proton beam in order to construct spaceborne laser systems. After irradiation of 30 krad, we measured the variation of transmittance for crystals. The variation for all crystals was less than 1%. Since 30 krad is the irradiation value received over 30 years in the International Space Station with a 1-mm-thick Al cover, we conclude that all of the laser crystals have sufficient resistance for a 3-year spaceborne lidar mission at the International Space Station

Seasonal variations in the potassium layer over Syowa station (69.0°S, 39.6°E), Antarctic

The 14th Symposium on Polar Science/Interdisciplinary sessions [IW] Whole Atmosphere, Wed. 15 Nov. / Entrance Hall (1st floor), National Institute of Polar Researc