Proper repair of double-strand breaks (DSBs) is key to ensure proper chromosome segregation. In this study, we found that the deletion of the SRS2 gene, which encodes a DNA helicase necessary for the control of homologous recombination, induces aberrant chromosome segregation during budding yeast meiosis. This abnormal chromosome segregation in srs2 cells accompanies the formation of a novel DNA damage induced during late meiotic prophase-I. The damage may contain long stretches of single-stranded DNAs (ssDNAs), which lead to aggregate formation of a ssDNA binding protein, RPA, and a RecA homolog, Rad51, as well as other recombination proteins inside of the nuclei. The Rad51 aggregate formation in the srs2 mutant depends on the initiation of meiotic recombination and occurs in the absence of chromosome segregation. Importantly, as an early recombination intermediate, we detected a thin bridge of Rad51 between two Rad51 foci or among the foci in the srs2 mutant, which is rarely seen in wild type. These might be cytological manifestation of the connection of two DSB ends and multi-invasion. The DNA damage with Rad51 aggregates in the srs2 mutant is passed through anaphase-I and -II, suggesting the absence of DNA damage-induced cell-cycle arrest after the pachytene stage.We propose that Srs2 helicase resolves early protein-DNA recombination intermediates to suppress the formation of aberrant lethal DNA damage during late prophase-I.

Magnetic orientational linear dichroism (MOLD) spectra of magnetic nanoparticles (MNPs) in the UV-Vis wavelength region were found to be useful as a probe to detect changes of the dispersion state due to a restriction of the rotational Brownian motion of MNPs; a change of the medium from liquid to resin and the formation of agglomerates in solution. The magnetic-field dependence of MOLD was analyzed by using the Langevin equation, which gave information about the magnetic moment of MNPs.

Abstract:The ultimately pure red OLED using new electrophosphorescent compound, bis(2,3-diphenylquinoxaline)iridium(acetylacetonate) [(QH) 2 Ir(acac)] is described. Electrophosphorescence peak wavelength and bandwidth were advanced for the purest red color stimulus to 680 nm with full width at half maximum of 89 nm by doping (QH) 2 Ir(acac) into a light emitting electron transport layer composed of 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole. The most vivid red electrophosphorescence with CIE chromaticity coordinates better than x = 0.70 and y = 0.28, which are the closest to the ultimate limit of pure red among reported OLEDs, was attained and maintained even in luminance brighter than 600 cd/m 2 . A very high maximum external electrophosphorescent quantum efficiency of 10.2% was also realized. Keywords: OLED, color purity, pure red, electrophosphorescence Classification: New functional devices and materials Forrest, "Very high-efficiency green organic light-emitting devices based on electrophosphorescence," Appl. Phys. Lett., vol. 75, no. 1, pp. 4-6, July 1999. [7] J. Kido, C. Ohtaki, K. Hongawa, K. Okuyama, and K. Nagai, "1,2,4-Triazole derivative as an electron transport layer in organic electroluminescent device," Jpn. References