Demethylation of DNA by purified chick embryo 5-methylcytosine-DNA glycosylase requires both protein and RNA

We have previously purified and characterized a 5-methylcytosine (5-MeC)-DNA glycosylase from 12 day old chick embryos [Jost,J.P. et al. (1995) J. Biol. Chem. 270, 9734-9739]. The activity of the purified enzyme is abolished upon treatment with proteinase K and ribonuclease A. RNA copurifies with 5-MeC-DNA glycosylase activity throughout all chromatographic steps and preparative gel electrophoresis. RNA with a length of ∼300-500 nucleotides was isolated from the gel purified enzyme. Upon extensive treatment with proteinase K, the gel eluted and labeled RNA did not show any significant change in molecular mass. The purified RNA incubated alone or in the presence of Mg2+ and deoxyribonucleotide phosphates had no 5-MeC-DNA glycosylase or demethylating activities. However, activity of 5-MeC-DNA glycosylase could be restored when the purified RNA was incubated with the inactive protein, free of RN

A novel detector system for KATRIN to search for keV-scale sterile neutrinos

International audienceSterile neutrinos appear in minimal extensions of the Standard Model of particle physics. If their mass is in the keV regime, they are viable dark matter candidates. One way to search for sterile neutrinos in a laboratory-based experiment is via the analysis of β-decay spectra, where the new neutrino mass eigenstate would manifest itself as a kink-like distortion of the β-decay spectrum. The objective of the TRISTAN project is to extend the KATRIN setup with a new multi-pixel silicon drift detector system to search for a keV-scale sterile neutrino signal. In this paper we describe the requirements of such a new detector, and present first characterization measurement results obtained with a 7 pixel prototype system

Experimental correlations for transient soot measurement in diesel exhaust aerosol with light extinction, electrical mobility and diffusion charger sensor techniques

A study of soot measurement deviation using a diffusion charger sensor with three dilution ratios was conducted in order to obtain an optimum setting that can be used to obtain accurate measurements in terms of soot mass emitted by a light-duty diesel engine under transient operating conditions. The paper includes three experimental phases: an experimental validation of the measurement settings in steady-state operating conditions; evaluation of the proposed setting under the New European Driving Cycle; and a study of correlations for different measurement techniques. These correlations provide a reliable tool for estimating soot emission from light extinction measurement or from accumulation particle mode concentration. There are several methods and correlations to estimate soot concentration in the literature but most of them were assessed for steady-state operating points. In this case, the correlations are obtained by more than 4000 points measured in transient conditions. The results of the new two correlations, with less than 4% deviation from the reference measurement, are presented in this paper.Bermúdez, V.; Pastor Soriano, JV.; López, JJ.; Campos, D. (2014). Experimental correlations for transient soot measurement in diesel exhaust aerosol with light extinction, electrical mobility and diffusion charger sensor techniques. Measurement Science and Technology. 25(6):1-13. doi:10.1088/0957-0233/25/6/065204S113256Davidson, C. I., Phalen, R. F., & Solomon, P. A. (2005). Airborne Particulate Matter and Human Health: A Review. Aerosol Science and Technology, 39(8), 737-749. doi:10.1080/02786820500191348Pope, C. A., Bates, D. V., & Raizenne, M. E. (1995). Health effects of particulate air pollution: time for reassessment? Environmental Health Perspectives, 103(5), 472-480. doi:10.1289/ehp.95103472Giechaskiel, B., Dilara, P., Sandbach, E., & Andersson, J. (2008). Particle measurement programme (PMP) light-duty inter-laboratory exercise: comparison of different particle number measurement systems. Measurement Science and Technology, 19(9), 095401. doi:10.1088/0957-0233/19/9/095401Park, K., Kittelson, D. B., & McMurry, P. H. (2004). Structural Properties of Diesel Exhaust Particles Measured by Transmission Electron Microscopy (TEM): Relationships to Particle Mass and Mobility. Aerosol Science and Technology, 38(9), 881-889. doi:10.1080/027868290505189LUO, C.-H., LEE, W.-M., & LIAW, J.-J. (2009). Morphological and semi-quantitative characteristics of diesel soot agglomerates emitted from commercial vehicles and a dynamometer. Journal of Environmental Sciences, 21(4), 452-457. doi:10.1016/s1001-0742(08)62291-3Matti Maricq, M. (2007). Chemical characterization of particulate emissions from diesel engines: A review. Journal of Aerosol Science, 38(11), 1079-1118. doi:10.1016/j.jaerosci.2007.08.001Smith, O. I. (1981). Fundamentals of soot formation in flames with application to diesel engine particulate emissions. Progress in Energy and Combustion Science, 7(4), 275-291. doi:10.1016/0360-1285(81)90002-2Haynes, B. S., & Wagner, H. G. (1981). Soot formation. Progress in Energy and Combustion Science, 7(4), 229-273. doi:10.1016/0360-1285(81)90001-0Bockhorn, H. (Ed.). (1994). Soot Formation in Combustion. Springer Series in Chemical Physics. doi:10.1007/978-3-642-85167-4Tree, D. R., & Svensson, K. I. (2007). Soot processes in compression ignition engines. Progress in Energy and Combustion Science, 33(3), 272-309. doi:10.1016/j.pecs.2006.03.002Kennedy, I. M. (1997). Models of soot formation and oxidation. Progress in Energy and Combustion Science, 23(2), 95-132. doi:10.1016/s0360-1285(97)00007-5Buonanno, G., Dell’Isola, M., Stabile, L., & Viola, A. (2011). Critical aspects of the uncertainty budget in the gravimetric PM measurements. Measurement, 44(1), 139-147. doi:10.1016/j.measurement.2010.09.037Symonds, J. P. R., Reavell, K. S. J., Olfert, J. S., Campbell, B. W., & Swift, S. J. (2007). Diesel soot mass calculation in real-time with a differential mobility spectrometer. Journal of Aerosol Science, 38(1), 52-68. doi:10.1016/j.jaerosci.2006.10.001Luque de Castro, M. D., & Priego-Capote, F. (2010). Soxhlet extraction: Past and present panacea. Journal of Chromatography A, 1217(16), 2383-2389. doi:10.1016/j.chroma.2009.11.027Wang, S. C., & Flagan, R. C. (1990). Scanning Electrical Mobility Spectrometer. Aerosol Science and Technology, 13(2), 230-240. doi:10.1080/02786829008959441Snegirev, A. Y., Makhviladze, G. ., & Roberts, J. . (2001). The effect of particle coagulation and fractal structure on the optical properties and detection of smoke. Fire Safety Journal, 36(1), 73-95. doi:10.1016/s0379-7112(00)00037-0Zhou, Z.-Q., Ahmed, T. U., & Y. Choi, M. (1998). Measurement of dimensionless soot extinction constant using a gravimetric sampling technique. Experimental Thermal and Fluid Science, 18(1), 27-32. doi:10.1016/s0894-1777(98)10005-5Arregle, J., Bermúdez, V., Serrano, J. R., & Fuentes, E. (2006). Procedure for engine transient cycle emissions testing in real time. Experimental Thermal and Fluid Science, 30(5), 485-496. doi:10.1016/j.expthermflusci.2005.10.002Bermúdez, V., Luján, J. M., Serrano, J. R., & Pla, B. (2008). Transient particle emission measurement with optical techniques. Measurement Science and Technology, 19(6), 065404. doi:10.1088/0957-0233/19/6/065404Giechaskiel, B., Maricq, M., Ntziachristos, L., Dardiotis, C., Wang, X., Axmann, H., … Schindler, W. (2014). Review of motor vehicle particulate emissions sampling and measurement: From smoke and filter mass to particle number. Journal of Aerosol Science, 67, 48-86. doi:10.1016/j.jaerosci.2013.09.003Lapuerta, M., Armas, O., & Gómez, A. (2003). Diesel Particle Size Distribution Estimation from Digital Image Analysis. Aerosol Science and Technology, 37(4), 369-381. doi:10.1080/02786820300970Desantes, J. M., Bermúdez, V., Molina, S., & Linares, W. G. (2011). Methodology for measuring exhaust aerosol size distributions using an engine test under transient operating conditions. Measurement Science and Technology, 22(11), 115101. doi:10.1088/0957-0233/22/11/115101Roessler, D. M. (1982). Diesel particle mass concentration by optical techniques. Applied Optics, 21(22), 4077. doi:10.1364/ao.21.004077Park, D., Kim, S., An, M., & Hwang, J. (2007). Real-time measurement of submicron aerosol particles having a log-normal size distribution by simultaneously using unipolar diffusion charger and unipolar field charger. Journal of Aerosol Science, 38(12), 1240-1245. doi:10.1016/j.jaerosci.2007.09.00

Naked mole-rats (Heterocephalus glaber) do not specialise in cooperative tasks

It has been proposed that naked mole-rat (Heterocephalus glaber) societies resemble those of eusocial insects by showing a division of labour among non-breeding individuals. Earlier studies suggested that non-breeders belong to distinct castes that specialise permanently or temporarily in specific cooperative tasks. In contrast, recent research on naked mole-rats has shown that behavioural phenotypes are continuously distributed across non-breeders and that mole-rats exhibit considerable behavioural plasticity suggesting that individuals may not specialise permanently in work tasks. However, it is currently unclear whether individuals specialise temporarily and whether there is a sex bias in cooperative behaviour among non-breeders. Here, we show that non-breeding individuals vary in overall cooperative investment, but do not specialise in specific work tasks. Within individuals, investment into specific cooperative tasks such as nest building, food carrying and burrowing is positively correlated, and there is no evidence that individuals show trade-offs between these cooperative behaviours. Non-breeding males and females do not differ in their investment in cooperative behaviours and show broadly similar age and body mass related differences in cooperative behaviours. Our results suggest that non-breeding naked mole-rats vary in their overall contribution to cooperative behaviours and that some of this variation may be explained by differences in age and body mass. Our data provide no evidence for temporary specialisation, as found among some eusocial insects and suggest that the behavioural organisation of naked mole-rats resembles that of other cooperatively breeding vertebrates more than that of eusocial insect species.DATA AVAILABILITY STATEMENT: The data and code are uploaded to figshare (https://doi.org/10.6084/m9.figshare.14222369.v1; Siegmann et al. 2021).The Crafoord Foundation; a NRF SARChI Chair (GUN 64756) and the Swedish Research Council.http://wileyonlinelibrary.com/journal/ethhj2022Mammal Research InstituteZoology and Entomolog

A chicken embryo protein related to the mammalian DEAD box protein p68 is tightly associated with the highly purified protein-RNA complex of 5-MeC-DNA glycosylase

We have shown previously that DNA demethylation by chick embryo 5-methylcytosine (5-MeC)-DNA glycosylase needs both protein and RNA. Amino acid sequences of nine peptides derived from a highly purified 5-MeC-DNA glycosylase complex were identified by Nanoelectrospray ionisation mass spec-trometry to be identical to the mammalian nuclear DEAD box protein p68 RNA helicase. Antibodies directed against human p68 helicase cross-reacted with the purified 5-MeC-DNA glycosylase complex and immunoprecipitated the glycosylase activity. A 2690 bp cDNA coding for the chicken homologue of mammalian p68 was isolated and sequenced. Its derived amino acid sequence is almost identical to the human p68 DEAD box protein up to amino acid position 473 (from a total of 595). This sequence contains all the essential conserved motifs from the DEAD box proteins which are the ATPase, RNA unwinding and RNA binding motifs. The rest of the 122 amino acids in the C-terminal region rather diverge from the human p68 RNA helicase sequence. The recombinant chicken DEAD box protein expressed in Escherichia coli cross-reacts with the same p68 antibodies as the purified chicken embryo 5-MeC-DNA glycosylase complex. The recombinant protein has an RNA-dependent ATPase and an ATP-dependent helicase activity. However, in the presence or absence of RNA the recombinant protein had no 5-MeC-DNA glycosylase activity. In situ hybridisation of 5 day-old chicken embryos with antisense probes of the chicken DEAD box protein shows a high abundance of its transcripts in differentiating embryonic tissue

Fate of Photoexcited Molecular Antennae - Intermolecular Energy Transfer versus Photodegradation Assessed by Quantum Dynamics

The present computational study aims to unravel the competitive photoinduced intermolecular energy transfer and electron transfer phenomena in a light-harvesting antenna with potential applications in dye-sensitized solar cells and photocatalysis. A series of three thiazole dyes with hierarchically overlapping emission and absorption spectra, embedded in a methacrylate-based polymer backbone, is employed to absorb light over the entire visible region. Intermolecular energy transfer in such antenna proceeds via energy transfer from dye-to-dye and eventually to a photosensitizer. Initially, the ground and excited state properties of the three push–pull-chromophores (e.g., with respect to their absorption and emission spectra as well as their equilibrium structures) are thoroughly evaluated using state-of-the-art multiconfigurational methods and computationally less demanding DFT and TDDFT simulations. Subsequently, the potential energy landscape for the three dyads, formed by the π-stacked dyes as occurring in the polymer environment, is investigated along linear-interpolated internal coordinates to elucidate the photoinduced dynamics associated with intermolecular energy and electron transfer processes. While energy transfer among the dyes is highly desired in such antenna, electron transfer, or rather a light-induced redox chemistry, leading to the degradation of the chromophores, is disadvantageous. We performed quantum dynamical wavepacket calculations to investigate the excited state dynamics following initial light-excitation. Our calculations reveal for the two dyads with adjusted optical properties exclusively efficient intermolecular energy transfer within 200 fs, while in the case of the third dyad intermolecular electron transfer dynamics can be observed. Thus, this computational study reveals that statistical copolymerization of the individual dyes is disadvantageous with respect to the energy transfer efficiency as well as regarding the photostability of such antenna