| 1. |
- Kivimaki, A., et al.
(författare)
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Fluorescence emission at core-to-Rydberg excitations in the N-2 molecule
- 2009
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:18
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Tidskriftsartikel (refereegranskat)abstract
- Fluorescence emission at the N 1s edge of the N-2 molecule has been studied with synchrotron radiation excitation. The partial fluorescence yields in the ultraviolet (250-320 nm) and visible (300-650 nm) wavelengths were collected by scanning the photon energy across the core-to-Rydberg excitations and the N 1s ionization potential (IP). When compared to the total ion yield, both fluorescence yields are most enhanced at the excitations to high Rydberg orbitals. A discrete structure appears just below the N 1s IP only in the UV yield and is assigned to core-valence doubly excited states. Dispersed fluorescence spectra in selected wavelength windows were measured at several photon energies in order to find out which fragments are responsible for the enhancement of fluorescence emission just below the N 1s IP. The excitation functions determined and considerations on de-excitation pathways indicate that the main responsible is the N+ ion.
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| 2. |
- Kivimaki, A., et al.
(författare)
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Line shape narrowing in the ultraviolet yield at the N 1s -> pi* resonance of the N-2 molecule
- 2009
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 42:7
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Tidskriftsartikel (refereegranskat)abstract
- The intensity of fluorescence emission in the wavelength region of 250-320 nm has been measured across the N 1s -> pi* resonance of the N-2 molecule. It displays a narrower line shape than the total ion yield recorded simultaneously. We explain the finding by the particularities of the resonant Auger transitions from the N 1s(-1) pi* state to the D-2 Pi(g) state in N-2(+) and by the subsequent D-2 Pi(g) -> A(2)Pi(u) emission.
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| 3. |
- Yeung, Edwina, et al.
(författare)
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Maternal age is related to offspring DNA methylation : a meta-analysis of results from the pace consortium
- 2024
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Ingår i: Aging Cell. - : John Wiley & Sons. - 1474-9718 .- 1474-9726.
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Tidskriftsartikel (refereegranskat)abstract
- Worldwide trends to delay childbearing have increased parental ages at birth. Older parental age may harm offspring health, but mechanisms remain unclear. Alterations in offspring DNA methylation (DNAm) patterns could play a role as aging has been associated with methylation changes in gametes of older individuals. We meta-analyzed epigenome-wide associations of parental age with offspring blood DNAm of over 9500 newborns and 2000 children (5–10 years old) from the Pregnancy and Childhood Epigenetics consortium. In newborns, we identified 33 CpG sites in 13 loci with DNAm associated with maternal age (PFDR < 0.05). Eight of these CpGs were located near/in the MTNR1B gene, coding for a melatonin receptor. Regional analysis identified them together as a differentially methylated region consisting of 9 CpGs in/near MTNR1B, at which higher DNAm was associated with greater maternal age (PFDR = 6.92 × 10−8) in newborns. In childhood blood samples, these differences in blood DNAm of MTNR1B CpGs were nominally significant (p < 0.05) and retained the same positive direction, suggesting persistence of associations. Maternal age was also positively associated with higher DNA methylation at three CpGs in RTEL1-TNFRSF6B at birth (PFDR < 0.05) and nominally in childhood (p < 0.0001). Of the remaining 10 CpGs also persistent in childhood, methylation at cg26709300 in YPEL3/BOLA2B in external data was associated with expression of ITGAL, an immune regulator. While further study is needed to establish causality, particularly due to the small effect sizes observed, our results potentially support offspring DNAm as a mechanism underlying associations of maternal age with child health.
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| 4. |
- Ha, Dang Trinh, et al.
(författare)
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Fragmentation Dynamics of Doubly Charged Methionine Phase
- 2014
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 118:8, s. 1374-1383
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Tidskriftsartikel (refereegranskat)abstract
- The dependence of the fragmentation of doubly charged gas-phase methionine (C5H11NO2S) on the electronic-state character of the parent ion is studied experimentally by energy-resolved electron ion-ion coincidence spectroscopy. The parent dication electronic states are populated by Auger transitions following site-specific sulfur 2p core ionization. Two fragmentation channels are observed to be strongly dependent on the electronic states with vacancies in weakly bound molecular orbitals. All-electron calculations are applied to assign doubly charged final states of sulfur 2p core ionized methionine. In addition, the Car-Parrinello method is applied to model fragmentation dynamics of doubly charged methionine molecules with various initial temperatures to understand the typical characteristics of the molecular dissociation and partly to support the interpretation of experimental data.
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| 5. |
- Itala, E., et al.
(författare)
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A comparative study of dissociation of thymidine molecules following valence or core photoionization
- 2013
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:21, s. 215102-
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the fragmentation of gas phase thymidine following valence and core ionization using synchrotron radiation, combined with electron energy and ion mass resolved detection in coincidence. To identify certain fragment masses C-13 labelled thymidine was also used. We find that in large part, the photofragmentation of thymidine can be described as separated thymine and 2-deoxy-D-ribose cations. However, also the intact thymidine radical cation, formation of intact base and sugar cations from glycosidic bond cleavage and several new thymidine-specific fragments are observed after valence ionization. Conversely, at the photoionization of C 1s electrons neither parent thymidine cations nor any fragments above 55 amu were detected, and only ion pairs with small masses survive core ionization, Auger decay and the subsequent Coulomb separation of the DNA sub-unit. This demonstrates the genotoxic nature of soft x-rays which in cells induce complex clustered damage similar to those yielded by heavy particles.
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| 6. |
- Itala, E, et al.
(författare)
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Molecular fragmentation of pyrimidine derivatives following site-selective carbon core ionization
- 2011
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 184:3-6, s. 119-124
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Tidskriftsartikel (refereegranskat)abstract
- Ionization-site-dependent fragmentation of three cyclic biomolecules - uracil, 5-bromouracil and thymine - has been studied using electron-energy-resolved photoelectronphotoion-photoion coincidence spectroscopy. Previous studies concerning ionization site dependent fragmentation have mainly been carried out with linear molecules. The results reported here show that all studied molecules have dicationic fragmentation channels whose intensity depends on the initial core-ionization site, although these channels cover only a relatively small fraction of the total fragment yield. The present study shows on one hand, that it is often the surrounding bond(s) of the ionized atom that will break following the initial core ionization, and on the other hand, that some specific fragmentation channels can display strong site-dependency where there is no direct correlation between the ionization site and the bond breakage locations.
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| 7. |
- Itälä, E., et al.
(författare)
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Photofragmentation of a DNA nucleoside thymidine; Valence-vs. core ionization
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:PART 2, s. 022078-
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Tidskriftsartikel (refereegranskat)abstract
- The photofragmentation of free thymidine molecule has been studied using combined electron- and ion spectroscopy. The results show that valence- and core ionization processes produce very different fragmentation patterns and that regardless of the photon energy, the photoionization leads almost always to dissociation of the thymidine molecule.
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| 8. |
- Itälä, E., et al.
(författare)
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Soft x-ray ionization induced fragmentation of glycine
- 2014
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 140:23, s. 234305-
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption commonly involves dissociative core ionization producing not only momentum correlated charged fragments but also low-and high-energy electrons capable of inducing damage in living tissue. This gives a natural motivation for studying the core ionization induced fragmentation processes in biologically important molecules such as amino acids. Here the fragmentation of amino acid glycine following carbon 1s core ionization has been studied. Using photoelectron-photoion-photoion coincidence technique, a detailed analysis on fragmentation of the sample molecule into pairs of momentum correlated cations has been carried out. The main characteristics of core ionization induced fragmentation of glycine were found to be the rupture of the C-C a bond and the presence of the CNH2+ fragment.
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