Sum Rules for Multi-Photon Spectroscopy of Ions in Finite Symmetry

Models describing one- and two-photon transitions for ions in crystalline environments are unified and extended to the case of parity-allowed and parity- forbidden p-photon transitions. The number of independent parameters for characterizing the polarization dependence is shown to depend on an ensemble of properties and rules which combine symmetry considerations and physical models.Comment: 16 pages, Tex fil

Targeting the histone methyltransferase G9a activates imprinted genes and improves survival of a mouse model of Prader–Willi syndrome

Prader–Willi syndrome (PWS) is an imprinting disorder caused by a deficiency of paternally expressed gene(s) in the 15q11–q13 chromosomal region. The regulation of imprinted gene expression in this region is coordinated by an imprinting center (PWS-IC). In individuals with PWS, genes responsible for PWS on the maternal chromosome are present, but repressed epigenetically, which provides an opportunity for the use of epigenetic therapy to restore expression from the maternal copies of PWS-associated genes. Through a high-content screen (HCS) of >9,000 small molecules, we discovered that UNC0638 and UNC0642—two selective inhibitors of euchromatic histone lysine N-methyltransferase-2 (EHMT2, also known as G9a)—activated the maternal (m) copy of candidate genes underlying PWS, including the SnoRNA cluster SNORD116, in cells from humans with PWS and also from a mouse model of PWS carrying a paternal (p) deletion from small nuclear ribonucleoprotein N (Snrpn (S)) to ubiquitin protein ligase E3A (Ube3a (U)) (mouse model referred to hereafter as m+/pΔS−U). Both UNC0642 and UNC0638 caused a selective reduction of the dimethylation of histone H3 lysine 9 (H3K9me2) at PWS-IC, without changing DNA methylation, when analyzed by bisulfite genomic sequencing. This indicates that histone modification is essential for the imprinting of candidate genes underlying PWS. UNC0642 displayed therapeutic effects in the PWS mouse model by improving the survival and the growth of m+/pΔS−U newborn pups. This study provides the first proof of principle for an epigenetics-based therapy for PWS

On the tensorial form of the relativistic magnetic dipole transition operator

info:eu-repo/semantics/nonPublishe

On the tensorial form of the relativistic magnetic dipole transition operator

info:eu-repo/semantics/publishe

On the tensorial form of the two-body part of the relativistic magnetic dipole transition operator

info:eu-repo/semantics/nonPublishe

A program to compute Isotope Shift in atomic spectra

info:eu-repo/semantics/publishe

Investigation into the Effects of a Trigonal Planar Ligand Field on the Electronic Properties of Lanthanide(II) Tris(silylamide) Complexes (Ln = Sm, Eu, Tm, Yb)

In recent work we have reported the synthesis and physical properties of near-linear Ln­(II) (Ln = lanthanide) complexes utilizing the bulky bis­(silylamide) {N­(Si^<i>i</i>Pr₃)₂}. Herein, we synthesize trigonal-planar Ln­(II) complexes by employing a smaller bis­(silylamide), {N­(Si^<i>t</i>BuMe₂)₂} (N**), to study the effects of this relatively rare Ln geometry/oxidation state combination on the magnetic and optical properties of complexes. We show that the charge-separated trigonal-planar Ln­(II) complexes [K­(2.2.2-cryptand)]­[Ln­(N**)₃] (Ln = Sm (<b>1</b>), Eu (<b>2</b>), Tm (<b>3</b>), Yb (<b>4</b>)) can be prepared by the reaction of 1.5 equiv of [{K­(N**)}₂] with LnI₂THF₂ (Ln = Sm, Yb) or LnI₂ (Ln = Eu, Tm) and 1 equiv of 2.2.2-cryptand in Et₂O. Complex <b>3</b> is the first structurally characterized trigonal-planar Tm­(II) complex. In the absence of 2.2.2-cryptand, [K­(DME)₃]­[Sm­(N**)₃] (<b>5</b>) and [Ln­(N**)₂(μ-N**)­K­(toluene)₂] (Ln = Sm (<b>6</b>), Eu (<b>7</b>)) were isolated in the presence of DME (dimethoxyethane) or toluene, respectively. The 1:1 reaction of [{K­(N**)}₂] with LnI₂THF₂ (Ln = Sm, Yb) in THF gave the four-coordinate pseudo-tetrahedral Lewis base adducts [Ln­(N**)₂(THF)₂] (Ln = Sm (<b>8</b>), Yb (<b>9</b>)) and the cyclometalated complex [Yb­(N**)­{N­(Si^<i>t</i>BuMe₂)­(Si^<i>t</i>BuMeCH₂)}­(THF)] (<b>10</b>). Complexes <b>1</b>–<b>10</b> have been characterized as appropriate by single-crystal XRD, magnetic measurements, multinuclear NMR, EPR, and electronic spectroscopy, together with CASSCF-SO and DFT calculations. The physical properties of <b>1</b>–<b>4</b> are compared and contrasted with those of closely related near-linear Ln­(II) bis­(silylamide) complexes