Browsing by Author "Lee, C"

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    Hydrogen-containing Na3HTi1–xMnxF8 narrow-band phosphor for light-emitting diodes
    (American Chemical Society, 2019-01-16) Fang, MH; Yang, TH; Lesniewski, T; Lee, C; Mahlik, S; Grinberg, M; Peterson, VK; Didier, C; Pang, WK; Su, CC; Liu, RS
    We synthesize the phosphor Na3HTi1–xMnxF8 (Na3HTiF8:Mn4+) material series using a coprecipitation method. We determine the complete phase and crystallographic structure of the Na3HTiF8 series end-member, including the determination of the H atoms at the 4b (0, 1/2, 0) crystallographic site within the Cmcm space group symmetry structure, resulting in a quantum efficiency of ∼44%, which is comparative to the Na2SiF6:Mn4+ phosphor materials. We successfully model the luminescent properties of the Na3HTi1–xMnxF8 material series, including temperature and time-dependent photoluminescence, providing a good prediction of the decay properties at low and high temperature and revealing the existence of Mn5+ during the ionization process. Notably, LED package data indicates that the Na3HTi1–xMnxF8 material series could be a promising candidate for high-level and back-lighting devices. This research reveals the role that hydrogen plays in determining fluoride phosphor structure and properties, revealing a new path for the synthesis of fluoride phosphors. Copyright © 2019 American Chemical Society
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    Solution structure of the LIM-homeodomain transcription factor complex Lhx3/Ldb1 and the effects of a pituitary mutation on key Lhx3 interactions
    (Public Libary of Science, 2012-07-25) Bhati, M; Lee, C; Gadd, MS; Jeffries, CM; Kwan, AH; Whitten, AE; Trewhella, J; Mackay, JP; Matthews, JM
    Lhx3 is a LIM-homeodomain (LIM-HD) transcription factor that regulates neural cell subtype specification and pituitary development in vertebrates, and mutations in this protein cause combined pituitary hormone deficiency syndrome (CPHDS). The recently published structures of Lhx3 in complex with each of two key protein partners, Isl1 and Ldb1, provide an opportunity to understand the effect of mutations and posttranslational modifications on key protein-protein interactions. Here, we use small-angle X-ray scattering of an Ldb1-Lhx3 complex to confirm that in solution the protein is well represented by our previously determined NMR structure as an ensemble of conformers each comprising two well-defined halves (each made up of LIM domain from Lhx3 and the corresponding binding motif in Ldb1) with some flexibility between the two halves. NMR analysis of an Lhx3 mutant that causes CPHDS, Lhx3(Y114C), shows that the mutation does not alter the zinc-ligation properties of Lhx3, but appears to cause a structural rearrangement of the hydrophobic core of the LIM2 domain of Lhx3 that destabilises the domain and/or reduces the affinity of Lhx3 for both Ldb1 and Isl1. Thus the mutation would affect the formation of Lhx3-containing transcription factor complexes, particularly in the pituitary gland where these complexes are required for the production of multiple pituitary cell types and hormones. © 2012 Bhati et al.