15 research outputs found
Excitonic and Confinement Effects of 2D Layered (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> Single Crystals
Recognition
of unusual optoelectronic properties for two-dimensional (2D) layered
organicāinorganic leadĀ(II) halide materials (C<sub><i>n</i></sub>H<sub>2<i>n</i>+1</sub>NH<sub>3</sub>)<sub>2</sub>PbX<sub>4</sub> (X = I, Br, and Cl) has attracted intense
renewed interest in this class of materials. Single crystals of the
2D layered materials (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> and pseudo-alloy (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbI<sub>2</sub>Br<sub>2</sub> were grown
for photophysical evaluation. A 10-carbon alkylammonium cation was
selected for investigation to provide strong dielectric screening
in order to highlight quantum confinement effects of the anionic (PbX<sub>4</sub><sup>2ā</sup>) semiconductor layer. Single crystals
of the 2D layered (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> compound display a characteristic free exciton
with a binding energy of ca. 280 meV. Observation of a short photoluminescence
lifetime of 2.8 Ā± 0.2 ns suggests that this electronic transition
for the PbBr<sub>4</sub>-based layered material has only singlet character.
Sheets of (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> with thicknesses of a few layers were fabricated,
and the dimensions were verified by AFM experiments. Excitonic emissions
from (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> and (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbI<sub>4</sub> exhibit relatively small spectral shifts from the
bulk down to a thickness of five layers indicative of the strong confinement
effect of the 10-carbon alkylammonium spacers. Single crystals of
the pseudo-alloy (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>2</sub>I<sub>2</sub> give an excitonic absorption
peak close to that of the tetrabromide (C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbBr<sub>4</sub> and an emission peak
with a large Stokes shift to a position similar to that of the tetraiodide
(C<sub>10</sub>H<sub>21</sub>NH<sub>3</sub>)<sub>2</sub>PbI<sub>4</sub>
Oxytricha trifallax macronuclear PCAP 2.1.8 assembly
Oxytricha trifallax macronuclear PCAP 2.1.8 assembl
Oxytricha trifallax macronuclear PE-Assembler/SSAKE assembly
Contigs in gzipped fasta format
Oxytricha trifallax macronuclear genome fosmids
Oxytricha trifallax macronuclear genome fosmid
Key features of <i>Oxytricha</i> protein-coding nanochromosomes.
<p>Representative nanochromosome features are not drawn to scale, but their lengths are indicated. UTR, untranslated region; UTS, untranscribed region. 3ā² UTRs and the subtelomeric signal overlap. The subtelomeric base composition bias signal found on either end of the nanochromosome is shown above the nanochromosome diagram.</p
Development of the <i>Oxytricha</i> macronuclear genome from the micronuclear genome.
<p>During conjugation of <i>Oxytricha</i> cells, segments of the micronuclear genome (MDSs) are excised and stitched together to form the nanochromosomes of the new macronuclear genome, and the remainder of the micronuclear genome is eliminated (including the IESs interspersed between MDSs). The old macronuclear genome is also degraded during development. The segments that are stitched together may be either in order (e.g., forming nanochromosome 1, on the left) or out of order or inverted (e.g., forming the two forms of nanochromosome 2), in which case they need to be āunscrambled.ā Two rounds of DNA amplification produce nanochromosomes at an average copy number of ā¼1,900 <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Prescott1" target="_blank">[2]</a>. Alternative fragmentation of DNA during nanochromosome development may also occur, irrespective of unscrambling, giving rise to longer (2a) and shorter (2b) nanochromosome isoforms. The mature nanochromosomes are capped on both ends with telomeres.</p
Comparison of key ciliate macronuclear genomes.
<p>The phylogeny represents the bootstrap consensus of 100 replicates from PhyML (with the HKY85 substitution model) based on a MUSCLE multiple sequence alignment of 18S rRNA genes from seven ciliates (<i>Oxytricha trifallax</i>āFJ545743; <i>Stylonychia lemnae</i>āAJJRB310497; <i>Euplotes crassus</i>āAJJRB310492; <i>Nyctotherus ovalis</i>āAJ222678; <i>Tetrahymena thermophila</i>āM10932; <i>Ichthyophthirius multifiliis</i>āIMU17354; and <i>Paramecium tetraurelia</i>āAB252009) rooted with two other alveolates (<i>Perkinsus marinus</i>āX75762 and <i>Plasmodium falciparum</i>āNC_004325). All bootstrap values are ā„80, except for the node between <i>Nyctotherus</i> and <i>Oxytricha</i>/<i>Stylonychia</i>/<i>Euplotes</i>, which has a boostrap value of 60. <i>Euplotes</i> and <i>Nyctotherus</i> both have nanochromosomes, like <i>Oxytricha</i>. Other than the genome statistics for <i>Oxytricha trifallax</i>, which were determined in this study, table statistics were obtained from the following sources: <sup>a</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Prescott1" target="_blank">[2]</a>, <sup>b</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Duerr1" target="_blank">[22]</a>,<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Lipps1" target="_blank">[116]</a>, <sup>c</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Nock1" target="_blank">[117]</a>, <sup>d</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Bender1" target="_blank">[99]</a>, <sup>e</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Ricard1" target="_blank">[94]</a>, <sup>f</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Eisen1" target="_blank">[56]</a> (the number of chromosomes is an estimate), <sup>g</sup> -<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Coyne3" target="_blank">[118]</a>, <sup>h</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-White1" target="_blank">[119]</a>, <sup>i</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Austerberry1" target="_blank">[120]</a>, <sup>j</sup>- <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Coyne2" target="_blank">[64]</a> (for a single stage of the <i>Ichthyophthirius</i> life cycle), <sup>k</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Aury1" target="_blank">[121]</a>, <sup>l</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Duret1" target="_blank">[69]</a>, <sup>m</sup> - <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Gardner1" target="_blank">[122]</a>. Table statistics for <i>Perkinsus marinus</i> are for the current assembly deposited in GenBank (GCA_000006405.1).</p
Length distributions of alternatively and nonalternatively fragmented nanochromosomes.
<p>The shortest nanochromosome isoforms produced from single (directional) alternative fragmentation sites are labeled as āShort isoform.ā The histograms show normalized frequencies for 1,587 alternatively fragmented nanochromosomes and 15,219 nonalternatively fragmented nanochromosomes. Alternatively fragmented nanochromosomes have at least one strongly supported (ā„10 Illumina reads) alternative fragmentation site >250 bp from either end of the nanochromosome (these nanochromosomes are >500 bp long).</p
Telomere end-binding protein-Ī± paralogs in ciliates.
<p>The phylogeny is an ML tree generated by PhyML <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Guindon1" target="_blank">[123]</a> with a single substitution rate category and the JTT substitution model, optimized for tree topology and branch length. Bootstrap percentages for 1,000 replicates are indicated at the tree nodes. The multiple sequence alignments underlying the phylogeny were produced with MAFFT (v 6.418b <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Katoh1" target="_blank">[124]</a>) (default parameters; BLOSUM 62 substitution matrix) and were trimmed with trimal1.2 <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-CapellaGutierrez1" target="_blank">[125]</a> with the ā-automated1ā parameter to remove excess gaps and poorly aligned regions. GenBank accessions are provided for the taxa unless otherwise indicated. <i>Euplotes crassus</i> is indicated in blue (Q06184 and Q06183), and an additional match from our preliminary <i>Euplotes</i> genome assembly is EUP_contig393834_f1_1. <i>Perkinsus marinus</i> is purple (EER00428) and <i>Oxytricha nova</i> is light green (P29549). <i>Tetrahymena thermophila</i> (salmon color) accessions are from the <i>Tetrahymena</i> genome database <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Stover1" target="_blank">[126]</a>āTTHERM_00378980 and TTHERM_00378990; <i>Paramecium tetraurelia</i>'s TeBP-Ī± protein (pink) is from ParameciumDB <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473-Arnaiz2" target="_blank">[127]</a> (GSPATP00001065001). All the nodes beginning with āContigā are <i>Oxytricha trifallax</i> TeBP-Ī± paralogs (dark green) and Contig22209.0.g66 is TeBP-Ī±1, the original TeBP-Ī±. The tree is rooted at the midpoint of the branch between <i>Arabidopsis thaliana</i> (Pot1aāAAX78213 and Pot1bāAAS99712) and <i>Homo sapiens</i> (Pot1āEAW83616; black) and the rest of the phylogeny. Gene expression levels are normalized RNA-seq counts (see <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.1001473#pbio.1001473.s059" target="_blank">Text S1</a>; Supporting Materials and Methods) before (āfedā) and during conjugation (0ā60 h) are shown for the <i>Oxytricha trifallax</i> TeBP-Ī± paralogs; coding sequence lengths are also indicated (in bp) for each of these paralogs.</p