16 research outputs found
Approximate Profile Maximum Likelihood
We propose an efficient algorithm for approximate computation of the profile
maximum likelihood (PML), a variant of maximum likelihood maximizing the
probability of observing a sufficient statistic rather than the empirical
sample. The PML has appealing theoretical properties, but is difficult to
compute exactly. Inspired by observations gleaned from exactly solvable cases,
we look for an approximate PML solution, which, intuitively, clumps comparably
frequent symbols into one symbol. This amounts to lower-bounding a certain
matrix permanent by summing over a subgroup of the symmetric group rather than
the whole group during the computation. We extensively experiment with the
approximate solution, and find the empirical performance of our approach is
competitive and sometimes significantly better than state-of-the-art
performance for various estimation problems
Chiral (SO)âNâ(SO) Sulfoxide Pincer Complexes of Mg, Rh, and Ir: NâH Activation and Selective Sulfoxide Reduction upon Ligand Coordination
Multigram
quantities of the optically pure aminoâbis-sulfoxide
ligand (<i>S,S</i>)-bisÂ(4-<i>tert</i>-butyl-2-(<i>p</i>-tolylsulfinyl)Âphenyl)Âamine ((<i>S,S</i>)-<b>3</b>) are accessible by in situ lithiation of bisÂ(2-bromo-4-<i>tert</i>-butylphenyl)Âamine (<b>1</b>) followed by a nucleophilic
displacement reaction with Andersenâs sulfinate <b>2</b>. Deprotonation of (<i>S,S</i>)-<b>3</b> with MgPh<sub>2</sub> yields the magnesium amidoâbis-sulfoxide salt (<i>S,S</i>)-<b>4</b> quantitatively. Metathetical exchange
of (<i>S,S</i>)-<b>4</b> with [RhClÂ(COE)<sub>2</sub>]<sub>2</sub> affords the optically pure pseudo-<i>C</i><sub>2</sub>-symmetric RhÂ(I)âamido bis-sulfoxide pincer complex <i>mer-</i>(<i>R,R</i>)-[RhÂ(bisÂ(4-(<i>tert</i>-butyl)-2-(<i>p</i>-tolylsulfinyl)Âphenyl)Âamide)Â(COE)] (<i>mer-</i>(<i>R,R</i>)-<b>5</b>). This complex
reacts with 3 equiv of HCl to give the facial RhÂ(III) complex <i>fac-</i>(<i>S,R,R</i>)-[RhÂ(bisÂ(4-(<i>tert</i>-butyl)-2-(<i>p</i>-tolylsulfinyl)Âphenyl)Âamine)ÂCl<sub>3</sub>] (<i>fac-</i>(<i>S,R,R</i>)-<b>6</b>),
in which one of the sulfoxide functions has been reduced to the sulfide
and in which the resulting sulfoxideâsulfideâamine ligand
is facially coordinated. The same complexes <b>5</b> and <b>6</b> form in a 1:2 ratio in a disproportionation reaction when
[RhClÂ(COE)<sub>2</sub>]<sub>2</sub> is treated with 2 equiv of neutral
ligand <b>3</b>. NâH activation is directly observed
in the reaction of [IrClÂ(COE)<sub>2</sub>]<sub>2</sub> with <b>3</b>, affording the amidoâhydridoâIrÂ(III) complex
[IrÂ(bisÂ(4-(<i>tert</i>-butyl)-2-(<i>p</i>-tolylsulfinyl)Âphenyl)Âamide)Â(Cl)Â(H)Â(COE)]
(<b>8</b>)
sâBlock Metal Dibenzoazepinate Complexes: Evidence for MgâAlkene Encapsulation
The dibenzoÂ[<i>b</i>,<i>f</i>]Âazepinate (DBAP)
complexes (DBAP)ÂLi·(THF)<sub>3</sub>, (DBAP)<sub>2</sub>Mg·(THF)<sub>2</sub>, and (DBAP)<sub>2</sub>Ca·(THF)<sub>3</sub> could be
isolated as highly air-sensitive compounds in yields of 93%, 72%, and 48%, respectively. Crystal structures
of these THF adducts reveal monomeric complexes in which the degree
of ring puckering depends on the nature of the metal. The most extreme
deviation from planarity is found for the most covalent bound metal,
Mg, but in all cases no interaction between the metal and the azepine
Cî»C bond is observed. The THF-free complex [(DBAP)<sub>2</sub>Mg]<sub>2</sub>, which could be obtained in 77% yield, crystallizes
as an unusual dimer with three bridging and one terminal DBAP ligand.
The bridging DBAP ligands are highly bent and span a cavity in which
a Mg<sup>2+</sup> ion is bound through three alkeneâMg interactions
with an average Mg···C distance of 2.794(3) Ă
.
Theoretical calculations support these contacts. A combination of
AIM and NPA analyses shows polarization of the alkene Ï-electron
density toward the metal (vertical polarization) but also demonstrates
a polarization of electron density toward the C atom closest to Mg
(horizontal polarization). Such metalâalkene interactions and
implicit Cî»C bond polarization are key features in main group
metal catalyzed alkene conversions
Developing PâStereogenic, PlanarâChiral PâAlkene Ligands: Monodentate, Bidentate, and Double Agostic Coordination Modes on Ru(II)
10-Phenyl-5<i>H</i>-dibenzÂ[<i>b</i>,<i>f</i>]Âazepine (<b>5</b>) is synthesized by Suzuki cross
coupling of the protected bromo alkene <b>4</b> with PhBÂ(OH)<sub>2</sub>. <b>5</b> reacts with PCl<sub>3</sub> to afford the
dichlorophosphanyl-azepine <b>6</b> in >90% yield. Alkylation
of <b>6</b> with 1 equiv of <i>t</i>-BuMgBr leads,
after recrystallization in Et<sub>2</sub>O, to the diastereomerically
enriched (<i>dr</i> > 98:2) chloride <i>rac</i>-<b>7</b>, which the crystal structure reveals to be the (p<i>S</i>,<i>R</i><sub>P</sub>)/(p<i>R</i>,<i>S</i><sub>P</sub>) pair. The fact that <i>rac</i>-<b>7</b> crystallizes in the Sohncke space group <i>P</i>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub> opens up the possibility
of a mechanical separation of the enantiomers. Methylation of <i>rac</i>-<b>7</b> is perfectly stereoselective with inversion
of configuration at the P atom to yield the new ligand <i>rac</i>-<b>8</b> as the (<i>R</i>,<i>R</i>)/(<i>S</i>,<i>S</i>) pair. The corresponding BH<sub>3</sub>-protected diastereomer <i>rac</i>-<b>9</b> (i.e.,
the (<i>R</i>,<i>S</i>)/(<i>S</i>,<i>R</i>) pair), is isolated after flash column chromatography
in 73% yield. Compounds <b>5</b>â<b>9</b> are accessible
in multigram quantities. X-ray crystal structures of RuÂ(II) complexes
demonstrate the ambidentate nature of ligand <i>rac</i>-<b>8</b>: Complex <b>10</b> is exclusively P-coordinated, while
in complex <b>11</b> two ligands bind Ru through their P donors
and stabilize the 14-electron metal center with a double agostic interaction.
In complex <b>12</b>, the ligand coordinates in a Îș<i>P</i>,η<sup>2</sup>-alkene bidentate fashion
<i>C</i><sub>2</sub>âSymmetric (SO)N(SO) Sulfoxide Pincer Complexes of Mg and Pd: Helicity Switch by Ambidentate <i>S</i>/<i>O</i>âCoordination and Isolation of a Chiral Pd-Sulfenate
Quinine-based (<i>R</i>)-<i>tert</i>-butylsulfinate <b>3</b> reacts with
tris-lithiated bis-arylamide <b>2</b> to
afford gram-quantities of optically pure (S*O)ÂNÂ(S*O) sulfoxide pincer
ligand (<i>R</i>,<i>R</i>)-<b>4</b>. Deprotonation
of (<i>R</i>,<i>R</i>)-<b>4</b> and <i>p</i>-Tol-substituted analogue (<i>S</i>,<i>S</i>)-<b>5</b> with MgPh<sub>2</sub> and BnK yields respective
Mg and K amido-bis-sulfoxides <b>6</b>â<b>9</b>. In Mg complexes <b>6</b> and <b>7</b>, the sulfoxide
functions are <i>O</i>-coordinated, thereby imparting a
pronounced helicity to the ligand backbone. Transmetalation of <b>6</b> and <b>7</b> with [PdCl<sub>2</sub>(NCPh)<sub>2</sub>] affords the <i>S</i>,<i>S</i>-coordinated <i>C</i><sub>2</sub>-symmetric and the <i>O</i>,<i>S</i>-coordinated <i>C</i><sub>1</sub>-symmetric chlorido
complexes <b>10</b> and <b>11</b>, respectively, and reaction
of potassium amides <b>8</b> and <b>9</b> with [PdClÂ(CH<sub>3</sub>)Â(COD)] leads to methyl-palladium pincer complexes <b>12</b> and <b>13</b>, respectively. The crystal structures of <b>6</b>, <b>7</b>, <b>12</b>, and <b>13</b> reveal
a chameleonic ligand system with predictable behavior: (<i>R</i>)-configured <b>4</b> induces pronounced λ backbone helicity
in the <i>O</i>-coordinated Mg-complex and weaker ÎŽ
helicity in <i>S</i>-coordinated Pd-complexes, while (<i>S</i>)-configured ligand <b>5</b> mirrors this stereochemistry. <i>S</i>-Coordination induces stronger, <i>C</i><sub>2</sub>-symmetric, steric crowding in the head-on quadrants compared
to <i>O</i>-coordination. When (<i>R</i>,<i>R</i>)-<b>4</b> is reacted with 2 equiv of [PdÂ(CH<sub>3</sub>)<sub>2</sub>(tmeda)], crystalline chiral Pd-sulfenate complex <b>16</b> forms by elimination of <i>iso</i>-butene and
methane with inversion of configuration at the sulfenate S atom
Additional file 13 of Differential distribution and enrichment of non-coding RNAs in exosomes from normal and Cancer-associated fibroblasts in colorectal cancer
: Multiple alignment of the 42 sncRNAs over represented in CAF-EXO samples. (FASTA 8 kb
Additional file 2: of Differential distribution and enrichment of non-coding RNAs in exosomes from normal and Cancer-associated fibroblasts in colorectal cancer
Absolute and average relative counts of reads mapped to each ncRNAs biotype per sample and fraction. (XLSX 15 kb
Additional file 11: of Differential distribution and enrichment of non-coding RNAs in exosomes from normal and Cancer-associated fibroblasts in colorectal cancer
Table S1. sncRNAs distributed differently in CAF-EXO samples from in NF-EXO ones. Highly significant lncRNAs and sncRNAs (FDRâ<â1E-04) are highlighted in bold. (DOCX 79 kb
Additional file 3: of Differential distribution and enrichment of non-coding RNAs in exosomes from normal and Cancer-associated fibroblasts in colorectal cancer
Excel document with the two count files used as input to EdgeR for differential expression analysis; one with the counts of reads of all samples mapped on the lncRNA references and another with the read counts of reads mapped on scnRNAs. (XLSX 221 kb
Additional file 8: of Differential distribution and enrichment of non-coding RNAs in exosomes from normal and Cancer-associated fibroblasts in colorectal cancer
Mini web site presenting a dynamic venn diagram showing the relationships between the results cellular or exosomal over represented in the two analyses performed between NF- and CAF- exosomes. Clicking on any intersected number, the web site opens a dialog summarizing the ncRNAs species that correspond to the intersection. (HTML 47 kb