Structural studies on polynuclear osmium carbonyl hydrides. 1. Crystal structures of the isomorphous species undecacarbonyldihydrotriosmium and dodecacarbonyltriosmium. Role of an equatorial .mu.2-bridging hydride ligand in perturbing the arrangement of carbonyl ligands in a triangular cluster

1977 ◽  
Vol 16 (4) ◽  
pp. 878-884 ◽  
Author(s):  
Melvyn Rowen. Churchill ◽  
Barry G. DeBoer
Keyword(s):  
Crystal Structures ◽  
Structural Studies ◽  
Carbonyl Ligands ◽  
Hydride Ligand ◽  
Osmium Carbonyl

scholarly journals Plasticity at the DNA recognition site of the MeCP2 mCG-binding domain

2019 ◽  
Author(s):  
Ming Lei ◽  
Wolfram Tempel ◽  
Ke Liu ◽  
Jinrong Min
Keyword(s):  
Crystal Structures ◽  
Transcriptional Repression ◽  
Consensus Sequence ◽  
Complex Structure ◽  
Structural Basis ◽  
Structural Studies ◽  
Transcription Activator ◽  
Methylated Dna ◽  
Attachment Region

AbstractMeCP2 is an abundant protein, involved in transcriptional repression by binding to CG and non-CG methylated DNA. However, MeCP2 might also function as a transcription activator as MeCP2 is found bound to sparsely methylated promoters of actively expressed genes. Furthermore, Attachment Region Binding Protein (ARBP), the chicken ortholog of MeCP2, has been reported to bind to Matrix/scaffold attachment regions (MARs/SARs) DNA with an unmethylated 5’-CAC/GTG-3’ consensus sequence. In this study, we investigated how MeCP2 recognizes unmethylated 5’-CAC/GTG-3’ motif containing DNA by binding and structural studies. We found that MeCP2-MBD binds to MARs DNA with a comparable binding affinity to mCG DNA, and the MeCP2-CAC/GTG complex structure revealed that MeCP2 residues R111 and R133 form base-specific interactions with the GTG motif. For comparison, we also determined crystal structures of the MeCP2-MBD bound to mCG and mCAC/GTG DNA, respectively. Together, these crystal structures illustrate the adaptability of the MeCP2-MBD toward the GTG motif as well as the mCG DNA, and also provide structural basis of a biological role of MeCP2 as a transcription activator and its disease implications in Rett syndrome.

Two complexes derived from the reaction ofM3(CO)12clusters (M= Ru, Os) with the 9-(triphenylphosphonio)fluorenide ylide: tricarbonyl[9-(triphenylphosphonio)fluorenylidene]ruthenium and nonacarbonyl-μ3-fluorenylidene-μ2-hydrido-triangulo-triosmium(III)

2013 ◽  
Vol 69 (4) ◽  
pp. 363-366 ◽  
Author(s):  
Alejandro Arce ◽  
Ysaura De Sanctis ◽  
Esperanza Galarza ◽  
María Teresa Garland ◽  
Ricardo Baggio
Keyword(s):  
Crystal Structures ◽  
Carbonyl Ligands ◽  
Weakly Interacting ◽  
Distorted Octahedral ◽  
Hydride Ligand

Tricarbonyl[9-(triphenylphosphonio)fluorenylidene]ruthenium, [Ru(C31H21P)(CO)3], (I), is mononuclear, consisting of a single Ru centre, to which three carbonyl units and a chelating μ3-9-(triphenylphosphonio)fluorenide ylide bind to generate a distorted octahedral RuC6core. Nonacarbonyl-μ3-fluorenylidene-μ2-hydrido-triangulo-triosmium(III), [Os3H(C13H7)(CO)9], (II), is trinuclear and presents a triangular triosmium core, nine carbonyl ligands and one fluorenylidene ligand. Two of the OsIIIcentres present a highly distorted hexacoordinated Os(Os2C4) core and are in turn bridged by a hydride ligand. The remaining OsIIIcation is octacoordinated, with an Os(Os2C6) nucleus. The crystal structures of both compounds are the result of nondirectional forces, much resembling the packing of weakly interacting quasi-spherical units,viz.the molecules themselves in (I) and centrosymmetric π–π-bonded dimers in (II).

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