Separation of the Rotational Isomers of Tetrakis(N-Methyl-2-pyridiniumyl)porphyrin and the Crystal Structure of .alpha.,.alpha.,.alpha.,.beta.-(Tetrakis(N-methyl-2-pyridiniumyl)porphyrin)copper Hexacyanoferrate

1995 ◽  
Vol 34 (20) ◽  
pp. 5073-5079 ◽  
Author(s):  
Tai Kaufmann ◽  
Bernard Shamsai ◽  
Roy Song Lu ◽  
Robert Bau ◽  
Gordon M. Miskelly
Keyword(s):  
Crystal Structure ◽  
Copper Hexacyanoferrate ◽  
Rotational Isomers ◽  
Alpha Beta

The Pseudo-Symmetric Structure of Pb(SPh)2

1997 ◽  
Vol 53 (3) ◽  
pp. 457-465 ◽  
Author(s):  
A. D. Rae ◽  
D. C. Craig ◽  
I. G. Dance ◽  
M. L. Scudder ◽  
P. A. W. Dean ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Structure Factor ◽  
Layer Structure ◽  
Partial Ordering ◽  
The Other ◽  
Monoclinic Space Group ◽  
Ordered Structure ◽  
Symmetric Structure ◽  
Polymeric Layer ◽  
Alpha Beta

The crystal structure of Pb(SC6H5)2 is pseudo-C-centred orthorhombic, a = 54.06 (1), b = 11.468 (1), c = 7.4387 (8) Å, \alpha = \beta = \gamma = 90°, Z = 16, and may be described as a partial ordering of a 1:1 disordered parent structure of symmetry Pmcn, Z = 4 (a′ = a/2, b′ = b/2, c′ = c), in which the mirror imposes a 1:1 disorder on two-dimensionally polymeric layers perpendicular to a*. An ideally ordered structure has monoclinic space group C1121/d (P21/c using an alternative axis system b, c, [a + b]/2), but may also be described as two inversion-related substructures of Cmc21 pseudo- symmetry, where the b-glide planes of one substructure coincide with the mirror planes of the other and vice versa. Moving one substructure by b/2 relative to the other creates a different orientation of the structure. The crystal studied showed a partial disorder of each substructure relative to origins b/2 apart [0.964 (4):0.036 for one substructure and 0.584 (3):0.416 for the other]. This lowers the symmetry of the average structure to C1121 with intensities realistically described as K 2[(1−\delta)|F(hkl)|2 + \delta|F(hkl)|2], where K 2 for h odd, k odd reflections is 0.444 (7) of the value for h even, k even reflections, \delta is 0.325 (5) and F(hkl) is the structure factor for an ideally ordered structure. Final values for R of 0.046 and 0.090 were obtained for the 844 h even, k even and 687 h odd, k odd reflections with I(h) > 3\sigma(I(h)) used in refinement. A bond-valence interpretation of the bonding within the polymeric layer structure is given.

The Crystal Structure of Me3SiNPPh2CH2PPh2 and NMR Investigations on its Proposed Thermal Isomerization

1990 ◽  
Vol 45 (4) ◽  
pp. 476-482 ◽  
Author(s):  
Hubert Schmidbaur ◽  
Graham A. Bowmaker ◽  
Otto Kumberger ◽  
Gerhard Müller ◽  
Werner Wolfsberger
Keyword(s):  
Crystal Structure ◽  
Ground State ◽  
Nmr Spectra ◽  
Bond Angle ◽  
Steric Effects ◽  
Pure Sample ◽  
Conformational Isomers ◽  
Rotational Isomers ◽  
Reproducible Method ◽  
Nmr Signals

The crystal structure of Me3SiNPPh2CH2PPh2 (1) has been determined in order to obtain information about the ground state conformation in the solid, and about unusual steric effects which could give rise to conformational isomers. It was recently proposed that such isomers exist due to restricted rotation about the P=N bond, and are generated by heating the compound to 160 C. The evidence for them was based on the observation of multiple NMR signals in CDCl3 solutions of samples which had been so treated. The crystal structure yields a P–N–Si bond angle of 150.2(2), a P–N bond length of 1.529(3) Å and a Si–N bond lengths of 1.668(3) A. It is clear that, as a result of the relatively large P–N–Si angle in 1, there is no steric hindrance to rotation about the P–N bond in this molecule. Attempts to study the energetics of the proposed isomerization by recording the NMR spectra of heated samples showed that the previously reported multiple NMR signals are not generated in this way. However, such signals are generated at ambient temperature under various circumstances, for example in the course of the reaction of a CDCl3 solution of 1 with methanol to produce HNPPh2CH2PPh2 (2). The observation that it is not necessary to heat 1 in order to generate these signals makes their assignment to rotational isomers rather less likely. In the absence of a reproducible method of producing these signals in a pure sample, the existence of such isomers should be regarded as not yet proven.

Crystal structure of the .alpha.,.beta.,.gamma.-tridentate manganese complex of adenosine 5'-triphosphate cocrystallized with 2,2'-dipyridylamine

Biochemistry ◽  
1985 ◽  
Vol 24 (26) ◽  
pp. 7827-7833 ◽  
Author(s):  
Michael Sabat ◽  
Renzo Cini ◽  
Tuli Haromy ◽  
M. Sundaralingam
Keyword(s):  
Crystal Structure ◽  
Manganese Complex ◽  
Alpha Beta

scholarly journals Structural Basis of the Inhibition of STAT1 Activity by Sendai Virus C Protein

2015 ◽  
Vol 89 (22) ◽  
pp. 11487-11499 ◽  
Author(s):  
Kosuke Oda ◽  
Yasuyuki Matoba ◽  
Takashi Irie ◽  
Ryoko Kawabata ◽  
Masaya Fukushi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Signal Transduction ◽  
Molecular Weight ◽  
Innate Immunity ◽  
Sendai Virus ◽  
Signal Transduction Pathways ◽  
C Protein ◽  
Parallel Form ◽  
Ifn Γ ◽  
Alpha Beta

ABSTRACTSendai virus (SeV) C protein inhibits the signal transduction pathways of interferon alpha/beta (IFN-α/β) and IFN-γ by binding to the N-terminal domain of STAT1 (STAT1ND), thereby allowing SeV to escape from host innate immunity. Here we determined the crystal structure of STAT1ND associated with the C-terminal half of the C protein (Y3 [amino acids 99 to 204]) at a resolution of 2.0 Å. This showed that two molecules of Y3 symmetrically bind to each niche created between two molecules of the STAT1ND dimer. Molecular modeling suggested that an antiparallel form of the full-length STAT1 dimer can bind only one Y3 molecule and that a parallel form can bind two Y3 molecules. Affinity analysis demonstrated anticooperative binding of two Y3 molecules with the STAT1 dimer, which is consistent with the hypothetical model that the second Y3 molecule can only target the STAT1 dimer in a parallel form. STAT1 with excess amounts of Y3 was prone to inhibit the dephosphorylation at Tyr701by a phosphatase. In an electrophoretic mobility shift assay, tyrosine-phosphorylated STAT1 (pY-STAT1) with Y3 associated with the γ-activated sequence, probably as high-molecular-weight complexes (HMWCs), which may account for partial inhibition of a reporter assay from IFN-γ by Y3. Our study suggests that the full-length C protein interferes with the domain arrangement of the STAT1 dimer, leading to the accumulation of pY-STAT1 and the formation of HMWCs. In addition, we discuss the mechanism by which phosphorylation of STAT2 is inhibited in the presence of the C protein after stimulation by IFN-α/β.IMPORTANCESendai virus, a paramyxovirus that causes respiratory diseases in rodents, possesses the C protein, which inhibits the signal transduction pathways of interferon alpha/beta (IFN-α/β) and IFN-γ by binding to the transcription factor STAT1. In virus-infected cells, phosphorylation of STAT1 at the Tyr701residue is potently enhanced, although transcription by STAT1 is inert. Here, we determined the crystal structure of the N-terminal domain of STAT1 associated with the C-terminal half of the C protein. Molecular modeling and experiments suggested that the two C proteins bind to and stabilize the parallel form of the STAT1 dimer, which are likely to be phosphorylated at Tyr701, further inducing high-molecular-weight complex formation and inhibition of transcription by IFN-γ. We also discuss the possible mechanism of inhibition of the IFN-α/β pathways by the C protein. This is the first structural report of the C protein, suggesting a mechanism of evasion of the paramyxovirus from innate immunity.

Crystal structure and moleculsr stereochemistry of .mu.-oxo-bis[.alpha.,.beta.,.gamma.,.delta.-tetraphenylporphinatoiron(III)]

1972 ◽  
Vol 94 (10) ◽  
pp. 3620-3626 ◽  
Author(s):  
A. B. Hoffman ◽  
D. M. Collins ◽  
V. W. Day ◽  
E. B. Fleischer ◽  
T. S. Srivastava ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Gamma Delta ◽  
Alpha Beta
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