Selenomethionine (SeMet) is a potentially toxic amino acid, and yet it is a valuable tool in the preparation of labeled proteins for multiwavelength anomalous dispersion or single-wavelength anomalous dispersion phasing in X-ray crystallography. The mechanism by which high levels of SeMet exhibits its toxic effects in eukaryotic cells is not fully understood. Attempts to use Saccharomyces cerevisiae for the preparation of fully substituted SeMet proteins for X-ray crystallography have been limited. A screen of the viable S. cerevisiae haploid null allele strain collection for resistance to SeMet was performed. Deletion of the CYS3 gene encoding cystathionine gamma-lyase resulted in the highest resistance to SeMet. In addition, deletion of SSN2 resulted in both increased resistance to SeMet as well as reduced levels of Cys3p. A methionine auxotrophic strain lacking CYS3 was able to grow in media with SeMet as the only source of Met, achieving essentially 100% occupancy in total proteins. The CYS3 deletion strain provides advantages for an easy and cost-effective method to prepare SeMet-substituted protein in yeast and perhaps other eukaryotic systems.
The novel hexacyclic title hydrocarbon, formed by an unusual oxidative dimerization of 3-phenylbicyclo[3,2,1]oct-2-ene, has been isolated and its structure elucidated by means of X-ray crystallography. The trivial name 4b-phenylmariontetraene is proposed for the hydrocarbon. Crystals are orthorhombic, Pbca; a = 21.87(2), b = 10.57(2), c = 17.41(2) Å from diffractometer measurements (Mo [Formula: see text] radiation). V = 4024.2 Å3, Z = 8, Dc = 1.21 Mg m−3, F(000) = 1584, μ = 0.34 cm−3. The structure was solved by direct phasing methods with MULTAN 78 and was refined by weighted full-matrix least-squares procedures to R = 0.046 for 2287 observed reflexions.
The structure of the
orthorhombic form of the title compound has been determined by X-ray crystallography.
The space group was found to be P212121
(No.19,D24 = V4) with a 10.01(5), b 5.944(6), c 17.5469(7) � and Z 4. The structure
was refined by least squares to R 0.0614. It consists of chains of molecules
with the carboxy oxygen atom, the amino nitrogen atom
and the two chlorine atoms forming an approximate square plane about the copper
atom, with two bridging chlorine atoms from two adjacent molecules completing a
distorted octahedron. Extensive hydrogen bonding links the chains together.
The crystal structure of
the title compound, [Cd(C12H8N2)(CS2OEt)2],
has been determined by X-ray crystallography using diffractometer data at 295 K
and refined by full matrix least squares to a residual of 0.06 for 1350
'observed' reflections. Crystals are orthorhombic, P bcn, a = 14.870(4), b =
14.549(8), c = 10.249(1) �, Z = 4.
The molecule lies on a twofold crystallographic axis; the phenanthroline
ligand is symmetrically bidentate [Cd-N, 2.386(8) �], while the ethylxanthateligand is somewhat
asymmetric [Cd-S, 2.647(3), 2.727(3)4 with a correspondingly asymmetric C-S
geometry [C-S, 1.72(1), 1.66(1) �].
Reaction of isobenzofuran-1(3H)-one ( phthalide ) and its derivatives with dimethylformamide dimethyl acetal in the presence of base gives small amounts (c. 10%)1 of the ylid trimethyl (3-oxido-1-oxoinden-2- yl )ammonium (3). The same compound is formed in higher yield from the corresponding 3-dimethylaminomethyleneisobenzofuran-1(3H)-one. Support for this structure comes from chemical degradation and its mode of synthesis, but relies mainly on X-ray crystallography. The title compound crystallizes as clear prisms in the monoclinic space group P21/n with a 15.992(2), b 9.329(4), c 7.112(3)Ǻ, β 90.15(3)° and Z 4. The structural final refinement of a full-matrix least-squares calculation converged with R 0.044 and Rw 0.045.
Cadmium(II) chloride reacts with toluene-3,4-dithiol (H2TDT) to give Cd (TDT), which is apparently a homopolymer in the solid state. Adducts with neutral monodentate and bidentate donors have been prepared. The structure of the salt (Ph4As)2 [Cd(TDT)2] was determined by X-ray crystallography. Crystals of this compound are monoclinic (P21/c), with a = 23.032 (4) Å, b = 12.396(4) Å, c = 22.529(5) Å, β = 111.106(2)°. The structure was refined by least-squares methods to a final R-valueof 0.0469 for 2523 "observed" reflections. The anion is a distorted tetrahedral, mononuclear species with Cd—S bond distances ranging from 2.488(5) Å to 2.531(4) Å. This anion is also a Lewis acid, forming complexes of the type [Cd(TDT)2L]2− with neutral bidentate ligands.
Genome-wide screen of Saccharomyces cerevisiae null allele strains identifies genes involved in selenomethionine resistance