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The absolute configuration of the title molecule, [Fe(C5H5)(C38H34NP2)]·CHCl3, is R,Rp. The molecular structure is similar to the structure of the solvent-free compound [Fukuzawa, Yamamoto & Kikuchi (2007). J. Org. Chem. 72, 1514-1517], but some torsion angles about the P-Cphenyl bonds differ by up to 25°. The P atoms and the N atom have a distorted trigonal-pyramidal geometry. The chloroform solvate group donates a C-H...[pi] bond to the central benzene ring and is also involved in six intermolecular C-H...Cl contacts with H...Cl distances between 2.96 and 3.13 Å. Key indicators: single-crystal X-ray study; T = 163 K; mean σ(C–C) = 0.003 Å; R factor = 0.039; wR factor = 0.088; data-to-parameter ratio = 24.2.
The absolute configuration of the title compound, [Fe(C5H5)(C36H29OP2)], is Sp at the ferrocene group and S at the asymmetric C atom. Both P atoms have a trigonal-pyramidal conformation. There is a short intramolecular C-H...P contact with an H...P distance of 2.56 Å. The hydroxy group is involved in an intramolecular O-H...[pi]phenyl interaction. The crystal packing shows five very weak intermolecular C-H...[pi] contacts, with H...Cg distances between 3.26 and 3.39 Å (Cg is the centroid of a phenyl or cyclopentadienyl ring). Key indicators: single-crystal X-ray study; T = 162 K; mean σ(C–C) = 0.004 Å; R factor = 0.038; wR factor = 0.083; data-to-parameter ratio = 22.3.
Geometric parameters of the title compound, C24H20N2O2S, are in the usual ranges. The central heterocycle makes dihedral angles of 41.29 (4) and 72.94 (5)° with the phenyl ring and the methoxyphenyl ring, respectively. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.002 Å; R factor = 0.038; wR factor = 0.103; data-to-parameter ratio = 14.1.
The asymmetric unit of the title compound, C10H20I2Si2, contains two half-molecules. Both complete molecules are generated by crystallographic inversion centers located at the mid-points of the central C-C single bonds; the butadiene groups are planar, with a trans conformation about the central C-C bond. The molecules show short intramolecular H...I contacts of 2.89 and 2.92 Å. The crystal packing shows no short intermolecular contacts. Key indicators: single-crystal X-ray study; T = 155 K; mean σ(C–C) = 0.002 Å ; R factor = 0.021; wR factor = 0.059; data-to-parameter ratio = 43.6.
In the title compound, C27H16F6N2O6, the nitro groups are almost coplanar with the aromatic rings to which they are attached [dihedral angles = 3.5 (5) and 6.2 (3)°]. The dihedral angles between adjacent aromatic rings are 78.07 (8) and 71.11 (8)° for nitrophenyl/phenyl and 69.50 (8)° for phenyl/phenyl. An intermolecular C-H...[pi] interaction seems to be effective in the stabilization of the structure. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.004 Å; R factor = 0.045; wR factor = 0.092; data-to-parameter ratio = 12.5.
The molecule of the title compound, C14H16N2O2, is located on a crystallographic twofold rotation axis. The central O-C-C-O bridge adopts a gauche conformation. One of the amine H atoms is disordered over two equally occupied positions. The crystal structure is stabilized by N-H...O and N-H...N hydrogen bonds. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.002 Å; disorder in main residue; R factor = 0.049; wR factor = 0.119; data-to-parameter ratio = 17.9.
The geometric parameters of the molecule of the title compound, C14H16O2P2, are in the usual ranges. It is a meso compound with the two chiral P atoms having opposite configurations. The P-CH2-CH2-P chain adopts a trans conformation [torsion angle -178.59 (17)°]. The P=O bonds are almost coplanar with the adjacent phenyl ring [torsion angles = 3.8 (3) and 0.3 (3)°]. Whereas one of them is synclinal [torsion angle = -59.0 (2)°] to the central C-C bond, the other is anticlinal [torsion angle = 56.6 (2)°] to the central C-C bond. The dihedral angle between the two phenyl rings is 5.2 (3)°. The molecules are linked by weak C-H...O hydrogen bonds. They crystallize in rows running along the c axis. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.005 Å; R factor = 0.038; wR factor = 0.093; data-to-parameter ratio = 15.2.
2-Aminopyrimidinium picrate
(2008)
The geometric parameters of the title compound, C4H6N3+·C6H2N3O7-, are in the usual ranges. While two nitro groups are almost coplanar with the aromatic picrate ring [dihedral angles 3.0 (2) and 4.4 (3)°], the third is significantly twisted out of this plane [dihedral angle 46.47 (8)°]. Anions and cations are connected via N-H...O hydrogen bonds. The molecules crystallize in planes parallel to (1\overline{2}1). Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.002 Å; R factor = 0.036; wR factor = 0.099; data-to-parameter ratio = 10.9.
The title compound, C16H14N2O2, was derived from 1-(2-hydroxyphenyl)-3-(2-methoxyphenyl)propane-1,3-dione. The molecule is essentially planar (r.m.s. deviation for all non-H atoms = 0.089 Å). Two intramolecular hydrogen bonds stabilize the molecular conformation and one N-H...O hydrogen bond stabilizes the crystal structure. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.003 Å; R factor = 0.035; wR factor = 0.091; data-to-parameter ratio = 9.3.
In the title compound, C12H14N22+·2Cl-, the 4,4'-dimethyl-2,2'-bipyridinium cation is essentially planar (r.m.s. deviation for all non-H atoms = 0.004 Å) and is located on a crystallographic inversion centre. The cations and chloride anions lie in planes parallel to (111) and are connected by N-H...Cl and C-H...Cl hydrogen bonds. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.003 Å; R factor = 0.036; wR factor = 0.080; data-to-parameter ratio = 14.7.
The title compound, [Fe2(C5H5)2(C24H22BP2)(CO)4][FeCl4]·CHCl3, is an oxidation product of CpFe(CO)2PPh2BH3. One pair of phenyl rings attached to the two different P atoms are almost parallel, as are the other pair [dihedral angles = 8.7 (5) and 8.9 (5)°]. The planes of the two cyclopentadienyl rings are inclined by 26.8 (7)° with respect to each other. The carbonyl groups at each Fe atom are almost perpendicular [C-Fe-C = 92.6 (6) and 94.3 (5)°]. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.019 Å; R factor = 0.112; wR factor = 0.177; data-to-parameter ratio = 16.8.
The title compound, [Re2(OH)(C10H8N2)2(CO)6][ReO4], is a mixed-valence rhenium compound containing discrete anions and cations. The ReI atoms are in a slightly distorted octahedral environment, whereas the ReVII atoms show the typical tetrahedral coordination mode. The dihedral angle between the two bipyridine groups is 34.3 (7)°. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.044 Å; R factor = 0.093; wR factor = 0.262; data-to-parameter ratio = 13.9.
A high-precision pressure probe is described which allows non-invasive online-monitoring of the water relations of intact leaves. Real-time recording of the leaf water status occurred by data transfer to an Internet server. The leaf patch clamp pressure probe measures the attenuated pressure, Pp, of a leaf patch in response to a constant clamp pressure, Pclamp. Pp is sensed by a miniaturized silicone pressure sensor integrated into the device. The magnitude of Pp is dictated by the transfer function of the leaf, Tf, which is a function of leaf patch volume and ultimately of cell turgor pressure, Pc, as shown theoretically. The power function Tf=f(Pc) theoretically derived was experimentally confirmed by concomitant Pp and Pc measurements on intact leaflets of the liana Tetrastigma voinierianum under greenhouse conditions. Simultaneous Pp recordings on leaflets up to 10 m height above ground demonstrated that changes in Tf induced by Pc changes due to changes of microclimate and/or of the irrigation regime were sensitively reflected in corresponding changes of Pp. Analysis of the data show that transpirational water loss during the morning hours was associated with a transient rise in turgor pressure gradients within the leaflets. Subsequent recovery of turgescence during the afternoon was much faster than the preceding transpiration-induced water loss if the plants were well irrigated. Our data show the enormous potential of the leaf patch clamp pressure probe for leaf water studies including unravelling of the hydraulic communication between neighbouring leaves and over long distances within tall plants (trees).
A mild synthetic method for N-formyl-Met-Leu-Phe-OH (1) is described. After Fmoc solid phase peptide synthesis, on-bead formylation and HPLC purification, more than 30 mg of the fully 13C/15N-labelled tripeptide 1 could be isolated in a typical batch. This peptide can be easily crystallised and is therefore well suited as a standard sample for setting up solid-state NMR experiments.
Bromotriphenylsilane
(2008)
The title compound, C18H15BrSi, crystallizes with two almost identical molecules (r.m.s. deviation for all non-H atoms = 0.074 Å) in the asymmetric unit. It is isomorphous with chlorotriphenylsilane. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.010 Å; R factor = 0.095; wR factor = 0.288; data-to-parameter ratio = 17.0.
C2-symmetric bisamidines : chiral Brønsted bases catalysing the Diels-Alder reaction of anthrones
(2008)
C2-symmetric bisamidines 8 have been tested as chiral Brønsted bases in the Diels- Alder reaction of anthrones and N-substituted maleimides. High yields of cycloadducts and significant asymmetric inductions up to 76% ee are accessible. The proposed mechanism involves proton transfer between anthrone and bisamidine, association of the resulting ions and finally a cycloaddition step stereoselectively controlled by the chiral ion pair.
The neuronal adaptor protein Fe65 is involved in brain development, Alzheimer disease amyloid precursor protein (APP) signaling, and proteolytic processing of APP. It contains three protein-protein interaction domains, one WW domain, and a unique tandem array of phosphotyrosine-binding (PTB) domains. The N-terminal PTB domain (Fe65-PTB1) was shown to interact with a variety of proteins, including the low density lipoprotein receptor-related protein (LRP-1), the ApoEr2 receptor, and the histone acetyltransferase Tip60. We have determined the crystal structures of human Fe65-PTB1 in its apo- and in a phosphate-bound form at 2.2 and 2.7A resolution, respectively. The overall fold shows a PTB-typical pleckstrin homology domain superfold. Although Fe65-PTB1 has been classified on an evolutionary basis as a Dab-like PTB domain, it contains attributes of other PTB domain subfamilies. The phosphotyrosine-binding pocket resembles IRS-like PTB domains, and the bound phosphate occupies the binding site of the phosphotyrosine (Tyr(P)) within the canonical NPXpY recognition motif. In addition Fe65-PTB1 contains a loop insertion between helix alpha2 and strand beta2(alpha2/beta2 loop) similar to members of the Shc-like PTB domain subfamily. The structural comparison with the Dab1-PTB domain reveals a putative phospholipid-binding site opposite the peptide binding pocket. We suggest Fe65-PTB1 to interact with its target proteins involved in translocation and signaling of APP in a phosphorylation-dependent manner.
The complete molecule of the title compound, [Sn(C6H5)2Cl2(C9H21OP)2], is generated by crystallographic inversion symmetry, the Sn atom is located on a special position of site symmetry \overline{1}. The Sn atom adopts an all-trans SnC2O2Cl2 octahedral geometry. As a consequence of the bulky substituents at the O atom, the P-O-Sn bond angle is 163.9 (3)°. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.012 Å; R factor = 0.058; wR factor = 0.099; data-to-parameter ratio = 18.6.
Mitochondrial complex I (NADH:ubiquinone oxidoreductase) undergoes reversible deactivation upon incubation at 30–37 °C. The active/deactive transition could play an important role in the regulation of complex I activity. It has been suggested recently that complex I may become modified by S-nitrosation under pathological conditions during hypoxia or when the nitric oxide:oxygen ratio increases. Apparently, a specific cysteine becomes accessible to chemical modification only in the deactive form of the enzyme. By selective fluorescence labeling and proteomic analysis, we have identified this residue as cysteine-39 of the mitochondrially encoded ND3 subunit of bovine heart mitochondria. Cysteine-39 is located in a loop connecting the first and second transmembrane helix of this highly hydrophobic subunit. We propose that this loop connects the ND3 subunit of the membrane arm with the PSST subunit of the peripheral arm of complex I, placing it in a region that is known to be critical for the catalytic mechanism of complex I. In fact, mutations in three positions of the loop were previously reported to cause Leigh syndrome with and without dystonia or progressive mitochondrial disease.
Location and orientation of serotonin receptor 1a agonists in model and complex lipid membranes
(2008)
Magic angle spinning (MAS) NMR has been used to investigate the location and orientation of five serotonin receptor 1a agonists (serotonin, buspirone, quipazine, 8-OH-DPAT, and LY-163,165) in single component model lipid and brain lipid membranes. The agonist locations are probed by monitoring changes in the lipid proton chemical shifts and by MAS-assisted nuclear Overhauser enhancement spectroscopy, which indicates the orientation of the agonists with respect to the 1,2-dioleoyl-sn-glycero-3-phosphocholine lipids. In the single component bilayer, the membrane agonists are found predominantly in the top of the hydrophobic chain or in the glycerol region of the membrane. Most of the agonists orient approximately parallel to the membrane plane, with the exception of quipazine, whose piperazine ring is found in the glycerol region, whereas its benzene ring is located within the lipid hydrophobic chain. The location of the agonist in brain lipid membranes is similar to the 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers; however, many of the agonists appear to locate close to the cholesterol in the membrane in preference to the phospholipids.