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31.
Rainer Dick 《Letters in Mathematical Physics》1989,18(3):255-265
Bases of holomorphic -differentials on N-punctured Riemann surfaces of arbitrary genus are constructed. The resulting extension of the Virasoro algebra on N-punctured spheres is displayed explicitly. 相似文献
32.
Hubert HuppertzRolf-Dieter Hoffmann Rainer Pöttgen 《Journal of solid state chemistry》2002,169(2):155-159
EuPd0.72In1.28 and EuPt0.56In1.44 were prepared under multianvil high-pressure (10.5 GPa) high-temperature (1500 and 1400 K) conditions from the precursor compounds EuPdIn and EuPtIn. They were investigated by X-ray diffraction on both powders and single crystals: MgZn2-type, space group P63/mmc, a=578.7(1) pm, c=944.9(3) pm, wR2=0.0734, 263 F2 values for EuPd0.72In1.28 and a=591.1(2) pm, c=933.8(2) pm, wR2=0.0853, 151 F2 values for EuPt0.56In1.44 with 13 variable parameters per refinement. Both structures are built up from face- and corner-sharing tetrahedra of palladium (platinum) and indium atoms. The europium cations are located in cavities within the three-dimensional [Pd0.72In1.28] and [Pt0.56In1.44] networks. The 2a and 6 h positions of the tetrahedral networks show mixed Pd/In and Pt/In occupancy in EuPd0.72In1.28 and EuPt0.56In1.44, respectively. The crystal chemistry of these indides is briefly discussed. 相似文献
33.
Silvio De Bernardini Georg Graf Colin A. Leach Peter Bühlmayer Felix Waldmeier Christoph Tamm 《Helvetica chimica acta》1983,66(2):639-651
The modified nucleoside Πd (1) was used in the synthesis of the oligonucleotide d (TpTpΠpCpGpTpCpApApApApTpC). Diester methodology being unsatisfactory, the triester synthesis was investigated with the unnatural nucleoside. An improved method of nucleoside phosphorylation was developed for the synthesis of the fully-protected nucleotide 2e. This molecule could be cleanly and selectively deprotected, and allowed the efficient synthesis of the desired oligonucleotide. 相似文献
34.
Vasyl' I. Zaremba Dariusz Kaczorowski Galyna P. Nychyporuk Ute Ch. Rodewald Birgit Heying Rainer Pttgen 《无机化学与普通化学杂志》2006,632(6):975-980
New indides Ce3Ge0.66In4.34 and Ce11Ge4.74In5.26 were synthesized from the elements by arc‐melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a high‐frequency furnace. Both compounds were investigated on the basis of X‐ray powder and single crystal data: I4/mcm, La3GeIn4 type, a = 848.8(1), c = 1192.0(2) pm, Z = 4, wR2 = 0.0453, 499 F2 values, 17 variables for Ce3Ge0.66In4.34 and I4/mmm, Sm11Ge4In6 type (ordered version of the Ho11Ge10 type), a = 1199.3(2), c = 1662.0(3) pm, wR2 = 0.0507, 1217 F2 values, 41 variables for Ce11Ge4.74In5.26. The Ce3Ge0.66In4.34 structure shows a mixed Ge/In occupancy on the 4c Wyckoff position. This site is octahedrally coordinated by cerium atoms. These octahedra share all edges, leading to a three‐dimensional network. The latter is penetrated by a two‐dimensional indium substructure which consists of flattened tetrahedra at In–In distances of 291 and 300 pm. The Ce11Ge4.74In5.26 structure contains three crystallographically independent germanium sites. The latter are coordinated by eight or nine cerium neighbors. These CN8 and CN9 polyhedra are condensed to a complex network which is penetrated by a three‐dimensional indium network with In–In distances of 301–314 pm. The 16m site shows a mixed In/Ge occupancy. Chemical bonding in both compounds is dominated by the p elements. Both ternaries studied exhibit localized magnetism due to the presence of Ce3+ ions. The compound Ce3GeIn4 remains paramagnetic down to 1.72 K, whereas Ce11Ge4In6 orders ferromagnetically at TC = 7.5 K. 相似文献
35.
Experiments have been carried out to study the behaviour of organoarsenicals treated with zeolites by means of speciation
analysis. IC-ICP-MS was applied to identify and quantify arsenite, arsenate and the following organoarsenicals: monomethylarsonic
acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium bromide (TMA+), arsenobetaine (AsB) and arsenocholine (AsC). Zeolites loaded with ferrous ions did not significantly increase the retention
of inorganic arsenic species compared to the native zeolites, while there was a ten-fold removal of arsenate relating to arsenite.
The formation of As(V) and DMA in the leachates containing clinoptilolites and mordenites was confirmed in the presence of
natural and synthetic zeolites. Arsenobetaine and arsenocholine yielded higher levels of arsenate than the methylated species. 相似文献
36.
Arie L. Gutman Marina Etinger Gennady Nisnevich Felix Polyak 《Tetrahedron: Asymmetry》1998,9(24):1022
The enantiomerically pure chiral benzocyclic amines 6–8 were obtained by asymmetric transamination of the corresponding prochiral ketones 9a–c. The method involves: (a) formation of chiral imines 10a–c from the prochiral ketones 9a–c and the inexpensive chiral auxiliary (R)- or (S)-phenylethylamine (PEA); (b) asymmetrically induced reduction of these imines to the diastereomeric amines 11a–c and 12a–c; (c) catalytic hydrogenation to remove the benzylic fragment of the chiral PEA auxiliary. The stereoselectivity of the imine reduction, as well as the regioselectivity of the catalytic hydrogenation, are strongly dependent on the size of the saturated ring condensed with the benzene ring. This approach was used to develop a convenient, high yielding, and stereoselective route to several practically important optically active α-amino substituted benzocyclic compounds. 相似文献
37.
Zepeck F Gräwert T Kaiser J Schramek N Eisenreich W Bacher A Rohdich F 《The Journal of organic chemistry》2005,70(23):9168-9174
[Structure: see text]. The IspG protein is known to catalyze the transformation of 2-C-methyl-d-erythritol 2,4-cyclodiphosphate into 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate in the nonmevalonate pathway of isoprenoid biosynthesis. We have found that the apparent IspG activity in the cell extracts of recombinant Escherichia coli cells as observed by a radiochemical assay can be enhanced severalfold by coexpression of the isc operon which is involved in the assembly of iron-sulfur clusters. The recombinant protein was isolated by affinity chromatography under anaerobic conditions. With a mixture of flavodoxin, flavodoxin reductase, and NADPH as the reducing agent, stringent assay methods based on photometry or on 13C NMR detection of multiply 13C-labeled substrate/product ratios afforded catalytic activities greater than 60 nmol mg(-1) min(-1) for the protein "as isolated" (i.e., without reconstitution of any kind). Lower apparent activities were found using photoreduced deazaflavin as an artifactual electron donor, whereas dithionite was unable to serve as an artificial electron donor. The apparent Michaelis constant for 2-C-methyl-D-erythritol 2,4-cyclodiphosphate was 700 microM. The enzyme was inactivated by EDTA and could be reactivated by Mn2+. The pH optimum was at 9.0. The protein contained 2.4 iron ions and 4.4 sulfide ions per subunit. The replacement of any of the three conserved cysteine residues afforded mutant proteins which were devoid of catalytic activity and contained less than 6% of Fe2+ and less than 23% of S2- as compared to the wild-type protein. Sequence comparison indicates that putative IspG proteins of plants, the apicomplexan protozoan Plasmodium falciparum, and bacteria from the Bacteroidetes/Chlorobi group contain an insert of about 170-320 amino acid residues as compared with eubacterial enzymes. 相似文献
38.
Kammerer B Kahlich R Ufer M Laufer S Gleiter CH 《Rapid communications in mass spectrometry : RCM》2004,18(4):458-464
Phenprocoumon is a commonly used oral anticoagulant of the coumarin type, and has found extensive clinical use in the treatment of thrombophlebitis, pulmonary embolism and atrial fibrillation. In the course of a clinical study to investigate the influence of genetic polymorphisms of the CYP2C9 enzyme on phenprocoumon metabolism, we developed a new enantioselective liquid chromatography/electrospray ionisation tandem mass spectrometry (LC/MS/MS) method to quantify (R)- and (S)-phenprocoumon in human plasma. HPLC separation of the enantiomers was achieved on a Chira-Grom-2 column under isocratic conditions using a water/acetonitrile/formic acid eluent. For detection and quantification a triple-quadrupole MS system was used in the selected reaction monitoring (SRM) mode. As an internal standard the structurally homologous compound warfarin was chosen. The detector response was linear with a correlation coefficient of 0.988-0.999 for (R)-phenprocoumon and 0.989-0.999 for (S)-phenprocoumon in the investigated concentration range between 62.5 and 1000 ng/mL (per enantiomer). The limit of detection (LOD) was 12.5 ng/mL. 相似文献
39.
The 3-trifluoromethylsulfonyloxy-1-hexeniminium triflate 1 reacts with two equivalents of an aliphatic nitrile or of benzonitrile to give the 4-(2-diethylaminovinyl)pyrimidinediium bis(triflates) 4 , which can be deprotonated to give the monoprotonated or neutral pyrimidines 5 and 6 , respectively. When the related 1-phenyl-substituted iminium salt 7 is heated in acetonitrile at 140°, 1,5-cyclization of the cation leading to indane derivative 8 competes with formation of the pyrimidinium salt 9 . X-ray crystal structure determination reveals significant differences in the bond lengths of mono-and diprotonated 4-(2-diethylaminovinyl)pyrimidines 5a and 4a . 相似文献
40.
Elaine C. Petronilho Murilo M. Pedrote Mayra A. Marques Yulli M. Passos Michelle F. Mota Benjamin Jakobus Gileno dos Santos de Sousa Filipe Pereira da Costa Adriani L. Felix Giulia D. S. Ferretti Fernando P. Almeida Yraima Cordeiro Tuane C. R. G. Vieira Guilherme A. P. de Oliveira Jerson L. Silva 《Chemical science》2021,12(21):7334
Mutant p53 tends to form aggregates with amyloid properties, especially amyloid oligomers inside the nucleus, which are believed to cause oncogenic gain-of-function (GoF). The mechanism of the formation of the aggregates in the nucleus remains uncertain. The present study demonstrated that the DNA-binding domain of p53 (p53C) underwent phase separation (PS) on the pathway to aggregation under various conditions. p53C phase separated in the presence of the crowding agent polyethylene glycol (PEG). Similarly, mutant p53C (M237I and R249S) underwent PS; however, the process evolved to a solid-like phase transition faster than that in the case of wild-type p53C. The data obtained by microscopy of live cells indicated that transfection of mutant full-length p53 into the cells tended to result in PS and phase transition (PT) in the nuclear compartments, which are likely the cause of the GoF effects. Fluorescence recovery after photobleaching (FRAP) experiments revealed liquid characteristics of the condensates in the nucleus. Mutant p53 tended to undergo gel- and solid-like phase transitions in the nucleus and in nuclear bodies demonstrated by slow and incomplete recovery of fluorescence after photobleaching. Polyanions, such as heparin and RNA, were able to modulate PS and PT in vitro. Heparin apparently stabilized the condensates in a gel-like state, and RNA apparently induced a solid-like state of the protein even in the absence of PEG. Conditions that destabilize p53C into a molten globule conformation also produced liquid droplets in the absence of crowding. The disordered transactivation domain (TAD) modulated both phase separation and amyloid aggregation. In summary, our data provide mechanistic insight into the formation of p53 condensates and conditions that may result in the formation of aggregated structures, such as mutant amyloid oligomers, in cancer. The pathway of mutant p53 from liquid droplets to gel-like and solid-like (amyloid) species may be a suitable target for anticancer therapy.Mutant p53 tends to form aggregates with amyloid properties, especially amyloid oligomers inside the nucleus, which are believed to cause oncogenic gain-of-function (GoF). 相似文献