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71.
The isolation and amino acid sequence of substance P from horse intestine is reported. The sequence, H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH2 is identical with the sequence reported for substance P isolated from bovine hypothalami. 相似文献
72.
Chester M. Mikulski William Henry Louis L. Pytlewski Nicholas M. Karayannis 《Transition Metal Chemistry》1977,2(1):135-140
Summary Complexes (2 : 1) of diethyl benzoylphosphonate (debp) with 3d metal perchlorates were synthesized and characterized by means of i.r. and electronic spectral, magnetic susceptibility and conductance measurements. In new complexes of the types [M(debp)2(OClO3)(OH2)](ClO4) (M = Fe, Co, Zn) and [Fe(debp)2(OClO3)(OH2)](ClO4)2, both debp ligands function as bidentate chelating agents, coordinating through the P=O and C=O oxygens. In contrast, in the manganese(II) and nickel(II) complexes, which are of the [M(debp)2(OClO3)(OH2)2](ClO4) type, one debp acts as a bidentate chelating ligand, while the second debp is unidentate, coordinating only through the P=O oxygen. Hexacoordination in the new cationic complexes is completed by coordination of aqua and unidentate perchlorato ligands, which are in competition for sites in the inner coordination sphere of the central metal ion with the weak debp ligand. On the other hand, debp, owing to its bulkiness, and especially the presence of the benzoyl substituent, introduces sufficiently severe steric hindrance during coordination. As a result of this, the formation of [M(debp)3]n+ tris-chelate cationic complexes with the 3 d metal ions under study does not seem to be possible. 相似文献
73.
Castro C Karney WL Valencia MA Vu CM Pemberton RP 《Journal of the American Chemical Society》2005,127(27):9704-9705
Density functional and coupled cluster calculations show that facile thermal configuration change in [12]annulene occurs via a twist-coupled bond-shifting mechanism. The transition state for this process is highly aromatic with M?bius topology. At the CCSD(T)/cc-pVDZ//BH&HLYP/6-311+G** level, the isomerization of tri-trans-[12]annulene 1a (CTCTCT) to its di-trans isomer 2 (CCCTCT) via such a mechanism has a barrier of 18.0 kcal/mol, in good agreement with earlier experiments. Two other aromatic M?bius bond-shifting transition states were located that result in configuration change for other [12]annulene conformers. This mechanism contrasts sharply with diradical configuration change for acyclic polyenes and with planar bond-shifting mechanisms generally assumed for annulenes. This constitutes evidence that neutral M?bius aromatic annulenes play a role in the dynamic processes of neutral [4n]annulenes. 相似文献
74.
Fomblin [poly(perfluoropropylene oxide)], PFK (perfluorokerosene) and FC-43 (perfluorotributylamine) are investigated as mass calibrants in electron-capture negative ionization mass spectrometry on a magnetic sector hybrod mass spectrometer. This work provides exact negative ion mass tables of these three calibrants obtained using high-resolution peak matching of representative ions of the calibrants against ions of known mass. The suitability of these calibrants for full data system control in the negative ionization mode is demonstrated for the techniques of high-resolution scanning, selected ion recording and calibration of the quadrupole sector of a hybrid instrument. 相似文献
75.
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78.
The synthesis of pyrazino[2,3-g]quinazolin-2,4-(1H,3H)dione ( 4 ) and its 7,8-dimethyl derivative ( 5 ), as linear benzo-separated lumazines, is reported. Also described is the preparation of 2-amino-6,7,8,9-tetrahydro-7,8-dimethylpyrazino[2,3-g]quinazolin-4-one ( 6 ), as a linear benzo-separated analog of a synthetic cofactor for phenylalanine hydroxylase. All of the syntheses began with ethyl 2,4,5-triaminobenzoate ( 8 ) and proceeded through the appropriate derivatives of ethyl 6-aminoquinoxaline-7-carboxylate ( 9, 10 , and 11 ) which were subsequently ring closed to 4, 5 , and 6 . 相似文献
79.
The spontaneous conversion of the title cation into the 1-phenyl[3](1,2) ferrocenophan-1-yl cation proceed by intra-ionic 1, 3-shift of a cyclopentadienyl α-ring proton to C(2) of the homoannular bridge; the letter cation undergoes deprotonation by stereospecific loss of the exo-proton adjacent to C+. 相似文献
80.
William H. Fink 《International journal of quantum chemistry》1973,7(6):1045-1050
The general problem of the transfer of the representation of a set of orthonormal functions from one basis to a different, nonequivalent one is considered and specialized to a matrix formulation convenient for use in molecular electronic structure calculations. A procedure is suggested for treating problems where the transfer of representation breaks into a subset of most interest and one of less interest as for example the occupied and virtual orbitals of a Hartree-Fock SCF calculation. These techniques are then applied to obtain a representation of a methyl group from an SCF wave function for methane. 相似文献