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991.
A. Paul Krapcho Mary E. Petry John J. Landi John Stallman Johanna F. Polsenberg Miles P. Hacker Silvano Spinelli Ambrogio Oliva Roberto Di Domenico Emesto Menta 《Journal of heterocyclic chemistry》1993,30(6):1565-1569
The synthesis of 6,9-difluorobenzo[g]quinoline-5,10-dione ( 3b ) is described. Facile ipso substitutions of the fluorides from 3b by diamines readily yield the corresponding 6,9-bis[(aminoalkyl)amino]benzo-[g]quinoline-5,10-diones 2 . The analogue 2d has been synthesized by side arm modifications of dione 8a . 相似文献
992.
The appearance rate of 1* (5p52P) following laser photolysis of molecular I2 1.2 kT below the dissociation limit o the I2 (B3 Πou+) state has been monitored by time-resolved atomic absorption as a function of I2 pressure. Data were also taken with N2 as an added gas. The results confirm the production of I* from the B state by a collisional process and reveal an additional process by which I* continues to appear for several hundred nanoseconds after the laser pulse even at N2 pressures as high as 750 torr. 相似文献
993.
The vapor phase absorption spectra of PF3, PF2Cl, PFCl2, and PCl3 are reported in the vacuum ultraviolet spectral region 2400—1200 A. These results are compared with information obtained from photoelectron spectra. A brief discussion of the spectra in terms of analogous absorption regions and results from CNDO/2 calculations are given. 相似文献
994.
Two mutations, R69D and K115E, converted a bacterial phosphatidylinositol-specific phospholipase C (PI-PLC) to a phosphatase with much higher specific activity toward glucose-6-phosphate than inositol-1-phosphate. PI-PLC single mutations R69D and K115E can cleave PI but lack any demonstrable phosphatase activity. The bacterial PI-PLC has no sequence homology with known glucose-6-phosphatase enzymes, which need His, Arg, and negatively charged residues (Asp or Glu) at the active site. The change in chemical reaction and substrate specificity can be rationalized by energy minimization of the mutant with I-1-P or G-6-P bound. 相似文献
995.
The T-shaped Pt(II) complex [PtMe(iPr3P)2][1-H-closo-CB11Me11], which is stabilised by an agostic interaction, undergoes acid-catalysed intramolecular C-H activation in the presence of THF to afford cyclometallated [Pt(THF)(iPr3P)(iPr2PCHMeCH2)][1-H-closo-CB11Me11]. 相似文献
996.
Reversible phosphorylation of proteins functions as a biological switching network for activation and inhibition of downstream biological processes. Since phosphorylations of these sites are often transient processes, and hence sub-stoichiometric, systematic characterization of phosphorylation sites is a formidable challenge. In this work, a new approach was developed to pinpoint phosphotyrosine sites on tyrosine-containing peptides. This required (1) the development of a new and highly sensitive nano-electrospray assembly and (2) validation of the concept that the specificity and detection limit for trace levels of phosphotyrosine immonium ion in peptide mixtures from protein digests can be increased by varying the collision energy. With our method, an automatic tandem mass spectrometric analysis of peptides eluted from a C(18) capillary liquid chromatographic column is triggered by a positive confirmation of phosphotyrosine immonium ion in a time-of-flight mass spectrometric survey. The approach was tested by analyzing the phosphorylation of human IRS-1 peptides that interact with the Src-homology 2 domain and mixtures of these peptides with tryptic digests of bovine serum albumin and horse heart myoglobin. 相似文献
997.
The purpose of this review is to highlight the versatility of membrane introduction mass spectrometry (MIMS) in environmental applications, summarize the measurements of environmental volatile organic compounds (VOCs) accomplished using MIMS, present developments in the detection of semi-volatile organic compounds (SVOCs) and forecast possible future directions of MIMS in environmental applications. 相似文献
998.
Several binuclear oxovanadium compounds of binucleating ligands are synthesised and investigated by magnetic, spectral and
esr methods. The experimental results show that there is weak exchange interaction mediated by the bridging organic molecules
between the vanadium centres. The magnitude of this interaction is more than that observed in the corresponding copper(II)
dimers. The possible reason for this is discussed. 相似文献
999.
5-p-Chlorophenyl-6,6-dimethyl-5,6-dihydro-3H-furano[2,3-d]pyrimidine-4-one is readily converted to 4,6-dichloro-5-β-β-dimethyl-α- (p-chlorostyryl)pyrimidine by warming in phosphorus oxychloride and acetic acid, behavior which is in strong contrast to that of the analogous 5-phenyl derivative. The reaction provides a convenient source of 4-amino-6-chloro-5β,β-dimethyl-α- (p-chlorostyryl)pyrimidines and 4,6-diamino-5-β,β-dimethyl-α- (p-chlorostyryl)pyrimidines, compounds of potential biological interest. 相似文献
1000.
Mary C. Salazar Indira Lugo Antonio J. Hernández Carlos Manzanares I 《Theoretical chemistry accounts》2006,115(4):246-252
In this contribution, ab initio methods have been used to study the open-shell CO+–He van der Waals (vdW) complex in both the ground and the first Π excited electronic state. Calculations were performed at the UCCSD(T) level of theory in the framework of the supermolecule approach using the cc-pVTZ basis set complemented with a set of standard bond functions in the middle of the vdW bond. Calculations predict a most-stable equilibrium conformation with β e=45°, R e =2.85 Å and D e =275 cm?1 for the ground CO+(X2Σ)–He(1S) state and β e=90°, R e =2.70 Å and D e =218 cm?1 for the excited CO +(A2Π)–He(1S) state. The dipole moment μ and independent components of the field polarizability α of the CO +–He vdW complex have been studied at the calculated equilibrium geometry of these states. The vertical excitation energies from the ground CO+(X 2Σ)–He(1S) to the excited CO+(A2Π)–He (1S) electronic state and corresponding shifts in the fluorescent spectrum with respect to the isolated CO+ molecule are also presented 相似文献