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21.
22.
Jií Davídek Miloslava Neméthová Josef Seifert 《Fresenius' Journal of Analytical Chemistry》1977,287(4-5):286-287
Summary An indirect polarographic method for the determination of phosmet was elaborated. It is based on the fact that N-hydroxymethylphthalimide formed by the reaction of phosmet with sulphuric acid is polarographically active and exhibits a behaviour during electrolysis at a Hg dropping-electrode similar to that of phthalimide. The method has been applied to the determination of phosmet in apples. The sensitivity is 0.1 ppm.
Indirekte polarographische Bestimmung von Phosmet O,O-Dimethyl-S-(phthalimidomethyl)dithiophosphat
Zusammenfassung Das Verfahren beruht darauf, daß N-Hydroxymethylphthalimid, das bei der Reaktion von Phosmet mit Schwefelsäure gebildet wird, polarographisch aktiv ist und sich bei der Elektrolyse mit der Quecksilber-Tropfelektrode ähnlich wie Phthalimid verhält. Die Methode wurde zur Bestimmung von Phosmet in Äpfeln angewandt. Die Empfindlichkeit beträgt 0,1 ppm.相似文献
23.
For many permanent cell lines the transition from a growing (P) to a resting (R) state is reversibly controlled by growth factors present in serum. This P-to-R transition was studied in a neuronal cell line (B104) with respect to the action of serum, dibutyryl cyclic AMP (DBcAMP), gangliosides, and a glioma cell-produced growth factor GGF. In this cell system gangliosides seem to act as differentiation and survival factors. The kinetics of uptake of radioactively labeled gangliosides and survival experiments both support the idea of the stable incorporation of exogenously added gangliosides into the cells. Based on the experimental evidence a new model of cell development is proposed. Thus in addition to the R or Go state, which in this cell system is rather unstable and probably regulated by cyclic nucleotides, we postulate a differentiated D state, which is controlled by gangliosides and which is characterized by its stability (survival time). This D compartment seems to be closer to the in vivo differentiated neuron than does the R or P state. tthe possible mechanisms for the action of gangliosides are discussed. 相似文献
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I. Popov T. Kunze S. Gemming G. Seifert 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):439-446
The preferred adsorption sites and the propensity for a self-organised growth of the molybdenum sulfide cluster Mo6S8 on the Au(111) surface are investigated by density-functional band-structure calculations with pseudopotentials and a plane
wave basis set. The quasi-cubic cluster preferentially adsorbs via a face and remains structurally intact.
It experiences a strong, mostly non-ionic attraction to the surface
at several quasi-isoenergetic adsorption positions. A scan of the potential energy surface exhibits only small barriers between
adjacent strong adsorption sites. Hence, the cluster may move in a potential well with degenerate local energy minima at room
temperature. The analysis of the electronic structure reveals a negligible
electron transfer and S-Au hybridised states, which indicate that the cluster-surface
interaction is dominated by S-Au bonds, with minor contributions from
the Mo atom in the surface vicinity. All results indicate that Mo6S8 clusters
on the Au(111) surface can undergo a template-mediated self-assembly to an ordered inorganic monolayer, which is still redox
active and may be employed as surface-active agent in the integration of noble metal and ionic or biological components within
nano-devices.
Therefore, a classical potential model was developed on the basis of the DFT data,
which allows to study larger cluster assemblies on the Au(111). 相似文献
29.
Probing the CH⋅⋅⋅π Weak Hydrogen Bond in Anesthetic Binding: The Sevoflurane–Benzene Cluster
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Nathan A. Seifert Dr. Daniel P. Zaleski Dr. Cristóbal Pérez Dr. Justin L. Neill Prof. Brooks H. Pate Montserrat Vallejo‐López Prof. Alberto Lesarri Dr. Emilio J. Cocinero Prof. Fernando Castaño Prof. Isabelle Kleiner 《Angewandte Chemie (International ed. in English)》2014,53(12):3210-3213
Cooperativity between weak hydrogen bonds can be revealed in molecular clusters isolated in the gas phase. Here we examine the structure, internal dynamics, and origin of the weak intermolecular forces between sevoflurane and a benzene molecule, using multi‐isotopic broadband rotational spectra. This heterodimer is held together by a primary C? H???π hydrogen bond, assisted by multiple weak C? H???F interactions. The multiple nonbonding forces hinder the internal rotation of benzene around the isopropyl C? H bond in sevoflurane, producing detectable quantum tunneling effects in the rotational spectrum. 相似文献
30.
Hydrogen Bond Cooperativity and the Three‐Dimensional Structures of Water Nonamers and Decamers
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Dr. Cristóbal Pérez Dr. Daniel P. Zaleski Nathan A. Seifert Dr. Berhane Temelso Prof. George C. Shields Prof. Zbigniew Kisiel Prof. Brooks H. Pate 《Angewandte Chemie (International ed. in English)》2014,53(52):14368-14372
Broadband rotational spectroscopy of water clusters produced in a pulsed molecular jet expansion has been used to determine the oxygen atom geometry in three isomers of the nonamer and two isomers of the decamer. The isomers for each cluster size have the same nominal geometry but differ in the arrangement of their hydrogen bond networks. The nearest neighbor O? O distances show a characteristic pattern for each hydrogen bond network isomer that is caused by three‐body effects that produce cooperative hydrogen bonding. The observed structures are the lowest energy cluster geometries identified by quantum chemistry and the experimental and theoretical O? O distances are in good agreement. The cooperativity effects revealed by the hydrogen bond O? O distance variations are shown to be consistent with a simple model for hydrogen bonding in water that takes into account the cooperative and anticooperative bonding effects of nearby water molecules. 相似文献