Summary If the passage time of the edges of the d lattice are stationary, ergodic and have finite moment of orderp>d, then a.s. the set of vertices that can be reached within timet, has an asymptotic shape ast. 相似文献
The recent development of an automated surface plasmon resonance technology for the measurement of biomolecular interactions (Pharmacia BIAcore) has provided new opportunities for the detection and analysis of protein-protein interactions. In the BIAcore, detection is based on changes in surface plasmon resonance which are monitored optically. Changes in surface plasmon resonance correspond to changes in surface concentration of macromolecules and can be monitored in real time.
We have found that the detection sensitivity obtainable with this technology (ng/ml concentrations of specific ligands are readily detectable for many applications) is complementary “in a bidirectional manner” to micropreparative HPLC. Thus micropreparative HPLC may be used to purify and characterise reagents for the biosensor, whilst the biosensor may be used to define chromatographic parameters such as elution conditions for affinity chromatography or serve as an affinity detector for fractions obtained during chromatographic purification.
Examples of such applications, including the potential of the biosensor to search for and monitor the purification of unknown ligands for which the target molecule has been identified, are shown. In particular, the use of the biosensor to monitor the purification of soluble epidermal growth factor receptor from A431 cell conditioned media is demonstrated. 相似文献
Isomerization of Protonated Aldehyde and Ketone Ions in the Mass-Spectrography Before the Loss of Water In mass spectrometry, protonated aldehyde and ketone ions isomerize before the loss of a molecule of water. In order to specify this process, the spectra of deuterium labelled protonated aldehydes and ketones have been compared to the spectra of the corresponding isomer ions. 相似文献
The preparation of the disaccharide 4 - O - (3,4 - di - O - acetyl - 2,6 - dideoxy - α - l - lyxo - hexopyranosyl) - 2, 3,6 - trideoxy - 3 - trifluoroacetamido - l - lyxo - hexopyranose, 11c, the N,N' - dimethyl derivative of which occurs naturally in numerous anthracyclines, is described. Glycosidation with daunomycinone followed by removal of the protecting groups led to 4' - O - (2 - deoxy - l - fucosyl) daunorubicine. 相似文献
A method is presented for screening immobilized dyes applicable to the purification of enzymes from haemolysate (haemolysate can be considered as a nearly pure solution of haemoglobin containing only marginal amounts of enzymes). Haemolysate is loaded on immobilized dye mini-columns until haemoglobin and the studied enzymes are found in the column eluate at the same concentrations as those present in the haemolysate. Such a frontal mode of screening allows those dyes to be selected which, displaying a higher affinity for the enzyme of interest than for haemoglobin, can be used to displace the unwanted protein (haemoglobin) from the column by the enzyme of interest (present at a much lower concentration). 相似文献
The fraction b.p. ≦ 84° (0.001 Torr) from Burley tobacco condensate was carefully investigated using fractional distillation and preparative column and gas liquid chromatography aided by GLC/MS coupling. Among the 193 compounds thus separated and characterized by their spectral data, 81 were newly identified tobacco constituents. Most of the compounds isolated in the course of this work display flavouring properties which make them highly suitable for improving the flavour and aroma of tobacco and tobacco smoke. 相似文献
We have synthesized (±)-loliolide ( 7 a ), (±)-actinidiolide ( 11 a ), (±)-dihydroactinidiolide ( 16 ), and (±)-isodihydroactinidiolide ( 18 ) through various reaction paths starting from homosafranic acid ( 4 a ). Thus, (±)-actinidiolide has been synthesized for the first time, and this result allows to discard the alternative formula 11 b for that compound [2]. By investigation of the sensitized photooxygenation of methyl homosafranate ( 4 b ), this reaction is shown to lead to an interesting spiro-peroxylactone 25 , beside the expected endo-peroxide 23 . Specific oxygenation of the tetrasubstituted double bond of methyl homosafranate, and cyclisation of the hydroperoxide 24 thus produced, are believed to account for the formation of such a particular compound. The base-catalysed rearrangement of the endo-peroxide 23 gives rise to two compounds, one being the expected keto-hydroxy-ester 26 . The other - to which is assigned the glycidic ester structure 27 - obviously results from an internal displacement reaction on oxygen in 23 . It is note-worthy that the sensitized photooxygenation of methyl homosafranate proceeds directly to the same glycidic ester when it is carried out in an alcaline solution. 相似文献
Large area excimer laser induced deposition of titanium on fused silica from TiCl4 is studied with an emphasis on process modeling. We show that several TiCl4 monolayers can be adsorbed if the surface is adequately prepared and that the Ti thin film growth occurs through the photodecomposition of this adsorbed TiCl4 layer. We propose two growth regimes. During an initiation phase, up to 3 nm in thickness, the adsorbed layer is photochemically decomposed giving a growth rate of 0.015 nm/pulse. In a second phase, the deposition rate increases to between 2 and 7 nm/pulse due to the laser heating of the preceding photochemically deposited titanium film. Between consecutive pulses, TiCl4 molecules primarily from the adsorbed layer diffuse to the reaction zone leading to a new adsorbed layer ready to be transformed to solid titanium. 相似文献
7Li, 31P, and 19F solid-state nuclear magnetic resonance (NMR) spectroscopy was used to investigate the local arrangement of oxygen and fluorine in LiVPO4F1-yOy materials, interesting as positive electrode materials for Li-ion batteries. From the evolution of the 1D spectra versus y, 2D 7Li radiofrequency-driven recoupling (RFDR) experiments combined, and a tentative signal assignment based on density functional theory (DFT) calculations, it appears that F and O are not randomly dispersed on the bridging X position between two X–VO4–X octahedra (X = O or F) but tend to segregate at a local scale. Using DFT calculations, we analyzed the impact of the different local environments on the local electronic structure. Depending on the nature of the VO4X2 environments, vanadium ions are either in the +III or in the +IV oxidation state and can exhibit different distributions of their unpaired electron(s) on the d orbitals. Based on those different local electronic structures and on the computed Fermi contact shifts, we discuss the impact on the spin transfer mechanism on adjacent nuclei and propose tentative signal assignments. The O/F clustering tendency is discussed in relation with the formation of short VIVO vanadyl bonds with a very specific electronic structure and possible cooperative effect along the chain. 相似文献