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131.
We have prepared an l-tyrosine derivative bearing a d-threo ketose moiety by a convenient chemoenzymatic route. This compound is of potential interest for developing stereospecific assays for enzymes catalyzing C-C bond cleavage such as transketolase. We showed in vitro by analytical studies (LC/MS and 31P NMR) that this compound can release l-tyrosine in the presence of wild type TK extract and bovine serum albumin. This assay is the first step towards a mutant TK selection test that could be developed for yeast cells auxotrophic for l-tyrosine. 相似文献
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Belinda F. Roettger Edward H. Hellen Thomas P. Burghardt Laurence J. Miller 《Journal of fluorescence》2001,11(3):237-246
Lateral movement of receptor molecules in the plane of the plasmalemma has important implications for signal transduction and receptor regulation, yet mechanisms affecting such movement are not well understood. We have studied the lateral mobility of the G protein-coupled cholecystokinin (CCK) receptor expressed in the natural milieu of the rat pancreatic acinar cell and in a model cell system, the CHO-CCKR cell, after occupation with fluorescent agonist and antagonist. Lateral diffusion characteristics were distinct in each type of cell and for receptors occupied by each type of ligand, fluorescent agonist, rhodamine-Gly-[(Nle28,31)CCK-26-33], and fluorescent antagonist, rhodamine-Gly-[(D-Trp30,Nle28,31)CCK-26-32]-phenethyl ester. Multiple states of mobility were detected for CCK receptors. The slowest population of mobile receptors on the CHO-CCKR cells moved at similar rates when occupied by both antagonist and agonist, while the faster-moving populations moved at a faster rate when occupied with antagonist than with agonist. The fastest component of mobile receptors may reflect unconstrained interactions of the antagonist-occupied receptors with signaling or anchoring structures, while the slowest component may represent the fraction of ligand-occupied receptors that ultimately undergo internalization. The intermediate mobility states may reflect receptor interactions with signal transduction and regulatory machinery. While only a single population of mobile receptors was demonstrable on the acinar cells, increased ligand concentrations (agonist and antagonist) resulted in increased percentages of mobile receptors, suggesting a stoichiometric limitation of immobilizing molecular constraints. Inhibition of protein kinase C had no significant effect on the lateral mobility of agonist-occupied CCK receptors. 相似文献
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Ashutosh A. Patwardhan Laurence A. Belfiore 《Journal of Polymer Science.Polymer Physics》1986,24(11):2473-2486
The Flory–Huggins lattice-theory expression for solvent activity in a polymer-solution is commonly used to calculate the thermodynamic interaction parameter χ with the aid of experimental data from vapor pressure osmometry. This expression assumes that χ is independent of composition. However, experimental data for a variety of polymer-solvent mixtures indicate that χ exhibits an appreciable concentration dependence. A group contribution method, UNIFAC (UNIQUAC Functional-Group Activity Coefficients) incorporating the free-volume correction of Oishi and Prausnitz is used to predict the dependence of χ on solvent concentration. Agreement with previously reported experimental data is within 15%. Calculated values of χ obtained from the Flory–Huggins expression for solvent activity and from the corresponding Gibbs free energy of mixing (which does not assume that χ is independent of composition) are compared. Calculations based on the Gibbs free energy of mixing predict a somewhat larger value of χ relative to those based on solvent activity. The specific Gibbs free energy of mixing for polystyrene-solvent mixtures is calculated using the UNIFAC model, and is found to represent qualitatively the phase equilibrium behavior. Quantitative discrepancies are observed, however, for the polystyrene-acetone system in light of the actual experimental solubility reported by Suh and Clark (20). Most of the thermodynamic predictions for polymer-solvent systems investigated herein are correlated qualitatively with the relative mismatch between solubility parameters of both components. 相似文献
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Thibault Schutz Isaure Sergent Georgette Obeid Laurence Oswald Dr. Abdelaziz Al Ouahabi Dr. Paul N. W. Baxter Dr. Jean-Louis Clément Dr. Didier Gigmes Prof. Laurence Charles Dr. Jean-François Lutz 《Angewandte Chemie (International ed. in English)》2023,62(45):e202310801
A library of phosphoramidite monomers containing a main-chain cleavable alkoxyamine and a side-chain substituent of variable molar mass (i.e. mass tag) was prepared in this work. These monomers can be used in automated solid-phase phosphoramidite chemistry and therefore incorporated periodically as spacers inside digitally-encoded poly(phosphodiester) chains. Consequently, the formed polymers contain tagged cleavable sites that guide their fragmentation in mass spectrometry sequencing and enhance their digital readability. The spacers were all prepared via a seven steps synthetic procedure. They were afterwards tested for the synthesis and sequencing of model digital polymers. Uniform digitally-encoded polymers were obtained as major species in all cases, even though some minor defects were sometimes detected. Furthermore, the polymers were decoded in pseudo-MS3 conditions, thus confirming the reliability and versatility of the spacers library. 相似文献
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Absorbing boundary conditions have been developed for various types of problems to truncate infinite domains in order to perform computations. But absorbing boundary conditions have a second, recent and important application: parallel computing. We show that absorbing boundary conditions are essential for a good performance of the Schwarz waveform relaxation algorithm applied to the wave equation. In turn this application gives the idea of introducing a layer close to the truncation boundary which leads to a new way of optimizing absorbing boundary conditions for truncating domains. We optimize the conditions in the case of straight boundaries and illustrate our analysis with numerical experiments both for truncating domains and the Schwarz waveform relaxation algorithm.