NMR study of C-kinetic isotope effects at C natural abundance to characterize oxidations and an enzyme-catalyzed reduction

¹³C-kinetic isotope effects (KIEs) of four cinnamyl alcohol oxidations and a xylose reductase-catalyzed cinnamyl aldehyde reduction have been determined by ¹³C NMR using competition reactions with reactants at natural ¹³C-abundance. Differences in KIEs among oxidations indicate dissimilarities between the respective hydrogen transfers. Their mechanistic implications are discussed. A low primary KIE of the enzymatic reduction is consistent with a kinetically complex mechanism in which steps other than the chemical step of hydride transfer from NADH are slow.     

Central European journal of operations research (CJOR) “operations research applied to health services (ORAHS) in Europe: general trends and ORAHS 2020 conference in Vienna,Austria”

Central European Journal of Operations Research - This articles provides a short summary of the research topics and latest research results of the European Working Group “Operations Research...     

Molecular Design in Practice: A Review of Selected Projects in a French Research Institute That Illustrates the Link between Chemical Biology and Medicinal Chemistry

Chemical biology and drug discovery are two scientific activities that pursue different goals but complement each other. The former is an interventional science that aims at understanding living systems through the modulation of its molecular components with compounds designed for this purpose. The latter is the art of designing drug candidates, i.e., molecules that act on selected molecular components of human beings and display, as a candidate treatment, the best reachable risk benefit ratio. In chemical biology, the compound is the means to understand biology, whereas in drug discovery, the compound is the goal. The toolbox they share includes biological and chemical analytic technologies, cell and whole-body imaging, and exploring the chemical space through state-of-the-art design and synthesis tools. In this article, we examine several tools shared by drug discovery and chemical biology through selected examples taken from research projects conducted in our institute in the last decade. These examples illustrate the design of chemical probes and tools to identify and validate new targets, to quantify target engagement in vitro and in vivo, to discover hits and to optimize pharmacokinetic properties with the control of compound concentration both spatially and temporally in the various biophases of a biological system.     

Optochemical Nanosensors and Subcellular Applications in Living Cells

What may be the smallest anthropogenic devices to date, spherical sensors (wireless and fiberless) with radii as small as 10?nm have been produced. This class of optochemical PEBBLE (Probe Encapsulated By Biologically Localized Embedding) sensors covers a wide range of analytes (pH, calcium, oxygen and potassium included here) with excellent spatial, temporal and chemical resolution. Examples of such sensors for the monitoring of intracellular analytes are given. Methods, such as pico-injection, liposomal delivery and gene gun bombardment, are used to inject PEBBLE sensors into single cells. These PEBBLEs have caused minimal perturbation when delivered and operated inside single mammalian cells, such as human neuroblastoma, mouse oocytes or rat alveolar macrophage.     

From heterobimetallic transition metal complexes to linear coordination polymers based on cis‐ and trans‐L2Pt(CCPh)2

The reaction of cis‐(2,2′‐bipyridine) Pt(CCPh)₂ cis‐(4,4′‐dimethyl‐2,2′‐bipyridine) Pt‐(CCPh)₂ and trans‐(Ph₃P)₂Pt(CCPh)₂ towards different group 11 transition‐metal salts [M′X] (M′ = Cu, Ag; X = inorganic ligand) to give heterobimetallic or linear oligomeric and polymeric transition metal complexes is described. Different coordination modes for M′, PhCC, PPh₃, and X were found in these species. The structural aspects as well as the preference for one coordination mode over another is discussed. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:521–533, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10097     

Preparation and Radical Oligomerization of anFe(II) Complex without Loss of Spin-Crossover Properties

 11-(4H-1,2,4-Triazol-4-yl)-undecylmethacrylate (1), a new ligand for Fe(II) spin-crossover (SCO) complexes containing a polymerizable group, was synthesized and characterized. The complex [Fe·1 ₃](BF₄)₂ (2) was obtained by reaction of 1 with Fe(BF₄)₂·6H₂O (molar ratio 1/Fe(II) = 3/1) in THF. Complex 2 showed a gradual spin-crossover between 80 and 230 K. The methacrylate units in the ligands of complex 2 could be oligomerized radically in solution (initiator: azoisobutyronitrile) without loss of the spin-crossover behaviour.     

The length of some diagonalization games

For X a separable metric space and an infinite ordinal, consider the following three games of length : In ONE chooses in inning an –cover of X; TWO responds with a . TWO wins if is an –cover of X; ONE wins otherwise. In ONE chooses in inning a subset of which has the zero function in its closure, and TWO responds with a function . TWO wins if is in the closure of ; otherwise, ONE wins. In ONE chooses in inning a dense subset of , and TWO responds with a . TWO wins if is dense in ; otherwise, ONE wins. After a brief survey we prove: 1. If is minimal such that TWO has a winning strategy in , then is additively indecomposable (Theorem 4) 2. For countable and minimal such that TWO has a winning strategy in on X, the following statements are equivalent (Theorem 9): a) TWO has a winning strategy in on . b) TWO has a winning strategy in on . 3. The Continuum Hypothesis implies that there is an uncountable set X of real numbers such that TWO has a winning strategy in on X (Theorem 10). Received: 14 February 1997     

Carbon stable isotope ratio of phloem sugars in mature pine trees throughout the growing season: comparison of two extraction methods

The study presents a comparison of two phloem sugar extraction methods. The amount of phloem sugar extracted and the carbon isotope composition (δ¹³C) of the total extracts and of the main phloem compounds separated by high‐performance liquid chromatography (sucrose, glucose, fructose and pinitol) are compared. These two phloem sap extraction methods are exudation in distilled water and a new method using centrifugation, which avoids the addition of any solvent. We applied both extraction methods on phloem discs sampled from 38‐year‐old Pinus pinaster trees in south‐western France throughout the period from June 2007 to December 2008 on different time‐scales: hourly, daily and monthly. We found that the centrifugation method systematically extracted ca. 50% less compounds from the phloem discs than the exudation method. In addition, the two extraction methods provided similar δ¹³C values of the total extracts, but the values obtained by the exudation method were 0.6‰ more negative than those calculated from the mass balance using the individual constituents. Over the growing season, both extraction methods exhibited lower total sugar content and more ¹³C‐enriched phloem sap in summer compared with winter values. These findings suggest that both extraction methods can be applied to study the carbon isotope composition of phloem sap, and the centrifugation method has the advantage that no solvent has to be added. The exudation method, however, is more appropriate for the quantification of the amounts of phloem sugars. Copyright © 2009 John Wiley & Sons, Ltd.