Automate parallèle à homotopie près (II)

One proves that the category of globular CW-complexes up to dihomotopy is equivalent to the category of flows up to weak dihomotopy. This theorem generalizes the classical theorem which states that the category of CW-complexes up to homotopy is equivalent to the category of topological spaces up to weak homotopy. To cite this article: P. Gaucher, C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Molar extinction coefficients of some carbohydrates in aqueous solutions

Molar extinction coefficients of some carbohydrates viz. l-arabinose (C₅H₁₀O₅), d-glucose (C₆H₁₂O₆), d-mannose (C₆H₁₂O₆), d-galactose (C₆H₁₂O₆), d(-) fructose (C₆H₁₂O₆) and maltose (C₁₂H₂₄O₁₂) in aqueous solutions have been determined at 81, 356, 511, 662, 1173 and 1332 keV by gamma ray transmission method in a narrow beam good geometry set-up. These coefficients have been found to depend upon the photon energy following a 4-parameter polynomial. These extinction coefficients for different sugars having the same molecular formula have same values varying within experimental uncertainty. Within concentration ranges studied, Beer-Lambert law is obeyed very well.     

Purete radiochimique du complexe113 mIn,acide diethylene-triamino pentaacetique

The radiochemical purity of the¹¹³ mIn-DTPA complex is determined by two methods whose principle is different: filtration on ‘Sephadex” gel, and ascending paperchromatography. The two techniques give slightly different values for non-complexed indium; any way less than 5% mean value. They show that the reproducibility of the method used to prepare the compound is satisfactory.      

Determination of cake thickness and porosity during cross-flow ultrafiltration on a plane ceramic membrane surface using an electrochemical method

The thickness and the porosity of a deposit during ultrafiltration experiments are determined using an electrochemical method. Twenty microelectrodes are mounted flush to a ceramic plane membrane and maps of deposit thickness are determined for three inlet/outlet distributors configurations. Combining an electrochemical method and a step transient method, the determination of the thickness and the porosity of a particles deposit is performed. These local thickness and porosity values are analyzed thanks to wall shear stress local measurements obtained in a previous work [Sep. Sci. Technol. 37 (10) (2002) 2251]. The results emphasize the heterogeneity of the deposit thickness, especially in zones of low wall shear stress. Furthermore, the porosity values of the deposit are ranged between 0.3 and 0.8 as a function of the location at the membrane surface.     

Structural and ITC Characterization of Peptide-Protein Binding: Thermodynamic Consequences of Cyclization Constraints,a Case Study on Vascular Endothelial Growth Factor Ligands

Macrocyclization constraints are widely used in the design of protein ligands to stabilize their bioactive conformation and increase their affinities. However, the resulting changes in binding entropy can be puzzling and uncorrelated to affinity gains. Here, the thermodynamic (Isothermal Titration Calorimetry) and structural (X-ray, NMR and CD) analysis of a complete series of lactam-bridged peptide ligands of the vascular endothelial growth factor, and their unconstrained analogs are reported. It is shown that differences in thermodynamics arise mainly from the folding energy of the peptide upon binding. The systematic reduction in conformational entropy penalty due to helix pre-organization can be counterbalanced by an unfavorable vibrational entropy change if the constraints are too rigid. The gain in configurational entropy partially escapes the enthalpy/entropy compensation and leads to an improvement in affinity. The precision of the analytical ITC method makes this study a possible benchmark for constrained peptides optimization.     

High-performance liquid chromatographic separation of novel atropic alpha,alpha-disubstituted-beta-amino acids, either on different beta-cyclodextrin-bonded phases or as their 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide derivatives.

The high-performance liquid chromatographic enantioresolution of free and N- and/or C-protected derivatives of (R,S)-2',1':1,2;1",2":3,4-dinaphthcyclohepta-1,3-diene-6-aminometh yl-6- carboxylic acid (beta 2-Bin) by direct and indirect methods is reported. The direct separation was carried out on native and different derivatized beta-cyclodextrin-bonded phases. The indirect resolution was achieved by applying pre-column derivatization with 1-fluoro-2,4-dinitrophenyl-5-L-alanine amide. The effects of different parameters such as the mobile phase composition and the structures of the compounds on the enantiomeric resolution are discussed.