Rheological properties of mixed gels made of microparticulated whey proteins and β-lactoglobulin

Microparticulated whey proteins (MWP) in suspension or included in a globular protein network revealed that the degree of flocculation was important in the final structure of the material. The MWP dispersions developed an antithixotropic character when low shear rate was applied to the system even at low temperature. Similar results were obtained on globular protein solutions and could be interpreted in terms of an orthokinetic aggregation. MWP participated to the formation and reinforcement of heat-induced β-lactoglobulin (BLG) gels. The mechanical properties of mixed gels demonstrated synergestic effects at low MWP massic fraction (BLG:MWP ratio higher than 2:1). A possible interpretation would be that both interaction of MWP with the network and flocculation of the MWP inside the pores could occur. However, increasing the fraction of MWP induced heterogeneities in the protein network. In particular, micro-phase separation due to steric hindrance effects or thermodynamic incompatibility between the two components could occur and decrease viscoelastic properties of mixed gels.     

Easy access to phosphonothioates

A new and particularly mild method for the formation of phosphorus-sulfur bonds has been achieved through base-catalyzed addition of thiocyanate to the corresponding H-phosphine oxide, phosphinate, or phosphonate. This reaction procedure offers many advantages: the use as starting material of a stable and not oxygen-sensitive phosphorus(v) species, particularly mild and nonaqueous reaction conditions and workup (a pivotal point for these sensitive phosphonothioates), and, through optimized access to thiocyanates, a wider scope of substrates. This method has been applied to achieve the synthesis of substrate analogues for the study of antibody-catalyzed hydrolysis of acetylcholinesterase inhibitor PhX (11).     

Formation of tubules and giant vesicles from large multilamellar vesicles

This study reports an observation of submicrometer multilamellar vesicles (MLVs) prepared by simply freeze-thawing a phospholipid dispersion at full hydration that transformed into giant vesicles (GVs) and tubules (TUs) when confined between microscope glass slides. Cover slide cleaning and surface treatment did not hamper the formation of GVs or TUs. However, when small unilamellar vesicles (SUV) were prepared or when MLVs were not confined but rather freely moved between the glass slides or when the phospholipid was in its gel phase, neither GVs nor TUs were observed. Altogether, our results suggested that MLVs would play a role as a lipid reservoir and that the liquid flow between the glass slides induces the peeling of the external bilayers, yielding the formation of tubules and giant unilamellar vesicles.     

Substituent Effects on Hydrogen Bonding in Watson–Crick Base Pairs. A Theoretical Study

We have theoretically analyzed Watson–Crick AT and GC base pairs in which purine C8 and/or pyrimidine C6 positions carry a substituent X = H, F, Cl or Br, using the generalized gradient approximation (GGA) of density functional theory at BP86/TZ2P. The purpose is to study the effects on structure and hydrogen bond strength if X = H is substituted by a halogen atom. Furthermore, we wish to explore the relative importance of electrostatic attraction versus orbital interaction in the above multiply hydrogen-bonded systems, using a quantitative bond energy decomposition scheme. We find that replacing X = H by a halogen atom has relatively small yet characteristic effects on hydrogen bond lengths, strengths and bonding mechanism. In general, it reduces the hydrogen-bond-accepting- and increases the hydrogen-bond-donating capabilities of a DNA base. The orbital interaction component in these hydrogen bonds is found for all substituents (X = H, F, Cl, and Br) to contribute about 41% of the attractive interactions and is thus of the same order of magnitude as the electrostatic component, which provides the remaining 59% of the attraction.     

Catalyse multifonctionnelle—VI : Isomerisation de la Δ-5 cholestenone par les melanges phenols-amines

Kinetic study of Δ-5 cholestenone isomerisation in benzene, catalysed by phenols-triethylamine mixtures indicates a transition state with a mole of phenol and a phenol-triethylamine complex. Catalytic activity of phenols-triethylamine mixtures according to versus those complexes association constants in benzene shows a clear maximum for m-nitrophenol. Besides, activation enthalpies are decreasing with phenols acidities, while activation entropies become more negative.     

Synthesis and cytotoxic and antitumor activity of 1,2-dihydroxy-1,2-dihydrobenzo[b]acronycine diacid hemiesters and carbamates

A series of cis-1,2-dihydroxy-1,2-dihydrobenzo[b]acronycine diacid hemiesters and dicarbamates were prepared by acylation of cis-1,2-dihydroxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one. The cytotoxicity of the dicarbamates depended on the steric hindrance of the esterifying groups at positions 1 and 2. Diacid hemiesters displayed significant in vitro cytotoxic activities and induced cell cycle perturbations similar to those obtained with cis-1,2-diacetoxy-1,2-dihydrobenzo[b]acronycine (S23906-1) currently under preclinical development. cis-1-Acetoxy-2-hemiglutaryloxy-1,2-dihydrobenzo[b]acronycine was the most promizing compound of the series, inducing complete inhibition of tumor growth when tested against C38 colon adenocarcinoma implanted in mice.