Multiple nucleosome positioning with unique rotational phasing on multimers of the light-responsive elements of pea rbcS-3A and rbcS-3.6 genes: comparison between experimental and theoretical mapping

Nucleosome positioning along two DNA tracts, corresponding to tetramers of the light-responsive elements of pea rbcS-3A and rbcS-3.6 genes, were studied by experimental (exonuclease III mapping and band shift electrophoresis) as well as theoretical methods. Multiple nucleosome positioning with unique rotational phase was derived from both methods in satisfactorily good agreement, if nucleosome dyad axis positions are considered. Theoretical and experimental distributions of nucleosome frequencies appear different, probably on account of DNA sequence dependent digestion kinetics of exonuclease III.     

Hypoantigenic (HA) milk formula and blood cholesterol level in infants at 3 months of age

A preliminary observation is reported concerning total and high-density lipoprotein blood cholesterol levels in 36 infants at 3 months of age fed with a hypoantigenic milk formula. The values are compared with those of 66 breastfed and 76 conventional formula-fed infants. Total and high-density lipoprotein-cholesterol levels in hypoantigenic formula-fed infants (152 and 65.7 mg dl(-1), respectively) were comparable to those of breastfed infants (148 and 61.8 mg dl(-1)) and significantly (p < 0.05) higher than those of conventional formula-fed infants (130 and 42.5 mg dl(-1)).     

Fate of solvents in the non-catalytic depolymerization of Kentucky bituminous coal

To study the fate of the solvents in the non-catalytic liquefaction of Kentucky bituminous coal, a number of batch liquefaction experiments have been carried out using hydrophenanthrenes and coal-derived hydrogenated recycle solvents. Filtrates from the first runs have been rehydrogenated and used as solvents for additional liquefaction experiments. The reactions have been followed by detailed analysis of the feeds and products.At constant temperature and reaction time, the conversion levels are affected by the amount of transferable hydrogen, H_s (up to a value of about 0.6 wt.% of the feed), by the coal concentration and, to a lesser extent, by the pressurizing gas.The solvents are depleted by isomerization, cracking, and adduction-polymerization reactions. Only about 50% of the initial solvent is available for use in the second-pass runs. In addition, the quality of the second-pass solvents is lower than that of the initial solvents due to a decrease of 6-membered hydroaromatic rings and an increase of 5-membered hydroaromatic rings which are poor hydrogen donors.     

Two distinct and independent sites on IL-6 trigger gp 130 dimer formation and signalling

The helical cytokine interleukin (IL) 6 and its specific binding subunit IL-6R alpha form a 1:1 complex which, by promoting homodimerization of the signalling subunit gp130 on the surface of target cells, triggers intracellular responses. We expressed differently tagged forms of gp130 and used them in solution-phase binding assays to show that the soluble extracellular domains of gp130 undergo dimerization in the absence of membranes. In vitro receptor assembly reactions were also performed in the presence of two sets of IL-6 variants carrying amino acid substitutions in two distinct areas of the cytokine surface (site 2, comprising exposed residues in the A and C helices, and site 3, in the terminal part of the CD loop). The binding affinity to IL-6R alpha of these variants is normal but their biological activity is poor or absent. We demonstrate here that both the site 2 and site 3 IL-6 variants complexed with IL-6R alpha bind a single gp130 molecule but are unable to dimerize it, whereas the combined site 2/3 variants lose the ability to interact with gp130. The binding properties of these variants in vitro, and the result of using a neutralizing monoclonal antibody directed against site 3, lead to the conclusion that gp130 dimer is formed through direct binding at two independent and differently oriented sites on IL-6. Immunoprecipitation experiments further reveal that the fully assembled receptor complex is composed of two IL-6, two IL-6R alpha and two gp130 molecules. We propose here a model representing the IL-6 receptor complex as hexameric, which might be common to other helical cytokines.     

Analogies between Kirchhoff plates and Saint-Venant beams under torsion

Torsion of linearly elastic homogeneous and orthotropic Saint-Venant beams is based on the solution of a Neumann-like boundary value problem for the cross-sectional warping. Equivalence of differential conditions of elastic equilibrium for the beam twist stresses in terms of warping function and for the bending-twisting moments in a Kirchhoff plate is assessed. The analogy provides new exact solutions in the theory of thin plates. Examples are developed for composite plates with no kinematic boundary constraints. Elliptic and equilateral triangle shapes provide useful benchmarks for computational mechanics.