Synthesis of unnatural 3′-phospha-2′-deoxyfuranose nucleoside analogues

This Letter describes the synthesis of racemic analogues of unnatural 2′-deoxy nucleoside with a phosphorus atom replacing the carbon atom in the 3′-position. A seven-step sequence was developed in racemic series to afford unnatural 3′-phospha-2′-deoxyfuranose nucleosides. The phospha nucleoside analogues were tested against HCV, but did not show any antiviral activity at a 10 μM maximum concentration used for the inhibition assays of analogues 2-T, 2-C and 4-Tα.     

Diastereoselective Michael addition of 2H-2-oxo-1,4,2-oxaza phosphinanes to olefins

Diastereoselective Michael additions of 2-hydrogeno-2-oxo-1,4,2-oxazaphosphinanes to olefins were described. Phosphinopeptide compounds were obtained in very good yield (up to 90%) and diasteromeric excesses ranging from 26 to 78%.     

A General Duality Scheme for Nonconvex Minimization Problems with a Strict Inequality Constraint

We establish a duality formula for the problem Minimize f(x)+g(x) for h(x)+k(x)<0 where g, k are extended-real-valued convex functions and f, h belong to the class of functions that can be written as the lower envelope of an arbitrary family of convex functions. Applications in d.c. and Lipschitzian optimization are given.     

Calculus rules for global approximate minima and applications to approximate subdifferential calculus

We provide calculus rules for global approximate minima concerning usual operations on functions. The formulas we obtain are then applied to approximate subdifferential calculus. In this way, new results are presented, for example on the approximate subdifferential of a deconvolution, or on the subdifferential of an upper envelope of convex functions.     

Zero Duality Gap for Convex Programs: A Generalization of the Clark–Duffin Theorem

This article uses classical notions of convex analysis over Euclidean spaces, like Gale & Klee’s boundary rays and asymptotes of a convex set, or the inner aperture directions defined by Larman and Brøndsted for the same class of sets, to provide a generalization of the Clark–Duffin Theorem. On this ground, we are able to characterize objective functions and, respectively, feasible sets for which the duality gap is always zero, regardless of the value of the constraints and, respectively, of the objective function.     

Spring constants and adhesive properties of native bacterial biofilm cells measured by atomic force microscopy

Bacterial biofilms were imaged by atomic force microscopy (AFM), and their elasticity and adhesion to the AFM tip were determined from a series of tip extension and retraction cycles. Though the five bacterial strains studied included both Gram-negative and -positive bacteria and both environmental and laboratory strains, all formed simple biofilms on glass surfaces. Cellular spring constants, determined from the extension portion of the force cycle, varied between 0.16+/-0.01 and 0.41+/-0.01 N/m, where larger spring constants were measured for Gram-positive cells than for Gram-negative cells. The nonlinear regime in the extension curve depended upon the biomolecules on the cell surface: the extension curves for the smooth Gram-negative bacterial strains with the longest lipopolysaccharides on their surface had a larger nonlinear region than the rough bacterial strain with shorter lipopolysaccharides on the surface. Adhesive forces between the retracting silicon nitride tip and the cells varied between cell types in terms of the force components, the distance components, and the number of adhesion events. The Gram-negative cells' adhesion to the tip showed the longest distance components, sometimes more than 1 microm, whereas the shortest distance adhesion events were measured between the two Gram-positive cell types and the tip. Fixation of free-swimming planktonic cells by NHS and EDC perturbed both the elasticity and the adhesive properties of the cells. Here we consider the biochemical meaning of the measured physical properties of simple biofilms and implications to the colonization of surfaces in the first stages of biofilm formation.