Antigen binding forces of single antilysozyme Fv fragments explored by atomic force microscopy

We used atomic force microscopy (AFM) to explore the antigen binding forces of individual Fv fragments of antilysozyme antibodies (Fv). To detect single molecular recognition events, genetically engineered histidine-tagged Fv fragments were coupled onto AFM tips modified with mixed self-assembled monolayers (SAMs) of nitrilotriacetic acid- and tri(ethylene glycol)-terminated alkanethiols while lysozyme (Lyso) was covalently immobilized onto mixed SAMs of carboxyl- and hydroxyl-terminated alkanethiols. The quality of the functionalization procedure was validated using X-ray photoelectron spectroscopy (surface chemical composition), AFM imaging (surface morphology in aqueous solution), and surface plasmon resonance (SPR, specific binding in aqueous solution). AFM force-distance curves recorded at a loading rate of 5000 pN/s between Fv- and Lyso-modified surfaces yielded a distribution of unbinding forces composed of integer multiples of an elementary force quantum of approximately 50 pN that we attribute to the rupture of a single antibody-antigen pair. Injection of a solution containing free Lyso caused a dramatic reduction of adhesion probability, indicating that the measured 50 pN unbinding forces are due to the specific antibody-antigen interaction. To investigate the dynamics of the interaction, force-distance curves were recorded at various loading rates. Plots of unbinding force vs log(loading rate) revealed two distinct linear regimes with ascending slopes, indicating multiple barriers were present in the energy landscape. The kinetic off-rate constant of dissociation (k(off) approximately = 1 x 10(-3) s(-1)) obtained by extrapolating the data of the low-strength regime to zero force was in the range of the k(off) estimated by SPR.     

Extension of the modified Sanderson method to ternary mixed oxides derived from hydrotalcite-like compounds and its correlation to CO2 (TPD-CO2) desorption peak maxima

A simple, intuitive and computationally non-intensive modified model, proposed first for the prediction of the catalyst basicity of binary mixed oxides, based simply on the chemical composition using the Sanderson Method was extended to ternary systems. The modification of the method allows the discrimination between the oxygen charge on different chemical environments (differences between local and global composition). TPD-CO₂ result was used to the validation between theoretical values and experimental results, letting us propose a correlation between the oxygen charge of the different clusters and the TPD-CO₂ peak maxima.     

Scaling laws in the vortex lattice model of turbulence

The lattice vortex model of the intertial range in turbulence theory is reviewed; the model consists of an array of vortex tubes whose axes coincide with the bonds on a regular lattice, subjected to random stretching and successive scaling, and constrained by conservation laws for energy, specific volume, circulation, helicity, and an energy/vorticity relation. The scaling laws for vorticity are examined in detail, a Hausdorff dimension for the active portion of the vortex array is calculated, the origin of intermittency is exhibited, and it is pointed out that the Kolmogorov — 5/3 power law already accounts for intermittency effects.Partially supported by the Office of Energy Research, U.S. Department of Energy, under contract DE-AC03-76SF0098, and in part by the Office of Naval Research under contract N00014-76-C-0316     

Odometer actions of the Heisenberg group

Let H₃(?) be the 3-dimensional real Heisenberg group. Given a family of lattices Γ₁ ? Γ₂ ? … ? H₃(?), let T be the associated uniquely ergodic H₃(?)-odometer, i.e., the inverse limit of the H₃(?)-actions by rotations on the homogeneous spaces H₃(?)/Γ_j, j ∈ ?. We describe explicitly the decomposition of the underlying Koopman unitary representation of H₃(?) into a countable direct sum of irreducible components and find the ergodic 2-fold self-joinings of T. We show that in general, the H₃(?)-odometers are neither isospectral nor spectrally determined.     

MIP models for production lot sizing problems with distribution costs and cargo arrangement

This study presents mixed integer programming (MIP) models for production lot sizing problems with distribution costs using unit load devices such as pallets and containers. Problems that integrate production lot sizing decisions and loading of the products in vehicles (bins) are also modelled, in which constraints such as weight limits, volume restrictions or the value of the cargo loaded in the bins are considered. In general, these problems involve a trade-off between production, inventory and distribution costs. Lot sizing decisions should take into account production capacity and product demand constraints. Distribution decisions are related to the loading and transport of products in unit load devices. The MIP models are solved by the branch-and-cut method of an optimization package and the results show that these approaches have the potential to address different practical situations.     

The formulation of dynamical contact problems with friction in the case of systems of rigid bodies and general discrete mechanical systems—Painlevé and Kane paradoxes revisited

The dynamics of mechanical systems with a finite number of degrees of freedom (discrete mechanical systems) is governed by the Lagrange equation which is a second-order differential equation on a Riemannian manifold (the configuration manifold). The handling of perfect (frictionless) unilateral constraints in this framework (that of Lagrange’s analytical dynamics) was undertaken by Schatzman and Moreau at the beginning of the 1980s. A mathematically sound and consistent evolution problem was obtained, paving the road for many subsequent theoretical investigations. In this general evolution problem, the only reaction force which is involved is a generalized reaction force, consistently with the virtual power philosophy of Lagrange. Surprisingly, such a general formulation was never derived in the case of frictional unilateral multibody dynamics. Instead, the paradigm of the Coulomb law applying to reaction forces in the real world is generally invoked. So far, this paradigm has only enabled to obtain a consistent evolution problem in only some very few specific examples and to suggest numerical algorithms to produce computational examples (numerical modeling). In particular, it is not clear what is the evolution problem underlying the computational examples. Moreover, some of the few specific cases in which this paradigm enables to write down a precise evolution problem are known to show paradoxes: the Painlevé paradox (indeterminacy) and the Kane paradox (increase in kinetic energy due to friction). In this paper, we follow Lagrange’s philosophy and formulate the frictional unilateral multibody dynamics in terms of the generalized reaction force and not in terms of the real-world reaction force. A general evolution problem that governs the dynamics is obtained for the first time. We prove that all the solutions are dissipative; that is, this new formulation is free of Kane paradox. We also prove that some indeterminacy of the Painlevé paradox is fixed in this formulation.     

Three‐Dimensional Control of DNA Hybridization by Orthogonal Two‐Color Two‐Photon Uncaging

We successfully introduced two‐photon‐sensitive photolabile groups ([7‐(diethylamino)coumarin‐4‐yl]methyl and p‐dialkylaminonitrobiphenyl) into DNA strands and demonstrated their suitability for three‐dimensional photorelease. To visualize the uncaging, we used a fluorescence readout based on double‐strand displacement in a hydrogel and in neurons. Orthogonal two‐photon uncaging of the two cages is possible, thus enabling complex scenarios of three‐dimensional control of hybridization with light.     

Equation of State Grid with the Quark-Meson-Coupling Model

In this work, we present the preliminary results of an equation of state (EoS) grid for possible use in core-collapse supernova simulations. We treat uniform matter made of nucleons using the quark-meson coupling (QMC) model. We show a table with a variety of thermodynamic quantities, which covers the proton fraction range Y _p = 0?0.65 with the linear grid spacing ΔY _p = 0.01 (66 points) and the density range ρ _B = 10¹⁴ ? 10¹⁶g cm^?3 with the logarithmic grid spacing Δlog₁₀(ρ _B /[g cm^?3]) = 0.1 (21 points). This preliminary study is performed at zero temperature, and our results are compared with the widely used EoS already available in the literature.     

Ultrafast Click Chemistry with Fluorosydnones

We report the synthesis and reactivity of 4‐fluorosydnones, a unique class of mesoionic dipoles displaying exquisite reactivity towards both copper‐catalyzed and strain‐promoted cycloaddition reactions with alkynes. Synthetic access to these new mesoionic compounds was granted by electrophilic fluorination of σ‐sydnone Pd^II precursors in the presence of Selectfluor. Their reactions with terminal and cyclic alkynes were found to proceed very rapidly and selectively, affording 5‐fluoro‐1,4‐pyrazoles with bimolecular rate constants up to 10⁴ m ^?1 s^?1, surpassing those documented in the literature with cycloalkynes. Kinetic studies were carried out to unravel the mechanism of the reaction, and the value of 4‐fluorosydnones was further highlighted by successful radiolabeling with [¹⁸F]Selectfluor.