Effect of molecular weight on the capillary absorption of polymer droplets

We study capillary absorption of small polymer droplets into nonwettable capillaries using coarse-grained molecular dynamics simulations and a simple analytical model. Studies of droplets of simple fluids have revealed that the capillary process depends on the ratio of tube-to-droplet radii [Willmott Faraday Discuss., 2010, 146, 233; Marmur J. Colloid Interface Sci. 1988, 122, 209]. Here we consider the absorption of droplets of polymers and study the effect of polymer chain length on the capillary absorption process. Our simulations reveal that for droplets of the same size (radius), the critical tube radius, below which there is no absorption, increases with the length of the polymer chains that constitute the droplets. We propose a model to explain this effect, which incorporates an entropic penalty for polymer confinement and find that this model agrees quantitatively with the simulations. We also find that the absorption dynamics is sensitive to the polymer chain length. In some cases during the capillary uptake transient partial absorption states, where the droplet is partially in and partially out of the tube, were observed. Such dynamics cannot be explained by a generalized Lucas-Washburn approach.     

The synthesis of active and stable diaminopimelate analogues of the lantibiotic peptide lactocin S

Lantibiotic peptides are potent antimicrobial compounds produced by Gram-positive bacteria. They can be used in food preservation, and some also show potential for clinical applications. Unfortunately, some of these peptides can be susceptible to inactivation by oxidation of the sulfur-containing amino acid lanthionine, limiting their use. Here we describe the synthesis and testing of diaminopimelate analogues of the lantibiotic lactocin S. These analogues were designed to improve the oxidative stability of the peptide by replacing the sulfur in lanthionine with a methylene unit. Lanthionine was systematically replaced with diaminopimelate during solid-phase peptide synthesis to produce several analogues. One analogue, A-DAP lactocin S, was found to retain full biological activity in addition to displaying increased stability. This is the first time a synthetic lanthionine ring analogue of a lantibiotic has retained natural activity levels. This methodology is potentially very promising for use in producing more stable, medically relevant lantibiotics.     

A one-pot sulfide to sulfone oxidation with m-chloroperoxybenzoic acid and sodium permanganate

A synthetic strategy towards [2-(1H-indol-5-yl)-6-morpholin-4-ylpyrimidin-4-yl]methylsulfones is described, utilising m-chloroperoxybenzoic acid and sodium permanganate in a one-pot sulfide-sulfone oxidation.     

Discrete Morse Theoretic Algorithms for Computing Homology of Complexes and Maps

We provide explicit and efficient reduction algorithms based on discrete Morse theory to simplify homology computation for a very general class of complexes. A set-valued map of top-dimensional cells between such complexes is a natural discrete approximation of an underlying (and possibly unknown) continuous function, especially when the evaluation of that function is subject to measurement errors. We introduce a new Morse theoretic preprocessing framework for deriving chain maps from such set-valued maps, and hence provide an effective scheme for computing the morphism induced on homology by the approximated continuous function.     

Semisimple types for p-adic classical groups

We construct, for any symplectic, unitary or special orthogonal group over a locally compact nonarchimedean local field of odd residual characteristic, a type for each Bernstein component of the category of smooth representations, using Bushnell–Kutzko’s theory of covers. Moreover, for a component corresponding to a cuspidal representation of a maximal Levi subgroup, we prove that the Hecke algebra is either abelian, or a generic Hecke algebra on an infinite dihedral group, with parameters which are, at least in principle, computable via results of Lusztig. In an appendix, we make a correction to the proof of a result of the second author: that every irreducible cuspidal representation of a classical group as considered here is irreducibly compactly-induced from a type.     

Stereoselective synthesis of chiral β-disubstituted-β-amino acid derivatives using Pd/In transmetallation cascade processes

A new, highly efficient synthesis of chiral β^2,3-disubstituted-β-amino acid derivatives has been developed, based on an allylation procedure employing allene and a catalytic Pd/In bimetallic process.     

Absorption Spectra of Lanthanide Complexes in Solution

Abstract

The 4f electrons of lanthanides yield three types of transitions: (i) Internal 4f-4f transitions which give rise to sharp, narrow bands of comparatively weak intensities which are Laporte forbidden. (ii) Allowed 4fⁿ?4f^n-1 (n – l)d, which are relatively broad and intense. (iii) Broad and often intense 4fⁿ?λ^?1 fⁿ⁺¹ electron transfer bands generally occurring in the ultraviolet region (λ^? represents a hole in the orbital concentratedmainly on the ligands).