Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.     

Temperature‐Modulated Water Filtration Using Microgel‐Functionalized Hollow‐Fiber Membranes

In the present work, we investigate the potential of aqueous polymer microgels in membrane technology, especially for filtration applications. The poly(N‐vinylcaprolactam)‐based microgels exhibit thermoresponsive behavior and were employed to coat hollow‐fiber membranes used for micro‐ and ultrafiltration. We discuss the preparation of microgel‐modified membranes (by “inside‐out” as well as “outside‐in” filtration in dead‐end mode). The clean‐water permeability and stability of these membranes was studied not only as a function of time, but also of temperature. The microgel‐modified membranes exhibit a reversible thermoresponsive behavior whereby both the resistance and the retention increased with decreasing temperature.     

A primitive model for hexamethylpararosaniline (crystal violet) monomolecular adlayer: a Monte Carlo simulation study

The NVT Monte Carlo simulation results are reported for a model of two-dimensional (2D) chemically associating fluid with six attractive sites per monomer disc. Three of these sites are of the type α and the other three of the type β. The sites α and β are fixed inside a hard core, they follow each other anticlockwise, with a `valence' angle of 60°. It is assumed that only α+β site–site association of two different discs occurs. Complex formation, dependent on the density and association energy, is much more sophisticated, in comparison to previously studied models of dimerizing and polymerizing discs. An analysis of complexes in terms of the fractions of singly, doubly,…, hexa-bonded particles is performed, and the dimensions and distributions of complexes are studied. We obtained the pair distribution functions of particles and structure factor in the fluid layer. The model was inspired by experiments on visualization of organic monolayers in the framework of scanning tunneling microscopy (STM). Currently it yields a preliminary insight into the molecular organization of crystal violet molecules on the iodine covered (111) single-crystal surface plane observed experimentally. Extensions of the model and methodology are discussed.     

Prognostic relevance of AgNORs in tumor pathology

The importance of the analysis of the silver-stained nucleolar organizer regions (AgNORs) for prognostic purposes in tumor pathology has been reviewed. Current available data from the literature demonstrate that the evaluation of the quantity of interphase AgNORs is an independent prognostic factor in several types of human tumors. Results of our investigations indicate that AgNORs are the most powerful variable predicting survival in patients with pharyngeal carcinoma, multiple myeloma, male breast and prostate carcinoma. The combination of AgNOR counts and histologic pattern allows the stratification of patients with multiple myeloma, pharyngeal and prostate carcinoma into low- and high-risk groups, which could benefit from different therapy. Moreover, AgNOR analysis predicts response to treatment in adult patients with acute myelogenous leukemia, and appears as an independent prognostic factor in a prospective study on renal cell carcinoma. Therefore, AgNOR analysis is a really important prognostic factor for several human neoplasias. The experimental and theoretical justifications for AgNORs as a prognostic factor are also reviewed, in particular the strict correlation between AgNOR quantity and tumor cell doubling time. Lastly, the lack of prognostic significance of AgNOR analysis in some circumstances is critically discussed.     

A universal matrix-assisted laser desorption/ionization cleavable cross-linker for protein structure analysis

The concept of protein cross-linking in combination with mass spectrometry holds great promise to derive structural information on protein conformation and protein-protein interactions. We recently presented a dissociative amine-reactive cross-linker (NHS-BuUrBu-NHS) that is shown herein to be universally applicable to protein structure analysis under matrix-assisted laser desorption/ionization tandem mass spectrometric (MALDI-MS/MS) conditions, based on the examples of the peptides substance P, luteinizing hormone releasing hormone (LHRH), and the 32-kDa ligand-binding domain of peroxisome proliferator-activated receptor alpha (PPARα). The characteristic fragment ion patterns and constant neutral losses of the cross-linker greatly simplify the identification of different cross-linked species from complex mixtures and drastically reduce the potential of identifying false-positive cross-links. Therefore, this cross-linker holds an enormous potential for deriving structural information of proteins and protein complexes in a highly automated fashion.     

Synthesis and mass cytometric analysis of lanthanide-encoded polyelectrolyte microgels

This article describes the synthesis and characterization of two series of functional polyelectrolyte copolymer microgels intended for bioassays based upon mass cytometry, a technique that detects metals by inductively coupled plasma mass spectrometry (ICP-MS). The microgels were loaded with Eu(III) ions, which were then converted in situ to EuF(3) nanoparticles (NPs). Both types of microgels are based upon copolymers of N-isopropylacrylamide (NIPAm) and methacrylic acid (MAA), poly(NIPAm/VCL/MAA) (VCL = N-vinylcaprolactam, V series), and poly(NIPAm/MAA/PEGMA) (PEGMA = poly(ethylene glycol)methacrylate, PG series). Very specific conditions (full neutralization of the MAA groups) were required to confine the EuF(3) NPs to the core of the microgels. We used mass cytometry to measure the number and the particle-to-particle variation of Eu ions per microgel. By controlling the amount of EuCl(3) added to the neutralized microgels. we could vary the atomic content of individual microgels from ca. 10(6) to 10(7) Eu atoms, either in the form of Eu(3+) ions or EuF(3) NPs. Leaching profiles of Eu ions from the hybrid microgels were measured by traditional ICP-MS.     

Catenation control in the two-dimensional coordination polymers based on tritopic carboxylate linkers and azamacrocyclic nickel(II) complexes

Four new coordination polymer frameworks, namely [(NiL(1))(3)(BTB)(2)]·6H(2)O, [(NiL(2))(3)(BTB)(2)]·6H(2)O, [(NiL(3))(3)(BTB)(2)]·6H(2)O and [(NiL(2))(3)(BTC)(2)]·10.25H(2)O (L(1) = 1,4,8,11-tetraazacyclotetradecane, L(2) = 3-methyl-1,3,5,8,12-pentaazacyclotetradecane, L(3) = 3,10-dimethyl-1,3,5,8,10,12-hexaazacyclotetradecane, BTC(3-) = benzene-1,3,5-tricarboxylate, BTB(3-) = 4,4',4'-benzene-1,3,5-triyl-tribenzoate) were prepared in water-N,N-dimethylformamide solutions. The molecular and crystal structures of these compounds are compared to the related coordination polymers formed by nickel(II) macrocyclic cations to examine the effect of carboxylate linker size on the framework architecture. Luminescent properties of the complexes based on the BTB(3-) bridging ligand are also discussed.     

Effective interaction between two giant spheres suspended in a size polydisperse hard-sphere fluid

Analytic expressions for the Laplace transform of the interaction energy and force between two exceedingly large hard spheres at infinite dilution in a polydisperse hard-sphere suspending fluid are presented. The equations are based on the Percus–Yevick approximation for the many-component suspending fluid, supplemented by the hypernetted chain approximation for the correlation function of the suspended spheres. By applying the Derjaguin approximation, the energy and force results for two spheres are related to the energy per unit area and the disjoining pressure between two flat walls suspended in a polydisperse fluid. Numerical results for the representative Schultz distributions of the diameters of the species comprising the suspending fluid are presented and discussed.     

Crystal and electronic structures of La2LiGe6−x (x = 0.21) and La2LiGe4Si2

The synthesis and characterization of a new ternary dilanthanum lithium hexagermanide, La₂LiGe_6−x (x = 0.21), belonging to the Pr₂LiGe₆ structure type, and a quaternary dilanthanum lithium tetragermanium disilicide, La₂LiGe₄Si₂, which crystallizes as an ordered variant of this type, are reported. In both structures, Li is on a site of mmm symmetry. All other atoms are on sites of m2m symmetry. These structures are new representatives of a homologous linear structure series based on structural fragments of the AlB₂, CaF₂ and ZrSi₂ structure types. The observed 17‐vertex polyhedra are typical for La atoms and the environment of the Li atom is cubic. Two Ge atoms are enclosed in a tetragonal prism with one added atom (nine‐vertex polyhedron). The trigonal prismatic coordination is typical for Ge or Si atoms. The metallic nature of the bonding is indicated by the interatomic distances and electronic structure calculations.     

On the role of the reference system in perturbation theory: An augmented van der Waals theory of simple fluids

In this study, we show that the inclusion of a short-range part of the total attractive interaction into a reference system allows a natural extension of the traditional first-order perturbation theory of simple fluids to practically all thermodynamic states. This theory is applied to the thermodynamic functions and the liquid–vapor coexistence curve of the Lennard-Jones-like medium range Yukawa fluid and to the Sutherland fluid. Comparison with computer simulation data and the second-order Barker–Henderson perturbation theory is discussed.