New difference sets in nonabelian groups of order 100

In two groups of order 100 new difference sets are constructed. The existence of a difference set in one of them has not been known. The correspondence between a (100, 45, 20) symmetric design having regular automorphism group and a difference set with the same parameters has been used for the construction. © 2001 John Wiley & Sons, Inc. J Combin Designs 9: 424–434, 2001     

Radiation‐grafted ion‐exchange membranes: Influence of the initial matrix on the synthesis and structure

A series of commercial fluoropolymer films was irradiated with an electron beam, grafted with styrene, and sulfonated. The influence of the initial fluoropolymer on the grafting yields and the properties of the grafted and sulfonated membranes were investigated. The same synthesis procedure can be followed for most fluoropolymers and samples with a similar degree of grafting, and a homogenous polystyrene distribution can be prepared by varying the absorbed dose. The main difference among different fluoropolymer‐based membranes is the water uptake from liquid water that has a roughly linear dependence on the crystallinity of the sample. The more amorphous the initial material, the greater the water uptake. Mechanical properties of the membranes at 50% relative humidity differ less than those of the starting materials and are comparable to those of Nafion® 105. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3008–3017, 2001     

Two isomorphous benzene­sulfon­amide crystal structures determined by intermolecular C—H⃛O,C—H⃛π and C—H⃛Cl interactions

The title compounds, N‐[5‐(4‐chloro­phenyl)­furan‐2‐yl­methyl]‐4‐methyl‐N‐(prop‐2‐ynyl)­benzene­sulfon­amide, (Ia), and N‐[5‐(2‐chloro­phenyl)­furan‐2‐yl­methyl]‐4‐methyl‐N‐(prop‐2‐ynyl)­benzene­sulfon­amide, (Ib), both C₂₁H₁₈ClNO₃S, have isomorphous crystal structures. The crystal packing is mainly determined by intermolecular C—H?O and C—H?π interactions. These interactions are very similar in (Ia) and (Ib). Additional intermolecular C—H?Cl interactions appear less important and are different in (Ia) and (Ib). The different positions of the Cl atoms result in small variations of the crystal packing of the two compounds.     

Nanoparticles from vesicle polymerization: Characterization and kinetic study

The polymerization of isodecyl acrylate (ISODAC) in vesicles made from an anionic surfactant—sodium di-2-ethylhexyl phosphate (SEHP)—and from water is studied by ¹H-NMR, transmission electron microscopy, and quasielastic light scattering. High polymerization rates and high conversion rates are achieved with both water-soluble initiator, K₂S₂O₈ (potassium persulfate), and oil-soluble initiator, AIBN (azoisobisbutyronitrile). ISODAC is probably located inside the vesicle bilayer(s) because of its high hydrophobicity. Particles stable at room temperature with a mean diameter of about 50 nm are obtained. Kinetic orders of ISODAC polymerization are determined and the characterization of the resulting particles during and after polymerization are studied. © 1996 John Wiley & Sons, Inc.     

Reactions of GeCl2 with the Thiolate LiSC(SiMe3)3: From thf Activation to Insertion of GeCl2 Molecules into C−S Bonds

The reaction system GeCl₂ ⋅ dioxane/LiSTsi (Tsi=C(SiMe₃)₃) opens a fruitful area in germanium chemistry, depending on the stoichiometry and solvent used during the reaction. For example, the reaction of GeCl₂ ⋅ dioxane in toluene with two equivalents of the thiolate gives the expected germylene Ge(STsi)₂ in excellent yield. This germylene readily reacts with hydrogen and acetylene, however, in a non-selective way. By using an excess amount of the thiolate and toluene as the solvent, the germanide [Ge(STsi)₃][Li(thf)] is obtained. Performing the same reaction in thf leads to a C−H activation of thf to give (H₇C₄O)Ge[STsi](μ²-S)₂Ge[STsi]₂, in which the thf molecule is still intact. Using a sub-stoichiometric amount of the thiolate leads to the heteroleptic compound [ClGe(STsi)]₂ and to the insertion product (thf)Ge[S-GeCl₂-Tsi]₂, in which additional GeCl₂ molecules insert into the C−S bonds of Ge(STsi)₂. The synthesis and the experimentally determined structures of all compounds are presented together with first reactivity studies of Ge(STsi)₂.     

Similarities and Differences between Crystal and Enzyme Environmental Effects on the Electron Density of Drug Molecules

The crystal interaction density is generally assumed to be a suitable measure of the polarization of a low-molecular weight ligand inside an enzyme, but this approximation has seldomly been tested and has never been quantified before. In this study, we compare the crystal interaction density and the interaction electrostatic potential for a model compound of loxistatin acid (E64c) with those inside cathepsin B, in solution, and in vacuum. We apply QM/MM calculations and experimental quantum crystallography to show that the crystal interaction density is indeed very similar to the enzyme interaction density. Less than 0.1 e are shifted between these two environments in total. However, this difference has non-negligible consequences for derived properties.     

Cacaoidin,First Member of the New Lanthidin RiPP Family

Lantibiotics are ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by the presence of lanthionine or methyllanthionine rings and their antimicrobial activity. Cacaoidin, a novel glycosylated lantibiotic, was isolated from a Streptomyces cacaoi strain and fully characterized by NMR, mass spectrometry, chemical derivatization approaches and genome analysis. The new molecule combines outstanding structural features, such as a high number of d -amino acids, an uncommon glycosylated tyrosine residue and an unprecedented N,N-dimethyl lanthionine. This latter feature places cacaoidin within a new RiPP family located between lanthipeptides and linaridins, here termed lanthidins. Cacaoidin displayed potent antibacterial activity against Gram-positive pathogens including Clostridium difficile. The biosynthetic gene cluster showed low homology with those of other known lanthipeptides or linaridins, suggesting a new RiPP biosynthetic pathway.     

Analytical Uncertainty in Modern Quantitative TLC

JPC – Journal of Planar Chromatography – Modern TLC - Experiments and calculations show the importance of analytical management to reliable analytical results. A method with a...     

Glass formation in the Sb2O3-ZnBr2 binary system

Glass formation has been investigated in the Sb₂O₃-ZnBr₂ binary system. Vitreous samples have been obtained for batches containing 20-90 mol% Sb₂O₃. Chemical analysis shows that bromine concentration is smaller than expected and real compositions belong to the Sb₂O₃-ZnBr₂-ZnO ternary system. However, the discrepancy between nominal and analyzed compositions is fair for Sb₂O₃ content larger than 50 mol%. Optical transmission lies between 400 nm and 7 μm and refractive index ranges from 2.0 to 2.1. Glass transition occurs around 300 °C, and crystallization exotherm does not appear in the differential scanning calorimetry scan at 10 K s⁻¹ for samples containing 50-60 mol% Sb₂O₃. Thermal expansion varies between 120 and 220×10⁻⁷ K⁻¹ as antimony content decreases. Microhardness is close to 200 kg/mm². These glasses have low phonon energy and make potential materials for infrared transmission and active fibers.     

Colloids for Catalysts: A Concept for the Preparation of Superior Catalysts of Industrial Relevance

Compared to conventional preparation methods for supported heterogeneous catalysts, the use of colloidal nanoparticles (NPs) allows for a precise control over size, size distribution, and distribution/location of the NPs on the support. However, common colloidal syntheses have restrictions that limit their applicability for industrial catalyst preparation. We present a simple, surfactant‐free, and scalable preparation method for colloidal NPs to overcome these restrictions. We demonstrate how precious‐metal NPs are prepared in alkaline methanol, how the particle size can be tuned, and how supported catalysts are obtained. The potential of these colloids in the preparation of improved catalysts is demonstrated by two examples from heterogeneous catalysis and electrocatalysis.