Hydrohysteretic Phenomena of “Extremely Diluted Solutions” Induced by Mechanical Treatments: A Calorimetric and Conductometric Study at 25 <Superscript>∘</Superscript>C

The purpose of this study was to obtain information about the influence of successive dilutions and succussions (violent shaking) on the structure of water. “Extremely diluted solutions” (EDS) are solutions obtained through the iteration of two processes: 1:100 dilution and succussion. Those two processes are repeated until extreme dilutions are reached, so that the chemical composition of the end solution is identical to that of the solvent. We measured the heats of mixing and the electrical conductivity of basic solutions of such EDS, and compared these results with the analogous heats of mixing and electrical conductivity of the untreated solvent. The measurements were carried out as a function of the age of the samples. We found some relevant exothermic excess heat of mixing, and higher electrical conductivity than those of the untreated solvent, also in function of time. The measurements show a good linear correlation between the two independent physico-chemical quantities, implying a single cause for this behavior of the extremely diluted solutions. The slopes of the linear correlation depend on the age of the EDS. Such a phenomenon could result from a variation of the shape of molecular aggregates that characterize the two different supramolecular structures of the water of different ages. This behavior could provide important support for understanding the nature of the phenomena described herein. A really intriguing phenomenon is the evolution of some physico-chemical properties with time. This hints at a “trigger” effect on the formation of molecular aggregates that result from the succussion procedure. We show that successive dilutions and succussions can permanently alter the physico-chemical properties of the aqueous solvent, the extent of which depends on the age of the samples.     

Are formalin‐fixed and paraffin‐embedded tissues fit for proteomic analysis?

Formalin‐fixed and paraffin‐embedded (FFPE)–tissue archives are potential treasure troves in the search for clinically interesting specimens. However, while the FFPE‐treatment provides excellent conservation of the three‐dimensional structure of the tissue and prevents degradation over decades, it also introduces numerous nonspecific and irreversible protein modifications. In this study, we have evaluated several published workflows for FFPE‐tissue by fit‐for‐purpose proteomics technologies. We demonstrate that many protein modifications and cross‐links remain after treatment and conclude that the proteomics of FFPE‐tissue is of value, but clear‐cut limitations must be kept in mind. The analysis of abundant proteins in FFPE is straightforward, but confident identification of low‐level proteins and/or biologically relevant modifications is seriously hampered by the FFPE‐treatment. Peptide assignment should only be performed on high‐quality spectra, even if this is at the cost of lower numbers of protein IDs. As Yergey and Coorssen stated in 2015: “Data quality is considered the primary criterion, and we thus emphasize that the standards of Analytical Chemistry must apply throughout any proteomic analysis.”     

Dense or Porous Packing? Two‐Dimensional Self‐Assembly of Star‐Shaped Mono‐, Bi‐, and Terpyridine Derivatives

The self‐assembly behavior of five star‐shaped pyridyl‐functionalized 1,3,5‐triethynylbenzenes was studied at the interface between an organic solvent and the basal plane of graphite by scanning tunneling microscopy. The mono‐ and bipyridine derivatives self‐assemble in closely packed 2D crystals, whereas the derivative with the more bulky terpyridines crystallizes with porous packing. DFT calculations of a monopyridine derivative on graphene, support the proposed molecular model. The calculations also reveal the formation of hydrogen bonds between the nitrogen atoms and a hydrogen atom of the neighboring central unit, as a small nonzero tunneling current was calculated within this region. The title compounds provide a versatile model system to investigate the role of multivalent steric interactions and hydrogen bonding in molecular monolayers.     

2‐Halogeno‐1,3,2‐diazaarsolenes and 2‐halogeno‐1,3,2‐diazastibolenes: Examples for spontaneous E?X bond heterolysis or not?

2‐X‐1,3,2‐diazaarsolenes and 2‐X‐1,3,2‐ stibolenes (X = Cl, Br) were prepared from appropriate α‐amino‐aldimine precursors via transamination with ClSb(NMe₂)₂ or via base‐induced dehydrohalogenation with EX₃ (E = As, Sb). The products were further converted into 2‐iodo‐derivatives via halide exchange with Me₃SiI, or into 1,3,2‐diazaarsolenium or 1,3,2‐stibolenium salts via halide abstraction using E′X₃ (E′ = Al, Ga, Sb) or Me₃SiOTf. All compounds synthesized were characterized by spectroscopic data and several of them by single‐crystal X‐ray diffraction studies. The results of these investigations confirmed that diazaarsolenium or stibolenium cations are stabilized by similar π‐delocalization effects as the corresponding diazaphospholenium cations. 2‐Halogeno‐1,3,2‐diazaarsolenes and 2‐halogeno‐132‐stibolenes are best addressed as molecular species whose covalent E X bonds are as in 2‐chloro‐diazaphospholenes weakened by intramolecular π(C₂N₂) → σ*(E X) and, in the case of the Sb‐containing heterocycles, inter‐ molecular n(X′) → σ*(E X) hyperconjugation between the σ* (E X) orbital and a lone‐pair of electrons on the halogen atom of a neighboring molecule. Correlation of structural and spectroscopic data and the evaluation of halide transfer reactions allowed to conclude that the extent of E X bond weakening in the 2‐X‐substituted heterocycles decreases and thus the Lewis acidity of the cations increases, with increasing atomic number of the pnicogen atom. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:327–338, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20098     

Evidence for d‐Orbital Aromaticity in Sn‐ and Pb‐Based Clusters: Is Sn2‐12 Aromatic?

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

Synthesis and Antimalarial‐Activity Evaluation of Tetraoxane?Triazine Hybrids and Spiro[piperidine‐4,3′‐tetraoxanes]

A series of tetraoxane? triazine hybrids and spiro[piperidine‐4,3′‐tetraoxanes] have been synthesized, and all the compounds were screened for in vitro antimalarial activity against chloroquine‐sensitive (D6) and chloroquine‐resistant (W2) strains of Plasmodium falciparum. Most of the spiro[piperidine‐4,3′‐tetraoxanes] exhibited moderate to good antimalarial activities, and two compounds have shown good antimalarial activity with IC₅₀ values in the range of 0.30 to 0.70 μM against both the strains with high selectivity index and no cytotoxicity towards mammalian kidney cell line.     

Gerührt oder geschüttelt? James‐Bond‐Cocktail

Starting from perfluoroheptane, saturated aqueous potassium carbonate solution, methanol, toluene and suitable dyes, a three‐phasic mixture is prepared initially. After shaking – not only stirring – four layers develop. Addition of pentane changes the sequence of two layers. The layers are added in a new sequence and the way of mixing demonstrates the complexity of multi‐phasic systems.     

Is wood pre‐treatment essential for tree‐ring nitrogen concentration and isotope analysis?

Tree-ring nitrogen concentrations and isotope ratios (δ(15)N) are gaining in popularity for environmental research although their use is still debated because of nitrogen mobility in tree stems. Modern studies generally present results on wood that is pre-treated to remove soluble nitrogen compounds and to minimize the impact of radial translocation on tree-ring nitrogen environmental records. However, the necessity to use such pre-treatment has never been fully assessed. Here we compare the nitrogen concentrations and δ(15)N values of two wood preparation protocols applied to beech and red spruce tree rings for the removal of soluble compounds from ring pairs with non pre-treated tree rings. For both tree species, pre-treatment did not minimize the radial patterns of tree-ring nitrogen concentrations and the increasing concentration trends that are coincident with the heartwood-sapwood boundary. Therefore, even if the tree-ring nitrogen concentrations are slightly modified by pre-treatment, these concentrations are considered to reflect internal stem processes rather than environmental conditions in both species. The δ(15)N values were similar for untreated and pre-treated ring pairs, suggesting that wood pre-treatment did not substantially change the δ(15)N values and temporal trends in ring series. In addition, tree-ring δ(15)N series of untreated and pre-treated wood did not show any sign of influence of the heartwood-sapwood boundary in either tree species, indicating that nitrogen translocation did not generate significant isotopic fractionation. We therefore suggest that untreated ring δ(15)N values of beech and red spruce trees can be used for environmental research.     

The Silane‐ene and Silane‐Acrylate Polymerization Process: A New Promising Chemistry?

The combination of silanes and enes yields highly reactive photopolymerizable mixtures that exhibit very low oxygen sensitivity. Diphenylsilane (SiH) has been used in combination with different multifunctional acrylates (AC) and conversions of 100% and about 25% for AC and SiH, respectively, have been reached. Final tack free polymers are obtained as a consequence of the fact that the polymerization rates are not affected by oxygen. When using vinylacetate (VA), divinylether (DVE), and allylether (AE) units, the final silane conversion still remains low (50, 20, and 20%, respectively) but are promising. The reactivity of the silyl radicals is investigated by laser flash photolysis. The role of the bond dissociation energy of the silane is outlined.

     

Nano‐Cu2O‐Catalyzed Formation of C?C and C?O Bonds: One‐Pot Domino Process for Regioselective Synthesis of α‐Carbonyl Furans from Electron‐Deficient Alkynes and 2‐Yn‐1‐ols

The formation of carbon–carbon and carbon–oxygen bonds continues to be an active and challenging field of chemical research. Nanoparticle catalysis has attracted considerable attention owing to its environmentally benign and high activity toward the reactions. Herein, we described a novel and effective nano‐Cu₂O‐catalyzed one‐pot domino process for the regioselective synthesis of α‐carbonyl furans. Various electron‐deficient alkynes with 2‐yn‐1‐ols underwent this process smoothly in moderate to good yields in the presence of air at atmospheric pressure. It is especially noteworthy that a novel 2,4,5‐trisubstituted 3‐ynylfuran was formed in an extremely direct manner without tedious stepwise synthesis. Additionally, as all of the starting materials are readily available, this method may allow the synthesis of more complex α‐carbonyl furans. An experiment to elucidate the mechanism suggested that the process involved a carbene intermediate.     

Non‐mammalian Hosts and Photobiomodulation: Do All Life‐forms Respond to Light?

Photobiomodulation (PBM), also known as low‐level laser (light) therapy, was discovered over 50 years ago, but only recently has it been making progress toward wide acceptance. PBM originally used red and near‐infrared (NIR) lasers, but now other wavelengths and non‐coherent light‐emitting diodes (LEDs) are being explored. The almost complete lack of side effects makes the conduction of controlled clinical trials relatively easy. Laboratory research has mainly concentrated on mammalian cells (normal or cancer) in culture, and small rodents (mice and rats) as models of different diseases. A sizeable body of work was carried out in the 1970s and 1980s in Russia looking at various bacterial and fungal cells. The present review covers some of these studies and a recent number of papers that have applied PBM to so‐called “model organisms.” These models include flies (Drosophila), worms (Caenorhabditis elegans), fish (zebrafish) and caterpillars (Galleria). Much knowledge about the genomics and proteomics, and many reagents for these organisms already exist. They are inexpensive to work with and have lower regulatory barriers compared to vertebrate animals. Other researchers have studied different models (snails, sea urchins, Paramecium, toads, frogs and chickens). Plants may respond to NIR light differently from visible light (photosynthesis and photomorphogenesis) but PBM in plants has not been much studied. Veterinarians routinely use PBM to treat non‐mammalian patients. The conclusion is that red or NIR light does indeed have significant biologic effects conserved over many different kingdoms, and perhaps it is true that “all life‐forms respond to light.”