Electron paramagnetic resonance (EPR) study of γ-radiation-induced radicals in 1,3,5-trithiane and its derivatives

Radicals formed in γ-irradiated 1,3,5-trithiane (TT) and its three derivatives, α- and β-2,4,6-trimethyl-1,3,5-trithiane (α-TMT and β-TMT), and 2,4,6-trimethyl-2,4,6-triphenyl-1,3,5-trithiane (TMTPT), were studied by the electron paramagnetic resonance (EPR) method in the solid state. The sulfur radical cations (>S^+•) were identified in all compounds at 77 K. In TT and its two derivatives, α-TMT and β-TMT, the >S^+• decay via deprotonation-forming C-centered radicals. Further increase of temperature up to 293 K results in the appearance of thiyl-type radicals (RS^•). In TMTPT, the >S^+• are stable up to 250 K. They formed the intermolecularly three-electron-bonded dimeric radical cations (S∴S)⁺ while RS^• radicals were not observed. Some of the radical assignments and their EPR parameters (g and a hyperfine splittings) obtained support from the DFT calculations.     

Capillary Model of Gravity Elution of High Viscosity Liquid from a Porous Bed with a Low-Viscosity Liquid

Modeling of the processes of elution from porous systems is essential importance for development of the removing oily contaminations from the soils and intensification of the oil recovery processes. In the paper, capillary model of gravitational elution of high viscosity substances from the porous medium by using low viscosity liquids was derived. This model allowed for the prediction of changes in time of such parameters like: level of bed saturation with oil, relative bed permeability, liquid flow rate, flow resistance, volume of eluted liquid during the process. When modeling, phenomena and the physical properties associated with the analyzed process, such as, for example, the effects of surface tension, fluids viscosity, specific size of the granular bed, initial oil saturation of bed, variable process driving force, and the flow of liquid through the preferential flow paths, were taken into account. This allowed for the more complete imaging of elution process. The model has been verified on the basis of the results of experimental studies. In addition, the discussion on the behavior of the model due to changes in values of various parameters was carried out.     

Arylsulfonylacetylenes as alkynylating reagents of Csp2-H bonds activated with lithium bases

Chameleon: a new strategy for the synthesis of a wide variety of alkynyl derivatives by the reaction of substituted arylsulfonylacetylenes with organolithium species is described. The high yields, the simplicity of the experimental procedure, the broad scope of this reaction, and the formation of C(sp)-C(sp2) bonds without using transition metals are the main features of this methodology.     

Detection of drug active ingredients by chemometric processing of solid-state NMR spectrometry data -- the case of acetaminophen

This paper presents a preliminary study in building discriminant models from solid-state NMR spectrometry data to detect the presence of acetaminophen in over-the-counter pharmaceutical formulations. The dataset, containing 11 spectra of pure substances and 21 spectra of various formulations, was processed by partial least squares discriminant analysis (PLS-DA). The model found coped with the discrimination, and its quality parameters were acceptable. It was found that standard normal variate preprocessing had almost no influence on unsupervised investigation of the dataset. The influence of variable selection with the uninformative variable elimination by PLS method was studied, reducing the dataset from 7601 variables to around 300 informative variables, but not improving the model performance. The results showed the possibility to construct well-working PLS-DA models from such small datasets without a full experimental design.     

Biomimetic Ketone Reduction by Disulfide Radical Anion

The conversion of ribonucleosides to 2′-deoxyribonucleosides is catalyzed by ribonucleoside reductase enzymes in nature. One of the key steps in this complex radical mechanism is the reduction of the 3′-ketodeoxynucleotide by a pair of cysteine residues, providing the electrons via a disulfide radical anion (RSSR^•−) in the active site of the enzyme. In the present study, the bioinspired conversion of ketones to corresponding alcohols was achieved by the intermediacy of disulfide radical anion of cysteine (CysSSCys)^•− in water. High concentration of cysteine and pH 10.6 are necessary for high-yielding reactions. The photoinitiated radical chain reaction includes the one-electron reduction of carbonyl moiety by disulfide radical anion, protonation of the resulting ketyl radical anion by water, and H-atom abstraction from CysSH. The (CysSSCys)^•− transient species generated by ionizing radiation in aqueous solutions allowed the measurement of kinetic data with ketones by pulse radiolysis. By measuring the rate of the decay of (CysSSCys)^•− at λ_max = 420 nm at various concentrations of ketones, we found the rate constants of three cyclic ketones to be in the range of 10⁴–10⁵ M⁻¹s⁻¹ at ~22 °C.     

Cationic Porphyrin-Graphene Oxide Hybrid: Donor-Acceptor Composite for Efficient Photoinduced Electron Transfer

Non-covalent nanohybrids composed of cationic 5,10,15,20-tetra(4-trimethylammoniophenyl)porphyrin tetra(p-toluenesulfonate) (TMAP) and the graphene oxide sheets were prepared under two pH values (6.2 vs. 1.8). The TMAP molecule was positively charged, regardless of the pH value during preparation. However, protonation of the imino nitrogens increased the overall charge of the porphyrin molecule from +4 to +6 (TMAP⁴⁺ and TMAP⁶⁺). It was found that at acidic pH, interaction of TMAP⁶⁺ with GO was largely suppressed. On the other hand, results of FTIR, Raman spectroscopy, thermogravimetric analysis, atomic force microscopy (AFM) and elemental analysis confirmed effective non-covalent functionalization of graphene oxide with cationic porphyrin at pH 6.2. The TMAP⁴⁺-GO hybrids exhibited well defined structure with a monolayer of TMAP⁴⁺ on the GO sheets as confirmed by AFM. Formation of the ground-state TMAP⁴⁺-GO complex in solution was monitored by the red-shift of the porphyrin Soret absorption band. This ground-state interaction between TMAP⁴⁺ and GO is responsible for the static quenching of the porphyrin emission. Fluorescence was not detected for the nanohybrid which indicated that a very fast deactivation process had to take place. Ultrafast time-resolved transient absorption spectroscopy clearly demonstrated the occurrence of electron transfer from the photoexcited TMAP⁴⁺ singlet state to GO sheets, as proven by the formation of a porphyrin radical cation.     

On Reciprocal Equivalence of Stäckel Systems

In this paper we investigate Stäckel transforms between different classes of parameter‐dependent Stäckel separable systems of the same dimension. We show that the set of all Stäckel systems of the same dimension splits to equivalence classes so that all members within the same class can be connected by a single Stäckel transform. We also give an explicit formula relating solutions of two Stäckel‐related systems. These results show in particular that any two geodesic Stäckel systems are Stäckel equivalent in the sense that it is possible to transform one into another by a single Stäckel transform. We also simplify proofs of some known statements about multiparameter Stäckel transform.     

Common Factors of Alzheimer’s Disease and Rheumatoid Arthritis—Pathomechanism and Treatment

The accumulation of amyloid plaques, or misfolded fragments of proteins, leads to the development of a condition known as amyloidosis, which is clinically recognized as a systemic disease. Amyloidosis plays a special role in the pathogenesis of neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease, and rheumatoid arthritis (RA). The occurrence of amyloidosis correlates with the aging process of the organism, and since nowadays, old age is determined by the comfort of functioning and the elimination of unpleasant disease symptoms in the elderly, exposure to this subject is justified. In Alzheimer’s disease, amyloid plaques negatively affect glutaminergic and cholinergic transmission and loss of sympathetic protein, while in RA, amyloids stimulated by the activity of the immune system affect the degradation of the osteoarticular bond. The following monograph draws attention to the over-reactivity of the immune system in AD and RA, describes the functionality of the blood–brain barrier as an intermediary medium between RA and AD, and indicates the direction of research to date, focusing on determining the relationship and the cause–effect link between these disorders. The paper presents possible directions for the treatment of amyloidosis, with particular emphasis on innovative therapies.     

Constructing free subgroups of integral group ring units

Let be an arbitrary group. It is proved that if contains a bicyclic unit , then is a nonabelian free subgroup of invertible elements.