Front Cover: Can Nanoplastics Alter Cell Membranes? (ChemPhysChem 1/2020)

Whilst the formation of plastic nanoparticles (nanoplastics) from plastic wastes has been unequivocally evidenced, little is known about the effects of these materials on living organisms at the subcellular or molecular levels. In the present contribution we show through molecular dynamics simulations that polyethylene nanoparticles dissolve in the hydrophobic core of lipid bilayers into a network of disentangled, single polymeric chains. The thereby induced structural and dynamic changes in the bilayer alter vital functions of the cell membrane, which if lacking a mechanism to decompose the polymer chains may result in the death of the cell.     

Structurally diverse and readily tunable photocrosslinked chondroitin sulfate based copolymers

Our group has previously reported on successful biofunctionalization of poly(ethylene glycol diacrylate) (PEGDA) gels using chondroitin sulfate (CS) and improving moduli of methacrylated‐CS (MCS) gels using short PEGDA comonomers. Here, we focused on understanding the composition‐property relationship of MCS‐PEGDA copolymers. By changing concentration, composition, and medium's ionic strength the gels were modified to show a diverse range of properties. Photopolymerized copolymers with >4:1 ratio of one component had compressive moduli of up to 24 times higher and up to 17 times lower swelling degree (q) than those of MCS alone. The increased moduli and lowered q were consistent with the hypothesis that PEGDA improves kinetic chain growth by overcoming the steric hindrances of the macromer. The swelling and moduli of the gels were tuned by changing the ratio of the comonomers. The swelling and moduli of the gels were lowered with presence of salt in solution while the fracture strain increased. These changes were hypothesized to be the result of transition of CS chain conformation from highly extended and non‐Gaussian to less extended and Gaussian distribution. The complete understanding of MCS‐PEGDA composition–property relationship provides a general strategy to tune the moduli or q of polysaccharide‐based hydrogels while avoiding undesirable phase separation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1070–1079     

Muon-pair production by atmospheric muons in CosmoALEPH

Data from a dedicated cosmic ray run of the ALEPH detector were used in a study of muon trident production, i.e., muon pairs produced by muons. Here the overburden and the calorimeters are the target materials while the ALEPH time projection chamber provides the momentum measurements. A theoretical estimate of the muon trident cross section is obtained by developing a Monte Carlo simulation for muon propagation in the overburden and the detector. Two muon trident candidates were found to match the expected theoretical pattern. The observed production rate implies that the nuclear form factor cannot be neglected for muon tridents.     

Structural evolution of melt-drawn transparent high-density polyethylene during heating and annealing: Synchrotron small-angle X-ray scattering study

The morphological development of melt-drawn transparent high-density polyethylene during heating was investigated employing in-situ synchrotron small-angle X-ray scattering (SAXS) technique. The results confirm that at lower temperatures only meridional scattering peaks aligned perpendicular to the extensional flow direction can be observed, indicating a highly oriented lamellar crystallite structure; whereas at higher temperatures an equatorial streak additional to the layer-like meridional scattering pattern develops, reflecting the presence of shish-kebab-like objects in the specimen under investigation. Upon heating, the average thickness of the kebab crystals remains essentially unaffected below 110 °C, and subsequently the selective melting of the less stable kebabs proceeds yielding thicker layered lamellar crystals. When the temperature is raised to 131 °C, the shish-like formation and the thermally stable kebab crystals melt simultaneously. In addition, the microstructure of the melt-drawn specimen subjected to annealing at elevated temperatures was probed at room temperature. As opposed to the SAXS patterns registered at high temperatures, the SAXS diagram measured after annealing shows no equatorial streak, suggesting that the cylindrical structures could be re-formed. This observation can be explained by assuming that the plate-like kebab crystals with their normal parallel to the stretching direction grow and impinge during cooling to room temperature due to secondary crystallization, which can be verified by in-situ SAXS experiments during annealing and subsequent cooling.     

Major and modified nucleosides in tRNA hydrolysates by high-performance liquid chromatography.

We describe a high-performance liquid chromatographic analytical method that can be readily placed in operation, and which is particularly well suited to scientists investigating tRNA structure, biosynthesis, and function, and for the determination of major and modified nucleosides of tRNA. The method is characterized by the following features: (1) Sensitivity at the nanogram level; (2) High chromatographic resolution and selectivity; (3) Direct measurement of nucleosides with accuracy and precision; (4) Analysis is non-destructive and the high capacity of this chromatographic system allows easy isolation of pure nucleosides for further characterization; (5) Rapid separation and measurement in ca. 1 h after hydrolysis to nucleosides; and (6) Quantitation without use of radiolabeled compounds; however, labeled compounds are readily isolated and measured.     

Radioactinide additions to the electronic Gamma-ray Spectrum Catalogue

With the completion of a CD ROM version of the original R. L. HEATH's Gamma-ray Spectrum Catalogue, it became obvious that a number of radionuclides are missing which are important to various fields of nuclear science and technology. With a large amount of transuranic waste awaiting permanent disposal across the Department of Energy (DOE) complex and the need for its assay in order to dispose of it, it was decided that the addition of the radioactinides encountered in transuranic waste should be the first priority. In response to this need, the spectra of ²³³U, ²³⁵U, ²³⁸U, ²³⁷Np, ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu, ²⁴²Pu, ²⁴¹Am and ²⁴³Am have been acquired with modern Ge detectors, and prepared for graphics presentation along with the parent and progeny decay chains and decay schemes. The associated tables of -ray energies and emission probabilities have been downloaded from the Evaluated Nuclear Structure Data file (ENSDF) database. This information is being incorporated into the Gamma-Ray Spectrometry Center Web Site at http://id.inel.gov/gamma