Resonant two photon ionization of phenanthrene via its transientS 2 state

We report the vibrationally resolved photoelectron spectrum of phenanthrene obtained by two photon ionization via theS ₂ electronic state. The experiments were performed with picosecond laser pulses with a bandwidth sufficiently large to span a significant fraction of the intermediate resonance state. Therefore the photoelectron spectrum is dominated by signal corresponding to the unrelaxed intermediate resonance, in spite of this state's 420 fs lifetime.     

Atomic and molecular fluorescence with long radiative decay times from laser excited Na2

Na₂ is excited (B¹Π_u←X¹Σ _g ⁺ ) in the presence of noble gases (20–700 Torr). The Na₂ fluorescence decay shows two lifetimes: a short component which corresponds to the well known lifetime of Na₂ in the B¹Π_u state [1], and a long component with a lifetime of about 0,1 μs which depends strongly on the noble gas density [2]. The same long lived radiative decay is also seen via the Na resonance fluorescence Na(3²S)←Na(3²P).     

Effect of Ion and Binding Site on the Conformation of Chosen Glycosaminoglycans at the Albumin Surface

Albumin is one of the major components of synovial fluid. Due to its negative surface charge, it plays an essential role in many physiological processes, including the ability to form molecular complexes. In addition, glycosaminoglycans such as hyaluronic acid and chondroitin sulfate are crucial components of synovial fluid involved in the boundary lubrication regime. This study presents the influence of Na+, Mg2+ and Ca2+ ions on human serum albumin–hyaluronan/chondroitin-6-sulfate interactions examined using molecular docking followed by molecular dynamics simulations. We analyze chosen glycosaminoglycans binding by employing a conformational entropy approach. In addition, several protein–polymer complexes have been studied to check how the binding site and presence of ions influence affinity. The presence of divalent cations contributes to the decrease of conformational entropy near carboxyl and sulfate groups. This observation can indicate the higher affinity between glycosaminoglycans and albumin. Moreover, domains IIIA and IIIB of albumin have the highest affinity as those are two domains that show a positive net charge that allows for binding with negatively charged glycosaminoglycans. Finally, in discussion, we suggest some research path to find particular features that would carry information about the dynamics of the particular type of polymers or ions.     

Medium Energy Inelastic Hadron Scattering and Nuclear Structure

Some aspects of medium energy (∼ 150 MeV to 1 GeV) proton and pion scattering theory from complex nuclei are reviewed with emphasis on inelastic scattering as a tool to extract nuclear structure information.     

Free Radicals, Salicylic Acid and Mycotoxins in Asparagus After Inoculation with Fusarium proliferatum and F. oxysporum

Electron paramagnetic resonance was used to monitor free radicals and paramagnetic species like Fe, Mn, Cu generation, stability and status in Asparagus officinalis infected by common pathogens Fusarium proliferatum and F. oxysporum. Occurrence of F. proliferatum and F. oxysporum, level of free radicals and other paramagnetic species, as well as salicylic acid and mycotoxins content in roots and stems of seedlings were estimated on the second and fourth week after inoculation. In the first term free and total salicylic acid contents were related to free radicals level in stem (P?=?0.010 and P?=?0.033, respectively). Concentration of Fe(3+) ions in porphyrin complexes (g?=?2.3, g?=?2.9) was related to the species of pathogen. There was no significant difference between Mn(2+) concentrations in stem samples; however, the level of free radicals in samples inoculated with F. proliferatum was significantly higher when compared to F. oxysporum.     

The Ligand‐Based Quintuple Bond‐Shortening Concept and Some of Its Limitations

Herein, the ligand‐based concept of shortening quintuple bonds and some of its limitations are reported. In dichromium–diguanidinato complexes, the length of the quintuple bond can be influenced by the substituent at the central carbon atom of the used ligand. The guanidinato ligand with a 2,6‐dimethylpiperidine backbone was found to be the optimal ligand. The reduction of its chromium(II) chloride–ate complex gave a quintuply bonded bimetallic complex with a Cr? Cr distance of 1.7056 (12) Å. Its metal–metal distance, the shortest observed in any stable compound yet, is of essentially the same length as that of the longest alkane C? C bond (1.704 (4) Å). Both molecules, the alkane and the Cr complex, are of remarkable stability. Furthermore, an unsupported Cr^I dimer with an effective bond order (EBO) of 1.25 between the two metal atoms, indicated by CASSCF/CASPT2 calculations, was isolated as a by‐product. The formation of this by‐product indicates that with a certain bulk of the guanidinato ligand, other coordination isomers become relevant. Over‐reduction takes place, and a chromium–arene sandwich complex structurally related to the classic dibenzene chromium complex was observed, even when bulkier substituents are introduced at the central carbon atom of the used guanidinato ligand.     

The surface charge of regenerated cellulose fibres

In this paper the influence of charged species on the sheet strength of viscose fibres was investigated. Four samples of chemical modified viscose fibres, as well as a reference fibre were studied. The swelling of these viscose fibres and the breaking length of hand sheets have been determined. Comparing the results, the influence of both, swelling and surface charge on the bonding force, is evident. The allocation of the charges, induced by cationic starch and Carboxmethylcellulose, has been analyzed by Titration, attenuated total reflection spectroscopy (ATR) and X-ray photoelectron spectroscopy (XPS). Titration was used to make a first estimation of the charge distribution within the fibre. Using ATR and XPS, more detailed information about the surface charge has been achieved. All measurement methods showed a significant amount of charge on the fibre surface.     

Size does matter! Label-free detection of small molecule–protein interaction

This review is focused on methods for detecting small molecules and, in particular, the characterisation of their interaction with natural proteins (e.g. receptors, ion channels). Because there are intrinsic advantages to using label-free methods over labelled methods (e.g. fluorescence, radioactivity), this review only covers label-free techniques. We briefly discuss available techniques and their advantages and disadvantages, especially as related to investigating the interaction between small molecules and proteins. The reviewed techniques include well-known and widely used standard analytical methods (e.g. HPLC-MS, NMR, calorimetry, and X-ray diffraction), newer and more specialised analytical methods (e.g. biosensors), biological systems (e.g. cell lines and animal models), and in-silico approaches.     

Borane Adducts of Aromatic Phosphorus Heterocycles: Synthesis,Crystallographic Characterization and Reactivity of a Phosphinine-B(C6F5)3 Lewis Pair

A phosphinine-borane adduct of a Me₃Si-functionalized phosphinine and the Lewis acid B(C₆F₅)₃ has been synthesized and characterized crystallographically for the first time. The reaction strongly depends on the nature of the substituents in the α-position of the phosphorus heterocycle. In contrast, the reaction of B₂H₆ with various substituted phosphinines leads to an equilibrium between the starting materials and the phosphinine–borane adducts that is determined by the Lewis basicity of the phosphinine. The novel phosphinine borane adduct ( 6 -B(C₆F₅)₃) shows rapid and facile insertion and [4+2] cycloaddition reactivity towards phenylacetylene. A hitherto unknown dihydro-1-phosphabarrelene is formed with styrene. The reaction with an ester provides a new, facile and selective route to 1-R-phosphininium salts. These salts then undergo a [4+2] cycloaddition in the presence of Me₃Si−C≡CH and styrene to cleanly form unprecedented derivatives of 1-R-phosphabarrelenium salts.     

Simplified,interpretable graph convolutional neural networks for small molecule activity prediction

Journal of Computer-Aided Molecular Design - We here present a streamlined, explainable graph convolutional neural network (gCNN) architecture for small molecule activity prediction. We first...