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The assessment of unregulated level of enzyme activity is a crucial parameter for early diagnoses in a wide range of pathologies. In this study, we propose the use of electron paramagnetic resonance (EPR) as an easy method to probe carboxylesterase (CE) enzymatic activity in vitro. For this application, were synthesized two amphiphilic, nitroxide containing esters, namely Tempo‐C12 (T‐C12) and Tempo‐2‐C12 (T‐2‐C12). They exhibit low solubility in water and form stable micelles in which the radicals are EPR almost silent, but the hydrolysis of the ester bond yields narrows and intense EPR signals. The intensity of the EPR signals is proportional to the enzymatic activity. CEs1, CEs2 and esterase from porcine liver (PLE) were investigated. The obtained results show that T‐C12 and T‐2‐C12‐containing systems display a much higher selectivity toward the CEs2, with a Limit of Detection of the same order of those ones obtained with optical methods. [ABSTRACT FROM AUTHOR]

EPR spectroscopic evidence for intramolecular electron transfer in anionic N‐substituted naphthalimides to yield persistent diradical anions and intermolecular electron transfer from a variety of carbanions to 6‐bromo‐N‐phenyl‐naphthalimide to yield persistent radical–radical anion pairs was recently claimed in two papers by Zhang et al. In this comment, it is shown that the EPR spectra published in both papers do not agree with the proposed triplet‐state species. Rather, the spectra are due to various doublet‐state radicals, deriving from minor side reactions. The misinterpretations invalidate the general conclusions of the papers. [ABSTRACT FROM AUTHOR]

β‐Peptides are an interesting new class of transmembrane model peptides based on their conformationally stable and well‐defined secondary structures. Herein, we present the synthesis of the paramagnetic β‐amino acid β3‐hTOPP (4‐(3,3,5,5‐tetramethyl‐2,6‐dioxo‐4‐oxylpiperazin‐1‐yl)‐d‐β3‐homophenylglycine) that enables investigations of β‐peptides by EPR spectroscopy. This amino acid adds to the, to date, sparse number of β‐peptide spin labels. Its performance was evaluated by investigating the helical turn of a 314‐helical transmembrane model β‐peptide. Nanometer distances between two incorporated β3‐hTOPP labels in different environments were measured by using pulsed electron/electron double resonance (PELDOR/DEER) spectroscopy. Due to the semi‐rigid conformational design, the label delivers reliable distances and sharp (one‐peak) distance distributions even in the lipid bilayer. The results indicate that the investigated β‐peptide folds into a 3.2514 helix and maintains this conformation in the lipid bilayer. Nitroxide radicals: New semi‐rigid spin label β3‐hTOPP has allowed the investigation of a β‐peptide structure by EPR spectroscopy. Well‐defined inter‐spin distances between two β3‐hTOPP labels in a model β‐peptide have been measured in lipid bilayers using pulsed electron/electron double resonance (PELDOR) spectroscopy. The labelling strategy has permitted to determine the peptide helical structure with resolution at molecular‐length scale (see figure). [ABSTRACT FROM AUTHOR]

This Correspondence reports on a structural and mechanistic misinterpretation of an observed EPR spectrum, a misleading presentation of DNA cleavage data, and the physicochemically unsupported assignment of nitric oxide as a major DNA cleaving agent in the article cited in the title. [ABSTRACT FROM AUTHOR]

A substrate‐independent and versatile coating platform for (spatially resolved) surface functionalization, based on nitroxide radical coupling (NRC) reactions and the formation of thermo‐labile alkoxyamine functional groups, was introduced. Nitroxide‐decorated poly(glycidyl methacrylate) (PGMA) microspheres, obtained through bioinspired copolymer surface deposition using dopamine and a nitroxide functional dopamine derivative as monomers, were conjugated with small functional groups in a rewritable process. Reversible coding of the nitroxide functional microspheres by NRC and decoding through thermal alkoxyamine fission were monitored and characterized by electron paramagnetic resonance (EPR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). In addition, this nitroxide coating system was exploited in "grafting‐to" polymer surface ligations of poly(methyl methacrylate) (PMMA) and poly(2,2,2‐trifluoroethyl methacrylate) (PTFEMA) in spatially confined areas. Polymer strands terminated with an Irgacure 2959 (2‐hydroxy‐4′‐(2‐hydroxyethoxy)‐2‐methylpropiophenone) photoinitiator were obtained through chain‐transfer polymerization, and subsequently coupled to nitroxide‐immobilized poly(dopamine) (PDA)‐coated silicon substrates by using rapid photoclick NRC reactions. Light‐driven polymer surface coding was visualized by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and XPS imaging. Coating with nitroxide: A versatile, bioinspired nitroxide functional coating platform is presented for precise programming of various materials. Nitroxide‐coated polymeric microspheres with rewritable properties were manufactured, exemplified in consecutive nitroxide radical coupling (coding) and thermal alkoxyamine fission (decoding) reaction steps. Photoinduced dual‐polymer‐patterned surfaces were further generated highlighting the broad applicability of our nitroxide coating system. [ABSTRACT FROM AUTHOR]

The dimesitylphosphinocyclopentene/HB(C6F5)2-derived vicinal trans-1,2-P/B frustrated Lewis pair (FLP) 4 shows no direct phosphane-borane interaction. Toward some reagents it behaves similar to an intermolecular FLP; it cleaves dihydrogen, deprotonates terminal alkynes, and adds to organic carbonyl compounds including CO2. It shows typical intramolecular FLP reaction modes (cooperative 1,1-additions) to mesityl azide, to carbon monoxide, and to NO. The latter reaction yields a persistent P/B FLPNO nitroxide radical, which undergoes H-atom abstraction reactions. The FLP 4 serves as a template for the CO reduction by [HB(C6F5)2] to generate a FLP-η2-formylborane. The formylborane moiety is removed from the FLP template by reaction with pyridine to yield a genuine pyridine stabilized formylborane that undergoes characteristic borane carbaldehyde reactions (Wittig olefination, imine formation). Most new products were characterized by X-ray diffraction. [ABSTRACT FROM AUTHOR]