Chemiluminescent self-reporting supramolecular transformations on macromolecular scaffolds

We introduce the synthesis of a self-reporting system with chemiluminescent output, which is regulated via dynamic supramolecular complex formation. By free radical polymerization and subsequent post-polymerization modification, a copolymer decorated with luminol and superbase (i.e. 1,5,7-triaza-bicyclo-[4.4.0]dec-5-ene (TBD)) moieties was synthesized, which in turn forms supramolecular host–guest-complexation with randomly methylated β-cyclodextrin (Me-β-CD). Upon hydrogen peroxide addition, the host–guest-interactions with the self-assembly are broken, and the luminol is oxidized to 3-aminophthalic acid (3-APA). Critically, no additional base, buffer or catalyst is required to generate the striking blue light emission of the polymeric system that is detectable by the naked eye. Thus, a fast and easy detection of reactive oxygen species (ROS), such as hydrogen peroxide, under mild conditions is established. The self-reporting system and its chemiluminescent properties are characterized by 1D and 2D NMR spectroscopy (particularly NOESY), dynamic light scattering (DLS), UV/Vis spectroscopy and chemiluminescence (CL) measurements

Determination of Configuration and Conformation of a Reserpine Derivative with Seven Stereogenic Centers Using Molecular Dynamics with RDC‐Derived Tensorial Constraints

NMR-based determination of the configuration of complex molecules containing many stereocenters is often not possible using traditional NOE data and coupling patterns. Making use of residual dipolar couplings (RDCs), we were able to determine the relative configuration of a natural product containing seven stereocenters, including a chiral amine lacking direct RDC data. To identify the correct relative configuration out of 32 possible ones, experimental RDCs were used in three different approaches for data interpretation: by fitting experimental data based singular value decomposition (SVD) using a single alignment tensor and either (i) a single conformer or (ii) multiple conformers, or alternatively (iii) using molecular dynamics simulations with tensorial orientational constraints (MDOC). Even though in all three approaches one and the same configuration could be selected and clear discrimination between possible configurations was achieved, the experimental data was not fully satisfied by the methods based on single tensor approaches. While these two approaches are faster, only MDOC is able to fully reproduce experimental results, as the obtained conformational ensemble adequately covers the conformational space necessary to describe the molecule with inherent flexibility

Heterobimetallic Eu(III)/Pt(II) single-chain nanoparticles: a path to enlighten catalytic reactions

We introduce the formation and characterization of heterometallic single-chain nanoparticles entailing both catalytic and luminescent properties. A terpolymer containing two divergent ligand moieties, phosphines and phosphine oxides, is synthesized and intramolecularly folded into nanoparticles via a selective metal complexation of Pt(II) and Eu(III). The formation of heterometallic Eu(III)/Pt(II) nanoparticles is evidenced by size exclusion chromatography, multinuclear NMR ($^{1}$H, $^{31}$P{$^{1}$H}, $^{19}$F, $^{195}$Pt) as well as diffusion-ordered NMR and IR spectroscopy. Critically, we demonstrate the activity of the SCNPs as a homogeneous and luminescent catalytic system in the amination reaction of allyl alcohol

Configuration determination by residual dipolar couplings: accessing the full conformational space by molecular dynamics with tensorial constraints

Residual dipolar couplings (RDCs) and other residual anisotropic NMR parameters provide valuable structural information of high quality and quantity, bringing detailed structural models of flexible molecules in solution in reach. The corresponding data interpretation so far is directly or indirectly based on the concept of a molecular alignment tensor, which, however, is ill-defined for flexible molecules. The concept is typically applied to a single or a small set of lowest energy structures, ignoring the effect of vibrational averaging. Here, we introduce an entirely different approach based on time averaged molecular dynamics with dipolar couplings as tensorial orientational restraints that can be used to solve structural problems in molecules of any size without the need of introducing an explicit molecular alignment tensor into the computation. RDC restraints are represented by their full 3D interaction tensor in the laboratory frame, for which pseudo forces are calculated using a secular dipolar Hamiltonian as the target. The resulting rotational averaging of each individual tensorial restraint leads to structural ensembles that best fulfil the experimental data. Using one-bond RDCs, the approach has been implemented in the force field procedures of the program COSMOS and extensively tested. A concise theoretical introduction, including the special treatment of force fields for stable and fast MD simulations, as well as applications regarding configurational analyses of small to medium-sized organic molecules with different degrees of flexibility, is given. The observed results are discussed in detail

Untargeted NMR Spectroscopic Analysis of the Metabolic Variety of New Apple Cultivars

Metabolome analyses by NMR spectroscopy can be used in quality control by generating unique fingerprints of different species. Hundreds of components and their variation between different samples can be analyzed in a few minutes/hours with high accuracy and low cost of sample preparation. Here, apple peel and pulp extracts of a variety of apple cultivars were studied to assess their suitability to discriminate between the different varieties. The cultivars comprised mainly newly bred varieties or ones that were brought onto the market in recent years. Multivariate analyses of peel and pulp extracts were able to unambiguously identify all cultivars, with peel extracts showing a higher discriminative power. The latter was increased if the highly concentrated sugar metabolites were omitted from the analysis. Whereas sugar concentrations lay within a narrow range, polyphenols, discussed as potential health promoting substances, and acids varied remarkably between the cultivars

Chemiluminescent self-reporting supramolecular transformations on macromolecular scaffolds

We introduce the synthesis of a self-reporting system with chemiluminescent output, which is regulated via dynamic supramolecular complex formation. By free radical polymerization and subsequent post-polymerization modification, a copolymer decorated with luminol and superbase (i.e. 1,5,7-triaza-bicyclo-[4.4.0]dec-5-ene (TBD)) moieties was synthesized, which in turn forms supramolecular host-guest-complexation with randomly methylated β-cyclodextrin (Me-β-CD). Upon hydrogen peroxide addition, the host-guest-interactions with the self-assembly are broken, and the luminol is oxidized to 3-aminophthalic acid (3-APA). Critically, no additional base, buffer or catalyst is required to generate the striking blue light emission of the polymeric system that is detectable by the naked eye. Thus, a fast and easy detection of reactive oxygen species (ROS), such as hydrogen peroxide, under mild conditions is established. The self-reporting system and its chemiluminescent properties are characterized by 1D and 2D NMR spectroscopy (particularly NOESY), dynamic light scattering (DLS), UV/Vis spectroscopy and chemiluminescence (CL) measurements. This journal is </p

Hydrogen bond formation may enhance RDC-based discrimination of enantiomers

The distinction of enantiomers based on residual anisotropic parameters obtained by alignment in chiral poly-gamma-benzyl-L-glutamate (PBLG) is among the strongest in high-resolution NMR spectroscopy. However, large variations in enantiodifferentiation among different solutes are frequently observed. One hypothesis is that the formation of hydrogen bonds between solute and PBLG is important for the distinction of enantiomers. With a small set of three almost spherical enantiomeric pairs, for which 1DCH residual dipolar couplings are measured, we address this issue in a systematic way: borneol contains a single functional group that can act as a hydrogen bond donor, camphor has a single group that may act as a hydrogen bond acceptor, and quinuclidinol can act as both hydrogen bond donor and acceptor. The results are unambiguous: although camphor shows low enantiodifferentiation with PBLG and alignment that can be predicted well by the purely steric TRAMITE approach, the distinction of enantiomers for the other enantiomeric pairs is significantly higher with alignment properties that must involve a specific interaction in addition to steric alignment.ISSN:0749-1581ISSN:1097-458

Degradable fluorescent single-chain nanoparticles based on metathesis polymers

We introduce the facile synthesis of fluorescent single-chain nano-particles (SCNPs) based on chain-shattering acyclic diene metathesis (ADMET) polymers featuring self-immolative azobenzene motifs. An electrophilic alkoxyetherification is utilized to introduce the photo-reactive moieties required for the subsequent chain collapse via UV-induced nitrile imine-mediated tetrazole-ene cycloaddition (NITEC)

La Patrie : journal quotidien, politique, commercial et littéraire

18 août 18951895/08/18 (A55)