Ein Chamäleon-Marker zur Anfärbung und quantitativen Bestimmung von Proteinen

Analysis of the Amine Submetabolome Using Novel Isotope-Coded Pyrylium Salt Derivatization and LC-MS: Herbs and Cancer Tissues as Cases

The amine submetabolome, including amino acids (AAs) and biogenic amines (BAs), is a class of small molecular compounds exhibiting important physiological activities. Here, a new pyrylium salt named 6,7-dimethoxy-3-methyl isochromenylium tetrafluoroborate ([d₀]-DMMIC) with stable isotope-labeled reagents ([d₃]-/[d₆]-DMMIC) was designed and synthesized for amino compounds. [d₀]-/[d₃]-/[d₆]-DMMIC-derivatized had a charged tag and formed a set of molecular ions with an increase of 3.02 m/z and the characteristic fragment ions of m/z 204.1:207.1:210.1. When DMMIC coupled with liquid chromatography-mass spectrometry (LC-MS), a systematic methodology evaluation for quantitation proved to have good linearity (R² between 0.9904 and 0.9998), precision (interday: 2.2-21.9%; intraday: 1.0-19.7%), and accuracy (recovery: 71.8-108.8%) through the test AAs. Finally, the methods based on DMMIC and LC-MS demonstrated the advantaged application by the nontargeted screening of BAs in a common medicinal herb Senecio scandens and an analysis of metabolic differences among the amine submetabolomes between the carcinoma and paracarcinoma tissues of esophageal squamous cell carcinoma (ESCC). A total of 20 BA candidates were discovered in S. scandens as well as the finding of 13 amine metabolites might be the highest-potential differential metabolites in ESCC. The results showed the ability of DMMIC coupled with LC-MS to analyze the amine submetabolome in herbs and clinical tissues.

Fingerprinting the Nature of Anions in Pyrylium Complexes: Dual Binding Mode for Anion-π Interactions

The interplay between noncovalent interactions that involve oxygenated heteroaromatic rings have been studied for the first time in this work. In particular, we report an advance in knowledge-based anion-π interactions together with (C-H)⁺ ⋅⋅⋅anion contacts. To understand how the anion modulates these interactions, the synthesis of pyrylium salts with a variety of anions was performed by using an anionic metathesis methodology. The synthesized pyrylium complexes were classified in series, for example, anions derived from halogens, from oxoacids, from p-block elements, and from transition metals. Crystallographic data, DFT calculations, and NMR spectroscopy methods provided access to an overall insight into the noncovalent behavior of the anion in this kind of system. Based on the DFT calculations and ¹ H NMR spectroscopy, pyrylium protons can be used as chemical tags to detect noncovalent interactions in this type of compound.

Novel pyridinium dyes that enable investigations of peptoids at the single-molecule level

Single-molecule microscopy is a powerful tool for investigating various uptake mechanisms of cell-penetrating biomolecules. A particularly interesting class of potential transporter molecules are peptoids. Fluorescence labels for such experiments need to comply with several physical, chemical, and biological requirements. Herein, we report the synthesis and photophysical investigation of new fluorescent pyridinium derived dyes. These fluorescent labels have advantageous structural variations and spacer units in order to avoid undesirable interactions with the labeled molecule and are able to easily functionalize biomolecules. In our case, cell-penetrating peptoids are successfully labeled on solid supports, and in ensemble measurements the photophysical properties of the dyes and the fluorescently labeled peptoids are investigated. Both fluorophores and peptoids are imaged at the single-molecule level in thin polymer gels. With respect to bleaching times and fluorescence lifetimes the dye molecules and the peptoids show only slightly perturbed optical behaviors. These investigations indicate that the new fluorophores fulfill well single-molecule microscopy and solid-phase synthesis requirements.

Synthesis and characterization of the first fluorescent nonpeptide NPY Y1 receptor antagonist

Cyanine-5-labelled neuropeptide Y (NPY) was demonstrated to be an ideal universal fluorescent ligand for the combined investigation of NPY Y(1), Y(2) and Y(5) receptors. With respect to improved stability, detection of receptor subtypes in cells and tissues, and prevention of receptor internalization, small nonpeptidic fluorescent antagonists should be superior. Here we present a set of four fluorescent nonpeptide NPY Y(1) receptor (Y(1)R) antagonists. The highest affinity was obtained by labelling an N(G)-(6-aminohexanoyl)argininamide derived from the Y(1)R antagonist BIBP 3226, with Py-1, a small pyrylium dye. The fluorescent pyridinium-type Y(1)R antagonist, compound 4 had K(i) values of 29 nM and 2.7 nM, which were determined by radioligand binding and flow cytometry under equilibrium conditions, respectively; 4 had a K(b) value of 0.6 nM (Ca(2+) assay). The large Stoke's shift (541 vs. 615 nm) in buffer (PBS, pH 7.4) in the presence of 1% BSA and the red emission (quantum yield 56%) are advantageous with respect to the signal-to-noise ratio. The new probe was successfully used in fluorescence-based binding experiments evaluated by flow cytometry and confocal microscopy; this demonstrates the potential of pyrylium dyes for the preparation of fluorescent ligands that are applicable for the study of G protein-coupled receptors on living cells.

A Resonance Energy Transfer Immunoassay Based on a Thiol-Reactive Ruthenium Donor Dye and a Longwave-Emitting Acceptor

A novel immunoassay is described that applies a thiol-reactive ruthenium metal-ligand complex as the donor dye in a luminescence energy transfer (LET) detection scheme. Unlike amine-reactive labels, the LET with a thiol label allows improved specificity and better reproducibility of labelling positions on proteins, because the number of reactive thiol groups of proteins is distinctly smaller. This helps to reduce the risk of over-labelling and self-quenching of the fluorophore. The synthesis of the thiol label was significantly improved, resulting in almost quantitative yields of pure product. The absorption and emission maxima of the ruthenium donor dye are at 460 nm and 600 nm, respectively, and a Stokes' shift of 140 nm warrants distinct separation of excitation and emission wavelengths even in turbid samples. A cyanine dye with an absorption maximum at 642 nm was chosen as the acceptor label because it has good overlap with the emission spectrum of the donor label. The emission of the acceptor peaks at 660 nm, thus further increasing the Stokes' shift (to an overall 200 nm). The quantification of anti-HSA with the LET immunoassay is possible with this new approach at concentrations as low as 220 pmol L(-1).

New chromogenic and fluorogenic reagents and sensors for neutral and ionic analytes based on covalent bond formation–a review of recent developments

To date, hydrogen bonding and Coulomb, van der Waals and hydrophobic interactions are the major contributors to non-covalent analyte recognition using ionophores, ligands, aptamers and chemosensors. However, this article describes recent developments in the use of (reversible) covalent bond formation to detect analyte molecules, with special focus on optical signal transduction. Several new indicator dyes for analytes such as amines and diamines, amino acids, cyanide, formaldehyde, hydrogen peroxide, organophosphates, nitrogen oxide and nitrite, peptides and proteins, as well as saccharides have become available. New means of converting analyte recognition into optical signals have also been introduced, such as colour changes of chiral nematic layers. This article gives an overview of recent developments and discusses response mechanisms, selectivity and sensitivity.