The Photocatalyzed Thiol-ene reaction: A New Tag to Yield Fast,Selective and reversible Paramagnetic Tagging of Proteins

Paramagnetic restraints have been used in biomolecular NMR for the last three decades to elucidate and refine biomolecular structures, but also to characterize protein-ligand interactions. A common technique to generate such restraints in proteins, which do not naturally contain a (paramagnetic) metal, consists in the attachment to the protein of a lanthanide-binding-tag (LBT). In order to design such LBTs, it is important to consider the efficiency and stability of the conjugation, the geometry of the complex (conformational exchanges and coordination) and the chemical inertness of the ligand. Here we describe a photo-catalyzed thiol-ene reaction for the cysteine-selective paramagnetic tagging of proteins. As a model, we designed an LBT with a vinyl-pyridine moiety which was used to attach our tag to the protein GB1 in fast and irreversible fashion. Our tag T1 yields magnetic susceptibility tensors of significant size with different lanthanides and has been characterized using NMR and relaxometry measurements.     

Structural Insight into IAPP‐Derived Amyloid Inhibitors and Their Mechanism of Action

Designed peptides derived from the islet amyloid polypeptide (IAPP) cross‐amyloid interaction surface with Aβ (termed interaction surface mimics or ISMs) have been shown to be highly potent inhibitors of Aβ amyloid self‐assembly. However, the molecular mechanism of their function is not well understood. Using solution‐state and solid‐state NMR spectroscopy in combination with ensemble‐averaged dynamics simulations and other biophysical methods including TEM, fluorescence spectroscopy and microscopy, and DLS, we characterize ISM structural preferences and interactions. We find that the ISM peptide R3‐GI is highly dynamic, can adopt a β‐like structure, and oligomerizes into colloid‐like assemblies in a process that is reminiscent of liquid–liquid phase separation (LLPS). Our results suggest that such assemblies yield multivalent surfaces for interactions with Aβ40. Sequestration of substrates into these colloid‐like structures provides a mechanistic basis for ISM function and the design of novel potent anti‐amyloid molecules.     

Alternating Current Electrolysis for the Electrocatalytic Synthesis of Mixed Disulfide via Sulfur–Sulfur Bond Metathesis towards Dynamic Disulfide Libraries

A novel approach of electrolysis using alternating current was applied in the sulfur–sulfur bond metathesis of symmetrical disulfides towards unsymmetrical disulfides. As initially expected, a statistical distribution in disulfides was obtained. Furthermore, the influence of electrode polarisation by alternating current was investigated on a two-disulfide matrix. The highly dynamic nature of this chemistry resulted in the creation of dynamic disulfide libraries by expansion of the matrices, consisting of up to six symmetrical disulfides. In addition, mixing of matrices and stepwise expanding of a matrix by using alternating current electrolysis were realised.     

Zur Kenntnis der Kristallstruktur von Melem C6N7(NH2)3

On the Crystal Structure of Melem C₆N₇(NH₂)₃ Single crystals of melem ( 1 ) were grown from both DMSO‐solutions and the gas phase. The structure of melem ( 1 ) was solved by single‐crystal X‐ray diffraction (P2₁/c, Z = 4, a = 741.66(15), b = 862.28(17), c = 1335.9(3) pm, β = 99.91(3)° R1 = 0.037 for 1098 reflections). The structure determination by X‐ray powder diffraction, which has been previously conducted, is in agreement with our data. The increased quality of the structural information allows for a more detailed understanding of the hydrogen bonding network.     

Synthesis and structural characterization of tris(2-oxo-1-tert-butylimidazolyl) and tris(2-oxo-1-methylbenzimidazolyl)hydroborato complexes: a new class of tripodal oxygen donor ligand

A new class of tripodal L(2)X ligands that feature three oxygen donors, namely the tris(2-oxo-1-tert-butylimidazolyl) and tris(2-oxo-1-methylbenzimidazolyl)hydroborato ligands, [To(Bu(t))] and [To(MeBenz)], has been synthesized via the reactions of NaBH(4) with the respective imidazolone. Structural and spectroscopic studies indicate that both [To(Bu(t))] and [To(MeBenz)] are significantly more sterically demanding but less electron donating than the related [O(3)] donor ligand, [CpCo{P(O)(OEt)(2)}(3)].     

4]Pseudorotaxanes with remarkable self-sorting selectivities

The synthesis and characterization of several self-assembled [4]pseudorotaxanes is reported, some of which form in a programmed way based on two similar yet orthogonal crown ether/secondary ammonium ion binding motifs. A preference for the formation of a [4]pseudorotaxane with an antiparallel rather than parallel alignment of crown ether building blocks is observed even in the absence of such orthogonal binding sites, when a homodivalent axle is used.     

The effect of data scaling on dual prices and sensitivity analysis in linear programs

In many practical situations scaling the data is necessary to solve linear programs. This note explores the relationships in translating the sensitivity analysis between the original and the scaled problems.     

Grundlegende technische Forderungen an Radioisotopen-Meßgeräte

In zunehmendem Maße werden Meßgeräte unter Verwendung von Radionuklid-Strahlungsquellen in der Industrie zum Zweck der Prozeßüberwachung, -messung und -regelung eingesetzt. Unter den rauhen Umgebungsbedingungen kommt es dabei besonders auf eine hohe Zuverlässigkeit der Geräte an, da Störungen oder Ausfälle der Meßtechnik – je nach dem Einsatzort – mitunter sehr unangenehme Ausfälle im Produktionsprozeß zur Folge haben. Ein Beispiel für den Einsatz eines Radioisotopen-Meßgerätes in der industriellen Fertigungstechnik ist die Flächengewichtsmeßanlage FMM 24004. Aus der Vielfalt der bei der Entwicklung solcher Geräte zu beachtenden Festlegungen, Vorschriften und Randbedingungen werden in dieser Arbeit, ohne Anspruch auf Vollständigkeit erheben zu können, einige wesentliche Aspekte dargestellt.     

Selective Inhibitors of FKBP51 Employ Conformational Selection of Dynamic Invisible States

The recently discovered SAFit class of inhibitors against the Hsp90 co‐chaperone FKBP51 show greater than 10 000‐fold selectivity over its closely related paralogue FKBP52. However, the mechanism underlying this selectivity remained unknown. By combining NMR spectroscopy, biophysical and computational methods with mutational analysis, we show that the SAFit molecules bind to a transient pocket in FKBP51. This represents a weakly populated conformation resembling the inhibitor‐bound state of FKBP51, suggesting conformational selection rather than induced fit as the major binding mechanism. The inhibitor‐bound conformation of FKBP51 is stabilized by an allosteric network of residues located away from the inhibitor‐binding site. These residues stabilize the Phe67 side chain in a dynamic outward conformation and are distinct in FKBP52, thus rationalizing the basis for the selectivity of SAFit inhibitors. Our results represent a paradigm for the selective inhibition of transient binding pockets.