A quantitative, real-time assessment of binding of peptides and proteins to gold surfaces

Interactions of peptides and proteins with inorganic surfaces are important to both natural and artificial systems; however, a detailed understanding of such interactions is lacking. In this study, we applied new approaches to quantitatively measure the binding of amino acids and proteins to gold surfaces. Real‐time surface plasmon resonance (SPR) measurements showed that TEM1‐β‐lactamase inhibitor protein (BLIP) interacts only weakly with Au nanoparticles (NPs). However, fusion of three histidine residues to BLIP (3H‐BLIP) resulted in a significant increase in the binding to the Au NPs, which further increased when the histidine tail was extended to six histidines (6H‐BLIP). Further increasing the number of His residues had no effect on the binding. A parallel study using continuous (111)‐textured Au surfaces and single‐crystalline, (111)‐oriented, Au islands by ellipsometry, FTIR, and localized surface plasmon resonance (LSPR) spectroscopy further confirmed the results, validating the broad applicability of Au NPs as model surfaces. Evaluating the binding of all other natural amino acid homotripeptides fused to BLIP (except Cys and Pro) showed that aromatic and positively‐charged residues bind preferentially to Au with respect to small aliphatic and negatively charged residues, and that the rate of association is related to the potency of binding. The binding of all fusions was irreversible. These findings were substantiated by SPR measurements of synthesized, free, soluble tripeptides using Au‐NP‐modified SPR chips. Here, however, the binding was reversible allowing for determination of binding affinities that correlate with the binding potencies of the related BLIP fusions. Competition assays performed between 3H‐BLIP and the histidine tripeptide (3 His) suggest that Au binding residues promote the adsorption of proteins on the surface, and by this facilitate the irreversible interaction of the polypeptide chain with Au. The binding of amino acids to Au was simulated by using a continuum solvent model, showing agreement with the experimental values. These results, together with the observed binding potencies and kinetics of the BLIP fusions and free peptides, suggest a binding mechanism that is markedly different from biological protein–protein interactions.     

Annulated Azuleno[2,1,8-ija]azulenes: Synthesis and Properties

Non-alternant non-benzenoid hydrocarbons exhibit very different optical and electronic properties than their well-studied benzenoid analogues. However, preparing such structures with extended conjugation length, remains challenging. Herein, we report the synthesis and properties of azuleno[2,1,8-ija]azulene derivatives using a two-step sequence involving a four-fold aldol condensation between aromatic dialdehydes and readily available tetrahydropentalene-2,5-(1H,3H)-dione. Molecules with band gap values ranging from 1.69 to 2.14 eV and molar extinction coefficients (ϵ) of nearly 3×10⁵ M⁻¹ cm⁻¹ have been prepared. These annulene-like structures exhibit significant diatropic ring currents (aromatic), as supported by ¹H NMR spectroscopy and DFT calculations. Field-effect transistors (OFETs) using azuleno[2,1,8-ija]azulene derivatives as semiconductors exhibit charge mobility values of up to 0.05 cm² V⁻¹ s⁻¹.     

Anionic polymerization of arylbismuth,lead and tin derivatives of styrene and α-methylstyrene

Styryl- and α-methylstyryldiphenylbismuth (I and II, respectively), and styryl and α-methylstyryltriphenyllead and the two corresponding tin-containing monomers (III, IV, V and VI, respectively) were synthesized. Compounds III through VI were obtained pure, but I and II contain substantial quantities of Ph₃Bi and di- and tri-vinyl derivatives. Homopolymers of I, III and V, as well as copolymers with methyl acrylate were synthesized radically. Monomers III, V, and VI yielded narrow MWD polymers with anionic initiators such as the potassium salt of the α-methylstyrene dimer carbanion in THF at −80°C, while I gave a broad, bimodal MWD. Monomers II and IV did not polymerize under these conditions due to side reactions with the initiator. Glass transition temperatures, thermal stabilities and radiopacities of a number of the polymers were determined.     

Realising countable groups as automorphisms of origamis on the Loch Ness monster

Archiv der Mathematik - It is known that every finite group can be represented as the full group of automorphisms of a suitable compact origami. In this paper, we provide a short argument to note...     

Dimerization of a Reactive Azaacene Diradical: Synthesis of a Covalent Azaacene Cage

Two series of regioisomeric dicyanomethylene substituted dithienodiazatetracenes with formal para- or ortho-quinodimethane subunits were synthesized and characterized. Whereas the para-isomers (p-n, diradical index y₀=0.01) are stable and isolable, the ortho-isomer (y₀=0.98) dimerizes into a covalent azaacene cage. Four elongated σ-CC bonds are formed and the former triisopropylsilyl(TIPS) -ethynylene groups transformed into cumulene units. The azaacene cage dimer (o-1)₂ was characterized by X-ray single crystal structure analysis and temperature-dependent infrared (IR), electron paramagnetic resonance (EPR, solid-state), nuclear magnetic resonance (NMR) and ultraviolet-visible (UV/Vis) spectroscopies (solution) indicating reformation of o-1.