No abstract

A general method for the non-oxidative functionalization of single-crystal silicon(111) surfaces is described. The silicon surface is fully acetylenylated using two-step chlorination/alkylation chemistry. A benzoquinone-masked primary amine is attached to this surface via Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition ("click" chemistry). The benzoquinone is electrochemically reduced, resulting in quantitative cleavage of the molecule and exposing the amine terminus. Molecules presenting a carboxylic acid have been immobilized to the exposed amine sites. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and contact angle goniometry were utilized to characterize and quantitate each step in the functionalization process. This work represents a strategy for providing a general platform that can incorporate organic and biological molecules on Si(111) with minimal oxidation of the silicon surface.

We describe a general synthetic strategy for developing high affinity peptide binders against specific epitopes of challenging protein biomarkers. The epitope of interest is synthesized as a polypeptide, with a detection biotin tag and a strategically placed azide (or alkyne) presenting amino acid. This synthetic epitope (SynEp) is incubated with a library of complementary alkyne or azide presenting peptides. Library elements that bind the SynEp in the correct orientation undergo the Huisgen cycloaddition, and are covalently linked to the SynEp. Hit peptides are tested against the full-length protein to identify a best binder. We describe epitope-targeted linear or macrocycle peptide ligands against 12 different diagnostic or therapeutic analytes. The general epitope targeting capability for these low molecular weight synthetic ligands enables a range of therapeutic and diagnostic applications, similar to those of monoclonal antibodies.

The development of a miniaturized sensing platform for the selective detection of chemical odorants could stimulate exciting scientific and technological opportunities. Oligopeptides are robust substrates for the selective recognition of a variety of chemical and biological species. Likewise, semiconducting nanowires are extremely sensitive gas sensors. Here we explore the possibilities and chemistries of linking peptides to silicon nanowire sensors for the selective detection of small molecules. The silica surface of the nanowires is passivated with peptides using amide coupling chemistry. The peptide/nanowire sensors can be designed, through the peptide sequence, to exhibit orthogonal responses to acetic acid and ammonia vapors, and can detect traces of these gases from "chemically camouflaged" mixtures. Through both theory and experiment, we find that this sensing selectivity arises from both acid/base reactivity and from molecular structure. These results provide a model platform for what can be achieved in terms of selective and sensitive "electronic noses."

Special agents for protein capture: Iterative in situ click chemistry (see scheme for the tertiary ligand screen) and the one‐bead–one‐compound method for the creation of a peptide library enable the fragment‐based assembly of selective high‐affinity protein‐capture agents. The resulting ligands are water‐soluble and stable chemically, biochemically, and thermally. They can be produced in gram quantities through copper(I)‐catalyzed cycloaddition.

We describe the use of iterative in situ click chemistry to design an Akt-specific branched peptide triligand that is a drop-in replacement for monoclonal antibodies in multiple biochemical assays. Each peptide module in the branched structure makes unique contributions to affinity and/or specificity resulting in a 200 nM affinity ligand that efficiently immunoprecipitates Akt from cancer cell lysates and labels Akt in fixed cells. Our use of a small molecule to pre-inhibit Akt prior to screening resulted in low micromolar inhibitory potency and an allosteric mode of inhibition, which is evidenced through a series of competitive enzyme kinetic assays. To demonstrate the efficiency and selectivity of the protein-templated in situ click reaction, we developed a novel QPCR-based methodology that enabled a quantitative assessment of its yield. These results point to the potential for iterative in situ click chemistry to generate potent, synthetically accessible antibody replacements with novel inhibitory properties

Auf Proteinfang: Iterative Klick‐Reaktionen (siehe Schema des dritten Liganden‐Screenings) und eine Methode zum Aufbau von Bibliotheken mit einer Verbindung pro Kügelchen ermöglichten die Synthese von selektiven, hoch affinen Proteineinfangagentien aus einzelnen Fragmenten. Die resultierenden Liganden sind wasserlöslich und (bio)chemisch sowie thermisch stabil. Durch Kupfer(I)‐katalysierte Cycloadditionen sind sie im Gramm‐Maßstab zugänglich.

We report on a robust and sensitive approach for detecting protective antigen (PA) exotoxin from Bacillus anthracis in complex media. A peptide-based capture agent against PA was developed by improving a bacteria display-developed peptide into a highly selective biligand through in situ click screening against a large, chemically synthesized peptide library. This biligand was coupled with an electrochemical enzyme-linked immunosorbent assay utilizing nanostructured gold electrodes. The resultant assay yielded a limit of detection of PA of 170 pg/mL (2.1 pM) in buffer, with minimal sensitivity reduction in 1% serum. The powdered capture agent could be stably stored for several days at 65 °C, and the full electrochemical biosensor showed no loss of performance after extended storage at 40 °C. The engineered stability and specificity of this assay should be extendable to other cases in which biomolecular detection in demanding environments is required.