Structures of peptide ligands in PCC Agent cocktail.

<p>Acetylene-presenting anchor peptides (black) were derived from the immunogenic epitope of HIV-1 gp41 (residues 600–612). A22-nindG (<b>i</b>) and A21-hnpfk (<b>ii</b>) were evolved from the original epitope appended with Pra at the C-terminus whereas A22-eihny (<b>iii</b>) utilizes the “substituted” anchor where residue Leu-607 is replaced with Pra. Secondary ligand branches (colored) were identified from the <i>in situ</i> click screen of a 5-mer OBOC library presenting an azide functionality. Biligands (<b>i</b>) and (<b>ii</b>) were raised against the target anti-HIV antibody 3D6, and the biligand (<b>iii</b>) was raised against the antibody 4B3.</p

Screening strategy for selecting capture agents against anti-HIV antibodies 3D6 and 4B3.

<p>The flow chart represents the use of the A21 and A22 cyclic peptides as anchor ligands for separate in situ click screens against a large OBOC azide-presenting peptide library.</p

A Chemically Synthesized Capture Agent Enables the Selective, Sensitive, and Robust Electrochemical Detection of Anthrax Protective Antigen

We report on a robust and sensitive approach for detecting protective antigen (PA) exotoxin from <i>Bacillus anthracis</i> 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 <i>in situ</i> 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

Correction to A Chemically Synthesized Capture Agent Enables the Selective, Sensitive, and Robust Electrochemical Detection of Anthrax Protective Antigen

Correction to A Chemically Synthesized Capture Agent Enables the Selective, Sensitive, and Robust Electrochemical Detection of Anthrax Protective Antige

Iterative in Situ Click Chemistry Assembles a Branched Capture Agent and Allosteric Inhibitor for Akt1

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 preinhibit 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