Templating a polymer-scaffolded dynamic combinatorial library

A water soluble polymer-scaffolded dynamic combinatorial library whose members can interconvert through acylhydrazone exchange was prepared and shown to re-equilibrate in the presence of macromolecular templates.     

Diastereoselective amplification of an induced-fit receptor from a dynamic combinatorial library

A high-affinity, induced-fit receptor for NMe4I was discovered using dynamic combinatorial chemistry. The addition of the guest to a dynamic combinatorial library made using a racemic mixture of chiral building blocks caused the strong and highly diastereoselective amplification of the receptor at the expense of other library components. The receptor and its mode of binding were characterized by NMR, ITC, and re-equilibration experiments, from which it was deduced that the receptor probably forms a folded four-stave barrel shape on binding of the guest.     

Highly diastereoselective amplification from a dynamic combinatorial library of macrocyclic oligoimines

Cadmium promoted diastereoselective amplification of a single member from a dynamic combinatorial library of stereoisomeric oligoimines of different sizes allows the efficient preparation of a new macrocyclic polyamine.     

Amplification of bifunctional ligands for calmodulin from a dynamic combinatorial library

A well known strategy to prepare high affinity ligands for a biological receptor is to link together low affinity ligands. DCC (dynamic combinatorial chemistry) was used to select bifunctional protein ligands with high affinity relative to the corresponding monofunctional ligands. Thiol to disulfide linkage generated a small dynamic library of bifunctional ligands in the presence of calmodulin, a protein with two independently mobile domains. The binding constant of the bifunctional ligand (disulfide) most amplified by the presence of calmodulin is nearly two orders of magnitude higher than that of the corresponding monofunctional ligand (thiol).     

Ligand amplification in a dynamic combinatorial glycopeptide library

N-acetyl glucosamine binding protein amplifies the concentration of one member in a dynamic combinatorial glycopeptide library based on exchanging disulfides.     

Tubulin-guided dynamic combinatorial library of thiocolchicine-podophyllotoxin conjugates

The use of tubulin as a target to influence the composition of the mixture from a dynamic combinatorial library, based on the disulfide bond exchange reaction, is described. ESI-FT-ICR-MS was used to determine the composition of the library. The heterodimeric compound amplified by this approach was used to design the homologous derivative with a two-carbon spacer in place of the disulfide function. The ability of the compounds to inhibit tubulin polymerization is reported and compared to thiocolchicine.     

Direct screening of a dynamic combinatorial library using mass spectrometry

A dynamic combinatorial library (DCL) screening approach is described that permits direct identification of the effective (from ineffective) combination of building blocks in the equilibrating DCL. The approach uses Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS) together with sustained off-resonance irradiation collision activated dissociation (SORI-CAD) to detect noncovalent protein-DCL ligand complexes under native conditions. It was shown that in a single, rapid experiment one could concurrently identify all the ligands of interest from the DCL against a background of inactive DCL ligands while still in the presence of the target protein. This result has demonstrated that mass spectrometry may provide a fast preliminary screening approach to identify DCL candidates for later verification with more traditional but time-consuming analysis. The MS/MS enables DCL mixtures to be effectively deconvoluted without the need for either chromatography, synthesis of DCL sub-libraries, conversion of the DCL to a static library, or disruption of the protein-ligand complexes before analysis--all typically necessary for the current screening method for DCLs.     

Target-induced selection of ligands from a dynamic combinatorial library of mono- and bi-conjugated oligonucleotides

A dynamic library of 15 mono- and bi-conjugated oligonucleotides was generated from a pool of three aldehydes and an oligonucleotide bearing two reactive amino groups. Addition of complementary target to the equilibrating mixture of imines resulted in selective amplification of one conjugate. UV-melting experiments confirmed that it was the best ligand among those that were tested. This study emphasizes that dynamic combinatorial chemistry can be used to simultaneously identify the type and the location of appended residues for stabilizing oligonucleotide complexes.     

Amplification of a cyclic mixed-metalloporphyrin tetramer from a dynamic combinatorial library through orthogonal metal coordination

A cyclic porphyrin tetramer, consisting of two bis-phosphine substituted zinc(II) porphyrin units and two Rh(III)TPP units, is selected and amplified virtually quantitatively from a dynamic combinatorial library using 4,4'-bipy as a scaffold and using orthogonal binding modes.     

Rapid identification of substrates for novel proteases using a combinatorial peptide library

Fluorogenic substrates for assaying novel proteolytic enzymes could be rapidly identified using an easy, solid-phase combinatorial assay technology. The methodology was validated with leader peptidase of Escherichia coli using a subset of an intramolecularly quenched fluorogenic peptide library. The technique was extended toward the discovery of substrates for a new aspartic protease of pharmaceutical relevance (human napsin A). We demonstrated for the first time known to us that potent fluorogenic substrates can be discovered using extracts of cells expressing recombinant enzyme to screen the peptide library. The straightforward and rapid optimization of protease substrates greatly facilitates the drug discovery process by speeding up the development of high throughput screening assays and thus helps more effective exploitation of the enormous body of information and chemical structures emerging from genomics and combinatorial chemistry technologies.     

Metal-ion induced amplification of three receptors from dynamic combinatorial libraries of peptide-hydrazones

Three building blocks of general structure (MeO)2 CH-aromatic linker-Pro-amino acid-NHNH2 have been prepared and tested in acid-catalysed dynamic combinatorial libraries. Exposure of these libraries to LiI and NaI led to the amplification of three macrocyclic pseudopeptide receptors. The receptors were isolated and their interactions with LiI and NaI were analysed using NMR, IR and ITC. Binding of the metal ions to the receptors is invariably entropy-driven. Nevertheless, all receptors were found to be flexible with substantial conformational rearrangements accompanying guest binding. This type of receptor is extremely difficult to access through rational design and the fact that dynamic combinatorial chemistry allows facile access to these challenging molecules underlines the power of the dynamic approach.