A relay FRET event in a designed trichromophoric pentapeptide containing an o-,m-aromatic-amino acid scaffold.

The concept of a relay FRET event is established in a designed trichromophoric pentapeptide containing an o-,m-aromatic amino acid scaffold in the backbone as a novel ß-turn mimetic ß-sheet folding nucleator. This system would find application in studying fundamental processes involving interbiomolecular interactions in chemical biology.

Homogeneous Catalysis: A Powerful Technology for the Modification of Important Biomolecules.

Homogeneous catalysis plays an important and ubiquitous role in the synthesis of simple and complex molecules, including drug compounds, natural products, and agrochemicals. In recent years, the wide-reaching importance of homogeneous catalysis has made it an indispensable tool for the modification of biomolecules, such as carbohydrates (sugars), amino acids, peptides, nucleosides, nucleotides, and steroids. Such a synthetic strategy offers several advantages, which have led to the development of new molecules of biological relevance at a rapid rate relative to the number of available synthetic methods. Given the powerful nature of homogeneous catalysis in effecting these synthetic transformations, this Focus Review has been compiled to highlight these important developments.

Uracil-amino acid as a scaffold for ß-sheet peptidomimetics: Study of photophysics and interaction with BSA protein.

We report herein the uracil-di-aza-amino acid (UrAA) as a new family of molecular scaffold to induce ß-hairpin structure with H-bonded ß-sheet conformation in a short peptide. This has been demonstrated in two conceptual fluorescent pentapeptides wherein triazolylpyrenyl alanine and/or triazolylmethoxynapthyl alanine (TPyAlaDo and/or TMNapAlaDo) are embedded into two arms of the uracil-amino acid via an intervening leucine. Conformational analysis by CD, IR, variable temperature and 2D NMR spectroscopy reveals the ß-hairpin structures for both the peptides. Study of photophysical property reveals that the pentapeptide containing fluorescent triazolyl unnatural amino acids TMNapAlaDo and TPyAlaDo at the two termini exhibits dual path entry to exciplex emission-either via FRET from TMNapAlaDo to TPyAlaDo or via direct excitation of a FRET acceptor, TPyAlaDo. The other pentapeptide with TPyAlaDo/TPyAlaDo pair shows excimer emission. Furthermore, both the peptides maintaining their fundamental photophysics are found to interact with BSA as only a test biomolecule.

Synthesis of Functionalized Pyrazoles via Vanadium-Catalyzed C-N Dehydrogenative Cross-Coupling and Fluorescence Switch-On Sensing of BSA Protein.

Vanadium-catalyzed C-N dehydrogenative cross-coupling of alkenyl hydrazones leading to functionalized pyrazoles is described in a 1:1 mixture of toluene/H2O using air as the terminal oxidant. Significant practical features include use of the commercial nontoxic VOSO4 as a recyclable catalyst, mild reaction conditions, scalability, and the broad substrate scope. Some of the product pyrazoles exhibit interesting photophysical properties. Fluorescence light-up sensing of BSA protein by one of the pyrazoles is also highlighted.

Triazolo-ß-aza-ε-amino acid and its aromatic analogue as novel scaffolds for ß-turn peptidomimetics.

Triazolo-ß-aza-ε-amino acid and its aromatic analogue ((Al)TAA/(Ar)TAA) in the peptide backbone mark a novel class of conformationally constrained molecular scaffolds to induce ß-turn conformations. This was demonstrated for (Al)TAA in a Leu-enkephalin analogue and in a designed pentapeptide wherein the FRET process was established. Restricted rotation induced chirality and turn conformation into the achiral aromatic amino acid scaffold, (Ar)TAA, which in a short tripeptide backbone acted as a ß-turn mimic as a ß-sheet folding nucleator.

Triazolyl-donor-acceptor chromophore-decorated unnatural amino acids and peptides: FRET events in a ß-turn conformation.

The ß-turn conformation and FRET process were established in the designed tripeptide containing fluorescent triazolyl donor and acceptor-decorated unnatural amino acids separated by a natural alanine.