Intracellular DNA Damage by Lysine-Acetylene Conjugates

Previously, we reported the design and properties of alkyne C-lysine conjugates, a powerful and tunable family of DNA cleaving reagents. We also reported that, upon photoactivation, these molecules are capable of inducing cancer cells death. To prove that the cell death stems from DNA cleavage by the conjugates, we investigated intracellular DNA damage induced by these molecules in LNCap cancer cells using single cell gel electrophoresis (SCGE) assays. The observation of highly efficient DNA damage confirmed that lysine acetylene conjugate is capable of cleaving the densely compacted intracellular DNA. This result provides a key mechanistic link between efficient DNA cleavage and cytotoxicity towards cancer cells for this family of light-activated anticancer agents

Organocatalytic sulfoxidation

Treatment of a sulfide with a catalytic amount of a 1,3 diketone in the presence of silica sulfuric acid as a co-catalyst and hydrogen peroxide (50% aq) as the stoichiometric oxidant leads to the corresponding sulfoxide product. The reaction is effective for diaryl, aryl-alkyl and dialkyl sulfides and is tolerant of oxidisable and acid sensitive functional groups. Investigations have shown that the tris-peroxide 2, formed on reaction of pentane-2,4-dione with hydrogen peroxide under acidic reaction conditions, can oxidise two equivalents of sulfide using the exocyclic peroxide groups whereas the endocyclic peroxide remains intact. Calculations provide a mechanism consistent with experimental observations and suggest the reaction proceeds via an initial acid catalysed ring opening of a protonated tris-peroxide prior to oxygen transfer to a sulfur nucleophile

Stalling chromophore synthesis of the fluorescent protein Venus reveals the molecular basis of the final oxidation step

Fluorescent proteins (FPs) have revolutionised the life sciences, but the mechanism of chromophore maturation is still not fully understood. Here we show that incorporation of a photo-responsive non-canonical amino acid within the chromophore stalls maturation of Venus, a yellow FP, at an intermediate stage; a crystal structure indicates the presence of O2 located above a dehydrated enolate form of the imidazolone (I) ring, close to the strictly conserved Gly67 that occupies a twisted conformation. His148 adopts an “open” conformation so forming a channel that allows O2 access to the immature chromophore. Absorption spectroscopy supported by QM/MM simulations suggest that the first oxidation step involves formation of a hydroperoxyl intermediate in conjunction with dehydrogenation of the methylene bridge. A fully conjugated mature chromophore is formed through release of H2O2 on, both in vitro and in vivo. The possibility of interrupting and photochemically restarting chromophore maturation, and the mechanistic insights opens up new approaches for engineering optically controlled fluorescent proteins

A Special Issue in Honor of Professor Josef Michl

This Special Issue of Chemistry is dedicated to Professor Josef Michl [...

A Special Issue in Honor of Professor Josef Michl

This Special Issue of Chemistry is dedicated to Professor Josef Michl [...