Hydrolysis of 5-methylfuran-2-yl to 2,5-dioxopentanyl allows for stable bio-orthogonal proximity-induced ligation

Triggerless Bio-Orthogonal Proximity-Induced PNA Ligation Using 2,5-Dioxopentanyl (DOP) Functionality

Peptide nucleic acids (PNAs) are emerging tools in the construction of nanostructures possessing self-assembly properties similar to those of DNA but featuring enhanced stability and chemical flexibility. Templated-ligation approaches can be exploited to stabilize the formed nanoproducts, with bio-orthogonal methods preferred for compatibility with natural components. This chapter outlines design requirements and protocols for conducting triggerless bio-orthogonal PNA ligation in solution and on glass surfaces, along with an electrophoretic monitoring protocol for assessing the outcome of solution ligation.

Proximity-Induced Ligation and One-Pot Macrocyclization of 1,4-Diketone-Tagged Peptides Derived from 2,5-Disubstituted Furans upon Release from the Solid Support

1,4-Dione-containing peptides are generated during the cleavage of 2,5-disubstituted furan-containing systems. The generated electrophilic systems then react with α-effect nucleophiles, following a Paal-Knorr-like mechanism, for the generation of macrocyclic peptides, occurring after simple resuspension of the crude peptide in water. Conveniently, the in situ generation of the electrophile from a stable furan ring avoids the complications associated with the synthesis of carbonyl-containing peptides. Detailed investigation of the reaction characteristics was first performed on supramolecular coiled-coil systems.

Synthesis and structure-activity relationship of peptide nucleic acid probes with improved interstrand-crosslinking abilities: application to biotin-mediated RNA-pulldown

The development of interstrand-crosslinking (ICL) probes for the covalent targeting of DNA and RNA sequences of interest has been extensively reported in the past decade. However, most of the reactions reported so far induce the formation of a stable adduct that cannot be reverted, thus rendering these chemistries less useful in applications where the reversibility of the reaction is needed for further downstream processing of the targeted and isolated sequences, such as enzymatic amplification steps. In this work, we report on the reversibility of the furan-mediated ICL reaction. ICL formation can be conveniently triggered by either chemical (N-bromo succinimide, NBS) or luminous stimuli (visible light irradiation in presence of a photosensitizer) and quantitative reversion can be achieved by heating the crosslinked sample at 95 °C, while maintaining the structure of the DNA/RNA targets intact. As a proof-of-concept and showing the benefits of the ICL reversibility, we apply furan-mediated ICL to the pulldown of a target RNA strand from cell lysate.

A Photosensitized Singlet Oxygen (1O2) Toolbox for Bio-Organic Applications: Tailoring 1O2 Generation for DNA and Protein Labelling, Targeting and Biosensing

Singlet oxygen (1O2) is the excited state of ground, triplet state, molecular oxygen (O2). Photosensitized 1O2 has been extensively studied as one of the reactive oxygen species (ROS), responsible for damage of cellular components (protein, DNA, lipids). On the other hand, its generation has been exploited in organic synthesis, as well as in photodynamic therapy for the treatment of various forms of cancer. The aim of this review is to highlight the versatility of 1O2, discussing the main bioorganic applications reported over the past decades, which rely on its production. After a brief introduction on the photosensitized production of 1O2, we will describe the main aspects involving the biologically relevant damage that can accompany an uncontrolled, aspecific generation of this ROS. We then discuss in more detail a series of biological applications featuring 1O2 generation, including protein and DNA labelling, cross-linking and biosensing. Finally, we will highlight the methodologies available to tailor 1O2 generation, in order to accomplish the proposed bioorganic transformations while avoiding, at the same time, collateral damage related to an untamed production of this reactive species.