Photo-oxidative cross-linking of thiol polydimethylsiloxane co-polymers via disulfide formation

Disulfide bonds are often employed as reductively cleavable sites in biomaterials and polymers. Here we demonstrate the aerobic photo-cross-linking of thiol-containing polymers through disulfide formation using a sensitizer and telluride catalyst.

A Phage-Compatible Strategy to Access Macrocyclic Peptides Featuring Asymmetric Molecular Scaffolds as Cyclization Units

The cyclization of peptides appended onto proteins or whole bacteriophages is typically achieved via disulfide formation, the use of symmetric crosslinkers or the incorporation of noncanonical amino acids. Unfortunately, neither of these strategies is amenable toward generating libraries for the selection of macrocyclic peptides (MPs) akin to those found in nature, which often feature asymmetric molecular scaffolds as cyclization units that improve binding to their targets. To meet this challenge, we present an efficient two-step strategy to access MPs via the programmed modification of a unique cysteine residue and an N-terminal amine. We demonstrate that this approach yields MPs featuring asymmetric cyclization units from both synthetic peptides and when linear precursors are appended onto a phage-coat protein. Given that the employed conditions are compatible with phage display protocols, our work paves the way for the selection of natural-product-like MPs from randomized peptide sequences by phage display.

A Phage-Compatible Strategy to Access Macrocyclic Peptides Featuring Asymmetric Molecular Scaffolds as Cyclization Units

The cyclization of peptides appended onto proteins or whole bacteriophages is typically achieved via disulfide formation, the use of symmetric crosslinkers or the incorporation of noncanonical amino acids. Unfortunately, neither of these strategies is amenable toward generating libraries for the selection of macrocyclic peptides (MPs) akin to those found in nature, which often feature asymmetric molecular scaffolds as cyclization units that improve binding to their targets. To meet this challenge, we present an efficient two-step strategy to access MPs via the programmed modification of a unique cysteine residue and an N-terminal amine. We demonstrate that this approach yields MPs featuring asymmetric cyclization units from both synthetic peptides and when linear precursors are appended onto a phage-coat protein. Given that the employed conditions are compatible with phage display protocols, our work paves the way for the selection of natural-product-like MPs from randomized peptide sequences by phage display.

Distinct roles and actions of PDI family enzymes in catalysis of nascent-chain disulfide formation

The mammalian endoplasmic reticulum (ER) harbors more than 20 members of the protein disulfide isomerase (PDI) family that act to maintain proteostasis. Herein, we developed an in vitro system for directly monitoring PDI- or ERp46-catalyzed disulfide bond formation in ribosome-associated nascent chains (RNC) of human serum albumin. The results indicated that ERp46 more efficiently introduced disulfide bonds into nascent chains with short segments exposed outside the ribosome exit site than PDI. Single-molecule analysis by high-speed atomic force microscopy further revealed that PDI binds nascent chains persistently, forming a stable face-to-face homodimer, whereas ERp46 binds for a shorter time in monomeric form, indicating their different mechanisms for substrate recognition and disulfide bond introduction. Similarly to ERp46, a PDI mutant with an occluded substrate-binding pocket displayed shorter-time RNC binding and higher efficiency in disulfide introduction than wild-type PDI. Altogether, ERp46 serves as a more potent disulfide introducer especially during the early stages of translation, whereas PDI can catalyze disulfide formation in RNC when longer nascent chains emerge out from ribosome.

New insights into the disulfide bond formation enzymes in epidithiodiketopiperazine alkaloids

A FAD-dependent oxidoreductase TdaR was responsible for α, β-disulfide formation in the biosynthesis of pretrichodermamide A. TdaR, together with its homologs AclT and GliT, catalysed not only α, α- but also α, β-disulfide formation in fungi.