A photosensitized singlet oxygen ( 1 O 2) toolbox for bio-organic applications : tailoring 1 O 2 generation for DNA and protein labelling, targeting and biosensing

Singlet oxygen (O-1(2)) is the excited state of ground, triplet state, molecular oxygen (O-2). Photosensitized O-1(2) 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 O-1(2,) discussing the main bioorganic applications reported over the past decades, which rely on its production. After a brief introduction on the photosensitized production of O-1(2), 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 O-1(2) generation, including protein and DNA labelling, cross-linking and biosensing. Finally, we will highlight the methodologies available to tailor O-1(2) 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

Equipping coiled-coil peptide dimers with furan warheads reveals novel cross-link partners

Using a coiled-coil peptide dimer as a model system to explore furan reactivity, we describe novel cross-link partners of furan warheads for site-specific cross-linking. We demonstrate that replacement of weak interhelical ionic contacts with a furan moiety and its potential cross-link partner affords covalently connected coiled-coil motifs upon furan activation. We describe for the first time the reaction of the activated furan warhead with cysteine and tyrosine, besides the previously reported lysine, thus enhancing the versatility of the furan cross-link methodology by the possibility to target different amino acids. The present in vitro validation of “furan-armed” α-helices provides further grounds for exploiting furan technology in the development of furan-modified ligands/proteins to target proteins in a covalent way through various amino acid side chains

Photo-induced crosslinking uncovers an antiparallel strand orientation in heterodimeric (EIAALEK)3/(KIAALKE)3 and (EIAALEK)3/(RIAALRE)3 coiled-coil systems

We describe for the first time the co-existence of the parallel and antiparallel conformation of the heterodimeric E3/K3 and E3/R3 coiled-coil systems in solution. The introduction of a furanylated amino acid in the (EIAALEK)(3) sequence allowed, upon photo-induced covalent crosslinking, freezing of the respective coiled-coil complexes present in solution. The occurrence of both parallel and antiparallel conformations in solution was supported by computational simulations and further confirmed by fluorescence experiments based on pyrene-pyrene stacking