Singlet oxygen-mediated one-pot chemoselective peptide–peptide ligation

Abstract

We here describe a furan oxidation based site-specific chemical ligation approach using unprotected peptide segments. This approach involves two steps: after photooxidation of a furan-containing peptide, ligation is achieved by reaction of the unmasked keto-enal with C- or N-terminal α-nucleophilic moieties of the second peptide such as hydrazine or hydrazide to form a pyridazinium or pyrrolidinone linkage respectively.

Visible-light triggered templated ligation on surface using furan-modified PNAs

“…As a rst step towards the construction of the envisaged system, the potential of light-induced furan-oxidation for efficient PNA-PNA ligation in solution was evaluated. Starting from the results previously obtained in peptide labelling and ligation, 58,59 the ligation of two complementary PNA probes was explored. In situ activation of the furan ring to its highly reactive keto-enal form was followed by reaction with a nucleophilic entity (i.e.…”

“…While hydrazines enable the formation of pyridazinium adducts, nucleophiles with a single nucleophilic nitrogen (such as amines, hydrazides, or semicarbazides) lead to the generation of pyrrolidinone species as previously demonstrated. 58,59 Preliminary ligation experiments performed on 11mer PNA systems demonstrated the feasibility of the approach, and, at the same time, the fact that HPLC-based techniques are not well suited to distinguish between true ligation products and very stable dsPNA:PNA complexes (data not shown).…”

“…[54][55][56] This methodology was subsequently applied as a means to immobilize DNA on surfaces, 57 and later on extended to the context of peptide labelling and peptide-peptide ligation, exploiting in the latter cases the chemo-selective reactivity of the activated furan moiety towards a-effect nucleophiles. 58,59 In this work the rst example of a light-triggered templated ligation exploiting a stable but pro-reactive furan moiety which can be oxidized to its reactive keto-enal form by light induced singlet oxygen ( 1 O 2 ) generation (Fig. 1C) 60 is shown.…”

“…The molecular weight of the formed products is in accordance with the calculated masses, based on the different mechanisms of ligation reported earlier. 59 From the HPLC-MS chromatograms, signals connected to collateral oxidative damage of the nucleobases have not been detected but signals relative to the degradation of hydrazide and semicarbazide functional groups in PNA-Hd1 and PNA-Sc1 respectively, were found to occur during the irradiation step (data not shown). This degradation seems to occur at the expense of the starting materials, as these by-products were also found when performing the experiments with mismatched and scrambled sequences, where products were not formed.…”

Visible Light Photochemical Reactions for Nucleic Acid-Based Technologies

“…Peptide nucleic acids are artificial nucleic acid mimics, and they have advantages with their electrically neutral backbone, such as lower electrostatic repulsion from DNA or RNA, naturally negatively charged phosphate backbones, and high stability under various experimental conditions. This group developed a furan oxidation-based interstrand cross-linking for nucleic acids [66] and expanded this methodology into peptide nucleic acid probes for DNA capture [67] and visible light-triggered peptide labeling [68,69].…”