ResearchApr 20, 20260 views

Peptide ligands to explore interactions with intrinsically disordered multidomain proteins: the case of SARS-CoV-2 nucleocapsid protein.

Peptide ligands just scored another win for research on tricky protein targets. This time, a team out of Florence used synthetic peptides to probe the SARS-CoV-2 nucleocapsid protein — the viral workhorse that packages RNA and keeps the coronavirus running. Instead of targeting the usual rigid binding sites, they went after the protein’s floppy, “intrinsically disordered” regions. These areas are notoriously tough for traditional small molecules.

Sci Rep

by Tino AS, Quagliata M, Schiavina M et al.

“Peptide ligands to explore interactions with intrinsically disordered multidomain proteins: the case of SARS-CoV-2 nucleocapsid protein. Tino AS(1)(2), Quagliata M(1)(3), Schiavina M(1)(2), Attanasio L(1)(2), Santos BPO(1)(2), Pacini L(1)(3), Papini AM(4)(5), Pierattelli R(6)(7), Felli IC(8)(9). Author information: (1)Department of Chemistry "Ugo Schiff", University of Florence, Via Della Lastruccia 3-13, 50019, Sesto Fiorentino, Florence, Italy. (2)Magnetic Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy. (3)Interdepartmental Research Unit of Peptide and Protein Chemistry and Biology (PeptLab), University of Florence, Via Della Lastruccia 13, 50019, Sesto Fiorentino, Florence, Italy. (4)Department of Chemistry "Ugo Schiff", University of Florence, Via Della Lastruccia 3-13, 50019, Sesto Fiorentino, Florence, Italy. annamaria.papini@unifi.it. (5)Interdepartmental Research Unit of Peptide and Protein Chemistry and Biology (PeptLab), University of Florence, Via Della Lastruccia 13, 50019, Sesto Fiorentino, Florence, Italy. annamaria.papini@unifi.it. (6)Department of Chemistry "Ugo Schiff", University of Florence, Via Della Lastruccia 3-13, 50019, Sesto Fiorentino, Florence, Italy. roberta.pierattelli@unifi.it. (7)Magnetic Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy. roberta.pierattelli@unifi.it. (8)Department of Chemistry "Ugo Schiff", University of Florence, Via Della Lastruccia 3-13, 50019, Sesto Fiorentino, Florence, Italy. isabellacaterina.felli@unifi.it. (9)Magnetic Resonance Center (CERM), University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy. isabellacaterina.felli@unifi.it. The SARS-CoV-2 nucleocapsid protein (N), essential for viral RNA packaging, comprises a structured RNA-binding domain, NTD(44-180), flanked by intrinsically disordered regions, IDR1 (1-43) and IDR2 (181-248). This extended, positively charged RNA-binding surface makes it an attractive target for synthetic ligands able to interfere with its function. In this study, peptide ligands were explored as synthetically accessible alternatives for modulating N interactions. After confirming the ability of a reference peptide (P0) in engaging IDRs in the interaction, we shifted our attention to key properties that modulate the interaction with the central domain NTD(44-180). Two new peptides (P1 and P2) were designed with identical amino acid compositions but distinct sequence arrangements. In each one a para-fluorinated phenylalanine residue was incorporated to introduce an aromatic component useful to mimic RNA bases and enable 19F NMR detection. Molecular dynamics simulations, circular dichroism, and NMR spectroscopy were combined to characterize the structural, dynamic and binding properties of P1 and P2. Both peptides involve the RNA-binding groove of the N protein (NTD(44-180)). While P1 demonstrated higher α-helical propensity and favorable electrostatic interactions, P2 displayed stronger interactions through enhanced conformational adaptability. 19F NMR experiments confirmed complex formation also from the ligand perspective. These findings support a modular peptide design strategy for targeting multidomain proteins. © 2026. The Author(s). Conflict of interest statement: Declarations. Competing interests: The authors declare no competing interests.”

Here’s how they pulled it off. First, they confirmed that a reference peptide (P0) could latch onto the nucleocapsid’s disordered segments. Then, they dialed up the complexity: the researchers designed two new peptides, P1 and P2, both with the same amino acids but different sequences. Each got a para-fluorinated phenylalanine, letting them track binding with 19F NMR and mimic some of RNA’s chemistry.

The results:

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Both peptides targeted the protein’s central RNA-binding groove.

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P1 packed more alpha-helix structure and played nice with the protein’s charge.

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P2, on the other hand, was flexible — and that adaptability led to even stronger binding.

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19F NMR confirmed that both new peptides actually formed complexes with the SARS-CoV-2 nucleocapsid.

Key takeaway: modular peptide design works. You don’t need to reinvent the wheel for every target. The right peptide backbone and a little fluorine chemistry can open up hard-to-drug proteins, especially ones full of disordered regions.

This is a solid example of why peptide research isn’t going anywhere. For more on custom sequences and how researchers are designing novel ligands, check the peptide research index. If you’re looking to source research peptides or compare suppliers, the vendor directory is the next stop.

Peptides continue to push the boundaries — even against viral proteins that refuse to sit still.

Back to News Read original on Sci Rep

Peptide ligands to explore interactions with intrinsically disordered multidomain proteins: the case of SARS-CoV-2 nucleocapsid protein.

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