Sequence-specific assignments in NMR spectra of paramagnetic systems: A non-systematic approach

Inês B. Trindade, Michele Invernici, Francesca Cantini, Ricardo O. Louro, Mario Piccioli

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)
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The complete assignment of 1H, 13C and 15N protein signals, which is a straightforward task for diamagnetic proteins provided they are folded, soluble and with a molecular mass below 30,000 Da, often becomes an intractable problem in the presence of a paramagnetic center. Indeed, the hyperfine interaction quenches signal intensity; this prevents the detection of scalar and dipolar connectivities and the sequential assignment of protein regions close to the metal ion(s). However, many experiments can be optimized and novel experiments can be designed to circumvent the problem and to revive coherences invisible in standard experiments. The small HiPIP protein PioC provides an interesting case to address this issue: the prosthetic group is a [Fe4S4]2+ cluster that is bound to the 54 amino acids protein via four cysteine residues. The four cluster-bound cysteine residues adopt different binding conformations and therefore each cysteine is affected by paramagnetic relaxation to different extent. A network of tailored experiments succeeded to obtain the complete resonance assignment of cluster bound residues.

Original languageEnglish
Article number119984
JournalInorganica Chimica Acta
Publication statusPublished - 1 Jan 2021


  • Biological inorganic chemistry
  • Iron-sulfur proteins
  • Metal ion in biological systems
  • Metalloproteins
  • Paramagnetic NMR


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