Nanometric distance measurements between Mn(ii)DOTA centers

Phys Chem Chem Phys. 2015 Sep 28;17(36):23368-77. doi: 10.1039/c5cp03487f. Epub 2015 Aug 19.


Pulse electron-electron double resonance (PELDOR) is a versatile technique for probing the structures and functions of complex biological systems. Despite the recent interest in high-spin metal-ions for high field/frequency applications, PELDOR measurements of Mn(ii) remain relatively underexplored. Here we present Mn(ii)-Mn(ii) PELDOR distance measurements at 94 GHz on polyproline II (PPII) helices doubly spin-labeled with Mn(ii)DOTA, which are distinguished by their small zero-field interaction. The measured Mn-Mn distances and distribution profiles were in good agreement with the expected values from molecular models. Additional features in the frequency-domain spectra became apparent at certain combinations of detect and pump frequencies. Spin-Hamiltonian calculations showed that they likely arose from contributions from the pseudo-secular component of the dipolar interaction that were found to be non-negligible for Mn(ii)DOTA. However, the influence of the pseudo-secular component on the distance distribution profiles apparently was limited. The results show the potential of Mn(ii)DOTA spin labels for high-field PELDOR distance measurements in proteins and other biological systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Coordination Complexes / chemistry*
  • Cysteine / chemistry
  • Electron Spin Resonance Spectroscopy
  • Heterocyclic Compounds, 1-Ring / chemistry*
  • Maleimides / chemistry
  • Manganese*
  • Models, Molecular
  • Peptides / chemistry*
  • Protein Structure, Secondary
  • Spin Labels*


  • Coordination Complexes
  • Heterocyclic Compounds, 1-Ring
  • Maleimides
  • Peptides
  • Spin Labels
  • 1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid
  • polyproline
  • maleimide
  • Manganese
  • Cysteine