Download MendeleyCucurbit[7]uril Enhances Distance Measurements of Spin-Labeled Proteins.
Yang, Z., Stein, R.A., Pink, M., Madzelan, P., Ngendahimana, T., Rajca, S., Wilson, M.A., Eaton, S.S., Eaton, G.R., Mchaourab, H.S., Rajca, A.(2023) J Am Chem Soc 145: 25726-25736
- PubMed: 37963181
- DOI: https://doi.org/10.1021/jacs.3c09184
- Primary Citation of Related Structures:
8F11 - PubMed Abstract:
We report complex formation between the chloroacetamide 2,6-diazaadamantane nitroxide radical (ClA-DZD) and cucurbit[7]uril (CB-7), for which the association constant in water, K a = 1.9 × 10 6 M -1 , is at least 1 order of magnitude higher than the previously studied organic radicals. The radical is highly immobilized by CB-7, as indicated by the increase in the rotational correlation time, τ rot , by a factor of 36, relative to that in the buffer solution. The X-ray structure of ClA-DZD@CB-7 shows the encapsulated DZD guest inside the undistorted CB-7 host, with the pendant group protruding outside. Upon addition of CB-7 to T4 Lysozyme (T4L) doubly spin-labeled with the iodoacetamide derivative of DZD, we observe the increase in τ rot and electron spin coherence time, T m , along with the narrowing of interspin distance distributions. Sensitivity of the DEER measurements at 83 K increases by a factor 4-9, compared to the common spin label such as MTSL, which is not affected by CB-7. Interspin distances of 3 nm could be reliably measured in water/glycerol up to temperatures near the glass transition/melting temperature of the matrix at 200 K, thus bringing us closer to the goal of supramolecular recognition-enabled long-distance DEER measurements at near physiological temperatures. The X-ray structure of DZD-T4L 65 at 1.12 Å resolution allows for unambiguous modeling of the DZD label (0.88 occupancy), indicating an undisturbed structure and conformation of the protein.
Organizational Affiliation:
Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, United States.
