Category Archives: CIDNP

Electron Spin Density Distribution in the Special Pair Triplet of Rhodobacter sphaeroides R26 Revealed by Magnetic Field Dependence of the Solid-State Photo-CIDNP Effect

Thamarath, S.S., et al., Electron Spin Density Distribution in the Special Pair Triplet of Rhodobacter sphaeroides R26 Revealed by Magnetic Field Dependence of the Solid-State Photo-CIDNP Effect. J. Am. Chem. Soc., 2012. 134(13): p. 5921-5930.

http://dx.doi.org/10.1021/ja2117377

Photo-CIDNP (photochemically induced dynamic nuclear polarization) can be observed in frozen and quinone-blocked photosynthetic reaction centers (RCs) as modification of magic-angle spinning (MAS) NMR signal intensity under illumination. Studying the carotenoidless mutant strain R26 of Rhodobacter sphaeroides, we demonstrate by experiment and theory that contributions to the nuclear spin polarization from the three-spin mixing and differential decay mechanism can be separated from polarization generated by the radical pair mechanism, which is partially maintained due to differential relaxation (DR) in the singlet and triplet branch. At a magnetic field of 1.4 T, the latter contribution leads to dramatic signal enhancement of about 80 000 and dominates over the two other mechanisms. The DR mechanism encodes information on the spin density distribution in the donor triplet state. Relative peak intensities in the photo-CIDNP spectra provide a critical test for triplet spin densities computed for different model chemistries and conformations. The unpaired electrons are distributed almost evenly over the two moieties of the special pair of bacteriochlorophylls, with only slight excess in the L branch.

A 10‚000-fold Nuclear Hyperpolarization of a Membrane Protein in the Liquid Phase via a Solid-State Mechanism

Daviso, E., et al., A 10‚000-fold Nuclear Hyperpolarization of a Membrane Protein in the Liquid Phase via a Solid-State Mechanism. J. Am. Chem. Soc., 2011. 133(42): p. 16754-16757.

http://dx.doi.org/10.1021/ja206689t

Several techniques rely on electron-nuclear interactions to boost the polarization of nuclear spins in the solid phase. Averaging out of anisotropic interactions as a result of molecular tumbling strongly reduces the applicability of such hyperpolarization approaches in liquids. Here we show for the first time that anisotropic electron-nuclear interactions in solution can survive sufficiently long to generate nuclear spin polarization by the solid-state photo-CIDNP mechanism. A 10,000-fold NMR signal increase in solution was observed for a giant biomolecular complex of a photosynthetic membrane protein with a tumbling correlation time in the submicrosecond regime, corresponding to a molecular weight close to 1 MDa.

A 10‚000-fold Nuclear Hyperpolarization of a Membrane Protein in the Liquid Phase via a Solid-State Mechanism

Daviso, E., et al., A 10‚000-fold Nuclear Hyperpolarization of a Membrane Protein in the Liquid Phase via a Solid-State Mechanism. J. Am. Chem. Soc., 2011. 133(42): p. 16754-16757.

http://dx.doi.org/10.1021/ja206689t

Several techniques rely on electron-nuclear interactions to boost the polarization of nuclear spins in the solid phase. Averaging out of anisotropic interactions as a result of molecular tumbling strongly reduces the applicability of such hyperpolarization approaches in liquids. Here we show for the first time that anisotropic electron-nuclear interactions in solution can survive sufficiently long to generate nuclear spin polarization by the solid-state photo-CIDNP mechanism. A 10,000-fold NMR signal increase in solution was observed for a giant biomolecular complex of a photosynthetic membrane protein with a tumbling correlation time in the submicrosecond regime, corresponding to a molecular weight close to 1 MDa.

Have a question?

If you have questions about our instrumentation or how we can help you, please contact us.