Spin-labeled heparins as polarizing agents for dynamic nuclear polarization.
A potentially biocompatible class of spin-labeled macromolecules, spin-labeled (SL) heparins, and their use as nuclear magnetic resonance (NMR) signal enhancers are introduced. The signal enhancement is achieved through Overhauser-type dynamic nuclear polarization (DNP). All presented SL-heparins show high (1)H DNP enhancement factors up to E=-110, which validates that effectively more than one hyperfine line can be saturated even for spin-labeled polarizing agents. The parameters for the Overhauser-type DNP are determined and discussed. A striking result is that for spin-labeled heparins, the off-resonant electron paramagnetic resonance (EPR) hyperfine lines contribute a non-negligible part to the total saturation, even in the absence of Heisenberg spin exchange (HSE) and electron spin-nuclear spin relaxation (T(1ne)). As a result, we conclude that one can optimize the use of, for example, biomacromolecules for DNP, for which only small sample amounts are available, by using heterogeneously distributed radicals attached to the molecule.
Dollmann
Björn C
BC
Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Kleschyov
Andrei L
AL
Sen
Vasily
V
Golubev
Valery
V
Schreiber
Laura M
LM
Spiess
Hans W
HW
Münnemann
Kerstin
K
Hinderberger
Dariush
D
D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006493:Heparin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D013113:Spin Labels
D013113:Spin Labels; D006493:Heparin