Journal of the American Chemical Society, Vol.127, No.1, 405-411, 2005
Polychromatic selective population inversion for TROSY experiments with large proteins
This paper presents polychromatic selective polarization inversion (PC-SPI) as an alternative to the polarization transfer methods recently developed for the application of NMR to large biological molecules. Theoretical and numerical considerations indicate that PC-SPI has the potential for more efficient polarization transfer under conditions of rapid transverse relaxation compared to J coupling- and cross-correlated relaxation-based transfers. The main advantage offered by the method presented here is the maintenance of near-optimal trajectories of inversion of the individual components of the spin magnetization while using broadband optimized pulses. A 2D experiment was implemented combining PC-SPI with TROSY-based chemical shift correlation. The experiment was applied to detect N-15-H-1 chemical shift correlation spectra of a 200 kDa complex consisting of an 80% H-2- and uniformly N-15,C-13-Iabeled 22 kDa portion of complement receptor type 1 and unlabeled C3b of complement (180 kDa).