Fig. 7
The observation of across-disulfide NOEs. (a) In a disulfide bond, dipolar interactions between the geminal protons cause problematic spin diffusion and hamper the quantitative analysis of the four across-disulfide NOEs. (b) By incorporating equimolar amounts of (2R,3S)- and (2R,3R)-[β-13C;α,β-2H2] Cys into a target protein, quantitative across-disulfide NOEs are observed in the complete absence of the geminal dipolar interactions. (c) In conventional UL proteins, the geminal NOEs are observed, and spin diffusion hampers the quantitative analysis of the across-disulfide NOEs. (d) In the ((2R, 3RS)-[3-13C;2,3-2H2] Cys, [U-2H])-labeled protein, the geminal NOEs are eliminated, and quantitative NOEs are observed (Reproduced from Takeda et al. [48] with permission)