A SPIN SYSTEM LABELED AND HIGHLY RESOLVED ED-H(CCO)NH-TOCSY EXPERIMENT FOR THE FACILITATED ASSIGNMENT OF PROTON SIDE-CHAINS IN PARTIALLY DEUTERATED SAMPLES

The introduction of deuterated and partially deuterated protein sample s has greatly facilitated the C-13 assignment of larger proteins. Here we present a new version of the HC(CO)NH-TOCSY experiment, the ed-H(C CO)NH-TOCSY experiment for partially deuterated samples, introducing a multi-quantum proton evolution period. This approach removes the main relaxation source (the dipolar coupling to the directly bound C-13 sp in) and leads to a significant reduction of the proton and carbon rela xation rates. Thus, the indirect proton dimension can be acquired with high resolution, combined with a phase labeling of the proton resonan ces according to the C-C spin system topology. This editing scheme, in dependent of the CHn multiplicity, allows to distinguish between proto n side-chain positions occurring within a narrow chemical shift range. Therefore this new experiment facilitates the assignment of the proto n chemical shifts of partially deuterated samples even of high molecul ar weights, as demonstrated on a 31 kDa protein.