Accurate Random Coil Chemical Shifts from an Analysis of Loop Regions in Native States of Proteins

We present a method for calculating accurate random coil chemical shift values of proteins. These values are obtained by analyzing the relationship between the amino acid sequences in flexible loop regions of native states and the corresponding experimentally measured chemical shifts. We estimate the errors in the random coil chemical shift scales to be 0.31 ppm for C-13(a), 0.37 ppm for C-13(B), 0.31 ppm for (CO)-C-13, 0.68 ppm for N-15, 0.09 ppm for H-1, and 0.04 ppm for H-1(a).