Quaternary Carbon Assignment HCC – Purine HCC – Pyrimidine Long-Range HSQC HNC Distance Determination HN NOESY Hydrogen Bond Experiments HNN COSY Non-Refocused HSQC J Coupling Determination Quantitative J HCP R1 and R1rho Trosy-detected 13C R1 Trosy-detected 13C R1rho 13C R1 13C R1rho