H spin system identifications of S-sulfonated insulin B chain with 2D-NMR

Resonance assignments of the 1H spectrum of insulin are the basis on which to investigate its solution conformation by using NMR method. Owing to the complicated aggregation behaviour of the molecule to give broadened n. m. r. lines, only limited resonance assignments have been reported. S-sulfonated A and B chains of insulin gave 1H spectra with good resolutions. Based on the 500 MHz absolute 2D-COSY spectrum and 400 MHz phase sensitive DQF-COSY, Relayed-COSY and NOESY spectra of B chain recorded in D2O, all of the spin system identifications of the non-labile protons in the S-sulfonated B chain of insulin were reported including the specific resonance assignments of eight residues: B3Asn, B9Ser, B16Tyr, B22Arg, B26Tyr, B27Thr, B28Pro and B29Lys. The pK values of B16 and B26 tyrosine are 10.65 and 10.60 respectively from pH titration.