Nuclear-magnetic-resonance-spectroscopic studies of the amino groups of insulin.
The amino groups of insulin have been studied by 1H and 13C nuclear magnetic resonance spectroscopy in insulin, zinc-free insulin and methylated insulin. By difference spectroscopy it is possible to follow the shift with pH of the epsilon-CH2 and delta-CH2 proton resonances of lysine-B29 in insulin. In methylated insulin the dimethyl proton resonances of glycine-A1, phenylalanine-B1 and lysine-B29 can be followed as a function of pH. In native insulin pKapp values of 6.7 and 8.0 are obtained for phenylalanine-B1 and glycine-A1 (the assignment is tentative) and 11.2 for lysine-B29. Separate resonances have been observed from the lysine-B29 Nepsilon-(CH3)2 group for the monomeric and dimeric forms of methylated insulin, which indicates a small change in the environment of lysine-B29 on dimerisation. The nuclear magnetic resonance spectral characteristics of these groups are, in general, consistent with the overall structure of the crystal form of the 2-zinc insulin hexamer.
D000588:Amines / Q000032:analysis; D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D006863:Hydrogen-Ion Concentration; D007328:Insulin; D008239:Lysine / Q000032:analysis; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D011487:Protein Conformation
D000588:Amines; D007328:Insulin; D008239:Lysine