1H NMR spectrum of the native human insulin monomer. Evidence for conformational differences between the monomer and aggregated forms.

摘要: The effects of high dilution on the 1H Fourier transform NMR spectrum native human insulin at pH* 8.0 and 9.3 have been examined 500 MHz resolution. dependence concentration comparison with a biologically highly potent monomeric mutant (SerB9----Asp) establish that 36 microM (pH* 9.3) or 18 8) no added buffer salts, is monomeric. Under these conditions dilution, ionic strength, pH*, SerB9----Asp exhibit nearly identical spectra. At higher concentrations (i.e. greater than to 0.91 mM), dimerizes, this aggregation causes change in conformation. Although there are many changes spectrum, TyrB26 ring H3,5 proton signals located 6.63 ppm methyl signal 0.105 (characteristics insulin) particularly distinct signatures conformation accompanies dimerization. Magnetization transfer experiments show shifts downfield new position 0.45 ppm. We conclude due which Leu group centered over van der Waals contact an aromatic side chain. Dimerization alters interaction, thereby causing shift. Nuclear Overhauser studies indicate involved within cluster chains closest ring-methyl interaction PheB24.