Crystallization of Enantiomerically Pure Proteins from Quasi-Racemic Mixtures: Structure Determination by X-Ray Diffraction of Isotope-Labeled Ester Insulin and Human Insulin

摘要

As a part of a program aimed towards the study of the dynamics of human insulin-protein dimer formation using two-dimensional infrared spectroscopy, we used total chemical synthesis to prepare stable isotope labeled [(1-C-13=O-18)Phe(B24))] human insulin, via [(1-C-13=O-18)Phe(B24))] ester insulin as a key intermediate product that facilitates folding of the synthetic protein molecule (see preceding article). Here, we describe the crystal structure of the synthetic isotope-labeled ester insulin intermediate and the product synthetic human insulin. Additionally, we present our observations on hexamer formation with these two proteins in the absence of phenol derivatives and/or Zn metal ions. We also describe and discuss the fractional crystallization of quasi-racemic protein mixtures containing each of these two synthetic proteins.