3 - The Chemistry of the Interstitial Cell-Stimulating Hormone of Ovine Pituitary Origin

Abstract

This chapter discusses the chemistry of the interstitial cell-stimulating hormone (ICSH) of ovine pituitary origin. The preparations of ovine ICSH described by Squire and Li, Papkoff et al., and Ward et al., have been extensively characterized by ultracentrifugation studies both from the standpoint of determining homogeneity and to determine molecular weights. Early determinations of the molecular weight of ICSH employed the sedimentation constant and some other parameter such as the diffusion coefficient. The value for the partial specific volume that is needed for such calculations was usually assumed to be near 0.73. The early preparations of Squire and Li, and Ward et al. were examined by the technique of free boundary electrophoresis. This procedure allowed not only the homogeneity of the hormone to be examined, but the determination of the isoelectric point (pI) as well. A cursory examination of the optical rotary dispersion (ORD) properties of ICSH by Jirgensons led him to conclude that ICSH contained few, if any, of its amino acid residues in an a-helix configuration.