Partial reactivation of impaired immune competence in aged mice by synthetic thymus factors

The stability of mouse uterine cytosol receptor-[³H]estradiol complex was evaluated in the presence of neutral salts of the Hoffmeister series. Marked increases in the rate of dissociation of the complex were observed with the more chaotropic anions (SCN^?, $\text{ClO}{}_4{}^{\mathrm{?}}$, $\text{NO}{}_3{}^{\mathrm{?}}$, Br^?), and the effects of these ions were greater at lower temperatures, where water assumes a more rigid structure. At higher temperatures F^? and CH₃COO^?, which tend to stabilize water structure, led to retardation of the rate of dissociation of the hormone-receptor complex. There was essentially no change in steroid specificity in the presence of the markedly chaotropic salts. The perturbation of water structure adjacent to the steroid binding site is a factor to be considered in the isolation of steroid receptor complexes.