Activity of artificial mutant variants of human growth hormone deficient in a disulfide bond between Cys53 and Cys165

In order to understand the role of Cys53 and Cys165 of human growth hormone (hGH) in receptor-binding and biological activity, artificial mutant variants of hGH were prepared in Escherichia coli by in vitro mutagenesis. Variants of hGH were constructed by replacement of Cys165 with Ala ([Ala165]hGH) or Ser ([Ser165]hGH), by replacement of Cys53 with Ala ([Ala53]hGH), by replacement of Cys53 and Cys165 with Ala ([Ala53, Ala165]hGH), or by replacement of Cys53 with Ala and Cys165 with Ser ([Ala53,Ser165]hGH). All of the variants constructed as well as reduced hGH exhibited less biological activity than that of intact hGH, and the decreases in biological activity were almost equal, as measured by a sensitive biological assay for growth hormone: adipose conversion assay using 3T3-F442A cells. These variants also showed less receptor-binding activity than that of intact hGH. These results suggest that it is possible neither the residue Cys53 nor Cys165 is directly involved in the receptor binding, and that the disulfide bridge between Cys53 and Cys165 in hGH may not always be crucial for the biological activity, though necessary to express full hGH activity.     

A highly sensitive spectrophotometric determination of beryllium with chromal blue G and cetyltrimethylammonium chloride

Chromal blue G in the presence of cetyltrimethylammonium chloride is proposed for the spectrophotometric determination of microgram amounts of beryllium. The sensitivity of color reaction between beryllium and chromai blue G has been greatly increased by the sensitizing action of cetyltrimethylammonium chloride (_626nm = 93,000). Beer's law is obeyed over the range 0.012–0.12 ppm of beryllium. Full color development occurs in 20 min at pH 5.5 and at 626 nm. The mole ratio of beryllium and chromai blue G in the complex is estimated to be 1:2. The proposed method is very sensitive and selective for determination of beryllium when EDTA is used as a masking agent.     

Chemoselective Catalytic Conjugate Addition of Alcohols over Amines

A highly chemoselective conjugate addition of alcohols in the presence of amines is described. The cooperative nature of the catalyst enabled chemoselective activation of alcohols over amines, allowing the conjugate addition to soft Lewis basic α,β‐unsaturated nitriles. Divergent transformation of the nitrile functionality highlights the utility of the present catalysis.     

On the global attractivity for a logistic equation with piecewise constant arguments

In this paper, we consider the following logistic equation with piecewise constant arguments: