sodium-bromide and lithium-bromide

Antidepressant drug imipramine hydrochloride (IMP) is amphiphilic which shows surfactant-like behavior in aqueous solutions. We have studied the effect of adding electrolytes and non-electrolytes on the micellar behavior of IMP by making cloud point (CP) and dye solubilization measurements. The CP of a 100mM IMP solution (prepared in 10mM sodium phosphate (SP) buffer) was found to decrease with increasing pH, both in the absence as well as presence of added salts. Increase in pH increased the visible absorbance of Sudan III dye solubilized in the drug micelles, implying micellar growth. Addition of increasing amounts of salts to 100mM IMP solutions (at pH 6.7) caused continuous increase in CP due to micellar growth. On the basis of these studies, the binding-effect orders of counter- and co-ions have been deduced, respectively, as: Br(-)>Cl(-)>F(-) and Li(+)

Topics: Azo Compounds; Bromides; Coloring Agents; Electrolytes; Emulsions; Hydrogen-Ion Concentration; Imipramine; Lithium Chloride; Lithium Compounds; Micelles; Potassium Chloride; Potassium Compounds; Quaternary Ammonium Compounds; Sodium Chloride; Sodium Compounds; Sodium Fluoride; Solubility; Solutions; Thiourea; Urea

The denaturation of ribonuclease A by guanidine hydrochloride, lithium bromide, and lithium chloride and by mixed denaturants consisting of guanidine hydrochloride and one of the denaturants lithium chloride, lithium bromide, and sodium bromide was followed by difference spectral measurements at pH 4.8 and 25 degrees C. Both components of mixed denaturant systems enhance each other's effect in unfolding the protein. The effect of lithium bromide on the midpoint of guanidine hydrochloride denaturation transition is approximately the sum of the effects of the constituent ions. For all the mixed denaturants tested, the dependence of the free energy change on denaturation is linear. The conformational free energy associated with the guanidine hydrochloride denaturation transition in water is 7.5 +/- 0.1 kcal mol-1, and it is unchanged in the presence of low concentrations of lithium bromide, lithium chloride, and sodium bromide which by themselves are not concentrated enough to unfold the protein. The conformational free energy associated with the lithium bromide denaturation transition in water is 11.7 +/- 0.3 kcal mol-1, and it is not affected by the presence of low concentrations of guanidine hydrochloride which by themselves do not disrupt the structure of native ribonuclease A.

Topics: Animals; Bromides; Calorimetry; Cattle; Chlorides; Guanidine; Guanidines; Kinetics; Lithium; Lithium Chloride; Lithium Compounds; Pancreas; Protein Denaturation; Ribonuclease, Pancreatic; Sodium; Sodium Compounds; Thermodynamics