Enhanced stability of two model proteins in an agitated solution environment using poloxamer 407.

To enhance the physical stability of two model proteins during solution agitation, we investigated the interaction of the nonionic surfactant poloxamer 407 (Pluronic F-127) with each protein. Vigorous agitation of aqueous solutions of interleukin-2 and urease which contained no poloxamer 407 and were maintained at 4 degrees C resulted in a greater than 50% loss in the biological activity at 12 and 24 hours, respectively. Similar aqueous solutions which were maintained at 4 degrees C and contained either urease or interleukin-2 and poloxamer 407 at a concentration of 10% w/w and 0.5% w/w, respectively lost negligible biological activity when left undisturbed for 96 hours. Moreover, when aqueous solutions of urease and interleukin-2 which contained poloxamer 407 at a concentration of 10% w/w and 0.5% w/w, respectively were maintained at 4 degrees C and subjected to agitation for 96 hours, no significant loss in the biological activity was observed for either protein. In addition, urease was observed to have increased enzymatic activity at early time points regardless of the hydrodynamic solution conditions and poloxamer 407 concentrations evaluated. In contrast, a negligible enhancement in the biological activity of interleukin-2 was observed when aqueous solutions of the protein were exposed to similar hydrodynamic conditions employed for urease solutions, but different poloxamer concentrations (0% w/w vs. 0.5% w/w). Results of molar ellipticity, [theta], versus wavelength, lambda, profiles using CD spectropolarimetry on individual aqueous solutions of both proteins containing 2% w/w poloxamer 407 were in close agreement to spectrum obtained with each protein in pH = 7 phosphate buffer (PB).(ABSTRACT TRUNCATED AT 250 WORDS)