PHYSICOCHEMICAL PROPERTIES OF PURIFIED STAPHYLOCOCCAL ENTEROTOXIN B

Abstract

Abstract : Staphylococcal enterotoxin B exhibited a high degree of molecular homogeneity as determined by synthetic boundary spreading, approach-to- equilibrium sedimentation, and sedimentation equilibrium distribution in a density gradient. Its partial specific volume and infrared spectral absorption were typical of simple protein b. The molecular weight by sedimentation-diffusion was found to be 35,300 and was in good agreement with results by the Archibald procedure. There was stability in sedimentation behavior over a wide pH range (5 to 10) and an observed transition to a more extended structural form at pH 3.8. A net hydration of 0.075 gram of water per gram of protein was evaluated by extrapolation to zero sedimentation rate in aqueous sucrose, and values of 0.158 and 0.136 gram per gram were obtained from measurements of enterotoxin density and solvated molecular weight (40,100), respectively, in buoyant cesium chloride solution. Intrinsic viscosity and sedimentation-diffusion data were combined to yield a value of 2.14 x 10 to the 6th power for the Scheraga-Mandelkern parameter beta. The latter is discussed in terms of its implications as to the nature of the hydrodynamic enterotoxin unit.