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Dual sedimentation of T2 bacteriophage of Escherichia coli

1957; Elsevier BV; Volume: 25; Linguagem: Inglês

10.1016/0006-3002(57)90466-3

1878-2434

Irwin J. Bendet, Louis G. Swaby, Max A. Lauffer,

Protein purification and stability

For T2 bacteriophage, diffusion coefficients of 3.25·10−8 cm2/sec and 2.63·10−8 cm2/sec were obtained in pH 5 and pH 7 buffers, respectively. The transition limits for dual sedimentation encompass approximately one-half pH units, with a central value at about pH 6.1. Sedimenting the virus from a medium of one pH directly into a second medium of greater density and different pH has indicated that the sedimentation rate change is quite sharp and complete within a few minutes after passing through the interface. s5/D5 differs significantly from s7/D7 but not enough to represent one-to-one aggregation. It is, therefore, assumed that the molecular weight is the same at pH 7 and pH 5. It follows from this assumption and the experimental results that fs7/fs5 is significantly greater than fD7/fD5. A model has been found which can account for all of these facts. It is assumed that at pH 5 the particle is tadpole-shaped but that at pH 7 it projects thin filaments laterally from the tail. Such filaments have been demonstrated with the electron microscope. Calculations of friction coefficients made for complex ellipsoidal models approximating the actual models discussed above yield results consistent with the experimental observations, if it is assumed that the particles are oriented randomly during diffusion but sediment in the direction of their longest axis.