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Swelling of brome mosaic virus as studied by intensity fluctuation spectroscopy

1977; Elsevier BV; Volume: 114; Issue: 2 Linguagem: Inglês

10.1016/0022-2836(77)90209-1

1089-8638

M. Zulauf,

Plant and Fungal Interactions Research

The swelling of brome mosaic virus induced by pH and temperature has been investigated with intensity fluctuation spectroscopy. A special light-scattering cell was designed which permits titrations within the cell in which Stokes radii, pH and temperature are measured simultaneously. Freshly prepared viruses in the presence of EDTA at 20 °C show a partially irreversible swelling in a first titration cycle (pH 5.8 to 7.2 to 5.8): the viruses do not recontract completely to the original compact form. All further titration cycles lead to a closed hysteresis with respect to the Stokes radii. These are stable in the swelling branch (obtained when adding base) of the titration cycle, but metastable in the contraction branch (i.e. when adding acid). In the latter, the Stokes radii relax to the values observed in the swelling branch within a few hours. If MgCl2 is present, fresh viruses have slightly bigger radii than with EDTA, and the initial titration cycle is closed. It exhibits a similarly pronounced hysteresis with a metastable contraction branch as in the abscence of divalent cations. However, further titrations do not exhibit significant hysteresis. An irreversible swelling of the viruses can be induced in the absence of Mg2+ by raising the temperature from 5 ° to 35 °C at a constant pH value. In the presence of MgCl2, Stokes radii are not affected by temperature.