Dynamic light-scattering study on changes in flexibility of filamentous bacteriophage Pf1 with temperature

The temperature dependence of the flexibility of bacteriophage Pf1 was investigated by dynamic light scattering, and the following results were obtained: The gamma/K2 values measured at 1 degree-25 degrees C and at various K values were T/eta-scaled to 20 degrees C, where gamma is the first cumulant of the field correlation function of scattered light, K is the length of the scattering vector, T is the absolute temperature, and eta is the solvent viscosity at T. And it was found that the scaled gamma/K2 values at low K values were independent of temperature, whereas those at high K values increased sigmoidally and reversibly against temperature. This suggests that the virion is more flexible at temperatures above the transition temperature Tt. This characteristic temperature Tt depended on the pH of the suspension: Tt = 11 degrees C at pH 6.9 and Tt = 8 degrees C at pH 8.2.