A DIFFERENTIAL SCANNING CALORIMETRIC STUDY OF NEWCASTLE-DISEASE VIRUS- IDENTIFICATION OF PROTEINS INVOLVED IN THERMAL TRANSITIONS

The irreversible thermal denaturation of Newcastle disease virus was i nvestigated using different techniques including high-sensitivity diff erential scanning calorimetry, thermal gel analysis intrinsic fluoresc ence, and neuraminidase activity assays. Application of a successive a nnealing procedure to the scanning calorimetric endotherm of Newcastle disease virus furnished four elementary thermal transitions below the overall endotherm; these were further identified as coming from the d enaturation of each viral protein. The shape of these transitions, as well as their scan-rate dependence, was explained by assuming that the rmal denaturation takes place according to the kinetic scheme N -->(k) D, where k is a first-order kinetic constant that changes with temper ature, as given by the Arrhenius equation; N is the native state; and D is the denatured state. On the basis of this model, activation energ y values were calculated. The data obtained with the other methods use d in this work support the proposed two-state kinetic model. (C) 1997 Academic Press.