Differential pulse-polarographic analysis of tobacco mosaic virus

The tobacco mosaic virus (TMV) strain vulgare and its mutant TMV 483 (with glutamine-9 replaced by histidine) and the denatured protein of TMV vulgare were analysed by direct current (d. c.) and differential (derivative) pulse polarography (DPP) in the basic electrolyte composed of 0.001 M Co(NH3)6Cl3, 0.1 M NH4Cl and 0.1 M NH3 at 0 degrees C. The DPP method gave a substantially better resolution of the polarographic catalytic maxima A and B, but a much lower resolution of the maxima B and C, as compared with the d. c. polarographic method. The clear differentiation of the maximum A from maximum B by DPP permitted to study the variation of maximum A in the course of alkaline degradation of TMV. But for the study of TMV protein denaturation the d. c. polarography is preferable, because the denaturation is accompanied by the appearance and rise of maximum C which can be clearly differentiated from maximum B by d. c. polarography rather than by DPP. The DPP method was more, sensitive than d. c. polarography. The denatured TMV protein can be determined by DPP at concentrations around 0.1 microgram/ml.