Examination of a purified A' influenza virus preparation by potentiometry.

Abstract

The potentiometric titration of a purified influenza A′ virus preparation revealed 100.7×10−4 M base and 68.8 × 10−4 M acid-binding capacity per g. of virus protein N. The titration curve was characterized by the following fourpK′ values:pK 1′ = 3.37;pK 2′ = 4.50;pK 3′ = 6.37, andpK 4′ = 9.75. The isoionic point was at pH 5.43. Attempt was made to identify the dissociating groups and it was found that the carboxylic groups (pK 1′ andpK 2′) may either be glutamyl or aspartyl groups, while the cationic groups are probably the imidazolium of histidine (pK 3′) and the ɛ-amino residues of lysine (pK 4′). Inaotivation of the hemagglutinating activity of the virus preparation by mild treatment with formaldehyde at pH 8.0 resulted in a simultaneous disappearence of the ɛ-amino groups of lysine (pK 4′). The same treatment at pH 9.0 resulted in the loss of all the cationic groups previously demonstrable. The possible role of the stable positive charges on the surface of the virus at physiological pH is discussed from the point of view of the physico-chemistry of the hemagglutination.