Presence of nucleoside triphosphates and calcium associated with mycobacteriophage 13

The association of nucleoside triphosphate molecules and calcium ions with purified particles of mycobacteriophage 13 has been documented. The content of nucleoside triphosphate has been determined to be 118 molecules per phage particle by equilibrium dialysis against labelled ATP or 148 molecules per phage particle by the direct determination of labelled nucleoside triphosphate. The concentration of bound Ca2+ exhibited a high degree of variation between different batches, which may be due to the nonspecific binding of Ca2+ by the virus particles. However, the tightly bound Ca2+ not removable by dialysis against calcium-specific chelating agent, showed a constant value of 2985 atoms/phage particle.