tively, and it is estimated that there are 180 and 1,070 molecules per virion, respectively (17, 18, 32, 33, 34). Polypeptide VII comprises approximately 14%7r of the viral protein, and it has been calculated that the arginine residues of this protein are sufficient to cover approximately 60% of the phosphate charges of the viral DNA (32). Laver (22) has suggested that the alanine/ arginine-rich protein molecules are evenly distributed along the DNA molecule. As yet, the arrangement of the core inside the adenovirion and the relation between the viral DNA and the core proteins have received little attention. Robinson et al. (36) and Doerfler et al. (11) have provided evidence that the viral DNA in the virion is kept in a circular configu-366

No abstract

The Group B Staphylococcus phage P11-M15 is shown to be 51%7C protein and 49%7, deoxyribonucleic acid (DNA). The intact virion has a molecular weight of 66.7 X 106 daltons. The purified viral DNA has a molecular weight of 32.7 x 106 daltons. The intact virion is shown to be composed of a polyhedral head which is attached at one of its vertices to a flexible tail having helical symmetry. The tail structure is terminated by a complex baseplate which has sixfold symmetry. The virion contains a single molecule of double-stranded DNA which has no apparent single-strand nicks or single-stranded terminal redundancies.

Highly purified human adenovirus type 2 directly penetrated the plasma membranes of KB cells. The process of membrane penetration resulted in the appearance of large numbers of adenovirions free in the cytoplasm of the infected cells. The virions underwent a morphological change as they penetrated the cell surface. Penetration of the plasma membranes and the accompanying alteration in virion morphology was dependent on a function associated with the intact cells, because neither event occurred when purified virions were added to isolated cell membranes. Inactivation of the adenovirions with heat or antibodies before inoculation of the cells reduced the infectivity of the virus population and prevented the appearance of virions free in the cytoplasm. The inactivation of the virions did not significantly reduce the number of virus particles which were found in cell vacuoles and pinocytotic vesicles.

When human adenovirus type 2 or 12 infects cells, either productively or nonproductively, three classes of viral deoxyribonucleic acid (DNA) are found within the cells: (i) viral DNA which cosediments with DNA extracted from infectious adenovirions at 31.3S for adenovirus type 2 and at 29.OS for adenovirus type 12, (ii) viral DNA which sediments at about 18S, and (iii) viral DNA which sediments at >45S and is apparently integrated into the cellular DNA. A precursor-product relationship is suggested as a working hypothesis; the intact viral DNA is hydrolyzed to slowly sedimenting DNA and the slowly sedimenting DNA is integrated into the cellular DNA. Both the parental and the newly synthesized viral DNA are altered by this route. The intact viral DNA within the cells apparently is cleaved into the slowly sedimenting DNA by a preformed enzyme. strain adenoid 6 was obtained from the American Type Culture Collection. The identity of every virus preparation was confirmed by the buoyant density of the virions and the buoyant density and sedimentation coefficient of the DNA extracted from the purified virions. KB cells (CCL17) were obtained from the American 707