Influence of embedding media on DNA structure in herpes simplex virus type 1

The organization of encapsidated herpes simplex viral DNA in situ was examined by use of the osmium-amine stain specific for DNA. After either formaldehyde or glutaraldehyde fixation the DNA is packaged in a compact toroid without inner structure with Epon or GMA embedment but revealed a complex inner structure with Lowicryl K4M embedment. In the latter there was an inner cylindrical core, 50 X 80 nm, around which were apposed one or more thick filaments of 5-8 nm diameter. Thinner DNA filaments of 3-4 nm diameter form a cage of loose coils around the core with an intervening space of approximately 15 nm. Lowicryl embedding may be considered as a tool to investigate the packaging of viral DNA in virions.