Projection structures of human immunodeficiency virus type 1 (HIV-1) observed with high resolution electron cryo-microscopy.

An electron microscopical study was made of human immunodeficiency virus type 1 (HIV-1) in the unstained, frozen, hydrated state at liquid helium temperature. The findings were compared with those obtained from negative staining and ultrathin sectioning. Electron cryo-microscopy confirms and extended the findings obtained by conventional methods. In particular, the virus is shown to be globular, the lipid membrane is clearly resolved as a bi-layer and the bi-layer was demonstrated to be non-uniform in width. The projections studied in the bi-layer are clearly observed to be knob-like and consist of a head, a stalk and a base.