The cell nucleus of eukaryotic organisms contains the genome surrounded by a nuclear envelope consisting of a double-lipid membrane with embedded nuclear pores and an underlying nuclear lamina. The uniformity in size and density makes it possible to isolate pure intact nuclei at high yields from tissue homogenates by centrifugation through a sucrose cushion. Nuclear envelopes can be prepared from isolated nuclei by enzymatic degradation of their nucleic acid content. The resulting nuclear envelope preparations contain structurally well-conserved inner and outer nuclear membranes with attached ribosomes, nuclear pore complexes and nuclear lamina. Reliable methods for preparation of nuclei and nuclear envelopes play an important role in the successful identification of components that are located in nuclei and in nuclear subcompartments.

Key Concepts:

• The genetic information in the nucleus of the eukaryotic cell is packaged in the form of chromatin and surrounded by a double-lipid membrane called the nuclear envelope.
  
• Pure intact nuclei can be isolated at high yields from tissue homogenates, and nuclear envelopes can be prepared from the isolated nuclei.
  
• The preparation of pure nuclei is important for the identification of nuclear and subnuclear components.