© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

8.5.4.1 Nuclear Envelope

The nuclear envelope enclosing the nucleus is a lipid bilayer similar in structure to the cell membrane, except that it is a double-layered membrane which is topologically more convenient for dissolution during mitosis and subsequent reassembly from vesicles. Each of the two lipid bilayer membranes is 7-8 nm thick. The outer nuclear membrane is occasionally continuous with the rough endoplasmic reticulum and is almost entirely surrounded by it (Fig. 8.45). Like the rough ER, the outer membrane is often studded on its outer surface with ribosomes involved in protein synthesis.⁹³⁹ Intermediate filaments extend outward from the outer membrane into the cytoplasm, anchored on the other end to the plasma membrane or other organelles, thus positioning the nucleus firmly within the cell and increasing its mechanical stiffness almost tenfold.⁹⁴²

The perinuclear space (or perinuclear cisterna) between the two membranes ranges in width from 10-70 nm but is usually a gap of 20-40 nm. This fluid-filled compartment is continuous with the cisternae of the rough ER (Fig. 8.46), thus providing one possible avenue for transporting substances between the nucleus and different parts of the cytoplasmic compartment.

The nuclear envelope disassembles at the onset of mitosis and is reassembled at the end of mitosis.¹¹⁴⁰

Last updated on 20 February 2003