The nuclear pore complex: biochemical machine or Maxwell demon?

The nuclear pore complex sits as the gateway between the genomic, nuclear environment and the primarily enzymatic realm of the cytoplasm. Large channels traversing the two membranes of the nuclear envelope, the nuclear pores govern the passage of specific molecules between these two major compartments of the cell. Its ability to limit passage to specific molecules, and furthermore to pump them against a gradient in concentration, raises intriguing physical questions. This article reviews basic aspects of the structure and operation of this biochemical pump, whose thermodynamic cycle differs from that of conventional machines.