subconductance

Subconductance refers to a conductance level that is smaller than the maximum open or fully conducting state of a system. It is used to describe partial or intermediate conduction in contexts where a system can adopt multiple conductive states, not just fully closed or fully open.

In biology, subconductance states are commonly reported for ion channels. These channels can display discrete current levels between zero and the full open level, corresponding to partial pore opening or activation of only a subset of channel subunits. Subconductance events are observed in various families, including voltage-gated and ligand-gated channels, and are detectable in single-channel recordings. They provide clues about gating mechanisms, subunit cooperativity, and the effects of ligands, toxins, or drugs on channel behavior.

Mechanistically, subconductance can arise from partial conformational changes within the channel, asymmetric subunit activation, or transient states where the pore is only partially conducive to ion passage. The existence of subconductance levels supports models with multiple intermediate states and helps describe the kinetics of opening and closing beyond a simple two-state framework.

Outside biology, subconductance appears in nanoscale and molecular electronics. In these systems, partial transmission due to weak coupling, defects, or metastable configurations yields conductance values below the maximum. Studying subconductance in such devices aids understanding of switching behavior, device reliability, and the role of microscopic states in macroscopic current.

Overall, subconductance is a useful concept for describing and analyzing intermediate conductive states across biological and nanoscale systems.