  Many biological and artificial transport channels function without direct
input of metabolic energy during a transport event and without structural
rearrangements involving transitions from a 'closed' to an 'open' state.
Nevertheless, such channels are able to maintain efficient and selective
transport. It has been proposed that attractive interactions between the
transported molecules and the channel can increase the transport efficiency and
that the selectivity of such channels can be based on the strength of the
interaction of the specifically transported molecules with the channel. Herein,
we study the transport through narrow channels in a framework of a general
kinetic theory, which naturally incorporates multi-particle occupancy of the
channel and non-single-file transport. We study how the transport efficiency
and the probability of translocation through the channel are affected by
inter-particle interactions in the confined space inside the channel, and
establish conditions for selective transport. We compare the predictions of the
model with the available experimental data - and find good semi-quantitative
agreement. Finally, we discuss applications of the theory to the design of
artificial nano-molecular sieves.
