  In a molecular communication network, transmitters may encode information in
concentration or frequency of signalling molecules. When the signalling
molecules reach the receivers, they react, via a set of chemical reactions or a
molecular circuit, to produce output molecules. The counts of output molecules
over time is the output signal of the receiver. The aim of this paper is to
investigate the impact of different reaction types on the information
transmission capacity of molecular communication networks. We realise this aim
by using a general molecular circuit model. We derive general expressions of
mean receiver output, and signal and noise spectra. We use these expressions to
investigate the information transmission capacities of a number of molecular
circuits.
