  Cooperativity arising from local interactions in equilibrium receptor systems
provides gain, but does not increase sensory performance, as measured by the
signal-to-noise ratio (SNR) due to a fundamental tradeoff between gain and
intrinsic noise. Here we allow sensing to be a nonequilibrium process and show
that energy dissipation cannot circumvent the fundamental tradeoff, so that SNR
is still optimal for independent receptors. For systems requiring high gain,
nonequilibrium 2D-coupled receptors maximize SNR, revealing a new design
principle for biological sensors.
