Chemical reaction inside a microdomain. Each free particle (white circle) moves according to a Brownian motion until it binds to a free site (black color). An occupied site cannot accept any other particles. A molecule is composed of a finite number of sites. Parts of the microdomain is reflective and the rest is absorbing.
Schematic reaction in a microdomain where channels are located on the boundary. Molecules move according to a Brownian motion inside the domain. When a particle hits a free channel, it can bound and stays there for a certain amount of time. Particles can escape through the absorbing boundary.
Normalized variance , for , 1, 2, 4.
The variance square equal to , for various values of the backward binding rate . The total number of substrate molecules is fixed at and .
Experimental analysis of the fluctuation in the number of open channel. The left panel corresponds to the current response for various concentration of the gating molecules (cGMP), in a detached patch experiment of a cone photoreceptors membrane. On the right panel, the variance is plotted vs the mean current, which is proportional to the number of gating molecules (cGMP). This picture was published in Ref. 4 (Fig. 2).
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