f1-7_77: Schematic representation of our system. A bead is placed at r = ξ, and it moves in a d-dimensional space (d = 1, 2, 3). The adsorption reaction occurs on the surface of the bead.

Mentions: Consider organelles or macromolecules that have a number of binding sites on their surface for reactions to occur; for example, nucleoprotein complexes (NCs) have several promoter sites to bind transcription factors. Let us model these biological elements simply as beads with several reaction sites to which molecules attach themselves, as shown in Figure 1. The bead is placed at r = ξ and moves in a d-dimensional space r ∈ Rd (d = 1, 2, 3). We consider an isothermal process that is homogeneous over space at a given temperature T. We also consider a chemical bath containing a chemical X with a spatially dependent concentration x(r) or, equivalently, the corresponding chemical potential μ(r). This gradient is assumed to be sustained externally. A molecule of X is attached to a binding site B on the bead and forms a complex Y (Fig. 1), as given by the reaction