  Steric or attractive interactions among reactants or between reactants and
inert crowders can substantially influence the total rate of a
diffusion-influenced reaction in the liquid phase. However, the role of the
product species, that has typically different physical properties than the
reactant species, has been disregarded so far. Here we study the effects of
reactant-product and product-product interactions as well as asymmetric
diffusion properties on the rate of diffusion-controlled reactions in the
classical Smoluchowski-setup for chemical transformations at a perfect
catalytic sphere. For this we solve the diffusion equation with appropriate
boundary conditions coupled by a mean-field approach on the second virial level
to account for the particle interactions. We find that all particle spatial
distributions and the total rate can change significantly, depending on the
diffusion and interaction properties of the accumulated products. Complex
competing and self-regulating (homeostatic) or self-amplifying effects are
observed for the system, leading to both decrease and increase of the rates, as
the presence of interacting products feeds back to the reactant flux and thus
the rate with which the products are generated.
