Classical theoretical assumptions, which are implausible for describing biological behavior in real systems include uniform fixed charge distribution in colloidal outer membrane layer, uniform dielectric constant throughout the membrane phase, and point charge for ionic sizes. In the present study, absorption of cations by fixed functional groups in the membrane layer, variation in dielectric constant in a system, and effect of ionic sizes are considered to investigate the deposition of biocolloids each covered with an ion-penetrable membrane. The simulated results reveal that a larger numbers of cations involved in the formation of a cations-fixed groups complex, a smaller dielectric constant near a biological uncharged core, a larger dielectric constant of the membrane phase, a smaller cation-absorption equilibrium constant, a smaller concentration of total functional groups in the membrane layer, a thicker membrane, smaller cations, larger anions, and larger functional groups yield a faster rate of deposition. (c) 2005 Elsevier Inc. All rights reserved.