The electrophoresis of a soft toroid, which comprises a rigid core and a porous layer, coaxially along the axis of a cylindrical pore is analyzed under the conditions of low surface potential and weak applied electric field. The geometry considered simulates the electrophoresis of various types of biocolloid such as bacterial DNA, plasmid DNA, and anabaenopsis. in a confined space. We show that under typical conditions the electrophoretic behavior of a soft toroid can be different from that of a rigid toroid. For instance, the effect that the presence of a boundary can raise the mobility of a rigid toroid may not be present for a soft toroid. Several interesting behaviors are also observed. For example, if the friction coefficient of the membrane layer of a toroid is small, the larger the friction coefficient the greater is the effect electroosmotic flow, and therefore, the larger the mobility, but the reverse trend is observed if the friction coefficient is sufficiently large. (C) 2009 Elsevier Ltd. All rights reserved.