Active Transport of Membrane Components by Self-Organization of the Min Proteins

ABSTRACTHeterogeneous distribution of components in the biological membrane is critical in the process of cell polarization. However, little is known about the mechanisms that can generate and maintain the heterogeneous distribution of the membrane components. Here we report that the propagating wave patterns of the bacterial Min proteins can impose corresponding steric pressure on the membrane to establish a directional accumulation of the membrane components, resulting in segregation of the components in the membrane. The diffusivity, influenced by the membrane anchor of the component, and the repulsed ability, influenced by the steric property of the soluble region of the component and molecular crowding, determine the differential spatial distribution of the component in the membrane. Thus, transportation of the membrane components by the Min proteins follows a simple physical principle, which resembles a linear peristaltic pumping process, to selectively segregate and maintain heterogeneous distribution of materials in the membrane.

Syntheses and characterization of a series of asymmetric porphyrins containing an 8-ethoxycarbonyl-1-naphthyl group

Using aldehydes with different substituents of the aryl groups, we have synthesized a series of asymmetric porphyrins containing an 8-ethoxycarbonyl-1-naphthyl group by one-pot reactions. Our studies suggest the steric property of substituents is the major factor to affect the reaction yields, the steric hindrance is unfavorable for such reaction. Compared with those para-substituted species, NMR studies of 2,6-substituted species show upfield shifts for their NH and ethyl protons, downfield shifts for their pyrrole protons, which is probably due to the decrease of porphyrin ring current. Three of them have been characterized by X-ray crystallography. Structures show that the ester group is hanging over the porphyrin plane, compound 3 and 4 have much different core conformations from compound 2, which is probably due to the π–π interactions in the solid state.