Birthing of a daughter vesicle in a model system for self-reproduction vesicles

Abstract

Sakuma and Imai [Phys. Rev. Lett. 107, 198101 (2011)] established a temperature-controlled cyclic process for a model system of self-reproducing vesicles without feeding. The vesicle generates a smaller inclusion vesicle called “daughter vesicle” inside the original vesicle (we call this “mother vesicle”) and then the daughter vesicle is expelled through a small pore on the mother vesicle. This self-reproducing process is called birthing. In the present study, we present a theoretical model on the birthing process of a single, rigid daughter vesicle through a pore. By using a simple geometric picture, we derive the free energy constituting the material properties of the bending, stretching, and line tension moduli of the mother vesicle, as a function of the distance between the centers of the daughter and mother vesicles, and the size of the daughter vesicle. We see clearly the disappearance of the energy barrier by selecting appropriate moduli. The dynamics of the system is studied by employing the Onsager principle. The results indicate that translocation time decreases as the friction parameter decreases or the initial size of the daughter vesicle decreases.

Significance of in situ quantitative membrane property–morphology relation (QmPMR) analysis

“…Previous research based on simulations by the Imai group 12 showed a similar phenomenon with DPPC/DPPE vesicles as ours and established a relationship between the ratio (Ratio r = r d / r p ) of the radius of the daughter vesicle ( r d ) and the parent vesicle ( r p ). In our study, we found a relationship between the success of the birthing process and the size of parent vesicles in all OA-containing vesicles.…”

“…(ii) In some cases, after morphological changes, budding or birth of vesicles are observed and are studied in terms of mechanical properties and free energy change. 12 However, these studies have not reported the membrane properties and composition of newborn vesicles because of the difficulty of analysis. (iii) Studies using a similar analysis method to the one presented here are often performed in the steady state (at a constant temperature) and are sometimes difficult to conduct in a time-lapse manner in a non-equilibrium state, such as heat flow, which imitates the environment of the cell and primordial protocells.…”

Division in synthetic cells

“…6(c) and (d)). 55,56 2.2.3 pH-induced changes in membrane curvatures. Changes in pH can affect the physicochemical properties of hydrophilic head groups of lipids (such as charges and solubility in water), which determine the hydrophile lipophilic balance (HLB) value of the lipids.…”

Protocells: Milestones and Recent Advances

“…Examples include thermally driven fission of protocells [243] and division by "birthing" of an internally assembled daughter vesicles due to membrane contraction and pore formation in the mother vesicle upon cooling. [244,245] The presence of the synthetic lipid DLPE appears to be necessary for the latter process. However, this does not strictly exclude that other lipid species or lipid mixtures would support similar pathways in nature.…”

“…[189,248] The "birthing" mechanism, where the size of the mother vesicle is not changing, is also a pseudo division phenomenon. [244,245] Besides these experimental works, there are computational division models. [249] Theoretical work on protocell growth and division will be discussed further in the section Protocells in silico.…”