Shape changes and budding of giant vesicles induced by an internal chemical trigger: an interplay between osmosis and pH change

Abstract

Shape transformation and self-division of phospholipid/fatty acid giant hybrid vesicles can be induced by an internal chemical stimulus (pH change) when coupled with an osmotic shock. In particular, an autocatalytic...

Effect of the Membrane Composition of Giant Unilamellar Vesicles on Their Budding Probability: A Trade-Off between Elasticity and Preferred Area Difference

“…A shift towards basic conditions inside the vesicles lumen causes the deprotonation of HOA to form oleate molecules readily dissolved in the aqueous medium. In a previous work [ 31 ], we demonstrated that the addition of urea in the outer solution generates an hypertonic condition, which, in turn, drives a deflation of the vesicles due to the osmotic shock. Thus, the addition of urea triggers a synergistic dynamics between the reduction of the vesicles volume ( changes from 1 to ∼0.7 at mM and ) and the increase of the area difference between the lipid leaflets in the bilayer, caused by the dissolution of oleate molecules in the aqueous lumen ( changes from 1 to ∼1.7 at mM and ).…”

“…For a few years our group has been studying a simple cell model having a diameter larger than 5 m (GUV) and based on a mixed phospholipid/fatty acid membrane encapsulating a pH clock reaction. We demonstrated that a simple pH change inside the vesicles lumen, coupled with an osmotic stress, is enough to induce shape transformations of the vesicles eventually leading to the fission of a mother GUV into two daughter GUVs [ 30 , 31 ]. Interestingly, our operative conditions are compatible with the slightly acidic pH suggested for the early Archean age oceans [ 57 ].…”

“…The energy can be expressed as where is the area of the vesicle, h is the distance between the neutral surfaces of the leaflets and the integral is calculated on the surface of the vesicle ( S ) [ 35 , 36 ]. The area difference can be calculated from the integral of the mean curvatures and values can be determined experimentally from images as well [ 30 , 31 ].…”

“…The model was described in details in ref. [ 31 ] and a short description can be found in the Supplementary Information (SI) .…”

“…In general, division occurs when the volume of the vesicles decreases (mostly due to an osmotic shock) and concurrently the inner surface area of the inner bilayer leaflet decreases in respect to the outer one. Recently, we reported that a pH change occurring inside the lumen of mixed 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine (POPC)/oleic acid (HOA) GUVs can be utilized to drive and govern the division process [ 30 , 31 ]. In particular, the urea–urease enzymatic reaction [ 32 , 33 , 34 ] inside the lumen of the vesicles, coupled to the cross-membrane transport of urea, can trigger the shape deformation of the pH-sensitive mixed membrane by promoting the solubilization of oleate molecules in the inner water phase.…”