Abstract
The self-assembly of lipid bilayer membranes to enclose functional biomolecules, thus defining a “protocell,” was a seminal moment in the emergence of life on Earth and likely occurred at the micro-environment of the mineral-water interface. Mineral-lipid interactions are also relevant in biomedical, industrial and technological processes. Yet, no structure-activity relationships (SARs) have been identified to predict lipid self-assembly at mineral surfaces. Here we examined the influence of minerals on the self-assembly and survival of vesicles composed of single chain amphiphiles as model protocell membranes. The apparent critical vesicle concentration (CVC) increased in the presence of positively-charged nanoparticulate minerals at high loadings (mg/mL) suggesting unfavorable membrane self-assembly in such situations. Above the CVC, initial vesicle formation rates were faster in the presence of minerals. Rates were correlated with the mineral’s isoelectric point (IEP) and reactive surface area. The IEP depends on the crystal structure, chemical composition and surface hydration. Thus, membrane self-assembly showed rational dependence on fundamental mineral properties. Once formed, membrane permeability (integrity) was unaffected by minerals. Suggesting that, protocells could have survived on rock surfaces. These SARs may help predict the formation and survival of protocell membranes on early Earth and other rocky planets, and amphiphile-mineral interactions in diverse other phenomena.
Highlights
In modern geochemical environments, orders of magnitude greater numbers of prokaryotic cells live in biofilm communities at the sediment-water interface than in the water column, because of the numerous metabolic and protective benefits provided by such interfaces[1,2,3]
We have shown here that the effects of minerals on the self-assembly of Single chain amphiphiles (SCAs) vesicles are related to the isoelectric point (IEP) and available reactive surface areas of the minerals
Even a small amount of adsorption is sufficient to catalyze vesicle self-assembly, but a large amount of lipid adsorption and removal from suspension is required to influence the thermodynamics of vesicle self-assembly (CVC) Membrane, membrane integrity of pre-formed vesicles is hardly affected by minerals
Summary
Orders of magnitude greater numbers of prokaryotic cells live in biofilm communities at the sediment-water interface than in the water column, because of the numerous metabolic and protective benefits provided by such interfaces[1,2,3]. The potential effect of minerals on the rate of formation of SCA vesicles as model protocell membranes has been examined previously[13,14]. The stability and formation kinetics of phospholipid bilayer membranes as well as the adhesion of prokaryotic and eukaryotic cells to oxide and aluminosilicate (muscovite mica) mineral surfaces is known to depend on the surface charge of minerals[18,19,20,21,22,23]. The goals of the present study were: (i) to examine the potential effects of minerals on the thermodynamics and kinetics of initial vesicle self-assembly and survival after formation, and (ii) to identify mineral-specific trends in these processes, if any. All solids will subsequently be referred to, sensu lato, as “minerals”
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call